Latest / Lost Civilizations: Ancient Aliens & Forgotten History / The Wow! Signal: 72 Seconds We Still Can’t Explain

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The Wow! Signal: 72 Seconds We Still Can’t Explain · Lost Civilizations: Ancient Aliens & Forgotten History

• 0:00
  Picture this. It's a warm August evening in
• 0:03
  1977. In Delaware, Ohio, there is a radio
• 0:08
  telescope that looks like an abandoned parking lot,
• 0:11
  with a few pointy metal structures scattered around.
• 0:14
  It's called Big Ear. It's the size of
• 0:16
  three football fields, and it's listening.
• 0:19
  Not to sound. To radio. To something
• 0:21
  that might, just might, be a message from
• 0:24
  another world.
• 0:25
  The telescope is one of the most unusual
• 0:28
  ever built. Instead of a giant dish that
• 0:31
  can swivel and point, it consists of a
• 0:34
  flat, tilted reflector at one end, 100 feet
• 0:38
  high, and a curved reflector at the other.
• 0:42
  Between them lies a large aluminum ground plane.
• 0:45
  In the middle of that plane are two
• 0:47
  receivers that look like giant funnels.
• 0:49
  When radio waves hit the flat reflector, they
• 0:53
  bounce over to the curved reflector, which focuses
• 0:56
  them down into the funnels.
• 0:58
  It's brilliant. And cheap. And it means that
• 1:01
  the telescope can't move. It just sits there,
• 1:05
  letting the Earth turn beneath it.
• 1:08
  Inside a small shed in the middle of
• 1:10
  the field sits an IBM 1130 computer, trying
• 1:13
  to keep track of 50 different radio channels
• 1:17
  at once.
• 1:17
  It has one megabyte of memory. That's about
• 1:20
  the same as a single photo from a
• 1:23
  smartphone today.
• 1:25
  The computer spits out its results on
• 1:28
  perforated paper rolls. Numbers. Row after row of
• 1:32
  numbers. Most of the time, it's just zeros
• 1:34
  and ones.
• 1:35
  A faint background hum from the universe. A
• 1:38
  three or a four is rare. A seven makes
• 1:41
  you sit up a little straighter in your
• 1:43
  chair. But on that night, August 15th, something
• 1:47
  happens.
• 1:48
  At 11:16 PM, one of the channels starts
• 1:52
  behaving strangely. First a 6, then an E,
• 1:57
  that's 14 times the background noise, then a
• 1:59
  Q, 26 times, and then a
• 2:04
  U. U means 30. Thirty times more
• 2:08
  powerful than anything the telescope had ever
• 2:12
  seen.
• 2:13
  Seventy-two seconds later, it's gone. As if it never
• 2:16
  was there.
• 2:18
  Three days later, a volunteer astronomer named Jerry
• 2:21
  Ehman sits at his kitchen table. He is
• 2:24
  not on the payroll. He was actually
• 2:27
  laid off from the project the year before,
• 2:29
  when the National Science Foundation cut funding, but
• 2:33
  he volunteered to keep reviewing the data. He
• 2:36
  does it for free. In the evenings. After
• 2:38
  dinner.
• 2:39
  He flips through stacks of paper filled with
• 2:41
  numbers that all look the same. And then
• 2:43
  he stops. 6EQUJ5. He circles it with a
• 2:49
  red pen. And next to it he writes
• 2:51
  one word: WOW!
• 2:55
  He has no idea that he has just
• 2:56
  created one of the most famous mysteries in
• 2:58
  the history of science.
• 3:24
  Why are we still talking about it?
• 3:26
  To understand why that word still matters nearly 50
• 3:29
  years later, we need to understand what Jerry
• 3:32
  Ehman actually saw.
• 3:33
  First: 6EQUJ5 is not a message from aliens.
• 3:38
  It's a measurement of signal strength.
• 3:41
  Big Ear had 50 channels. Each channel measured
• 3:44
  the intensity of the radio waves in a
• 3:47
  72-second window. Normally, the intensity was between
• 3:51
  1 and 5.
• 3:53
  If it went above 9, they started
• 3:56
  using letters.
• 3:57
  A stands for 10, B for 11,
• 4:00
  and U stands for
• 4:03
  30.
• 4:03
  So what Ehman saw was a signal that
• 4:06
  was 30 times more powerful than the background
• 4:09
  noise.
• 4:10
  It wasn't just unusual. It was unheard of.
• 4:13
  "It was the biggest thing we ever saw,"
• 4:15
  he later said in an interview.
• 4:17
  But the strength was only one thing.
• 4:20
  What really made astronomers' eyes pop was the
• 4:23
  frequency.
• 4:24
  The signal was exactly at 1420 MHz.
• 4:30
  That is what is called the hydrogen line
• 4:32
  or the 21-centimeter line.
• 4:35
  It's the frequency that neutral hydrogen atoms
• 4:41
  emit when they change energy states.
• 4:45
  So, when the electron's spin flips relative to the
• 4:50
  proton. Hydrogen is the most common element in
• 4:53
  the universe. It makes up about 75
• 4:55
  % of all normal matter in the cosmos.
• 4:58
  So when hydrogen emits radio, it does it
• 5:02
  at a frequency that any civilization with
• 5:06
  radio astronomy will know.
• 5:11
  Back in 1959, two physicists, Giuseppe Cocconi and
• 5:18
  Philip Morrison, published a paper in Nature arguing
• 5:21
  that if an advanced civilization wanted to contact
• 5:25
  us, they would use exactly that frequency.
• 5:29
  They called it the "water hole," a naturally
• 5:32
  quiet spot in the electromagnetic spectrum where everyone
• 5:36
  could meet.
• 5:38
  And the signal was narrowband.
• 5:41
  That means it only existed on one narrow
• 5:44
  frequency rather than spread across a wide spectrum.
• 5:49
  Natural radio sources like stars, galaxies, and pulsars
• 5:53
  so on are almost always broadband.
• 5:56
  They transmit on many frequencies at once. Technology
• 6:00
  It's narrowband.
• 6:01
  It's about energy efficiency.
• 6:03
  Why waste power broadcasting on many frequencies when
• 6:07
  one will do?
• 6:09
  So, here was a signal that was 30
• 6:12
  times more powerful than the background noise.
• 6:16
  On the frequency you would expect an intelligent
• 6:21
  civilization to use, narrowband like technology, and coming
• 6:26
  from the direction of Sagittarius, near the center
• 6:30
  of the Milky Way, where there are
• 6:32
  lots of stars.
• 6:33
  Everything fit, except for one thing.
• 6:37
  It never came back.
• 6:43
  Big Ear wasn't built to find aliens.
• 6:46
  It was built to map the sky.
• 6:48
  The telescope was designed by John D.
• 6:50
  Kraus, one of the 20th century's most accomplished antenna
• 6:54
  engineers.
• 6:55
  Kraus was a professor at Ohio State University
• 6:58
  and he had a dream to build the
• 7:00
  most sensitive radio telescope for the least amount
• 7:04
  of money.
• 7:05
  He got $250,000 from the National Science
• 7:09
  Foundation, a modest sum even for the 1950s,
• 7:13
  and he got his students to build it.
• 7:16
  They worked in their spare time.
• 7:20
  Some of them weren't even engineering students.
• 7:23
  The best welder was a pre-dental student.
• 7:28
  From 1965 to 1971, Big Ear conducted the
• 7:33
  Ohio Sky Survey and cataloged over 20,000
• 7:37
  radio sources, twice as many as were known
• 7:40
  at the time.
• 7:41
  They discovered quasars and created some of the
• 7:45
  first detailed maps of the radio sky.
• 7:47
  But in 1972, the money ran out.
• 7:50
  The National Science Foundation shifted focus to larger
• 7:55
  national facilities like Green Bank and Arecibo.
• 8:01
  Universities like Ohio State were deprioritized.
• 8:06
  Kraus's assistant, Bob Dixon, proposed a new direction.
• 8:09
  Instead of looking for natural radio sources, the
• 8:15
  telescope could search for narrowband signals, technological signatures
• 8:21
  from alien civilizations.
• 8:25
  It was a perfect match with the emerging
• 8:29
  SETI movement.
• 8:30
  From 1973 to 1998, for 25 years, Big
• 8:36
  Ear listened for signs of intelligence in
• 8:38
  space.
• 8:39
  It became the longest-running SETI program
• 8:42
  in history.
• 8:42
  And it was during this period that it
• 8:45
  happened.
• 8:47
  The telescope was unusual.
• 8:49
  Instead of moving like a parabolic dish, it
• 8:52
  was fixed.
• 8:53
  It used the Earth's rotation to scan the
• 8:55
  sky.
• 8:57
  That is why it could only observe a
• 9:00
  given point for 72 seconds before the Earth
• 9:04
  rotated it away.
• 9:05
  That is why the signal lasted exactly 72
• 9:09
  seconds.
• 9:09
  When Ehman discovered this signal, he called Kraus.
• 9:19
  Kraus later wrote a letter to Carl Sagan
• 9:24
  saying: "The signal is highly suggestive of
• 9:27
  extraterrestrial origin, but little more can be said
• 9:31
  until it returns for further study."
• 9:34
  The problem?
• 9:35
  It never returned.
• 9:36
  Big Ear tried to find it again for
• 9:39
  30 days.
• 9:40
  Nothing.
• 9:41
  Other telescopes have searched for it for decades.
• 9:44
  Nothing.
• 9:46
  Amateur astronomer Robert Gray spent his life looking
• 9:49
  for it with a 12-foot dish in
• 9:51
  his backyard, with the Harvard META array in
• 9:55
  1987 and 1989, with the Very Large Array
• 10:01
  in New Mexico in 1995 and in 1996,
• 10:04
  and with telescopes in Tasmania.
• 10:07
  He found nothing.
• 10:09
  So, why are we still talking about it?
• 10:11
  Because the absence of an explanation is not
• 10:14
  the same as the absence of a mystery.
• 10:19
  If we look at the first cracks,
• 10:23
  we need to know why it is so strange.
• 10:28
  First of all, why only one feed
• 10:30
  horn?
• 10:31
  Big Ear had two feed horns, two receivers
• 10:35
  that scanned the same strip of sky
• 10:38
  three minutes apart.
• 10:40
  If the signal came from a fixed source
• 10:43
  in space, both horns should have caught it,
• 10:46
  but only one did.
• 10:48
  That means that either the signal turned on
• 10:52
  or off during the three minutes between the
• 10:55
  two observations.
• 10:57
  A comet can't do that.
• 10:58
  A satellite can't do that.
• 10:59
  A natural radio source can't do that either,
• 11:02
  unless it is something that blinks very rarely and is
• 11:06
  unpredictable.
• 11:07
  Second, where did it come from?
• 11:11
  We know it came from an area near
• 11:14
  the M55 globular cluster in Sagittarius,
• 11:23
  but exactly where, we don't know, because we
• 11:26
  do not know which feed horn caught it.
• 11:28
  There are two possible positions.
• 11:30
  They are separated by 7.24 arcminutes, which
• 11:35
  in space translates to enormous distances.
• 11:39
  And here is an interesting
• 11:42
  detail: the ecliptic.
• 11:44
  The plane of the solar system passes through
• 11:48
  Sagittarius, so the signal could theoretically come
• 11:53
  from something in our own solar system, but
• 11:57
  no known planets were in that area.
• 12:00
  Third, was it a message?
• 12:04
  Big Ear couldn't detect modulation.
• 12:07
  It could not tell whether the signal contained information. It only
• 12:11
  measured the intensity.
• 12:13
  So there could have been a message, we
• 12:15
  just don't know it.
• 12:17
  Jerry Ehman explained this himself in an interview.
• 12:21
  The method was to take a short sample
• 12:23
  about a millisecond of each of the 50
• 12:26
  channels, then repeat that for 10 seconds, and
• 12:30
  then add the numbers together.
• 12:32
  You can't detect modulation with 10 isolated millisecond
• 12:37
  samples, so even if there was a message,
• 12:39
  we couldn't see it.
• 12:41
  Fourth, why was it never repeated?
• 12:45
  Some say a genuine extraterrestrial signal would be
• 12:49
  repeated, but we haven't done that ourselves.
• 12:52
  For instance, in 1974, the Arecibo Observatory sent
• 12:57
  a single message to the globular cluster M13.
• 13:02
  It was never repeated.
• 13:03
  If somebody on the other side had caught
• 13:05
  it, they would have their own Wow! Signal.
• 13:11
  Seth Shostak, a senior astronomer at the SETI Institute,
• 13:15
  put it precisely.
• 13:17
  In science, if you get an experimental result
• 13:22
  that can't be repeated, it's impossible to say
• 13:25
  you know what caused it.
• 13:29
  And then we have the alternative theories.
• 13:35
  Because over the years, several explanations for the
• 13:38
  Wow! Signal have been proposed.
• 13:40
  First, we have the comet hypothesis.
• 13:43
  In 2016, astronomer Antonio Paris suggested that the
• 13:47
  signal could come from two comets.
• 13:49
  It could be 266P Christensen or it could
• 13:53
  be 335P/Gibbs, which was in the area
• 13:57
  in 1977.
• 14:00
  They were not cataloged at that time, so no
• 14:03
  one thought of them.
• 14:04
  Paris argued that their hydrogen clouds could emit
• 14:08
  signals on the hydrogen line.
• 14:10
  It sounds possible, but it didn't hold up.
• 14:13
  Jerry Ehman himself dismissed it.
• 14:15
  If a comet emitted a 1420 MHz signal,
• 14:21
  radio astronomers would have detected it by now.
• 14:26
  And the Big Ear staff stated that we
• 14:28
  do not believe that the two-comet
• 14:30
  theory can explain the Wow! Signal.
• 14:33
  Then we have the spy satellite theory.
• 14:37
  Maybe it was a Soviet spy satellite
• 14:40
  illegally transmitting on a protected frequency.
• 14:43
  The problem is that the signal was stationary
• 14:47
  in the sky.
• 14:49
  Satellites move.
• 14:50
  And transmitting on the most monitored frequency
• 14:54
  in the world is a bad idea for
• 14:56
  a spy.
• 14:58
  Then we have interstellar scintillation.
• 15:02
  Perhaps a weak signal was amplified by turbulence
• 15:06
  in the interstellar medium like stars twinkling in
• 15:09
  the atmosphere.
• 15:10
  But that would require amplification to happen
• 15:15
  on only one frequency and only
• 15:21
  for 72 seconds.
• 15:23
  That is extremely unlikely.
• 15:25
  We have also the theory of a software
• 15:27
  glitch.
• 15:28
  But Big Ear ran flawlessly for 25 years.
• 15:31
  No similar error was ever found.
• 15:34
  So that theory doesn't hold either.
• 15:36
  Then we have the Sun.
• 15:37
  In August 1977, solar activity was low, and
• 15:42
  the signal came from a completely different direction
• 15:45
  than the Sun.
• 15:46
  So all the mundane explanations fell one by
• 15:49
  one.
• 15:52
  Then we have the new theory, the hydrogen
• 15:55
  cloud maser.
• 15:57
  In 2024, something new emerged.
• 16:01
  Abel Méndez, astrobiologist at the Planetary Habitability Laboratory
• 16:08
  at the University of Puerto Rico, was searching
• 16:13
  for radio signals from red dwarf stars with
• 16:15
  potentially habitable planets.
• 16:18
  His team was going through archive data from
• 16:21
  Arecibo Observatory, data collected between 2017 and 2020
• 16:25
  with the now-collapsed 305-meter telescope, and
• 16:30
  they found something that they hadn't expected.
• 16:34
  Weaker signals, and lots of them.
• 16:36
  With almost the same characteristics as the Wow!
• 16:40
  signal, same narrowband profile, same frequency near the
• 16:46
  hydrogen line, just not as powerful.
• 16:50
  Méndez realized they were looking at something
• 16:53
  that no one had ever seen before: cold
• 16:55
  hydrogen clouds that suddenly brightened.
• 16:59
  The hypothesis goes like this.
• 17:01
  Out in space, there are enormous clouds of
• 17:04
  cold hydrogen.
• 17:05
  They are called HI clouds.
• 17:08
  They normally emit weak radio signals on the
• 17:12
  hydrogen line, so weak that they are barely
• 17:15
  detectable.
• 17:16
  But if a powerful radiation source like a
• 17:19
  magnetar hit the cloud from just the right
• 17:23
  angle, it can trigger a maser effect.
• 17:25
  The cloud becomes a kind of cosmic laser.
• 17:28
  It amplifies the radio signal and sends it
• 17:31
  out in a narrow beam.
• 17:33
  A magnetar is a neutron star with a
• 17:35
  magnetic field billions of times stronger than
• 17:38
  Earth's.
• 17:39
  When one of these flares up, it
• 17:42
  can send out energy that could illuminate an
• 17:45
  entire hydrogen cloud.
• 17:47
  Méndez and his team found several signals
• 17:50
  that fit this model.
• 17:52
  They were all weaker than the wow signal,
• 17:54
  but they looked like it in every other
• 17:57
  way.
• 17:59
  In 2025, they published a follow-up analysis
• 18:03
  showing that the wow signal was four times
• 18:06
  more powerful than previously thought.
• 18:09
  It was at least 250 Janskys instead of
• 18:12
  the 54 to 200 that have often been
• 18:16
  cited.
• 18:17
  Let's put that in perspective.
• 18:19
  A Jansky is an extremely small unit: 10
• 18:22
  to the minus 26 watts per square meter per hertz.
• 18:28
  For comparison, the Sun emits about 1,000 Janskys
• 18:32
  when it's quiet.
• 18:34
  The entire Milky Way emits about 1 million
• 18:37
  Janskys.
• 18:38
  And a smartphone a kilometer away emits 110
• 18:42
  million Janskys, but only over a very short
• 18:45
  distance.
• 18:46
  So 250 Janskys from an interstellar distance is
• 18:50
  extraordinary.
• 18:52
  It puts the Wow! Signal in the same
• 18:53
  category as the most powerful radio sources in
• 18:57
  the universe, quasars and magnetars.
• 19:02
  Méndez's team were also able to refine the
• 19:04
  frequency.
• 19:06
  It is now 1420.726 MHz instead of
• 19:15
  1420.4556 MHz.
• 19:22
  That tiny change means that the source was
• 19:25
  moving about 84 kilometers per second, which fits
• 19:30
  nicely with the motion of hydrogen clouds
• 19:33
  in the Milky Way.
• 19:35
  They called them intermediate velocity clouds, clouds that
• 19:39
  move between normal galactic rotation and extremely
• 19:43
  fast clouds.
• 19:44
  So the hypothesis is the Wow! Signal was
• 19:48
  a maser flare in a cold hydrogen cloud.
• 19:51
  It was triggered by a magnetar outburst or
• 19:54
  a similar transient source.
• 19:56
  And it only happened once because the alignment
• 19:58
  between the magnetar, the cloud, and Earth
• 20:00
  was extremely rare.
• 20:02
  That is why we've never seen it again.
• 20:04
  It's a natural explanation.
• 20:06
  No aliens.
• 20:08
  But it's also not a glitch or a
• 20:10
  comet or a satellite.
• 20:11
  It was a real astrophysical phenomenon.
• 20:15
  Just one we'd never seen before.
• 20:18
  Méndez himself says, "Our study suggests that the
• 20:22
  Wow! Signal was likely the first
• 20:24
  recorded case of maser-like emission of
• 20:27
  the hydrogen line."
• 20:32
  Then we of course have the rabbit hole.
• 20:35
  So the story does not stop here.
• 20:39
  To reach this hypothesis, Méndez and his team
• 20:42
  had to dig into data that was nearly lost
• 20:46
  forever.
• 20:47
  In 1998, Big Ear was torn down.
• 20:51
  The area became a golf course.
• 20:53
  Most of the telescope's paper printouts were thrown
• 20:57
  out or were stored in basements where they
• 20:59
  rotted.
• 21:00
  But one man, amateur astronomer Robert Gray, decided
• 21:03
  that this should not happen.
• 21:07
  Between 2006 and 2017, he photographed over 75,
• 21:13
  000 pages of the original printouts.
• 21:15
  It took him 11 years.
• 21:18
  He did it himself, without funding, without help.
• 21:22
  He used an ordinary camera and photographed page
• 21:25
  after page in university basements where the paper
• 21:28
  was gathering dust.
• 21:30
  When he was done, he created a digital
• 21:32
  archive of 1.24 terabytes.
• 21:37
  It was Gray who made Méndez's analysis
• 21:40
  possible.
• 21:41
  Without his photographs, the data would have been
• 21:44
  lost forever.
• 21:45
  Gray died in December 2021, but his work
• 21:49
  lives on.
• 21:51
  The new analysis has also changed our understanding
• 21:55
  of the signal position.
• 21:57
  Previously, the location was uncertain.
• 21:59
  Now Méndez's team has narrowed it down to
• 22:02
  an area three times more precise than before.
• 22:05
  That makes it easier to search for similar
• 22:07
  signals in the future.
• 22:09
  And then there is Wow 2 and Wow 3, two
• 22:13
  weaker signals that Méndez's team has found in
• 22:15
  the old data.
• 22:16
  They fit the hydrogen cloud model perfectly.
• 22:19
  So maybe the Wow! Signal isn't unique.
• 22:23
  Maybe it's just the most powerful example of
• 22:26
  a phenomenon that happens more often than we
• 22:31
  thought.
• 22:36
  Then we have the critics.
• 22:37
  But the hypothesis isn't without
• 22:44
  its critics.
• 22:45
  In April 2026, another research team posted
• 22:50
  a response titled "No Natural Source. Yet?
• 22:56
  The 1977 WOW! Signal Cannot Be a Cold Hydrogen
• 23:01
  Cloud."
• 23:02
  They make three independent arguments.
• 23:05
  There is no hydrogen cloud.
• 23:08
  They looked at the GASS III data, a survey
• 23:14
  of the galactic hydrogen and found no cloud
• 23:17
  with the speed Méndez's model predicts.
• 23:20
  GASS III is the most detailed map of hydrogen
• 23:23
  in the Milky Way, and if there were
• 23:26
  a cloud, it should be there.
• 23:28
  Second, the temperature is too high to produce
• 23:31
  a signal of 250 Janskys.
• 23:34
  The cloud would need a brightness temperature of about
• 23:37
  16,800 Kelvin.
• 23:41
  That's three orders of magnitude higher than what
• 23:45
  a cold hydrogen cloud can produce.
• 23:48
  It's like an icicle melting at
• 23:53
  room temperature.
• 23:55
  Third, the mechanism does not exist.
• 23:59
  No known physics can produce a 21-centimeter
• 24:04
  maser in cold interstellar gas, and no natural
• 24:09
  21-centimeter maser has ever been observed.
• 24:12
  Masers exist in space.
• 24:15
  They are known from regions around young stars
• 24:19
  and dying stars but never at 21 centimeters
• 24:23
  in cold gas.
• 24:24
  In other words, the hypothesis is theoretically possible
• 24:28
  but it requires physics we don't know and
• 24:31
  a cloud we can't find.
• 24:33
  Jason Wright, an astronomer at Penn State, said
• 24:36
  that the hypothesis proposed a phenomenon that has
• 24:40
  never actually been observed.
• 24:43
  Radio astronomer Yvette Cendes called it "promising,
• 24:47
  but the details are still pretty scant," and
• 24:51
  even Méndez admits that the idea is "definitely
• 24:55
  a bit speculative."
• 24:57
  So we are left with a hypothesis
• 25:00
  that explains a lot but has not been
• 25:03
  proved?
• 25:07
  Then in 2025 another interesting theory appeared.
• 25:13
  Astrophysicist Avi Loeb, known for his controversial
• 25:16
  theories about interstellar objects, noticed the Wow! Signal
• 25:19
  came from almost the same direction as the
• 25:22
  interstellar object 3I/Atlas.
• 25:25
  The difference was only 9 degrees.
• 25:28
  Loeb calculated that the chance of a random
• 25:30
  alignment was 0.6%. He speculated that the
• 25:35
  3I/Atlas, an object that passed through
• 25:38
  our solar system in 2025, could have sent
• 25:41
  the signal in 1977.
• 25:44
  At the time the object was 600 times
• 25:47
  further from us than the sun but it
• 25:50
  could theoretically have had a transmitter of about one
• 25:54
  gigawatt equivalent to a nuclear power plant.
• 25:59
  Loeb encouraged radio astronomers to look for the
• 26:02
  signals from 3I/Atlas, but there is no
• 26:05
  evidence, and most astronomers are skeptical of Loeb's
• 26:10
  approach, which is often criticized for jumping to conclusions.
• 26:15
  So the 3I/Atlas hypothesis is speculation, but
• 26:19
  it shows how many possibilities still remain
• 26:22
  open.
• 26:25
  What actually holds up?
• 26:27
  Let's separate the pieces.
• 26:29
  What do we know for certain?
• 26:31
  We know that a powerful narrowband signal was
• 26:33
  detected on August 15, 1977.
• 26:37
  It was on or near the hydrogen line.
• 26:41
  It lasted 72 seconds.
• 26:44
  It has never been repeated and it came
• 26:46
  from the direction of Sagittarius.
• 26:50
  If you look at what is likely, it
• 26:53
  didn't come from Earth.
• 26:57
  The frequency is internationally protected.
• 27:01
  It didn't come from a known satellite.
• 27:03
  None of them were in the area.
• 27:06
  It didn't come from a comet.
• 27:07
  No known comet emits signals
• 27:10
  that strong.
• 27:11
  It didn't come from the Sun.
• 27:13
  The solar activity was also low in 1977.
• 27:16
  If you look at what's possible but uncertain,
• 27:20
  it is that it came from a hydrogen
• 27:23
  cloud illuminated by a magnetar.
• 27:25
  That fits the data but the mechanism is
• 27:27
  unknown.
• 27:29
  It came from another natural source we don't
• 27:31
  know yet. Or it came from an interstellar
• 27:35
  object like 3I/Atlas, but now we are
• 27:37
  in pure speculation.
• 27:40
  If you jump to pure speculation, then it
• 27:43
  is that the signal contained a message.
• 27:46
  It was proof of aliens, and Méndez's hypothesis
• 27:51
  is definitively proven.
• 27:52
  This is pure speculation.
• 27:55
  Jerry Ehman said in 2019, "I am convinced
• 27:59
  the Wow! Signal has the potential to be the
• 28:02
  first signal from extraterrestrial intelligence, but I
• 28:05
  can't prove it."
• 28:07
  And that may be the most powerful thing
• 28:09
  to say about the entire story.
• 28:15
  In 2022, Robert Gray and David Kipping published
• 28:21
  a statistical analysis of the Wow! Signal.
• 28:25
  They tried to answer if the signal repeats
• 28:28
  randomly what the probability is that we only
• 28:33
  saw it once.
• 28:34
  They built a simulator of the Big Ear
• 28:36
  telescope and all subsequent observations.
• 28:40
  They found the best fit gave a probability
• 28:43
  about 1.8%, about 1 in 50.
• 28:47
  That's unlikely but it's not impossible.
• 28:50
  It corresponded to 2.4 sigma and science
• 28:55
  typically requires 3 sigma to reject a hypothesis.
• 29:00
  They concluded about 1,500 hours of additional
• 29:05
  observation would be needed to definitively determine whether
• 29:11
  the Wow! Signal repeats.
• 29:13
  That is about 62 days of intensive telescope
• 29:17
  time.
• 29:18
  Gray and Kipping wrote, "Wow! is still alive
• 29:21
  — just barely."
• 29:24
  And then there is the human dimension.
• 29:26
  Gray spent his life searching for the signal.
• 29:30
  He was a data analyst by day, but
• 29:33
  in the evenings and on weekends he
• 29:35
  was hunting Wow.
• 29:35
  He wrote the book The Elusive Wow and
• 29:41
  built his own telescope in his
• 29:43
  backyard.
• 29:44
  When he died in 2021, he didn't have
• 29:46
  an answer, but he had an insight.
• 29:53
  So where does it leave us in 2026?
• 29:58
  The Wow signal is still unexplained.
• 30:01
  The best natural hypothesis, a hydrogen cloud maser
• 30:05
  triggered by a magnetar, is plausible but is
• 30:08
  not proven.
• 30:09
  The counterarguments are strong.
• 30:11
  The mechanism is unknown.
• 30:13
  The predicted cloud hasn't been found and the
• 30:17
  theory requires physics we don't know.
• 30:20
  The extraterrestrial hypothesis is not ruled out but
• 30:23
  is also not proven and without a repeat
• 30:27
  it can never be.
• 30:28
  Maybe the Wow signal is a natural phenomenon,
• 30:32
  we just don't understand it yet.
• 30:35
  Maybe it's a signal from another civilization, maybe
• 30:38
  maybe it's something else entirely.
• 30:42
  What makes the story so fascinating isn't that
• 30:45
  we have an answer, it is that we
• 30:48
  don't.
• 30:49
  That a single 72-second signal can keep us
• 30:53
  uncertain for nearly 50 years.
• 30:57
  A volunteer astronomer with a red pen can
• 31:00
  create a mystery that is still debated today.
• 31:07
  In a 2019 interview, Jerry Ehman said, "I'm convinced that the
• 31:11
  Wow! Signal has the potential to be the first
• 31:13
  signal from extraterrestrial intelligence," but he also
• 31:17
  added, "But I can't prove it."
• 31:19
  Maybe that's the most beautiful part of the
• 31:22
  whole story, that we are still looking, that
• 31:26
  we are still uncertain, that we are still
• 31:29
  gazing up at the sky and asking, who
• 31:32
  sent it and why didn't they say something
• 31:34
  more?
• 31:35
  Maybe we never get the answer, maybe we'll
• 31:37
  have it tomorrow.
• 31:38
  Until then, the Wow! Signal is proof
• 31:40
  that the universe can still surprise us.
• 31:43
  That there are still things that
• 31:46
  we don't understand.
• 31:48
  Science isn't just a collection of finished
• 31:51
  answers, but an endless series of questions that
• 31:54
  keep getting better.
• 31:56
  And that, I suppose, is also a kind
• 31:58
  of wow.