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Science for Sleep. How the Moon Controls the Ocean. Documentary for Sleep · Night Science Stories

• 0:00
  Speaker 1: Hi guys, welcome to Night Science Stories. Settle in, breathe
• 0:05
  Speaker 1: at an easy pace, and let your thoughts soften like
• 0:09
  Speaker 1: a shoreline at twilight. Tonight we will listen to the
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  Speaker 1: quiet conversation between the moon and the ocean. Imagine the
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  Speaker 1: earth wrapped in a thin, mobile shell of ocean water.
• 0:24
  Speaker 1: It is not very deep. Compared with the size of
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  Speaker 1: the planet, if the Earth were a smooth sphere, the
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  Speaker 1: ocean would be a film of blue only a few
• 0:34
  Speaker 1: kilometres thick. Because water can flow, it can respond to
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  Speaker 1: small differences in pull. The Moon tugging on one side
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  Speaker 1: of Earth does not yank the whole planet. It draws
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  Speaker 1: very slightly more on the side that faces it, and
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  Speaker 1: very slightly less on the far side. This tiny difference
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  Speaker 1: is enough to raise a broad swell in the ocean.
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  Speaker 1: Think of it as a long, slow hill of water
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  Speaker 1: that tries to stay lined up with the moon as
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  Speaker 1: the earth turns. The height of that hill in the
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  Speaker 1: open sea is rarely more than a metre or two,
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  Speaker 1: often less than that, but its span is vast, stretching
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  Speaker 1: across entire ocean basins. A faint force applied to a
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  Speaker 1: compliant medium over a very large area becomes an unmistakable signal.
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  Speaker 1: The idea that two tide crests exist at once can
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  Speaker 1: feel counterintuitive until we look at the whole system. The
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  Speaker 1: Moon pulls more strongly on the near side of Earth
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  Speaker 1: because it is closer and less strongly on the far
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  Speaker 1: side because it is farther away. Inside the Earth-Moon pair
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  Speaker 1: there is a shared centre of motion, the common balance
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  Speaker 1: point where both bodies orbit. Water on the near side
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  Speaker 1: is drawn a little toward the Moon and away from
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  Speaker 1: the centre of Earth. Water on the far side is
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  Speaker 1: left a little behind because the solid Earth is pulled
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  Speaker 1: a little more strongly than the distant ocean. The result
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  Speaker 1: is a pair of bulges, one facing the Moon and
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  Speaker 1: one opposite the Moon. Between them, along the band where
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  Speaker 1: the pull is balanced by the spin of the Earth,
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  Speaker 1: the sea surface is slightly lower. As the Earth rotates,
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  Speaker 1: coasts pass under these slow-moving hills and valleys of water
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  Speaker 1: like a city standing beside a river that rises and
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  Speaker 1: falls as the river sways from bank to bank. The
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  Speaker 1: Sun also speaks into this conversation. Though the Sun is
• 2:47
  Speaker 1: far away, it is immensely massive and it adds its
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  Speaker 1: own tide-raising pull. When the Sun and the Moon line
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  Speaker 1: up with Earth, during the times of New Moon and
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  Speaker 1: Full Moon, their tugs join. The two bulges grow taller
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  Speaker 1: and the lows grow lower. Along coasts, you can hear
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  Speaker 1: mariners speak of spring tides. Spring here means to leap,
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  Speaker 1: not the season. Water doesn't remember our calendar. These higher swings,
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  Speaker 1: born of alignment, are common and predictable. People who harvest
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  Speaker 1: shellfish plan their work around them. Birds that nest on
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  Speaker 1: low islands listen to them as to a clock. When
• 3:34
  Speaker 1: the sun and the moon are at right angles as
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  Speaker 1: seen from Earth, the picture changes. During the first and
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  Speaker 1: the last quarter of the moon, the solar pull works
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  Speaker 1: sideways to the lunar pull and the sea does not
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  Speaker 1: stretch as far. The higher waters do not climb quite
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  Speaker 1: so high and the lower waters do not fall so low.
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  Speaker 1: These are called neap tides, quiet waters that leave a
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  Speaker 1: gentler mark along the shore. After the stronger spring tides,
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  Speaker 1: neap tides bring a slower breathing to estuaries and tidal creeks.
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  Speaker 1: Animals that depend on precise water levels, like some crabs
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  Speaker 1: and wading birds, adjust their foraging to this softer beat.
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  Speaker 1: Fishermen watch the nippy days for calmer currents in narrow passages.
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  Speaker 1: While the sun and the moon set the rhythm, the
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  Speaker 1: spin of earth sets the tempo you feel at any
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  Speaker 1: single place. The earth turns once in about 24 hours.
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  Speaker 1: The lunar bulge makes a full lap relative to the
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  Speaker 1: surface in a little more than that, because the moon
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  Speaker 1: moves forward in its own path around earth. The interval
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  Speaker 1: between one high tide and the next high tide at
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  Speaker 1: the same dock is about 12 hours and 25 minutes.
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  Speaker 1: You can test this with a notebook near any harbour.
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  Speaker 1: Record a time when the water touches a mark on
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  Speaker 1: a piling, return the next day at the same clock
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  Speaker 1: time and you will find the sea a little late.
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  Speaker 1: That small daily delay is the voice of the orbiting moon.
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  Speaker 1: Now add another element of motion, the effect of Earth
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  Speaker 1: rotating beneath moving water. In the northern hemisphere, currents are
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  Speaker 1: turned a little to the right of their direction of travel.
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  Speaker 1: In the southern hemisphere, they are turned a little to
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  Speaker 1: the left. This is the Coriolis effect, not a force
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  Speaker 1: from outside, but a pattern that emerges in a spinning frame.
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  Speaker 1: Because of it, the large-scale tide waves tend to rotate
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  Speaker 1: around ocean basins. Along the edges of continents, the tide
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  Speaker 1: signal can press into the coastline as a special kind
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  Speaker 1: of wave that keeps the coast on one side and
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  Speaker 1: deeper water on the other. These are Kelvin waves, quiet
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  Speaker 1: runners that carry the tide for great distances while hugging
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  Speaker 1: the land. In the Northern Hemisphere, They creep with the
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  Speaker 1: coast to their right. In the southern, they keep the
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  Speaker 1: coast to their left. Even in their quiet ways, they
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  Speaker 1: help explain why the same moon can lead to very
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  Speaker 1: different timing and heights at ports that are not so
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  Speaker 1: far apart. The most basic picture of tides is called
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  Speaker 1: the equilibrium view, where the ocean simply bulges under the
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  Speaker 1: moon and the sun, and the earth turns under those bulges.
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  Speaker 1: It is a useful introduction, but real oceans have continents, peninsulas, islands,
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  Speaker 1: and irregular bottoms. The tide cannot sweep smoothly under a landmass.
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  Speaker 1: It must detour, reflect, and sometimes slosh inside a basin
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  Speaker 1: as water would in a broad bowl. This moves us
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  Speaker 1: to the dynamic view of tides. In this view, we
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  Speaker 1: track the tide as a wave that travels, bends, and
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  Speaker 1: even sets up standing patterns like the sway of tea
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  Speaker 1: in a cup after you nudge it. The geometry of
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  Speaker 1: basins and the depth of water matter as much as
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  Speaker 1: the pull that starts the whole show. When an ocean
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  Speaker 1: basin or a long gulf has a natural period of
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  Speaker 1: slosh that happens to match the timing of the incoming tide,
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  Speaker 1: the two motions add together. The result is resonance, which
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  Speaker 1: can produce spectacular heights. The great stage for this is
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  Speaker 1: a bay with a long, narrowing shape that focuses the wave.
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  Speaker 1: Many listeners have heard of a Canadian inlet where the
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  Speaker 1: sea climbs a cliff of coastline twice a day. The
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  Speaker 1: geography there, its length, its depth, and its mouth open
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  Speaker 1: to the ocean, all help the bay swing in step
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  Speaker 1: with the passing tide wave, piling water higher than almost
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  Speaker 1: anywhere else on earth, in smaller bodies of water such
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  Speaker 1: as long harbours or sounds. Similar standing waves called seiches
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  Speaker 1: can grow when wind or air pressure pushes water and
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  Speaker 1: then lets it rebound. Seiches and resonant tides together give
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  Speaker 1: local coasts their personality, which you hear in the way
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  Speaker 1: a marina creaks or mudflats glisten. Approaching land, the tide
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  Speaker 1: wave meets the continental shelf. that wide underwater terrace that
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  Speaker 1: rings many continents. The shelf is shallower than the blue
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  Speaker 1: depths offshore, and the front edge of the tide wave
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  Speaker 1: slows down. The water behind continues to move faster, so
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  Speaker 1: the wave grows taller much as a line of runners
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  Speaker 1: compresses when the leaders slow. Friction with the bottom also
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  Speaker 1: changes the timing or phase of the tide. so the
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  Speaker 1: moment of high water may arrive later on a beach
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  Speaker 1: than offshore. In some places, a large river mouth and
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  Speaker 1: a narrowing channel act like a horn, raising the tide
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  Speaker 1: even more as it pushes inland. Where the shape is
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  Speaker 1: just right, a tidal bore can form, a single rolling
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  Speaker 1: front that travels up the river as a small wall
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  Speaker 1: of water. In other places with broad shelves and many sandbanks,
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  Speaker 1: The tide becomes a complex lacework of streams and whirlpools
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  Speaker 1: that turn vast sand shoals from one shape to another
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  Speaker 1: through the seasons. All of these ingredients come together to
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  Speaker 1: decide the local style of the tide chart. Some coasts
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  Speaker 1: experience two high waters and two low waters of similar
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  Speaker 1: height in each lunar day. This is called a semidurnal regime.
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  Speaker 1: Many North Atlantic shores follow this pattern, almost like a
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  Speaker 1: heartbeat that keeps even time. Other places see only one
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  Speaker 1: high water and one low water in about 24 hours.
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  Speaker 1: That is a diurnal regime found in parts of the
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  Speaker 1: Gulf of Mexico and along some Pacific islands. Still other
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  Speaker 1: coasts show a mixed regime, with two highs and two lows,
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  Speaker 1: but of different magnitudes, a rhythm that feels syncopated. The
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  Speaker 1: mixture reflects how the lunar and solar pulls arrive at
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  Speaker 1: a particular harbour after winding around islands and shelves, and
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  Speaker 1: after being bent by the spin of the Earth. Local bathymetry,
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  Speaker 1: the undersea topography, is the arranger of this music. Let
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  Speaker 1: us stay a little longer with the opening concept because
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  Speaker 1: the theme of small cause and large effect carries useful calm.
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  Speaker 1: The moon is not trying to lift towers of water
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  Speaker 1: the way a person lifts a stone. Instead, it nudges
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  Speaker 1: parts of the ocean very slightly differently and water does
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  Speaker 1: the rest by flowing. Because the ocean is connected, The
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  Speaker 1: response is not loud in one place and silent in another.
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  Speaker 1: It is a low rumble everywhere that rings more loudly
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  Speaker 1: where shape and depth allow it. Think of a child
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  Speaker 1: pushing a swing with gentle, regular taps. If the timing
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  Speaker 1: is right, the swing arcs higher with each pass. The
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  Speaker 1: taps are small. The motion grows large through patience and
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  Speaker 1: matching rhythms. So it is with the lunar pull and
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  Speaker 1: the geometry of seas. On a clear night, if you
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  Speaker 1: walk ashore as the tide turns, you can feel the
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  Speaker 1: meeting of cosmic order and earthly detail. The moon alone
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  Speaker 1: in a cold sky tells you one part of the story.
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  Speaker 1: The cove in front of you, with its curved beach,
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  Speaker 1: its rocks, and its channel tells you the rest, the
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  Speaker 1: height and timing you witness are the sum of many
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  Speaker 1: small contributions that your senses fold into a single experience.
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  Speaker 1: The wind, if it has blown on shore all day,
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  Speaker 1: may have pushed the water up a little higher than
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  Speaker 1: the tables predicted. A passing region of low air pressure
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  Speaker 1: might lift the sea surface by the height of a
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  Speaker 1: few millimetres For every hectopascal drop, a small nudge that
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  Speaker 1: can matter during a very high spring tide, a distant
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  Speaker 1: storm can send long waves that ride in like extra
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  Speaker 1: breaths between the regular rise and fall. The simplicity of
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  Speaker 1: lunar pull meets the complexity of an earthly coast, and
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  Speaker 1: together they draw the line where your footprints will be erased.
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  Speaker 1: To weave together these ideas, picture a point in the
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  Speaker 1: open ocean, far from coastlines. There the tide looks most
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  Speaker 1: like the gentle hill of the equilibrium view, a broad
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  Speaker 1: rise and fall that does not vary dramatically from day
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  Speaker 1: to day. As the wave approaches land, the Coriolis turning
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  Speaker 1: begins to matter, shelves bend the flow, and the wave
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  Speaker 1: is squeezed and reflected. Around the edges of basins the
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  Speaker 1: tide rotates about quiet nodes called amphidromic points, where the
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  Speaker 1: height hardly changes but the phase spins like the hand
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  Speaker 1: of a clock pointing to a different hour at each
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  Speaker 1: surrounding port. Draw that map in your mind. Small circles
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  Speaker 1: drawn over offshore nodes. arrows swirling around them with numbers
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  Speaker 1: at coasts marking the time of high water as the
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  Speaker 1: wave sweeps by. It is a living atlas that never
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  Speaker 1: lies still. That moving atlas explains some of the striking
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  Speaker 1: records along the planet. In narrow passages where the tide
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  Speaker 1: must squeeze through a gap, currents can run like a river.
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  Speaker 1: Sailors time their crossings through these gates with care. In
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  Speaker 1: funnel-shaped bays that invite resonance, the sea climbs the shore
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  Speaker 1: in twice-daily strides that set world marks. In wide coral lagoons,
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  Speaker 1: the tide may be so damped by friction that the
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  Speaker 1: range is only a modest rise at the beach. And
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  Speaker 1: on isolated seamounts, as the tide flows around, it can
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  Speaker 1: create internal waves in the layered ocean that break like
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  Speaker 1: underwater surf. stirring nutrients from the dark into the sunlit
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  Speaker 1: layers above. Even where few people watch, the tide is
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  Speaker 1: at work as quiet labour. All living things along the
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  Speaker 1: shore have listened to this music for a very long time.
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  Speaker 1: Along rocky coasts you can trace tidy bands of life
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  Speaker 1: that match the typical reach of the water. Barnacles and
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  Speaker 1: mussels occupy a high zone where they are wetted twice
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  Speaker 1: each day but spend long hours in air. Seaweeds drape
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  Speaker 1: lower ledges that are rarely exposed. Eelgrass makes gardens in
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  Speaker 1: the soft mud of estuaries, where still water follows just
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  Speaker 1: behind the turning points of the tide. Crabs leave their
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  Speaker 1: burrows when the flats are warm and shallow. Wading birds
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  Speaker 1: time their flights to arrive when the mud is uncovered
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  Speaker 1: and rich. Human communities do the same. Fishers know the
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  Speaker 1: slack moments when a tide turns and nets can be
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  Speaker 1: set without strain. Bathers learn to meet the ocean when
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  Speaker 1: the surf is kindest. Coastal people have turned the heartbeat
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  Speaker 1: of water into calendars and stories. When you recall that
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  Speaker 1: the period between one high water and the next at
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  Speaker 1: the same place is about 12 hours and 25 minutes.
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  Speaker 1: You can see why the timing marches slowly through the day.
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  Speaker 1: A noon high water today becomes a high water a
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  Speaker 1: little after midnight in a few days. In some towns,
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  Speaker 1: you can watch street markets and ferry schedules adapt to
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  Speaker 1: that moving appointment. The tide chart is like a poem
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  Speaker 1: posted each day at the harbour. It anticipates not only
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  Speaker 1: the timing but the height, whether the day will bring
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  Speaker 1: a gentle rise or a proud reach. People who work
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  Speaker 1: close to the water learn to read the chart with
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  Speaker 1: an intimacy that resembles the way a farmer reads the sky.
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  Speaker 1: Questions often arise when one hears that there are two bulges.
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  Speaker 1: If that is so, why do some places have a
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  Speaker 1: single high water most days rather than two? The answer
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  Speaker 1: is that the ocean is not a single clear belt.
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  Speaker 1: The path of the lunar tide wave is distorted by
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  Speaker 1: the shape of the basins and the presence of land.
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  Speaker 1: When an island shelf carves the wave, or when reflection
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  Speaker 1: mixes different frequencies of motion, the pattern that reaches a
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  Speaker 1: port may be dominated by a once-daily component. Elsewhere, the
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  Speaker 1: twice-daily component is strongest. In many places, the two are
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  Speaker 1: of similar strength, and the result is a mixed tide
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  Speaker 1: with alternating high waters of different height. The melody is
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  Speaker 1: the same. but the harmony varies with every harbour. The
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  Speaker 1: forces that begin the tide also very slowly change the
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  Speaker 1: earth itself. As water is dragged across the seabed twice
• 18:31
  Speaker 1: a day, energy is dissipated as heat, and a tiny
• 18:35
  Speaker 1: amount of the rotational momentum of earth is transferred to
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  Speaker 1: the moon. Over great spans of time, the length of
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  Speaker 1: day has crept longer by tiny fractions of a second.
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  Speaker 1: and the moon has drifted farther from Earth by small
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  Speaker 1: amounts each year. In the far future, this will change
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  Speaker 1: the pace and the power of tides. That thought is
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  Speaker 1: not meant to trouble sleep. It is a reminder that
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  Speaker 1: nothing in nature is permanently still, not even the slow
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  Speaker 1: dance between the Earth and its companions. For now you
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  Speaker 1: can take comfort in the steadiness of the cycle. In
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  Speaker 1: a remote cove the sea creeps up through the grass,
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  Speaker 1: pauses and retreats, and the same motion is mirrored on
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  Speaker 1: a different shore across the world. The tide is one
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  Speaker 1: of the few truly global rhythms that the senses can
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  Speaker 1: perceive directly without instruments. You can extend your hand and
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  Speaker 1: feel it. You can sit at evening and watch a
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  Speaker 1: rock that was wet become dry again. You can row
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  Speaker 1: a boat and sense the moment when the current slackens
• 19:52
  Speaker 1: and then begins to move the other way. All of
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  Speaker 1: this comes from a very slight difference in gravity across
• 20:00
  Speaker 1: the diameter of a planet and from the patient turn
• 20:04
  Speaker 1: of the Earth beneath a travelling wave Let that thought
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  Speaker 1: be the constant line that weaves through the details. The
• 20:12
  Speaker 1: moon calls with a force that is small. The ocean
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  Speaker 1: answers with a movement that is grand. The sun adds
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  Speaker 1: its accent, sometimes amplifying, sometimes softening. The spin of the
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  Speaker 1: earth guides the tide along coasts and through straits. Basins
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  Speaker 1: and shelves shape and sometimes dramatize the response. Out of
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  Speaker 1: these elements, you can build a mental picture of the
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  Speaker 1: tide that is both simple and rich. When you next
• 20:46
  Speaker 1: see a diagram of phases of the moon, you may
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  Speaker 1: also see the quiet breadth of bays and estuaries drawn
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  Speaker 1: around our planet. As the night deepens, imagine yourself aboard
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  Speaker 1: a gentle research vessel far offshore. The sea is not rough.
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  Speaker 1: only long swells under a sky of stars. A soft
• 21:11
  Speaker 1: red light glows above the chart table. On the paper
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  Speaker 1: are arcs and lines showing the predicted times of high
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  Speaker 1: water at distant ports, and a pencilled note that the
• 21:24
  Speaker 1: tide here in the open ocean will be only a
• 21:27
  Speaker 1: modest rise. The radio murmurs a weather forecast. A scientist
• 21:33
  Speaker 1: steps out to release a float that will measure the
• 21:36
  Speaker 1: tide as a small change of pressure with depth. The
• 21:40
  Speaker 1: instrument will report the passing of the long wave, the
• 21:44
  Speaker 1: very hill of water that began with the lunar pull
• 21:47
  Speaker 1: many time zones away. You can feel the ship rise
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  Speaker 1: slightly and fall. You can feel the planet breathe. In
• 21:57
  Speaker 1: the morning that same wave will be running into a
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  Speaker 1: wide estuary. It will lift the river and reverse its
• 22:05
  Speaker 1: surface flow for a while, bringing salt farther inland. It
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  Speaker 1: will slacken around docks so that boats can slide into
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  Speaker 1: their berths with gentler hands. It will creep over a
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  Speaker 1: flat and then slip away, leaving the shining paths of
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  Speaker 1: snails and crabs printed in the mud. It will rock
• 22:27
  Speaker 1: the kelp forests and swing their blades in arcs that
• 22:31
  Speaker 1: feed them fresh water. It will exploit every channel and
• 22:35
  Speaker 1: curl around every island, always following the shape of earth
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  Speaker 1: and the laws of fluid motion. And somewhere a child
• 22:45
  Speaker 1: will build a wall of sand and watch it dissolve,
• 22:48
  Speaker 1: not by chance, but on schedule, because the moon, is
• 22:53
  Speaker 1: passing a particular line in the sky. Allow all of
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  Speaker 1: this to form a single quiet image, a silver moon,
• 23:03
  Speaker 1: a blue planet, and between them an ocean that is
• 23:07
  Speaker 1: sensitive to the slightest difference. The story begins with gravity
• 23:12
  Speaker 1: and ends at the tips of grass in a salt marsh.
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  Speaker 1: It is a chain without a broken link. As you
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  Speaker 1: drift toward rest, you can hold one thought with you.
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  Speaker 1: The world has many clocks. The tide is one of
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  Speaker 1: the oldest and one of the kindest. It keeps time softly,
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  Speaker 1: and it does not ask for our permission to continue.
• 23:41
  Speaker 1: The music of the tides becomes clearer when we learn
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  Speaker 1: its alphabet. Oceanographers speak of harmonics and constituents, quiet notes
• 23:52
  Speaker 1: that add together to make the daily song heard at
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  Speaker 1: a harbour. Each note has a name and a period
• 24:00
  Speaker 1: that never changes. The most powerful of all is the
• 24:03
  Speaker 1: lunar semi-diurnal constituent called M2. The letter tells you it
• 24:09
  Speaker 1: is lunar, the word 2 tells you it repeats about
• 24:12
  Speaker 1: twice in one lunar day. Close behind is S2, the
• 24:17
  Speaker 1: solar partner that also repeats twice in one lunar day,
• 24:21
  Speaker 1: but is set by the Sun rather than the Moon.
• 24:24
  Speaker 1: Then come the slower once-daily notes. K1 blends both lunar
• 24:29
  Speaker 1: and solar effects into a single steady stroke and can
• 24:33
  Speaker 1: dominate at some islands. O1 is mainly lunar and once daily.
• 24:40
  Speaker 1: There are many others, such as N2 which is a
• 24:43
  Speaker 1: smaller lunar partner to M2, and P1 which is solar
• 24:47
  Speaker 1: and once daily. Imagine these notes as pure tones. At
• 24:51
  Speaker 1: any pier, the water level you see is a chord,
• 24:55
  Speaker 1: the sum of many tones at once. Scientists can measure
• 24:59
  Speaker 1: a year or more of water levels. Separate the record
• 25:03
  Speaker 1: into these notes with patient mathematics, and then forecast the
• 25:08
  Speaker 1: tide by adding the notes back together. It is as
• 25:14
  Speaker 1: if we have learned the sheet music of that particular harbour.
• 25:19
  Speaker 1: Once you hear the alphabet, you will notice the slow
• 25:23
  Speaker 1: hands that modulate it. The moon does not simply circle
• 25:28
  Speaker 1: in a perfect loop. There are several lunar cycles that
• 25:32
  Speaker 1: touch the height of tides. The synodic cycle is the
• 25:36
  Speaker 1: one we know from the moon's phases, the steady march
• 25:40
  Speaker 1: from new to full and back again over a little
• 25:43
  Speaker 1: more than four weeks. This cycle organises the spring tides
• 25:48
  Speaker 1: when sun and moon align and the neap tides when
• 25:52
  Speaker 1: they stand at right angles. Another cycle is the anomalistic one.
• 25:58
  Speaker 1: which tracks how the Moon moves closer to Earth for
• 26:01
  Speaker 1: a time and then farther for a time. When the
• 26:05
  Speaker 1: Moon is nearer, the tide-raising pull is stronger. When it
• 26:10
  Speaker 1: is farther, the pull is gentler. A third cycle has
• 26:15
  Speaker 1: to do with declination, the tilt of the Moon's path
• 26:19
  Speaker 1: north and south of the equator. When the Moon rides
• 26:23
  Speaker 1: high above one hemisphere and low above the other for
• 26:26
  Speaker 1: many days, The once daily constituents become more prominent, and
• 26:32
  Speaker 1: the two daily highs can differ. These three rhythms lay
• 26:37
  Speaker 1: a slow pulse under the daily pattern, like a tide
• 26:42
  Speaker 1: within the tide. Every so often these cycles line up.
• 26:46
  Speaker 1: and the sea steps closer to the land than usual.
• 26:50
  Speaker 1: When the moon is near its closest approach, and when
• 26:54
  Speaker 1: it is new or full so that sun and moon align,
• 26:58
  Speaker 1: the two conditions join. Ocean folk call the resulting higher
• 27:02
  Speaker 1: waters Parisian spring tides. Along some coasts, people have taken
• 27:08
  Speaker 1: to calling them royal tides, a name that lives easily
• 27:13
  Speaker 1: on the tongue. These are not floods born of storms.
• 27:17
  Speaker 1: They are simply the regular spring swing made a little
• 27:20
  Speaker 1: broader by the nearer moon. They can overtop sea walls
• 27:25
  Speaker 1: that are usually just high enough. They can wake sleeping
• 27:29
  Speaker 1: salt marshes and refill shallow lagoons. With thoughtful planning, they
• 27:35
  Speaker 1: become useful. Communities that restore wetlands time their work to
• 27:41
  Speaker 1: these visits from the larger tide. Photographers love the way
• 27:45
  Speaker 1: harbours look when boats hover higher than usual beside stone quays.
• 27:51
  Speaker 1: For those who live near low ground, these days bring
• 27:55
  Speaker 1: a gentle reminder that the line between sea and street
• 28:00
  Speaker 1: is not fixed by concrete but by gravity and the
• 28:05
  Speaker 1: turn of the heavens. there is an even slower sway
• 28:09
  Speaker 1: written into the tide through the tilt of the lunar orbit.
• 28:13
  Speaker 1: The path of the Moon is not anchored to one
• 28:16
  Speaker 1: permanent angle. It nods, slowly and predictably, over a cycle
• 28:22
  Speaker 1: that lasts about 18 years and a little more than
• 28:26
  Speaker 1: a half year. This is the nodal cycle. When the
• 28:30
  Speaker 1: node that marks the intersection of lunar and solar paths shifts,
• 28:35
  Speaker 1: the range of lunar declination that the Moon can reach
• 28:39
  Speaker 1: also shifts. The result for coasts is a slow change
• 28:44
  Speaker 1: in the relative strength of the twice-daily and once-daily constituents.
• 28:50
  Speaker 1: In some harbours, the difference between the higher high water
• 28:54
  Speaker 1: and the lower high water grows and then shrinks over
• 28:58
  Speaker 1: this long cycle. Tide tables quietly include a correction for
• 29:03
  Speaker 1: nodal stage, so that predictions stay faithful to the true rhythm.
• 29:09
  Speaker 1: Marinas that were built during one part of the cycle
• 29:13
  Speaker 1: sometimes discover that their clearances feel different nearly two decades later,
• 29:20
  Speaker 1: even though the Moon has not changed its mass or
• 29:23
  Speaker 1: distance in any dramatic way. This very slow metronome is
• 29:29
  Speaker 1: a reminder that the sea listens to distant geometry as
• 29:33
  Speaker 1: much as to local wind. When we move from time
• 29:37
  Speaker 1: to space, another form of tide map appears. one that
• 29:41
  Speaker 1: looks at first like a dance chart. In the open
• 29:45
  Speaker 1: ocean and in wide seas, the tide often rotates around
• 29:49
  Speaker 1: points where the range is tiny. These are amphidromic points.
• 29:54
  Speaker 1: Places of near silence. Around them, the hour of high
• 29:58
  Speaker 1: water changes as steadily as the numbers on a clock face.
• 30:03
  Speaker 1: Follow a circle around such a point, and high water
• 30:06
  Speaker 1: marches forward hour by hour until you're back where you began.
• 30:11
  Speaker 1: The cause is the combination of basin shape, the depth
• 30:15
  Speaker 1: of water, and the turning of earth that bends the
• 30:19
  Speaker 1: tide into a rotating wave. On a map of the
• 30:22
  Speaker 1: world there are many such systems, some large and some small.
• 30:28
  Speaker 1: Coasts on one side of an amphidromic system will see
• 30:33
  Speaker 1: the tide wave arrive from the south, while coasts on
• 30:37
  Speaker 1: the other side see it arrive from the north. Draw
• 30:41
  Speaker 1: lines on such a map. and you will see bands
• 30:44
  Speaker 1: where the tide reaches greatest height, and other bands where
• 30:49
  Speaker 1: times change quickly, but heights remain modest. Navigators may never
• 30:55
  Speaker 1: use the word amphidromic at sea, but they learn the
• 30:59
  Speaker 1: pattern by touch from the way currents set in a straight,
• 31:04
  Speaker 1: and from the order in which harbours begin to stir.
• 31:09
  Speaker 1: Beneath the familiar surface, slosh, there are fronts and waves
• 31:13
  Speaker 1: that most eyes never see. Where water masses of different
• 31:18
  Speaker 1: temperature or salinity meet, a narrow boundary can form, a
• 31:22
  Speaker 1: tidal front. Along such a line, the tide acts like
• 31:26
  Speaker 1: a hand at the edge of a rug, rucking the
• 31:29
  Speaker 1: boundary back and forth. The energy that is lost at
• 31:33
  Speaker 1: the edge becomes turbulence, which mixes nutrients upward from dark
• 31:38
  Speaker 1: layers into the lighted zone where phytoplankton can use them.
• 31:42
  Speaker 1: At some banks and shelves, this mixing makes seasonal blooms
• 31:48
  Speaker 1: that feed fish and birds and the people who depend
• 31:52
  Speaker 1: on them. Still deeper within the layered interior of the ocean,
• 31:57
  Speaker 1: the tide can excite internal waves that are 100 meter
• 32:01
  Speaker 1: tall yet calmly invisible at the surface. They move slowly,
• 32:06
  Speaker 1: break on underwater slopes, and stir the abyss the way
• 32:10
  Speaker 1: a spoon stirs a pot. Such mixing helps set the
• 32:14
  Speaker 1: temperature structure of the global ocean. The moon, working through tides,
• 32:20
  Speaker 1: therefore plays a quiet role in the climate machine by
• 32:25
  Speaker 1: helping heat and salt to reorganise in the depths. Return
• 32:31
  Speaker 1: now to the shoreline and walk the living stair that
• 32:35
  Speaker 1: the tide draws twice each day. This is the literal world,
• 32:40
  Speaker 1: the band between low tide and high tide where rock
• 32:44
  Speaker 1: and sand and mud spend part of each day in
• 32:47
  Speaker 1: air and part underwater. Life here has learned the art
• 32:53
  Speaker 1: of patience and the art of clinging. On wave-washed headlands,
• 32:58
  Speaker 1: barnacles build close-packed cities, whose walls resist drying winds. Mussels
• 33:04
  Speaker 1: braid themselves with bissell threads, so they become one strong
• 33:08
  Speaker 1: mat that waves cannot strip away. Seaweeds anchor with holdfasts
• 33:14
  Speaker 1: shaped like fingers gripping a crack. In sandy places, clams
• 33:19
  Speaker 1: and worms move with the tide, riding the wet front
• 33:22
  Speaker 1: line a little up and then a little down. Every
• 33:26
  Speaker 1: step has its own guild of residents. High on the rocks,
• 33:31
  Speaker 1: splash zones host lichens and tough snails that graze on film.
• 33:36
  Speaker 1: Lower down, tide pools become pockets where fish and anemones
• 33:41
  Speaker 1: endure hours of isolation until the sea returns. If you
• 33:47
  Speaker 1: have ever wondered how a shore can feel both busy
• 33:50
  Speaker 1: and calm, think of the clock that runs there. It
• 33:54
  Speaker 1: is shorter than a day, yet it never tires. That
• 33:58
  Speaker 1: steadiness allows creatures to evolve. Exquisite timing. Timing shapes bodies
• 34:05
  Speaker 1: and behaviors from the inside as well. Many coastal animals
• 34:10
  Speaker 1: do not simply react. to the arrival of the tide.
• 34:14
  Speaker 1: They predict it with internal clocks that keep circutidal time.
• 34:19
  Speaker 1: A shore crab held in still water far from the
• 34:22
  Speaker 1: beach will still become more active at the hours when
• 34:26
  Speaker 1: it would normally forage on exposed flats. Mussels open and
• 34:31
  Speaker 1: close in a schedule that matches the waterline at their
• 34:34
  Speaker 1: home rocks even when kept in a laboratory at constant
• 34:39
  Speaker 1: water level. Some birds that feed on intertidal worms adjust
• 34:45
  Speaker 1: their flights and their stomach emptying to match the hour
• 34:49
  Speaker 1: when food will be available. These clocks are not identical
• 34:53
  Speaker 1: to the daily circadian ones that match daylight and darkness.
• 34:58
  Speaker 1: They are built of cellular chemistry that can be entrained
• 35:02
  Speaker 1: by gentle floods and ebbs and then run free for
• 35:06
  Speaker 1: many days like the echo of a bell. The moon
• 35:11
  Speaker 1: has been ringing this bell long enough for genes to
• 35:14
  Speaker 1: have learned the rhythm. In this way, the story of
• 35:19
  Speaker 1: gravity writes itself into the molecules of crabs and clams.
• 35:25
  Speaker 1: The patient push and pull of water moves sand and
• 35:30
  Speaker 1: mud in ways that no single wave ever could. Along
• 35:34
  Speaker 1: shallow coasts the tide sets up currents that accelerate in
• 35:38
  Speaker 1: narrow places and slacken on wide flats. Each pulse can
• 35:43
  Speaker 1: pick up grains for a moment and let them settle
• 35:46
  Speaker 1: in a different place when the speed falls. Over weeks
• 35:50
  Speaker 1: and months, sand is sculpted into ridges and ripples whose
• 35:55
  Speaker 1: crests mirror the path of strongest flow, where two tidal
• 36:00
  Speaker 1: streams divide a channel A sandbar can grow like the
• 36:04
  Speaker 1: tongue of a river delta. On broad shoals that feel
• 36:08
  Speaker 1: a steady two-way sweep, long tidal dunes march very slowly
• 36:14
  Speaker 1: across the bottom, developed by the alternating stress of flood
• 36:18
  Speaker 1: and ebb. Where the tidal ellipse is a tight circle,
• 36:22
  Speaker 1: mud can be winnowed from sand to form clean banks
• 36:26
  Speaker 1: that show delicate current marks when the water leaves them.
• 36:31
  Speaker 1: Harbourmasters learn these rearrangements as if they were the moods
• 36:36
  Speaker 1: of a neighbour. Channels must be dredged where bars move.
• 36:41
  Speaker 1: Beacons must be shifted to guide boats over shifting ground.
• 36:46
  Speaker 1: What looks from a cliff like a simple beach is
• 36:49
  Speaker 1: in truth a mosaic laid by countless individual grains travelling
• 36:54
  Speaker 1: one short jump at a time. The meeting of river
• 36:58
  Speaker 1: and sea is the stage where all these strands join.
• 37:02
  Speaker 1: An estuary is not merely a drowned valley, it is
• 37:06
  Speaker 1: a breathing device. With each flood, the tide pushes salt
• 37:10
  Speaker 1: water inland along the bottom, while the river slides seaward above,
• 37:16
  Speaker 1: cleaner and lighter. The result is a salt wedge that
• 37:20
  Speaker 1: advances and retreats. Where the two layers shear against one another,
• 37:25
  Speaker 1: small eddies mix fresh and salt into a third flavour
• 37:30
  Speaker 1: that is brackish. The mixing is strongest, where bottom roughness
• 37:34
  Speaker 1: and channel turns stir the flow. To see this structure
• 37:38
  Speaker 1: with your mind, hold a clear glass of water, pour
• 37:43
  Speaker 1: in a thread of blue dye at the bottom and
• 37:46
  Speaker 1: a thread of clear water at the top, and then
• 37:49
  Speaker 1: slowly stir. Tip the glass from side to side. You
• 37:53
  Speaker 1: will see layers and interleavings that resemble the estuarine dance.
• 37:59
  Speaker 1: Life thrives where the mixing is real but not too violent.
• 38:04
  Speaker 1: Oyster reefs flourish on firm ground within reach of the
• 38:08
  Speaker 1: salt wedge, filtering water that brings them food from both
• 38:12
  Speaker 1: river and sea. Marsh grasses grow in fans along the
• 38:17
  Speaker 1: banks where fine sediment is trapped by their roots, building
• 38:22
  Speaker 1: ground that keeps pace with the daily rise and fall.
• 38:27
  Speaker 1: People have long built their towns at these meetings, for
• 38:32
  Speaker 1: they offer calm water and access to inland farms and
• 38:37
  Speaker 1: to the open coast. The alphabet of tide notes, the
• 38:42
  Speaker 1: lunar cycles that weight those notes, the large-scale dance around
• 38:47
  Speaker 1: quiet ocean centres, the hidden fronts and internal waves that
• 38:51
  Speaker 1: stir the deep, the literal belts of rock and sand
• 38:56
  Speaker 1: where life has made a truce with exposure, the internal
• 39:00
  Speaker 1: clocks that keep time with moving water, The labour of
• 39:05
  Speaker 1: tides that carries sediment grain by grain, and the estuaries
• 39:10
  Speaker 1: that translate between fresh and salt together, give the tide
• 39:14
  Speaker 1: its full meaning. It is not only a rise and fall,
• 39:18
  Speaker 1: but a composer of landscapes and a tutor of living things.
• 39:23
  Speaker 1: It writes deltas and bays. It times migrations. It shapes
• 39:29
  Speaker 1: human plans whether we notice or not. Consider a night
• 39:33
  Speaker 1: when the moon is bright enough to cast a silver
• 39:36
  Speaker 1: path over a bay. Somewhere offshore, M2 is running at
• 39:41
  Speaker 1: full strength, its companion S2 adding or subtracting a little
• 39:46
  Speaker 1: depending on the angle of the sun. The once daily
• 39:50
  Speaker 1: K1 and O1 notes provide a slow undulation that will
• 39:56
  Speaker 1: make one high stand a little higher than the next.
• 40:00
  Speaker 1: If the moon happens to be near its closer point
• 40:03
  Speaker 1: in the long anomalistic swing, the tone will be fuller.
• 40:08
  Speaker 1: If the nodal cycle happens to be in a phase
• 40:11
  Speaker 1: that emphasizes once daily motion, the two high stands will
• 40:16
  Speaker 1: differ perceptibly. The rotating tide around the nearest amphidromic point
• 40:22
  Speaker 1: will decide whether it arrives from the south or from
• 40:26
  Speaker 1: the north. Over the shelf, a quiet kelvin wave will
• 40:31
  Speaker 1: lean against the coast and help guide the pulse through
• 40:34
  Speaker 1: the bends of the estuary. At the boundary between a
• 40:38
  Speaker 1: cool ocean tongue and a warmer shelf, see, a tidal
• 40:43
  Speaker 1: front will tremble, mixing trapped nutrients upward. Down in the interior,
• 40:49
  Speaker 1: an internal wave will be climbing the slope of a
• 40:52
  Speaker 1: bank and breaking like a slow avalanche. On the rocks,
• 40:57
  Speaker 1: a row of muscles will tighten slightly as a ripple
• 41:01
  Speaker 1: of pressure tells them that a new hour is coming.
• 41:05
  Speaker 1: In the marsh, a small crab will test the air
• 41:09
  Speaker 1: with its antennae and come out on schedule. On a sandbar,
• 41:13
  Speaker 1: a new rib of grains will be laid, and an
• 41:17
  Speaker 1: older rib will soften, and up the river a salt
• 41:20
  Speaker 1: wedge will pause, then begin to reverse its direction, while
• 41:25
  Speaker 1: a heron steps with perfect timing onto the fresh, exposed flats.
• 41:31
  Speaker 1: Reading the tide becomes in this way an act of
• 41:35
  Speaker 1: calm literacy. The names M2 and K1 are not merely
• 41:40
  Speaker 1: symbols in a table, They are letters that spell the
• 41:44
  Speaker 1: behaviour of water where you stand. The cycles of the
• 41:48
  Speaker 1: moon are not only astronomical, they are practical announcements to
• 41:53
  Speaker 1: shellfish harvesters, surfers and engineers who plan bridges. The amphidromic
• 42:00
  Speaker 1: map is not only an academic drawing, it is a
• 42:04
  Speaker 1: chart that tells a sailor which way the current will
• 42:07
  Speaker 1: turn under a certain headland. Tidal fronts and internal waves
• 42:13
  Speaker 1: are not only studies in a journal, they are engines
• 42:17
  Speaker 1: that feed fisheries. The literal is not just a strip
• 42:21
  Speaker 1: of inconvenient wetness for builders. It is a layered city
• 42:25
  Speaker 1: whose residents keep the shore resilient. Biological clocks are not curiosities,
• 42:32
  Speaker 1: they are the way shore life makes a living. Sediment
• 42:36
  Speaker 1: transport is not dull. It is the hand that moves
• 42:40
  Speaker 1: the pieces of a mobile sculpture. Estuaries are not merely
• 42:45
  Speaker 1: places for port facilities. They are complicated hearts that circulate
• 42:51
  Speaker 1: fresh and salt. If you ever wish to learn this
• 42:55
  Speaker 1: literacy for yourself, Pick one simple place. A short jetty
• 43:00
  Speaker 1: will do, or a tidal creek with a footbridge. Visit
• 43:04
  Speaker 1: it through one lunar month. Bring a small notebook. On
• 43:09
  Speaker 1: each visit, write the phase of the moon. Whether new
• 43:12
  Speaker 1: or slender crescent, or bright round disk, write the time
• 43:17
  Speaker 1: you arrived, not by digits, but with the words morning
• 43:21
  Speaker 1: or afternoon or near dusk. Look at a piling or
• 43:25
  Speaker 1: a waterline stain. and write whether the tide is higher
• 43:29
  Speaker 1: or lower than your last visit. Watch for the direction
• 43:33
  Speaker 1: of the tiny floating leaves. Listen for the sound the
• 43:37
  Speaker 1: current makes against the stones. Mark in your mind when
• 43:42
  Speaker 1: the fiddler crabs come out or when sandpipers begin to run.
• 43:48
  Speaker 1: After many visits, you will begin to hear the separate notes.
• 43:53
  Speaker 1: You will know, without looking at a table, that the
• 43:56
  Speaker 1: two high waters of a mixed regime are falling out
• 44:00
  Speaker 1: of symmetry because the Moon has climbed high in declination.
• 44:05
  Speaker 1: You will sense that a higher than usual spring tide
• 44:09
  Speaker 1: is coming because the Moon looks a touch larger and
• 44:13
  Speaker 1: brighter than the week before. you will become intimate with
• 44:17
  Speaker 1: the idea that the sea is not a single body,
• 44:21
  Speaker 1: but a mosaic of moving water. Under this soft education,
• 44:27
  Speaker 1: you may find yourself experiencing a form of comfort that
• 44:32
  Speaker 1: used to belong to farmers who knew the habits of
• 44:35
  Speaker 1: their fields. The tide gives the same gift, only in water.
• 44:40
  Speaker 1: Understanding does not make the sea less mysterious. It makes
• 44:44
  Speaker 1: the mystery friendlier. The large cycles from the synodic to
• 44:49
  Speaker 1: the nodal become like seasons layered inside seasons. The daily
• 44:55
  Speaker 1: swing becomes the metronome that holds them together. From this
• 44:59
  Speaker 1: quiet vantage, the moon is not only a distant sphere.
• 45:04
  Speaker 1: It is the conductor of real events that touch marsh grass,
• 45:09
  Speaker 1: sand grain, muscle shell, and human plan. Salt marshes and
• 45:15
  Speaker 1: mangrove forests teach a gentle lesson about how tides build shelter.
• 45:21
  Speaker 1: Where the land is soft and low, the regular rise
• 45:24
  Speaker 1: and fall of water lays down fine grains of silt
• 45:28
  Speaker 1: and clay. Marsh grasses grip those grains with a patient
• 45:33
  Speaker 1: weave of roots, raising the ground a little each year,
• 45:37
  Speaker 1: often by only a few millimeters, yet always in step
• 45:42
  Speaker 1: with the water that nourishes them. Every flood brings suspended
• 45:46
  Speaker 1: particles and dissolved nutrients. Every ebb leaves a thin film
• 45:52
  Speaker 1: of new soil. In temperate regions, cordgrass stands like a
• 45:57
  Speaker 1: green comb, slowing the flow and catching more of the
• 46:01
  Speaker 1: soft rain of mud. In the tropics, mangrove trees take
• 46:06
  Speaker 1: over the same apprenticeship with the tide. Their arching prop
• 46:10
  Speaker 1: roots and pencil-thin breathing roots create a maze where water
• 46:15
  Speaker 1: lingers long enough to drop its load. Young fish hide
• 46:19
  Speaker 1: among the pillars. Crabs graze on the leaf litter. Birds
• 46:24
  Speaker 1: come with the turning of the light to hunt. These
• 46:27
  Speaker 1: tidal forests also store what scientists call blue carbon. Leaves
• 46:32
  Speaker 1: become peat. Roots turn into a quiet, fibrous library that
• 46:37
  Speaker 1: can lock away carbon for centuries if left unbroken. When
• 46:42
  Speaker 1: storms arrive, the pliant stems and roots turn violent water
• 46:47
  Speaker 1: into slow water. A surge that would gnaw at a
• 46:50
  Speaker 1: bare shoreline spends itself in the soft resistance of stems
• 46:55
  Speaker 1: and trunks. Villages behind intact mangroves and marshes often see
• 47:00
  Speaker 1: flood levels lower and currents gentler. The tide that builds
• 47:05
  Speaker 1: these living edges is the same tide that protects them,
• 47:09
  Speaker 1: a rhythm that both gives and guards. Coral reefs and
• 47:14
  Speaker 1: their wide flats live by another chapter of the lunar book.
• 47:18
  Speaker 1: On clear tropical evenings near the turn from spring tide
• 47:22
  Speaker 1: to neb, or back again, entire reefs take their cue
• 47:26
  Speaker 1: from the Moon. Corals release packets of eggs and sperm
• 47:31
  Speaker 1: in mass events that last a few warm nights each year.
• 47:36
  Speaker 1: The timing is so certain that scientists can plan their
• 47:40
  Speaker 1: work weeks in advance by reading the phase of the Moon,
• 47:45
  Speaker 1: the water temperature, and the gentle slope of the tidal curve.
• 47:51
  Speaker 1: Flood tides carry the fragile bundles away from the hungry
• 47:55
  Speaker 1: mouths that live on the reef. Ebb tides leave parts
• 47:59
  Speaker 1: of the flat exposed just long enough for air and
• 48:03
  Speaker 1: sunlight to clean the surface, a natural reset that keeps
• 48:07
  Speaker 1: some rivals in check. Fish that use the reef as
• 48:11
  Speaker 1: a nursery match their movements to the tide as well.
• 48:15
  Speaker 1: Juveniles ride the incoming flow to seagrass beds and mangroves
• 48:20
  Speaker 1: where they can grow in safety, then return with the
• 48:24
  Speaker 1: outgoing flow as they mature. On the long, thin platform
• 48:30
  Speaker 1: of a reef flat, a difference of only a few
• 48:33
  Speaker 1: tens of centimetres in water level can change the entire script.
• 48:38
  Speaker 1: The tide writes calendars for mass spawning. It schedules the
• 48:44
  Speaker 1: cleaning of tide pools. It opens and closes the door
• 48:48
  Speaker 1: between lagoon and open sea in a way that makes
• 48:52
  Speaker 1: the reef both sheltered and refreshed. Near the poles, the
• 48:57
  Speaker 1: tide whispers through ice. The floating shelves that extend from
• 49:02
  Speaker 1: Antarctica and from Greenland bend gently with every rise and fall.
• 49:08
  Speaker 1: The creaking sound that explorers hear at night is the
• 49:12
  Speaker 1: flex of a slab as large as a country. Beneath
• 49:16
  Speaker 1: these shelves, tidal currents move through subglottal channels like rivers
• 49:22
  Speaker 1: under a roof. They bring slightly warmer water into caves
• 49:26
  Speaker 1: of blue light and carry colder, fresher water out, balancing
• 49:31
  Speaker 1: the melt and the freeze. Satellites can see the tide
• 49:35
  Speaker 1: in the ice as faint ripples of motion that repeat
• 49:39
  Speaker 1: every 12 or 24 hours. Seals find breathing holes where
• 49:44
  Speaker 1: fracture lines open and close to the rhythm of that lift.
• 49:49
  Speaker 1: Penguins and polar bears time their crossings to the stable
• 49:53
  Speaker 1: hours when the water sits still. In the darkness under
• 49:57
  Speaker 1: the ice, Small crustaceans gather where tidal mixing brings the
• 50:02
  Speaker 1: finest particles. Even in a world that looks frozen and still,
• 50:08
  Speaker 1: the moon sets a slow metronome that keeps the entire
• 50:13
  Speaker 1: sheet breathing. Where the geometry of water and land line
• 50:18
  Speaker 1: up just so, the tide becomes a theatre performance. The
• 50:22
  Speaker 1: Bay of Fundy, between the Canadian provinces of New Brunswick
• 50:27
  Speaker 1: and Nova Scotia holds the world's best-known stage for extreme range.
• 50:34
  Speaker 1: The basin length is tuned so that the natural slosh
• 50:38
  Speaker 1: matches the twice-daily beat of the lunar tide. The result
• 50:42
  Speaker 1: is a range that can exceed more than 15 metres
• 50:46
  Speaker 1: between low and high on certain days, enough to empty
• 50:50
  Speaker 1: coves entirely. and to leave boats resting on the ground
• 50:55
  Speaker 1: like stranded beetles until the water returns. Farther north in
• 51:00
  Speaker 1: Ungava Bay, the funnelling effect is even greater in some inlets,
• 51:05
  Speaker 1: and the bore and range can be astonishing for places
• 51:09
  Speaker 1: so far toward the Arctic. Across the ocean, the shallow
• 51:14
  Speaker 1: plains around Mont Saint-Michel in France turn from land to
• 51:18
  Speaker 1: mirror and back again, As the tide rushes across the flats,
• 51:23
  Speaker 1: the abbey stands like a stone mast above an ocean
• 51:27
  Speaker 1: that comes and goes. In these places people build staircases
• 51:32
  Speaker 1: down cliffs not with steps but with anchor rings for
• 51:37
  Speaker 1: moorings at different states of water. The local vocabulary grows
• 51:42
  Speaker 1: rich with words for the many ways that water can
• 51:46
  Speaker 1: arrive and depart. Sometimes the tide comes not with a
• 51:52
  Speaker 1: gentle slope but as a moving wall. Tidal bores occur
• 51:57
  Speaker 1: where a strong flood tide runs up a river whose
• 52:01
  Speaker 1: mouth is shaped like a funnel and whose bed is
• 52:05
  Speaker 1: shallow enough to focus the incoming water into a single push.
• 52:11
  Speaker 1: The Chiantang River in China hosts a bore that has
• 52:15
  Speaker 1: been famous for centuries. It runs as a rolling cliff
• 52:19
  Speaker 1: of water that can carry small boats with it if
• 52:23
  Speaker 1: they are not carefully prepared. The roar can be heard
• 52:27
  Speaker 1: far upstream before the crest arrives. In the Amazon, the
• 52:32
  Speaker 1: Pororoca is the name given to a boar that rises
• 52:36
  Speaker 1: on certain days and travels against the flow for many kilometers.
• 52:41
  Speaker 1: Surfers have learned to ride it, gliding past forest and
• 52:46
  Speaker 1: floating villages on a wave that lasts longer than any
• 52:50
  Speaker 1: ocean swell. On the River Severn in Britain, the boar
• 52:54
  Speaker 1: sweeps around bends that reveal it in a long, shining line.
• 52:59
  Speaker 1: Bores reshape channels, flatten sandbars, and require a special art
• 53:05
  Speaker 1: of timing from pilots and fishers who use the rivers
• 53:09
  Speaker 1: they visit. They are the dramatic cousins of the familiar tide,
• 53:14
  Speaker 1: born from the same moon but given a different costume
• 53:18
  Speaker 1: by the shape of the land. Every harbour has its
• 53:22
  Speaker 1: rules and its windows, the quiet moments when a captain
• 53:26
  Speaker 1: may enter or leave safely. An incoming ship seeks enough
• 53:31
  Speaker 1: clearance under the keel, and so pilots wait for the
• 53:35
  Speaker 1: higher water of a flood. But the safest moment is
• 53:39
  Speaker 1: often at slack, when the current pauses between flood and ebb.
• 53:45
  Speaker 1: In narrow channels, a strong cross-set can push a large
• 53:49
  Speaker 1: hull toward a bank, Despite a powerful engine, tidal streams
• 53:53
  Speaker 1: can also create standing waves and boils near bridge piers.
• 53:59
  Speaker 1: Patches of water that look smooth yet pull at a
• 54:03
  Speaker 1: rudder with surprising force. Charts and tide tables are tools,
• 54:08
  Speaker 1: but the best pilots also carry a mental map of
• 54:11
  Speaker 1: the sequence of eddies that appear as the tide turns.
• 54:16
  Speaker 1: Some ports with shallow bars put their harbour entrance along
• 54:20
  Speaker 1: a natural deep that only aligns for a short span
• 54:24
  Speaker 1: of minutes during certain phases of the tide. That span
• 54:29
  Speaker 1: is the pilot window. A captain missing it must wait
• 54:33
  Speaker 1: another 12 hours or more. Lighthouses, range lights and modern
• 54:39
  Speaker 1: beacons exist to shorten the margin for error. Yet the
• 54:43
  Speaker 1: rhythm of the moon still sets the master clock of
• 54:46
  Speaker 1: arrival and departure. Long before computers, people set out to
• 54:52
  Speaker 1: tame the tide with arithmetic and brass. Pierre Simon Laplace
• 54:57
  Speaker 1: cast the physics into equations that relate the motion of
• 55:01
  Speaker 1: the ocean to the pull of celestial bodies and the
• 55:05
  Speaker 1: turning of Earth. Later, in the 19th century, scientists learned
• 55:11
  Speaker 1: to take long records from tide gauges and separate them
• 55:15
  Speaker 1: into harmonic constituents with careful calculation. The result could be
• 55:21
  Speaker 1: reassembled to predict future tides. Lord Kelvin designed an analogue
• 55:27
  Speaker 1: machine that performed this task with pulleys and chains. Each
• 55:32
  Speaker 1: constituent was represented by a wheel and a shaft. As
• 55:37
  Speaker 1: the shafts turned, their motions were added through a clever
• 55:41
  Speaker 1: linkage to draw a continuous curve on paper. A trained
• 55:46
  Speaker 1: operator could set the date and read out the heights
• 55:50
  Speaker 1: and times for the year to come. These machines served
• 55:54
  Speaker 1: working ports for decades. Modern methods use digital versions of
• 56:00
  Speaker 1: the same idea. They now blend harmonics with models of
• 56:05
  Speaker 1: basin shape and satellite observations. Yet at heart the promise
• 56:11
  Speaker 1: remains the same as in the age of brass. If
• 56:15
  Speaker 1: you have enough past notes from the Symphony of the Sea,
• 56:18
  Speaker 1: you can compose the next movement with confidence. From orbit,
• 56:24
  Speaker 1: satellites have added a new ear to the listening. Radar
• 56:28
  Speaker 1: altimeters aboard missions such as Topex, Poseidon, and the series
• 56:33
  Speaker 1: that followed measure the sea surface height by sending pulses
• 56:38
  Speaker 1: of energy and timing their return. By flying very regular
• 56:42
  Speaker 1: ground tracks for many years, these instruments can see the
• 56:46
  Speaker 1: repeating patterns of M2, S2, K1, and the others stamped
• 56:52
  Speaker 1: onto the global ocean. The maps that result show amphidromic
• 56:57
  Speaker 1: systems as elegant spirals with colours standing in for phase
• 57:03
  Speaker 1: and amplitude. Blind spots near coasts and ice still exist,
• 57:08
  Speaker 1: but the broad picture is now sharp. Scientists combine satellite
• 57:13
  Speaker 1: data with floating buoys and with models that account for
• 57:17
  Speaker 1: seafloor depth, coast shape. and the gentle bend imposed by
• 57:23
  Speaker 1: the rotation of the planet. The accuracy can reach a
• 57:27
  Speaker 1: few centimetres when all methods are united, certainly close enough
• 57:32
  Speaker 1: to improve tables for shipping and to test how tidal
• 57:37
  Speaker 1: energy flows into the deep. This view from above has
• 57:42
  Speaker 1: also shown that tides interact with seafloor mountains far offshore
• 57:47
  Speaker 1: to generate internal waves that travel for hundreds of kilometers.
• 57:52
  Speaker 1: The moon leaves a trace in places that no human
• 57:57
  Speaker 1: eye can reach, and satellites learn to read it. Weather
• 58:02
  Speaker 1: and tide sometimes walk hand in hand, and sometimes they
• 58:07
  Speaker 1: do not. A storm surge is the pile of water
• 58:10
  Speaker 1: driven toward a coast by wind and by the lower
• 58:14
  Speaker 1: air pressure at the heart of a storm. It is
• 58:16
  Speaker 1: not the same as a tide. But if the surge
• 58:20
  Speaker 1: arrives at the same hour as a high spring tide,
• 58:24
  Speaker 1: the two can add together. The barometric effect alone can
• 58:28
  Speaker 1: raise sea level by about one centimetre for every one
• 58:33
  Speaker 1: hectopascal drop in pressure. Strong onshore winds push water against
• 58:38
  Speaker 1: the coast, tilt the surface and slow the natural ebb.
• 58:42
  Speaker 1: On quiet days, the tide drains estuaries in a neat pattern.
• 58:48
  Speaker 1: Under a gale, the same estuary may hardly empty at all.
• 58:53
  Speaker 1: Emergency planners learn to watch the calendar of the moon
• 58:56
  Speaker 1: as well as the track of a cyclone. If a
• 58:59
  Speaker 1: royal tide is due on the same weekend as an
• 59:02
  Speaker 1: approaching storm, they order barriers closed and pumps prepared. Conversely,
• 59:07
  Speaker 1: a storm that arrives on a neap tide may pass
• 59:12
  Speaker 1: with minor flooding where the same storm would have been
• 59:15
  Speaker 1: serious two weeks earlier. The dance is one of addition
• 59:20
  Speaker 1: and subtraction, and the moon is often the partner that
• 59:24
  Speaker 1: decides how dramatic the final movement becomes. Because the word
• 59:30
  Speaker 1: tide is familiar and comforting, people sometimes use it for
• 59:35
  Speaker 1: waves that are not tides at all. A tsunami is
• 59:39
  Speaker 1: a long gravity wave set in motion by a sudden
• 59:42
  Speaker 1: disturbance such as an undersea earthquake, a landslide, or a
• 59:48
  Speaker 1: volcanic collapse. It can cross an ocean at the speed
• 59:52
  Speaker 1: of a jet. In deep water, its crest is gentle
• 59:56
  Speaker 1: and low, hardly noticed by ships. But as it reaches
• 1:00:00
  Speaker 1: the shallows near a coast, the wave slows and rises,
• 1:00:04
  Speaker 1: compressing into something high and fast. Unlike the regular turn
• 1:00:09
  Speaker 1: of high and low water, a tsunami arrives as a
• 1:00:13
  Speaker 1: train of waves over minutes and hours and then slowly
• 1:00:17
  Speaker 1: eases away. It does not repeat every 12 or 24 hours.
• 1:00:23
  Speaker 1: It ignores the phase of the moon. Warning centres read
• 1:00:27
  Speaker 1: seismographs and ocean-bottom pressure sensors to decide whether such a
• 1:00:32
  Speaker 1: wave has been born. Sirens and alerts follow. Knowing the
• 1:00:37
  Speaker 1: difference matters. A harbour that can handle a spring tide
• 1:00:42
  Speaker 1: with ease may be at risk from a tsunami of
• 1:00:46
  Speaker 1: only modest height because the speed and momentum are so great.
• 1:00:51
  Speaker 1: The moon rules the daily life of the sea. but
• 1:00:54
  Speaker 1: the rare great shocks come from the deep earth or
• 1:00:58
  Speaker 1: the abrupt slip of slopes. The ocean holds both kinds
• 1:01:04
  Speaker 1: of stories, the steady and the sudden, and learning the
• 1:01:08
  Speaker 1: difference helps keep coasts safe. The farther you follow these chapters,
• 1:01:15
  Speaker 1: the more the whole begins to resemble a single organism.
• 1:01:19
  Speaker 1: Carbon rests in muddy roots that the tide feeds. Coral
• 1:01:24
  Speaker 1: reefs attune their reproduction to the lunar cycle. Ice shelves
• 1:01:30
  Speaker 1: flex and breathe on a schedule set by the moon.
• 1:01:34
  Speaker 1: Extreme ranges and bores show what geometry can do. Navigation
• 1:01:40
  Speaker 1: remains a craft of reading the right moment in a
• 1:01:43
  Speaker 1: tidal day. Prediction grew from notebook to brass machine. to
• 1:01:48
  Speaker 1: satellite constellation without losing its reliance on listening to the
• 1:01:52
  Speaker 1: true notes. Weather adds its own loud percussion, and sometimes
• 1:01:57
  Speaker 1: it asks the moon for accompaniment. And out beyond familiar shores,
• 1:02:03
  Speaker 1: the rare tsunami reminds us that gravity has many ways
• 1:02:07
  Speaker 1: to travel. Through all of it, the same quiet force acts,
• 1:02:12
  Speaker 1: far above the sea, yet woven into every shorebird flight,
• 1:02:16
  Speaker 1: every marsh blade, every pile of oyster shell that marks
• 1:02:20
  Speaker 1: a human harbour. Energy from the tide begins with the
• 1:02:25
  Speaker 1: simplest observation. Twice each lunar day there is moving water
• 1:02:30
  Speaker 1: in places where at other hours the sea seems almost asleep.
• 1:02:35
  Speaker 1: The oldest designs for drawing power from this motion look
• 1:02:39
  Speaker 1: like mill ponds. A low wall across a narrow estuary
• 1:02:45
  Speaker 1: closes when the ebb runs out, trapping water behind gates.
• 1:02:50
  Speaker 1: When the flood returns, the gates open and water rushes
• 1:02:54
  Speaker 1: through chambers where turbines spin. Later generations revised the plan
• 1:03:00
  Speaker 1: by building open lagoons in shallow bays that fill and
• 1:03:04
  Speaker 1: empty through turbine houses, farther from land in fast channels
• 1:03:10
  Speaker 1: between headlands or islands. Engineers lower nacelles into the current
• 1:03:15
  Speaker 1: so that turning blades harvest energy from the steady flow,
• 1:03:19
  Speaker 1: much as a wind turbine does in air. In some regions,
• 1:03:24
  Speaker 1: long channels guide the stream to speed it just enough
• 1:03:28
  Speaker 1: for practical work, yet keep the seabed open for fish
• 1:03:33
  Speaker 1: and for drifting spores. What sounds straightforward becomes a conversation
• 1:03:39
  Speaker 1: with the coast itself. A wall across a tidal flat
• 1:03:43
  Speaker 1: changes how sediment moves. Mud that would have settled on
• 1:03:47
  Speaker 1: the marsh gets trapped in a basin. If designers do
• 1:03:51
  Speaker 1: not provide a new path for fine grains, the marsh
• 1:03:55
  Speaker 1: behind the wall may starve and sink. Fish learn passage
• 1:04:00
  Speaker 1: routes by smell and by current. A barrage that redirects
• 1:04:04
  Speaker 1: the flood without careful passages can confuse migrations. Some species
• 1:04:10
  Speaker 1: can use slow water and spiral fish locks. Others need
• 1:04:15
  Speaker 1: large gates opened at precise times to align their inner
• 1:04:19
  Speaker 1: compass with the taste of the river. Engineers therefore test
• 1:04:23
  Speaker 1: their plans in scale basins and in computer worlds where
• 1:04:28
  Speaker 1: the water and the animals follow rules drawn from field notes.
• 1:04:33
  Speaker 1: The best projects today borrow ideas from living shorelines They
• 1:04:38
  Speaker 1: use rock reefs and eelgrass to calm waves and to
• 1:04:42
  Speaker 1: keep sand in place around foundations. Turbines are tuned to
• 1:04:47
  Speaker 1: turn slowly so that a large fish sees and avoids
• 1:04:52
  Speaker 1: the blades. Acoustic surveys check whether new machines add distracting
• 1:04:57
  Speaker 1: noise to the underwater soundscape. Maintenance crews plan with birds
• 1:05:02
  Speaker 1: in mind. If bolts must be tightened on a winter day,
• 1:05:07
  Speaker 1: When a tidal sandbar hosts thousands of resting migrants, the
• 1:05:12
  Speaker 1: work moves to a quieter hour. When these questions are respected,
• 1:05:17
  Speaker 1: a tidal plant can provide reliable power through decades, rising
• 1:05:22
  Speaker 1: and falling with the moon exactly when a city needs
• 1:05:27
  Speaker 1: the steady pulse of a base supply and a predictable
• 1:05:30
  Speaker 1: complement to the gusts of wind and the glare of sun.
• 1:05:35
  Speaker 1: When the questions are ignored, The same plant becomes an
• 1:05:39
  Speaker 1: object lesson that a fast fix on the shore is
• 1:05:43
  Speaker 1: never truly fast and never a fix. The moon is
• 1:05:49
  Speaker 1: not the only place where tides write themselves into the
• 1:05:52
  Speaker 1: story of energy. Far away in the cold spaces around
• 1:05:56
  Speaker 1: giant planets, small worlds glow with a heat that they
• 1:06:00
  Speaker 1: have no right to own. The reason is the same
• 1:06:04
  Speaker 1: push and pull. that moves our ocean. The little moon,
• 1:06:09
  Speaker 1: called Io, orbits the huge planet Jupiter on an oval path.
• 1:06:14
  Speaker 1: As Io swings close to Jupiter, gravity stretches it. As
• 1:06:18
  Speaker 1: Io swings away, it relaxes. That millions of years long
• 1:06:22
  Speaker 1: massage needs the interior, melting rock and driving volcanoes that
• 1:06:28
  Speaker 1: throw fountains high above the surface. Another moon named Europa
• 1:06:33
  Speaker 1: carries a shell of ice above an ocean that is
• 1:06:36
  Speaker 1: believed to be global. Tidal flexing within the ice makes
• 1:06:41
  Speaker 1: it crack and moan. Below, the ocean may be kept
• 1:06:44
  Speaker 1: liquid by the same slow kneading, with heat venting through
• 1:06:48
  Speaker 1: the seafloor in a darkness lit only by chemistry. Farther
• 1:06:53
  Speaker 1: out in the Saturn system, a small body called Enceladus
• 1:06:58
  Speaker 1: shakes under a patterned pull from its parent planet and
• 1:07:02
  Speaker 1: from neighbouring moons, through cracks near its south pole, the
• 1:07:07
  Speaker 1: little world exhales plumes of water and salts that show
• 1:07:11
  Speaker 1: it holds an inner sea in contact with warm rock.
• 1:07:16
  Speaker 1: The mathematics that explains these places comes from the same
• 1:07:20
  Speaker 1: set of ideas that explains our coastal tides. Gravity moves
• 1:07:26
  Speaker 1: water and it also moves stones. When the pull changes rhythm,
• 1:07:31
  Speaker 1: the motion turns to heat, and heat turns to geology,
• 1:07:35
  Speaker 1: and maybe to biology. In that sense, the tide is
• 1:07:40
  Speaker 1: a thread that connects the bays where shorebirds feed with
• 1:07:43
  Speaker 1: the hidden seas of worlds that we have touched only
• 1:07:47
  Speaker 1: with our eyes. On our own planet, the tide leaves
• 1:07:51
  Speaker 1: a very slow mark on time itself. Friction between moving
• 1:07:56
  Speaker 1: water and the solid earth saps a tiny part of
• 1:07:59
  Speaker 1: the energy of rotation. The moon that raises the bulges
• 1:08:04
  Speaker 1: drags ahead of earth by a small angle. Over deep
• 1:08:09
  Speaker 1: intervals of time this drag transfers angular momentum outward. The
• 1:08:14
  Speaker 1: moon takes the gift and slips a little farther away
• 1:08:18
  Speaker 1: from us by about three and a half centimeters each year,
• 1:08:22
  Speaker 1: a distance that is measured by bouncing light off small
• 1:08:26
  Speaker 1: mirrors placed on the lunar surface by astronauts. Earth pays
• 1:08:31
  Speaker 1: for the gift by turning a little more slowly. The
• 1:08:35
  Speaker 1: length of one day grows by only a few thousandths
• 1:08:39
  Speaker 1: of a second in a century, far less than human
• 1:08:43
  Speaker 1: senses can know. enough that historians must account for it
• 1:08:49
  Speaker 1: when they compare ancient eclipses recorded on clay tablets with
• 1:08:54
  Speaker 1: the positions predicted by strict celestial mechanics. If one lets
• 1:08:59
  Speaker 1: the imagination walk across millions of years, one sees the
• 1:09:04
  Speaker 1: dance continue. Days will become longer. The moon will become
• 1:09:08
  Speaker 1: a smaller disc in our sky. The tide will keep
• 1:09:12
  Speaker 1: its rhythm, but the drum will beat more softly. That
• 1:09:16
  Speaker 1: same thought leads to the next. What might the future
• 1:09:20
  Speaker 1: of the moon and the sea look like long after us?
• 1:09:24
  Speaker 1: As the lunar companion drifts outward, the strength of its
• 1:09:28
  Speaker 1: pull on our water will wane. The sun, always the
• 1:09:32
  Speaker 1: junior partner in our present tide, will carry a relatively
• 1:09:36
  Speaker 1: larger share of the job. The mixed pattern of ocean
• 1:09:40
  Speaker 1: movement will adjust and the extremes of range in places
• 1:09:45
  Speaker 1: that today host dramatic coasts may soften. The change will
• 1:09:50
  Speaker 1: be so slow that continents will shift their outlines and
• 1:09:54
  Speaker 1: mountain chains will rise and fall while the tide continues
• 1:09:59
  Speaker 1: to visit twice each lunar day, as faithful as an
• 1:10:03
  Speaker 1: old friend whose voice becomes gentler with age. The far future...
• 1:10:08
  Speaker 1: is a landscape of patience. Over calendars that make our
• 1:10:14
  Speaker 1: eras look like a minute, gravity composes long notes that
• 1:10:19
  Speaker 1: only geology can hear. Back in the living present, cities
• 1:10:24
  Speaker 1: learn to keep time with the moon. Harbours have always
• 1:10:28
  Speaker 1: done so. Now, entire metropolitan regions rediscover the clock. Transit
• 1:10:34
  Speaker 1: stations post real-time warnings for underpasses that fill during extreme surges.
• 1:10:41
  Speaker 1: Floodable parks settle along the waterfront as new kinds of
• 1:10:45
  Speaker 1: rooms that welcome high water and release it without harm.
• 1:10:50
  Speaker 1: Steps become broad stone shelves that vanish in high spring
• 1:10:54
  Speaker 1: tides and display mosaics at knee apes. Sports fields are
• 1:11:00
  Speaker 1: built with soils and grasses that tolerate an occasional wet visit,
• 1:11:05
  Speaker 1: instead of carving channels that promise dryness forever. Planners in
• 1:11:10
  Speaker 1: the most forward-looking places choose amphitheatres with drains sized for
• 1:11:16
  Speaker 1: once rare but now more frequent combinations of storm wind
• 1:11:21
  Speaker 1: and royal tide. When a neighbourhood sits in a low bowl,
• 1:11:26
  Speaker 1: architects design homes that can float a little on concealed
• 1:11:31
  Speaker 1: guides during the few hours of a deep flood and
• 1:11:34
  Speaker 1: then return to their moorings. The view of the river
• 1:11:39
  Speaker 1: becomes a shared full-length porch rather than a back fence.
• 1:11:44
  Speaker 1: This is not surrender. It is a practical truce. By
• 1:11:49
  Speaker 1: living with the known schedule of the tide and with
• 1:11:53
  Speaker 1: the new statistics of storms, a city gains resilience and
• 1:11:58
  Speaker 1: keeps its daily beauty. To work with water, one needs maps,
• 1:12:04
  Speaker 1: and modern mapmakers trace lines that shift with each season.
• 1:12:08
  Speaker 1: From orbit, satellite radars sweep the texture of the sea
• 1:12:13
  Speaker 1: surface and can tell when waves run against hidden ridges.
• 1:12:18
  Speaker 1: Along coasts, aircraft and drones carry instruments that use light
• 1:12:23
  Speaker 1: pulses to measure terrain at centimetre scale, a method known
• 1:12:27
  Speaker 1: in full words as light detection and ranging. When the
• 1:12:32
  Speaker 1: tide is low, they scan mudflats and marsh blades. When
• 1:12:36
  Speaker 1: the tide is high, they sketch the outlines of channels
• 1:12:39
  Speaker 1: and banks. Together with gauges on pilings and with inexpensive
• 1:12:45
  Speaker 1: sensors in citizen hands, These tools feed dynamic charts. On
• 1:12:50
  Speaker 1: a phone, a mariner or a walker can see not
• 1:12:53
  Speaker 1: only the present line of water, but also the line
• 1:12:57
  Speaker 1: at the next hour and the line that will be
• 1:13:00
  Speaker 1: there when a storm of a given track arrives. Digital
• 1:13:05
  Speaker 1: atlases link their vertical measure to solid marks called datums
• 1:13:10
  Speaker 1: so that engineers and artists speak the same language when
• 1:13:14
  Speaker 1: they imagine a new pier or artwork along a seawall.
• 1:13:18
  Speaker 1: As the moon rises, the map breathes. That slow inhale
• 1:13:23
  Speaker 1: and exhale is the new legend in the corner, as
• 1:13:27
  Speaker 1: essential as the compass rose. The coast has always been
• 1:13:32
  Speaker 1: a musical instrument. Tides play it with a patience that
• 1:13:36
  Speaker 1: turns physics into sound. In narrow inlets, the standing wave
• 1:13:41
  Speaker 1: that returns with each flood sets up a note you
• 1:13:45
  Speaker 1: can feel in your feet if you stand on a
• 1:13:48
  Speaker 1: wooden jetty. Sea caves act like bottles. As the water rises,
• 1:13:54
  Speaker 1: it forces air through cracks and vents, and the cliff
• 1:13:58
  Speaker 1: sings a deep chord that changes with the state of
• 1:14:02
  Speaker 1: the tide. In certain bays, the geometry supports a slow
• 1:14:06
  Speaker 1: sway of the entire surface that scientists call a seash.
• 1:14:11
  Speaker 1: Fish seem to use these throb rhythms as part of
• 1:14:15
  Speaker 1: their own navigation. Every coast also has a scrim of
• 1:14:19
  Speaker 1: small percussive sounds. Bubbles from breaking ripples pop like tiny drums.
• 1:14:25
  Speaker 1: Pebbles roll back and forth and clatter. The faint hiss
• 1:14:30
  Speaker 1: that remains when waves calm to barely moving water is
• 1:14:34
  Speaker 1: the whisper of millions of microbursts where films of air fail.
• 1:14:40
  Speaker 1: Some cities celebrate this with crafted instruments. There is a
• 1:14:43
  Speaker 1: sea organ on a European shore where stone steps hold
• 1:14:47
  Speaker 1: pipes that let waves breathe notes into a promenade. On
• 1:14:51
  Speaker 1: a still night the sound is almost like a choral rehearsal.
• 1:14:55
  Speaker 1: The moon conducts the tempo in silence. People have long
• 1:15:00
  Speaker 1: told stories to put a face to the moving edge,
• 1:15:04
  Speaker 1: fisher calendars etched on woodless lucky hours that match faithful
• 1:15:09
  Speaker 1: observations of incoming and outgoing streams and the position of
• 1:15:14
  Speaker 1: the moon in the sky. Stone fish traps built on
• 1:15:19
  Speaker 1: flats by early coastal communities in many parts of the
• 1:15:23
  Speaker 1: world show a simple and elegant way to work with water.
• 1:15:28
  Speaker 1: Curved walls let fish enter during the flood and hold
• 1:15:32
  Speaker 1: them when the ebb leaves only pools. In northern islands,
• 1:15:37
  Speaker 1: there are causeways that can be walked at low water
• 1:15:41
  Speaker 1: to reach a monastery or a fort, and legends that
• 1:15:45
  Speaker 1: warn late travellers to watch the first trickle around their
• 1:15:49
  Speaker 1: feet because it means the path will soon be lost.
• 1:15:54
  Speaker 1: In other lands, The tide is called the breath of
• 1:15:57
  Speaker 1: a sea dragon who snores when it sleeps and wakes
• 1:16:00
  Speaker 1: twice daily to visit the shore. These tales are not quaint.
• 1:16:05
  Speaker 1: They encode an intimacy with the ebb and flow that
• 1:16:09
  Speaker 1: modern charts only formalise. In the stories, devotion and caution
• 1:16:16
  Speaker 1: are taught by the same voice. Beyond culture, the tide
• 1:16:21
  Speaker 1: is also medicine for the sea itself. The deep ocean
• 1:16:25
  Speaker 1: is wild and strong, yet even this vast body needs
• 1:16:29
  Speaker 1: its slow stirring. Where a moving tide meets a ridge
• 1:16:34
  Speaker 1: or a continental slope, it sets off internal waves that
• 1:16:38
  Speaker 1: travel along layers of density as mountain ranges would guide wind.
• 1:16:44
  Speaker 1: These waves break far from shore and mix water masses
• 1:16:48
  Speaker 1: that would otherwise remain stacked like pages. The result is
• 1:16:53
  Speaker 1: a transport of oxygen into depths where animals live at
• 1:16:57
  Speaker 1: a slow pace and a rise of nutrients into sunlit
• 1:17:01
  Speaker 1: layers where tiny floating plants grow. This invisible conveyor feeds
• 1:17:07
  Speaker 1: the base of the food web. It also participates in
• 1:17:10
  Speaker 1: the very large circulation that traps and releases heat and carbon.
• 1:17:18
  Speaker 1: Part of the energy that drives these processes comes from
• 1:17:21
  Speaker 1: lunar gravity. In this sense, the Moon assists Earth in
• 1:17:26
  Speaker 1: keeping the ocean from stratifying into a still and separate
• 1:17:30
  Speaker 1: set of layers. The mixing does not erase structure. It
• 1:17:35
  Speaker 1: softens it and carries just enough of the deep to
• 1:17:39
  Speaker 1: the surface, and just enough of the surface to the deep,
• 1:17:43
  Speaker 1: so that life can link its different rooms. When you
• 1:17:46
  Speaker 1: stand at the shore at night and listen, all of
• 1:17:50
  Speaker 1: these chapters blend to a single quiet lesson. Engines that
• 1:17:55
  Speaker 1: turn with the tide need humility and care so that
• 1:17:59
  Speaker 1: the marshes and fish that share the water find their
• 1:18:03
  Speaker 1: way through. Distant moons teach us that gravity writes warmth
• 1:18:09
  Speaker 1: under ice and turns silence into movement half a billion
• 1:18:13
  Speaker 1: kilometers from our homes. The slow breaking of Earth and
• 1:18:18
  Speaker 1: the retreat of the moon are the softest ticking of
• 1:18:21
  Speaker 1: a clock older than mountains. Cities that choose to live
• 1:18:26
  Speaker 1: by the moon's schedule gain a touch of grace that
• 1:18:29
  Speaker 1: rigid walls never hold. Mapmakers draw in layers of time
• 1:18:35
  Speaker 1: as well as space, and the new atlases thrum with
• 1:18:39
  Speaker 1: tides as living annotations. Coasts are instruments, and even a
• 1:18:45
  Speaker 1: breath of wind over the mouth of a sea cave
• 1:18:48
  Speaker 1: can sound like a choir charging itself for the next
• 1:18:52
  Speaker 1: change of water. People have always read the pull of
• 1:18:56
  Speaker 1: the moon in their own language, whether with notches on
• 1:19:00
  Speaker 1: a stick, stones set on a flat, or a song
• 1:19:04
  Speaker 1: about the breath of a great animal asleep under the sky.
• 1:19:09
  Speaker 1: And the sea, that patient physician, mixes and cleanses itself
• 1:19:13
  Speaker 1: by this same gentle force. Now imagine the hour before dawn.
• 1:19:19
  Speaker 1: The moon is not yet set. The reef hums softly.
• 1:19:24
  Speaker 1: The marsh waits for the first glimmer. In the channel,
• 1:19:27
  Speaker 1: a green light drifts as a pilot boat idles near
• 1:19:31
  Speaker 1: the edge of the fairway. its captain resting a hand
• 1:19:35
  Speaker 1: on the throttle while watching the clock that blends the
• 1:19:38
  Speaker 1: tide table and the radio weather. Somewhere far offshore, internal
• 1:19:44
  Speaker 1: waves roll across an unseen slope and scatter the glow
• 1:19:48
  Speaker 1: of plankton like the wake of a slow fish. In
• 1:19:53
  Speaker 1: a river up the coast, a boar gathers for its run,
• 1:19:56
  Speaker 1: silent as a cat at the edge of a porch.
• 1:20:00
  Speaker 1: In the far sky above all of this, a small
• 1:20:02
  Speaker 1: spacecraft passes over the dark Earth and pings the sea
• 1:20:07
  Speaker 1: with radar pulses, reciting the uneven poem of heights and
• 1:20:12
  Speaker 1: phases that will be read later by anyone who wants
• 1:20:16
  Speaker 1: to learn the next day's story. The tide turns, the
• 1:20:21
  Speaker 1: flood begins, currents lean into the piers, sand grains tumble
• 1:20:27
  Speaker 1: and settle into new ripples that only a gull might notice.
• 1:20:31
  Speaker 1: The estuary breathes in, and birds lift from their roosts
• 1:20:35
  Speaker 1: to follow uncovering edges. Houses set back on their stilts
• 1:20:41
  Speaker 1: watch the first thin ribbon of water spread across the
• 1:20:45
  Speaker 1: lowest lawns of a floodable park by design. On a
• 1:20:50
  Speaker 1: different coast, the outbreath exposes a chain of tide pools
• 1:20:54
  Speaker 1: where children tomorrow will learn the names of anemones. Because
• 1:20:58
  Speaker 1: this hour of retreat cleans the basins and sets their
• 1:21:02
  Speaker 1: calendar of air and sun, tidal plants upriver taste the
• 1:21:07
  Speaker 1: easing of salt and pull a little extra sweetness into
• 1:21:11
  Speaker 1: their leaves. In all these rooms, living things listen. When
• 1:21:17
  Speaker 1: the tide has filled its shape and slack arrives, a
• 1:21:21
  Speaker 1: moment of perfect balance settles across the water. There is
• 1:21:25
  Speaker 1: no hiss on stones, no shear against a piling, only
• 1:21:30
  Speaker 1: the faintest tremor of sand moving in slow motion. Then
• 1:21:35
  Speaker 1: the ebb begins and the cycle repeats, a gift given
• 1:21:39
  Speaker 1: by a companion world that does nothing more than circle
• 1:21:42
  Speaker 1: the earth and keep its face turned toward us. The
• 1:21:46
  Speaker 1: lesson is plain and kind. Power does not require noise.
• 1:21:51
  Speaker 1: Timing is everything, and patience keeps the bridge between the
• 1:21:56
  Speaker 1: seen and the unseen strong. The moon asks nothing in
• 1:22:01
  Speaker 1: return for this lesson, except that we pay attention. Let
• 1:22:06
  Speaker 1: that attention carry you into sleep. Picture the curve of
• 1:22:10
  Speaker 1: the bay as a gentle bowl and the surface of
• 1:22:13
  Speaker 1: the sea as a soft sheet that lifts and falls
• 1:22:17
  Speaker 1: twice in every lunar day. Imagine harbours waiting for their
• 1:22:22
  Speaker 1: quiet windows, marsh grasses combing the flow and coral flats
• 1:22:27
  Speaker 1: reading the calendar written in light and water. Think of
• 1:22:32
  Speaker 1: ice that flexes with a sigh the size of a
• 1:22:35
  Speaker 1: continent and of distant moons that glow inside from the
• 1:22:39
  Speaker 1: same rhythm. With each breath you take, quietly count the
• 1:22:44
  Speaker 1: steps of the tide. In your mind, walk the sand
• 1:22:48
  Speaker 1: that will be wet by morning, and watch the stars
• 1:22:51
  Speaker 1: reflected in the first trickle across the flat stones. The
• 1:22:56
  Speaker 1: sea is turning its page. The moon is steady in
• 1:23:00
  Speaker 1: the sky. The night belongs to their conversation. And you
• 1:23:06
  Speaker 1: are invited to listen. Let us end this journey with
• 1:23:10
  Speaker 1: a quiet thought experiment. Imagine a clear night when the
• 1:23:15
  Speaker 1: sea is calm and the wind is soft and the
• 1:23:18
  Speaker 1: moon does not rise. The familiar silver path on the
• 1:23:22
  Speaker 1: water never appears. The shorebirds do not wait for a
• 1:23:26
  Speaker 1: high tide that is higher than most. The reefs do
• 1:23:30
  Speaker 1: not glow in time with a full moon. The clocks
• 1:23:34
  Speaker 1: of countless creatures tick, but they are listening for a
• 1:23:38
  Speaker 1: bell that never rings. Could this ever happen, and what
• 1:23:42
  Speaker 1: would Earth become without its companion? First, it helps to
• 1:23:47
  Speaker 1: say what the moon is doing at every moment, because
• 1:23:51
  Speaker 1: the answer lives there. Our satellite pulls on the oceans,
• 1:23:56
  Speaker 1: but also on the rock of the continents, and on
• 1:23:59
  Speaker 1: the thin shell of the air. The result is more.
• 1:24:03
  Speaker 1: than a tide. It is a transfer of energy and
• 1:24:07
  Speaker 1: a transfer of time. Tidal friction very slowly turns some
• 1:24:12
  Speaker 1: of the spin of Earth into heat in the sea.
• 1:24:15
  Speaker 1: That tiny loss of spin lengthens our day by a
• 1:24:18
  Speaker 1: small slice of a second every century. The same tidal
• 1:24:23
  Speaker 1: interaction pushes the Moon a little farther away each year
• 1:24:26
  Speaker 1: by a few fingers' width on a school ruler. The
• 1:24:30
  Speaker 1: moon is therefore not falling toward us. It is drifting outward,
• 1:24:36
  Speaker 1: and it is doing so far too slowly to leave
• 1:24:40
  Speaker 1: Earth behind before the distant future when the sun ages
• 1:24:45
  Speaker 1: and changes into a red giant. In plain words, there
• 1:24:49
  Speaker 1: is no natural path in the near future by which
• 1:24:52
  Speaker 1: the moon simply disappears. Still, thought experiments are useful. Let
• 1:24:58
  Speaker 1: us imagine that the moon were removed by magic, or
• 1:25:02
  Speaker 1: that we wake to a world in which it never formed.
• 1:25:06
  Speaker 1: What changes would be immediate, and what would arrive on
• 1:25:10
  Speaker 1: slow feet? The first change would be written on the
• 1:25:15
  Speaker 1: face of the ocean. tides would not vanish. The Sun
• 1:25:19
  Speaker 1: pulls as well, and the Sun would still raise the sea.
• 1:25:24
  Speaker 1: The lunar part of the tide is stronger because the
• 1:25:27
  Speaker 1: Moon is close. It contributes a larger share of the
• 1:25:31
  Speaker 1: present range, roughly two-thirds in most places. What would remain
• 1:25:37
  Speaker 1: is the solar part, which is weaker but not small.
• 1:25:42
  Speaker 1: Every coast would still feel the rise and fall, but
• 1:25:45
  Speaker 1: the average range would shrink to perhaps one-third or a
• 1:25:50
  Speaker 1: little more of what people know now. Places that thrive
• 1:25:54
  Speaker 1: on resonance, such as narrow bays that match the natural
• 1:25:58
  Speaker 1: tempo of a tidal basin, would keep some of their
• 1:26:01
  Speaker 1: drama but with lower crests. The great stage of the
• 1:26:06
  Speaker 1: Bay of Fundy would not fall silent. Yet, Its applause
• 1:26:12
  Speaker 1: would be softer. Smaller tides would change the shape of
• 1:26:16
  Speaker 1: work along the shore. Harbours that rely on windows of
• 1:26:20
  Speaker 1: water to cross a bar would have a new timetable.
• 1:26:24
  Speaker 1: Inlets continually dredged by a swift ebb and flow would
• 1:26:28
  Speaker 1: collect more sand. Salt marshes and mangrove forests that drink
• 1:26:35
  Speaker 1: and breathe with the tide would still pulse. but they
• 1:26:38
  Speaker 1: would spend more hours either flooded or dry, reshaping the
• 1:26:43
  Speaker 1: mix of plants that can live there. Flats that presently
• 1:26:47
  Speaker 1: appear at very low water would be revealed less often,
• 1:26:53
  Speaker 1: and many birds that feed there would have fewer meals.
• 1:26:57
  Speaker 1: The chapters of life that open when the sea pulls
• 1:27:01
  Speaker 1: back would be shorter. The second change would be seen
• 1:27:05
  Speaker 1: in the sky and felt in the rhythms of living things.
• 1:27:10
  Speaker 1: No moon means no eclipses in the way we know them.
• 1:27:14
  Speaker 1: There would be no soft rings of light around a
• 1:27:17
  Speaker 1: lunar disk during a total solar eclipse and no earth-cast
• 1:27:23
  Speaker 1: shadow slowly covering the moon on warm summer nights. Moonlight,
• 1:27:29
  Speaker 1: which is sunlight scattered by rock and dust, would no
• 1:27:32
  Speaker 1: longer set a monthly lantern over the sea. Nights would
• 1:27:36
  Speaker 1: be darker by a wide margin, and most people would
• 1:27:40
  Speaker 1: see more faint stars with the naked eye than at
• 1:27:43
  Speaker 1: any time in human memory. But darker nights are not
• 1:27:47
  Speaker 1: only a gift to stargazers. Many animals use lunar light
• 1:27:51
  Speaker 1: as a cue. Coral reefs in the tropics release reproductive
• 1:27:56
  Speaker 1: cells in astonishing mass events that line up with the
• 1:28:01
  Speaker 1: phase of the moon and the timing of spring tides.
• 1:28:05
  Speaker 1: Horseshoe crabs climb beaches on the highest waters of the month,
• 1:28:09
  Speaker 1: and shorebirds plan migrations to match that feast. Some fish
• 1:28:14
  Speaker 1: spawn in pulses that follow the lunar cycle, and many
• 1:28:19
  Speaker 1: predators time their hunting to moonlit nights. Without the moon,
• 1:28:24
  Speaker 1: these patterns would not stop, but they would detach from
• 1:28:29
  Speaker 1: a neat monthly signal. Evolution would search for other clocks,
• 1:28:34
  Speaker 1: perhaps the length of the night itself, perhaps the beat
• 1:28:38
  Speaker 1: of the seasons, and some species would adapt faster than others.
• 1:28:43
  Speaker 1: A few might disappear from certain coasts, not because life
• 1:28:48
  Speaker 1: is fragile in principle, but because life is precise in practice.
• 1:28:55
  Speaker 1: A deeper, slower change lies inside the planet. The tug
• 1:29:00
  Speaker 1: of the moon acts on the whole spinning Earth. It
• 1:29:04
  Speaker 1: is the main hand on the lever that slows the
• 1:29:07
  Speaker 1: rotation little by little. If that hand were removed, Earth
• 1:29:11
  Speaker 1: would largely stop giving away its spin to the sea.
• 1:29:15
  Speaker 1: Days would still lengthen across geological time, but far more slowly.
• 1:29:21
  Speaker 1: The story of ancient corals hints at this. Fossil corals
• 1:29:26
  Speaker 1: record growth rings like trees. In some very old specimens,
• 1:29:31
  Speaker 1: those rings imply that there were once about 370 days
• 1:29:36
  Speaker 1: in a year. That is a shorter day. The reason
• 1:29:40
  Speaker 1: is the old dance with a closer moon and stronger tides.
• 1:29:45
  Speaker 1: Without a lunar partner, The day would not run backwards
• 1:29:49
  Speaker 1: toward those short values, but the present length would change
• 1:29:54
  Speaker 1: at a crawl. The moon also steadies the tilt of Earth.
• 1:29:58
  Speaker 1: Our axis leans by a little less than one quarter
• 1:30:03
  Speaker 1: of a right angle, and the direction of that lean
• 1:30:06
  Speaker 1: wobbles slowly like a spinning top. The moon adds a
• 1:30:10
  Speaker 1: strong correction to that wobble. Planets without a large moon,
• 1:30:15
  Speaker 1: such as Mars, seem to suffer episodes when the tilt
• 1:30:19
  Speaker 1: of the axis can wander from small to very large
• 1:30:23
  Speaker 1: angles over long spans of time under the combined pull
• 1:30:27
  Speaker 1: of the Sun and of the giant planets. A world
• 1:30:31
  Speaker 1: whose axis leans much more than now would have extreme seasons.
• 1:30:37
  Speaker 1: In one era, the poles might tip toward the Sun
• 1:30:40
  Speaker 1: for long summers and then away for long winters. Ice
• 1:30:44
  Speaker 1: caps could grow and vanish and deserts could migrate to
• 1:30:49
  Speaker 1: latitudes that are now mild. Without the moon, our own
• 1:30:54
  Speaker 1: axis would not start swinging wildly overnight. The change would
• 1:30:59
  Speaker 1: be slow, but the calculations suggest that across millions of years,
• 1:31:04
  Speaker 1: the tilt could vary far more than people have known,
• 1:31:08
  Speaker 1: and climate would feel that wandering hand. In simple terms,
• 1:31:13
  Speaker 1: The moon is a quiet flywheel for our seasons. Another
• 1:31:18
  Speaker 1: slow change would hide in the interior of the sea.
• 1:31:22
  Speaker 1: Tides do more than lift the surface. As the tide
• 1:31:26
  Speaker 1: moves over rough bottom and around slopes, it excites internal
• 1:31:31
  Speaker 1: waves in the layers of the ocean. Those hidden waves
• 1:31:35
  Speaker 1: carry energy downward and contribute a great share of the
• 1:31:39
  Speaker 1: mixing that brings cold, deep water up. and sends surface
• 1:31:44
  Speaker 1: water down. This mixing helps close the global loop of
• 1:31:49
  Speaker 1: ocean circulation. Remove the lunar part of the tide, and
• 1:31:54
  Speaker 1: the total mixing energy falls by a large fraction. The
• 1:31:58
  Speaker 1: deep sea would likely become more stably layered in some regions.
• 1:32:03
  Speaker 1: Oxygen brought downward would move more slowly. Nutrients stirred upward
• 1:32:09
  Speaker 1: from depth would be fewer. The great engine that moves
• 1:32:13
  Speaker 1: heat across the planet would still run since winds and
• 1:32:18
  Speaker 1: the contrast between polar and equatorial waters also drive it.
• 1:32:23
  Speaker 1: Yet its cadence would change. A little less stirring over
• 1:32:28
  Speaker 1: a very long time can steer climate in ways that
• 1:32:33
  Speaker 1: are not obvious from the beach. Would volcanoes, earthquakes or
• 1:32:39
  Speaker 1: the magnetic field notice the loss? No catastrophe is expected.
• 1:32:44
  Speaker 1: The Moon does create earth tides in rock measured in centimetres,
• 1:32:49
  Speaker 1: and there are intriguing hints that stress from those tiny
• 1:32:53
  Speaker 1: flexes can slightly shift the timing of small earthquakes along
• 1:32:59
  Speaker 1: faults that are already close to slipping. That is a nudge.
• 1:33:04
  Speaker 1: rather than a cause. The magnetic field lives in flows
• 1:33:08
  Speaker 1: of liquid iron in the core and does not rely
• 1:33:12
  Speaker 1: on the Moon for power. Plate tectonics is forced by
• 1:33:17
  Speaker 1: mantle convection and the cooling of the planet and would
• 1:33:21
  Speaker 1: go on. The Moon is a metronome for the surface
• 1:33:25
  Speaker 1: and the air and the shallow sea, not an engine
• 1:33:28
  Speaker 1: for the deep interior. How could the Moon disappear at all?
• 1:33:34
  Speaker 1: The realistic answer is that it almost certainly cannot within
• 1:33:38
  Speaker 1: the span of human history. The Moon is drifting outward
• 1:33:42
  Speaker 1: by a few centimetres each year, but it is held
• 1:33:46
  Speaker 1: by Earth's gravity, and the two bodies share angular momentum.
• 1:33:52
  Speaker 1: Over extremely long time, the pair tends toward a state
• 1:33:56
  Speaker 1: where Earth rotates at the same rate that the Moon orbits,
• 1:34:00
  Speaker 1: and then both face the same side in a slow embrace.
• 1:34:05
  Speaker 1: The Sun will begin its giant phase before that state arrives.
• 1:34:09
  Speaker 1: A dramatic loss of the Moon would require an event
• 1:34:12
  Speaker 1: on the scale of a giant impact, like the one
• 1:34:16
  Speaker 1: that likely formed it. That is not part of the
• 1:34:19
  Speaker 1: quiet future that astronomy expects. Capture by the Sun would
• 1:34:25
  Speaker 1: require a complex three-body ballet that current orbits do not permit.
• 1:34:31
  Speaker 1: Fragmentation by tides would require the Moon to move much closer,
• 1:34:36
  Speaker 1: crossing a limit named after Roche, and the Moon is
• 1:34:40
  Speaker 1: moving the other way. If the thought experiment demands a cause,
• 1:34:45
  Speaker 1: then only magic or an impossible accident will do. Suppose
• 1:34:51
  Speaker 1: the magic is granted, what would people notice the first
• 1:34:55
  Speaker 1: evening the disappearance of lunar light would make the milky
• 1:34:59
  Speaker 1: way and faint nebulae leap out over the countryside, sea
• 1:35:04
  Speaker 1: turtles that use a bright horizon to orient after hatching
• 1:35:09
  Speaker 1: might struggle for a time, then find new cues such
• 1:35:13
  Speaker 1: as the shine of starlight on waves. Night-flowering plants that
• 1:35:18
  Speaker 1: open under full moon brightness would shift their timing toward
• 1:35:22
  Speaker 1: dusk or dawn. Owls that use moonlight to hunt small
• 1:35:27
  Speaker 1: mammals would have fewer bright nights and might change their patterns.
• 1:35:33
  Speaker 1: Humans would revise calendars. Many cultures still mark time by
• 1:35:38
  Speaker 1: the synodic month the long breath from one full moon
• 1:35:42
  Speaker 1: to the next. The idea of a month would remain
• 1:35:47
  Speaker 1: as custom, but its natural anchor would be gone. Mariners
• 1:35:52
  Speaker 1: would adjust. In a moonless world, the largest storm surges
• 1:35:57
  Speaker 1: would still occur. Storm surge is wind and pressure moving water.
• 1:36:02
  Speaker 1: The timing of especially high water caused by a king
• 1:36:06
  Speaker 1: tide when the lunar and solar pulls align would vanish
• 1:36:11
  Speaker 1: because there would be no lunar partner to align with
• 1:36:15
  Speaker 1: the sun. But storm surges would continue to arrive on
• 1:36:19
  Speaker 1: their own schedule. In one way that is better, and
• 1:36:23
  Speaker 1: in one way it is worse. It is better because
• 1:36:27
  Speaker 1: a truly dangerous coincidence of a strong storm with an
• 1:36:31
  Speaker 1: extreme astronomical tide would be rarer. It is worse because
• 1:36:36
  Speaker 1: people have long used the monthly tidal rhythm as a
• 1:36:40
  Speaker 1: kind of heartbeat for coastal risk. Losing that heartbeat removes
• 1:36:46
  Speaker 1: a layer of predictability that sailors and port pilots quietly
• 1:36:51
  Speaker 1: rely on. Back on land, the long cycle of the
• 1:36:56
  Speaker 1: precession of the equinoxes would change. That slow drift of
• 1:37:00
  Speaker 1: the direction of Earth's axis currently completes a full circle
• 1:37:05
  Speaker 1: in about many tens of centuries. The torque from the
• 1:37:09
  Speaker 1: Moon is a main driver Remove it, and the period
• 1:37:13
  Speaker 1: would lengthen, and the pace of that tiny celestial clock
• 1:37:18
  Speaker 1: would be different. Calendars that slide stars against seasons over
• 1:37:23
  Speaker 1: very long spans would need new corrections. Astronomy would rewrite
• 1:37:29
  Speaker 1: a few tables, and culture would rewrite a few myths.
• 1:37:34
  Speaker 1: There are questions people ask that are not really physical,
• 1:37:38
  Speaker 1: but are part of the answer. Would the night be
• 1:37:42
  Speaker 1: lonelier without a companion disc rising and setting? Would poetry
• 1:37:47
  Speaker 1: lose a star muse? The truth is that people fill
• 1:37:51
  Speaker 1: the sky with meaning no matter what lights it. But
• 1:37:55
  Speaker 1: there is a practical grace in a nearby world that
• 1:37:58
  Speaker 1: shows phases, hosts, eclipses, and ties our biology to a
• 1:38:03
  Speaker 1: gentle monthly rhythm. Without it, our civilization would not be crippled,
• 1:38:10
  Speaker 1: but it would feel as if a page had been
• 1:38:13
  Speaker 1: torn from a very old book. One last question remains.
• 1:38:19
  Speaker 1: If the moon is not going to vanish, will it
• 1:38:21
  Speaker 1: stay the same? The answer is no. And that fact
• 1:38:25
  Speaker 1: is also a comfort. The moon is moving outward. The
• 1:38:30
  Speaker 1: extra distance will subtly reduce tidal range in the far
• 1:38:34
  Speaker 1: future as the lunar pull grows weaker. Days will continue
• 1:38:39
  Speaker 1: to lengthen by tiny amounts. The beat of the sea
• 1:38:43
  Speaker 1: will slow very slightly. Human beings will not live long
• 1:38:48
  Speaker 1: enough to notice But the ocean will. If we step
• 1:38:51
  Speaker 1: back far enough in imagination, we can watch the whole
• 1:38:55
  Speaker 1: film in reverse. Early in Earth history, when the moon
• 1:38:59
  Speaker 1: was much closer, tides were giants that swept coasts with
• 1:39:03
  Speaker 1: large range and quick rhythm. As the partner moved outward,
• 1:39:08
  Speaker 1: they softened. The present age sits in the middle of
• 1:39:12
  Speaker 1: that slow music. There is no cliff edge ahead. only
• 1:39:16
  Speaker 1: the long fade of a drum that never fully stops.
• 1:39:20
  Speaker 1: So could the moon disappear? In any practical sense, no.
• 1:39:25
  Speaker 1: What would happen if it did? The sea would still
• 1:39:28
  Speaker 1: rise and fall under the sun, but by less. Coasts
• 1:39:33
  Speaker 1: and marshes would redraw themselves. The inner clocks of sea
• 1:39:37
  Speaker 1: life would search for new signals. Nights would deepen. The
• 1:39:42
  Speaker 1: climate would keep its seasons, but gain a greater tendency
• 1:39:47
  Speaker 1: to drift over very long time, because the tilt of
• 1:39:51
  Speaker 1: earth would be less tightly guided. Our days would lengthen
• 1:39:55
  Speaker 1: more slowly than they do now. Eclipses would belong to memory,
• 1:40:00
  Speaker 1: and the lesson would be as quiet as a low
• 1:40:02
  Speaker 1: tide at dawn. A small body far away holds many threads.
• 1:40:07
  Speaker 1: Pull on that knot, and whole tapestries slacken, For tonight
• 1:40:12
  Speaker 1: the moon still walks the sky. It leans over the
• 1:40:16
  Speaker 1: water and the water leans back. If you listen, you
• 1:40:20
  Speaker 1: can hear the shore breathe with that ancient exchange. Thank
• 1:40:24
  Speaker 1: you for wandering through the math and the myths and
• 1:40:28
  Speaker 1: the living tides. May the soft pull of that distant
• 1:40:32
  Speaker 1: companion help your thoughts settle. the way the sea settles
• 1:40:38
  Speaker 1: when the wind drops and the current turns. Rest well,
• 1:40:43
  Speaker 1: and let the steady rhythm that shaped the coasts of
• 1:40:46
  Speaker 1: the world carry you into sleep.