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Gravitational Waves, Cosmic What-Ifs & Dark Energy Dilemmas · Space Nuts: Astronomy Insights & Cosmic Discoveries

• 0:00
  Andrew Dunkley: While the world takes a little bit of a rest
• 0:01
  over the Christmas New Year period. We
• 0:03
  thought we would, too. But we're not going to
• 0:06
  leave you hanging. We've dug into the
• 0:08
  archives and found a few of the biggest
• 0:10
  episodes of recent times. So sit
• 0:13
  back and enjoy those. And we'll be back with
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  new episodes of Space Nuts, probably in
• 0:18
  the middle of January. See you then, Space
• 0:21
  Nuts. Hi there. Thanks for joining us. This
• 0:23
  is Space Nuts, Q and A. My name is Andrew
• 0:26
  Dunkley, your host. And coming up on this
• 0:29
  episode, we've got a question about
• 0:31
  gravitational waves and the Big Bang. We're
• 0:33
  also going to look, at a what if question.
• 0:35
  Love the what if questions. which is asking
• 0:38
  about, the life of Earth. Not life on
• 0:41
  Earth, the life of Earth. if
• 0:43
  the sun never died. Interesting,
• 0:47
  angle. And we're also going to look at,
• 0:50
  time and dark energy. That's all
• 0:52
  coming up on the Q A edition of
• 0:55
  space nuts.
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  Generic: 15 seconds. Guidance is internal.
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  10, 9. Ignition
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  sequence time. Space nuts. 5, 4, 3,
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  2, 1. 2, 3, 4, 5, 5, 4,
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  Andrew Dunkley: And joining me once again is Professor Fred
• 1:14
  Watson, astronomer at large. Hello, Fred.
• 1:16
  Professor Fred Watson: Hey, Andrew. How are you doing?
• 1:18
  Andrew Dunkley: I'm doing as much as I can.
• 1:20
  Professor Fred Watson: Good, good, good. Good to be Q and A with
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  you.
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  Andrew Dunkley: Yes, you too. shall we get stuck
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  straight in?
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  Professor Fred Watson: Why not? Yes, why not?
• 1:29
  Andrew Dunkley: All right. our first question comes. I'm not
• 1:31
  sure if it's BO or boa. I'll have to listen
• 1:33
  more carefully. Here we go.
• 1:36
  Beau: Hello, Fred and Andrew. It's Bo here from
• 1:39
  Melbourne. I hope you're well. I have a
• 1:41
  question for you. And it is not about dark
• 1:44
  energy, nor it is about dark matter,
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  but it is about gravitational waves.
• 1:50
  It's a straightforward question. Did the
• 1:53
  Big Bang produce gravitational waves
• 1:56
  as we understand it? Gravitational waves, are
• 1:58
  generated when two massive bodies such as
• 2:00
  neutron stars and black holes collided with
• 2:03
  each other and cause that ripple in the
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  fabric of space time. But
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  when the universe has just
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  began, infinite density and so forth.
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  When it came into existence via the Big Bang,
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  did it produce gravitational waves or echoes?
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  And can we detect those echoes in space and
• 2:24
  time? Very much like the cosmic microwave
• 2:26
  background radiation that we see today.
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  Anyway, I hope that made sense. I'd love to
• 2:31
  hear your answer. Thank you very much.
• 2:33
  Andrew Dunkley: Thank you. Boa. that's a good question.
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  We talk about the Big Bang a lot. We get a
• 2:39
  lot of questions about it.
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  and, I mean, it was
• 2:45
  a massive event. We don't know why
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  we don't know a lot, but, we
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  know we can see that it happened through the
• 2:53
  cosmic microwave background radiation that's
• 2:55
  still evident today. But
• 2:58
  gravitational waves would. I
• 3:01
  mean, if the universe didn't exist at
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  the moment of the Big Bang and was being
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  created as a consequence of that,
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  I'm not sure gravitational waves could have
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  happened the way we understand them with
• 3:14
  other events in our universe.
• 3:17
  I'm not sure about this one.
• 3:19
  Professor Fred Watson: So, the thing is, Andrew,
• 3:22
  Yes, the universe was created in that
• 3:25
  instant, of the Big Bang.
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  and so you're right. you know, in the
• 3:30
  conventional theory, standard Einsteinian
• 3:33
  physics, we imagine that time
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  and space didn't exist before the Big Bang.
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  So, you've got to create some space for your
• 3:40
  gravitational waves to go through. which is
• 3:43
  kind of what.
• 3:44
  Andrew Dunkley: That's what I'm thinking.
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  Professor Fred Watson: Yeah. And so, And so, yes,
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  there was the instant of the Big Bang that
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  created this singularity in
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  time and space, followed by this
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  period. Was it 10 to the minus 33 of a
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  second, something like that in duration,
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  which we call the period of inflation when
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  the. When the expansion really
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  took hold. and it, you know, the universe
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  went from the size of a football to the size
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  of a galaxy in something like 10 to the minus
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  33 of a second. And,
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  the thinking is, and I'm
• 4:20
  actually dragging this up from reading a few
• 4:23
  years ago, but yes,
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  that inflationary period, as we call it,
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  would have created gravitational waves,
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  or maybe a gravitational wave.
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  Andrew Dunkley: But I was about to say maybe just
• 4:39
  one big one at that point.
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  Professor Fred Watson: But the issue is, that,
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  it is a gravitational wave, a
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  very, very, very low frequency.
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  So, the gravitational waves that we get from
• 4:53
  colliding neutron stars, for example,
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  they produce waves
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  which are, basically have a frequency which
• 5:02
  is in the audio range. Which is why we can,
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  you know, turn those, gravitational wave
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  signals into an signal very easily
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  after you've amplified it up a bit and after
• 5:12
  LIGO has done its magic on it. And that's
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  where we get this chirp signal
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  as two neutron stars, m or whatever, merge
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  together, and eventually, because
• 5:23
  they're spinning ever more rapidly, and so
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  the frequency goes up of the waves that are
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  being emitted and then stop, at a high
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  point because that's where they've coalesced
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  into a single object. now
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  you can think of those,
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  audio frequencies. you know,
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  we might talk about something like 500 hertz
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  as an audio frequency. Or
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  you could take 440 hertz as the frequency
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  of, the standard, a note
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  in the musical spectrum.
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  so let's stick with 500 because that's an
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  easy one. so the, the period
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  of time between one peak of the
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  wave and the next, is
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  1-500th of a second. And so
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  if you think that's the interval of time
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  of a characteristic gravitational wave from
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  two colliding objects. Now the
• 6:19
  issue as I understand it, is that
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  the interval between peaks
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  in a gravitational wave,
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  produced by inflation
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  is about the same as the age of the universe.
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  Now it's not 1-500th
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  of a second, it's you know,
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  several billion years, perhaps even
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  tens of billions of years. it's quite a while
• 6:44
  since I read up on this. So normal
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  gravitational wave technology is simply not
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  equipped to detect these low frequency,
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  ultra ultra low frequency gravitational
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  waves. But there might be other ways of
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  seeing them. and one of the things people
• 7:00
  have looked for, and I'm not really
• 7:03
  very well up on this, but
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  there is a potential signal
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  in the cosmic microwave background radiation,
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  the flash of the Big Bang that we see, that
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  gives us what the Universe looked like
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  380,000 years after the Big Bang. That's what
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  we're seeing there. that
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  radiation, contains information
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  not just on its brightness, but also on its
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  polarization. you know, that
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  radiation is polarized, a bit like light can
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  be polarized. And I'm not
• 7:35
  really drawing the links very
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  strongly here, but I understand that there
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  are links between very low frequency
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  gravitational waves and that polarization
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  signal. So it's one of the things that people
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  are looking for to try and detect this
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  polarization, within cosmic matter
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  wave background radiation. So it's not at all
• 7:54
  a daft question, but it's quite a complex
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  answer.
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  Andrew Dunkley: Yeah, yeah, but the, the Big Bang itself
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  could have initially been
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  one created one gravitational wave.
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  Professor Fred Watson: That's right, yeah. That's more or less it.
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  Andrew Dunkley: M goa. you're right on the money.
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  It's just a matter of finding a way of
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  seeing them. is it possible these
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  gravitational waves still bouncing around
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  like the cosmic microwave background radio?
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  Professor Fred Watson: Yes, yes, but at such a low frequency that
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  you don't actually know it's there. You've
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  got to find other, you've got to find other
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  ways of detecting it because there's not
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  going to be any change in the gravitational
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  wave signal over, you know, a human
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  experimental lifetime. If you've got
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  a frequency whose time interval is measured
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  in billions of years, forget it.
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  Andrew Dunkley: Yeah, that's a tough one.
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  Professor Fred Watson: Thanks.
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  Andrew Dunkley: Boa. That's a great question and thanks for
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  sending it in.
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  we've got a question from one of our
• 8:53
  regulars, Rennie, who is from sunny West
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  Hills, California. this is a what if
• 8:58
  question. Theoretically, if the sun were
• 9:00
  never to die, let's assum. Assume it's just
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  never going to die. Would the Earth
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  eventually erode, decay
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  and die on its own?
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  Professor Fred Watson: yeah.
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  Andrew Dunkley: Well, my answer is no, because we'll destroy
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  it first.
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  Professor Fred Watson: It could be very different. I mean, so if
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  what Ren is saying is that, yes, the sun, we
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  know it's going to evolve over the next few
• 9:23
  billion years, and it will change and that
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  will eventually result in the Earth being
• 9:27
  swamped by the outer atmosphere of the sun,
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  which might not be very nice for anybody left
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  on Earth. but if that
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  didn't happen, if the sun just
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  went on its merry way, being a normal star,
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  there will be a few things that will happen
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  over that time scale
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  which we know won't happen because
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  the sun turning into a red giant is going to
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  overtake it. One of them is,
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  the tidal
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  breaking of the Earth's rotation so that it
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  always, faces the Moon. So the Earth's
• 10:02
  day will change from
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  24 hours to something like, if I remember
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  rightly, it's 42 days, that it's about that
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  length of time, and that's it turning once.
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  And the Moon will go around the
• 10:16
  sky, around the Earth in the same time. So
• 10:19
  the Earth and the Moon will constantly face
• 10:21
  one another with ah, a month and a day, which
• 10:23
  are both equivalent to, I think it's about
• 10:25
  42, 43 days, something like that.
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  so that's going to change things quite a bit.
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  so that would certainly alter the
• 10:34
  atmospheric dynamics of the Earth if one
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  side's getting warmed up for 20 days rather
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  than just one day, of day and night. So
• 10:42
  a lot of things change. and yeah,
• 10:45
  the constant bombardment by the
• 10:48
  magnetic particles from the sun,
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  I don't know to what extent the Earth's
• 10:53
  magnetic field might erode, but there will
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  certainly be changes, may
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  even be.
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  Andrew Dunkley: What about.
• 10:59
  Professor Fred Watson: So go ahead, go on.
• 11:01
  Andrew Dunkley: No, I was just going to say if humans were
• 11:04
  still around in that period, would we.
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  Well, okay, no, let me rephrase. Would we
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  adapt as these things changed and
• 11:13
  reached that point? Would we be able to adapt
• 11:15
  as a species and other life on Earth, adapt
• 11:17
  to live in that kind of environment?
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  Professor Fred Watson: Well, it certainly is. All these changes are
• 11:21
  ones that take place very slowly indeed. and
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  over kind of longer periods than the
• 11:27
  characteristic evolution time to get
• 11:30
  from, you know, one mutation to another,
• 11:32
  whatever that might be for humans.
• 11:35
  so yeah, they're slow and
• 11:38
  I'm sure humans could adapt to them. we're a
• 11:41
  pretty adaptive species. We might also by
• 11:43
  then be capable of building the
• 11:46
  megastructures that might protect us from
• 11:47
  some of the sun's funny things going on.
• 11:50
  it's hard to know really, isn't it? But
• 11:53
  I think generally speaking, I mean, Rennie's
• 11:55
  question's a good. What happens if
• 11:58
  nothing happens to the sun? does the Earth
• 12:00
  just sort of survive? It probably
• 12:03
  survives. It will be changed. We might find
• 12:06
  we're all living in plastic domes or
• 12:08
  something by then, rather than because the
• 12:11
  atmosphere has been so messed about with. But
• 12:13
  yes, I think I'm an
• 12:16
  optimist that humankind would survive.
• 12:19
  Andrew Dunkley: Yeah, no, it's interesting because.
• 12:23
  Andrew Dunkley: I mean we know what's going to happen. We
• 12:24
  kind of know when it's going to happen. But
• 12:27
  if it didn't, it would create a whole array
• 12:30
  of new challenges for humanity because we
• 12:32
  would have to learn to live in a, very
• 12:37
  somewhat hostile environment, I imagine,
• 12:39
  because, the planet would not be the same
• 12:41
  and I can't imagine what it would be like to
• 12:44
  have a 42 long, 42 day,
• 12:47
  long day. well, you know, birthdays
• 12:50
  would be few and far between, wouldn't they?
• 12:51
  Professor Fred Watson: they would. But you, you know, we're gonna,
• 12:53
  we're gonna know what that's like very soon
• 12:55
  because the, the day on the moon is 20, you
• 12:58
  know, 29 days effectively from
• 13:01
  one right moon to another. So yeah, so
• 13:04
  we've, we've, we've already got something
• 13:06
  like that, in store for people to experience.
• 13:09
  It'll be very interesting to see what even
• 13:11
  the Artemis astronauts on the moon make of
• 13:14
  all that.
• 13:16
  Andrew Dunkley: Yeah, yeah, very interesting. Rennie, that's
• 13:18
  a great question. Thanks for sending it in,
• 13:20
  much appreciated.
• 13:21
  And next up we've got
• 13:23
  Daniel. this is a sort of dark
• 13:26
  energy question, sort of.
• 13:29
  Generic: Hey guys, Daniel from Adelaide here. There
• 13:32
  seems to be more and more discoveries lately
• 13:34
  in the very early universe that shouldn't be
• 13:36
  possible because not enough time has passed
• 13:38
  like size of galaxies or black holes. Now
• 13:40
  I've got a far out theory I'd love to share.
• 13:42
  What if time and dark energy were actually
• 13:45
  the same thing? So we know for about the
• 13:47
  second half of the universe that dark energy
• 13:49
  has been accelerating its expansion. Could
• 13:51
  this therefore mean that there was Less dark
• 13:53
  energy in the first half. And if that's the
• 13:55
  case, what if time actually went slower in
• 13:57
  the early universe? So from our perspective,
• 13:59
  what took a really short amount of time
• 14:02
  actually happened in normal time, with normal
• 14:04
  being in quotes. I'd previously asked the
• 14:06
  question on the show whether dark energy is
• 14:08
  related to black holes. I think there was a
• 14:10
  paper around the time that kind of suggested
• 14:12
  that it was. And we know, that black holes do
• 14:14
  distort time. So if time is part of the
• 14:16
  fabric of space, maybe dark
• 14:19
  energy is too. But it's actually one of the
• 14:22
  same thing. I'm expecting a very quick,
• 14:24
  simple no, but I wanted to ask anyway.
• 14:26
  Professor Fred Watson: Thanks. All right. Thanks.
• 14:28
  Andrew Dunkley: Daniel. yeah. Is, time and dark energy,
• 14:31
  are they the same thing?
• 14:33
  Professor Fred Watson: Yeah, you never get a quick and simple no
• 14:35
  from me, Daniel. It's always a long, drawn
• 14:38
  out complex. No, it's not always.
• 14:42
  I think in this case, yeah. Your thinking's
• 14:45
  interesting. we've talked recently as well
• 14:48
  about, the fact that
• 14:53
  this new controversial theory from Joe Silk
• 14:55
  et al, over in Baltimore,
• 14:58
  suggesting that perhaps black holes,
• 15:00
  supermassive black holes, came first, they
• 15:02
  were formed in the early universe. And that
• 15:04
  goes a long way to explaining, the conundrum
• 15:06
  that you mentioned at the start of your
• 15:08
  question there, that a lot seems to have
• 15:09
  happened in the first, in the first,
• 15:12
  few millions or hundreds of millions
• 15:15
  of years of the universe's existence.
• 15:18
  so we kind of understand
• 15:22
  the gravitational time dilation, effects
• 15:25
  pretty well. And they're actually quite
• 15:27
  small, from our vantage point
• 15:30
  here, 13.8 billion
• 15:32
  years later.
• 15:35
  But you're right to make the point that, dark
• 15:38
  energy only, seems to have appeared
• 15:42
  over the second half of the age of the
• 15:44
  universe. But that's more likely to be,
• 15:48
  because its measurable effect has only become
• 15:51
  apparent. We think that during the first
• 15:54
  half of the universe's age,
• 15:57
  the galaxies within the universe were close
• 16:00
  enough to each other. The gravitational
• 16:02
  attraction would have basically kept
• 16:05
  the expansion due to dark energy in check.
• 16:07
  The accelerated expansion, due to dark
• 16:10
  energy, and so it's only when you get
• 16:13
  past a kind of tipping point where
• 16:15
  suddenly the, the mass of galaxies in the
• 16:18
  universe is not enough, not strong enough
• 16:20
  gravitationally to break the
• 16:23
  acceleration of the expansion. By that I mean
• 16:25
  B R A K rather than B R E A K,
• 16:29
  it's not enough to slow it down and so the
• 16:31
  acceleration takes over. and that's why
• 16:34
  it's a tricky thing just to try and
• 16:38
  tease out. And we've talked about this
• 16:39
  recently as well. Whether the, dark
• 16:42
  energy is a constant, whether it's something
• 16:44
  that's a, factor that
• 16:47
  hasn't changed in terms of, its release
• 16:51
  as space expands. it's because there is
• 16:54
  this added impact of the gravitational pull
• 16:57
  of the galaxies, stopping us from basically
• 17:00
  seeing the effect of dark energy, the
• 17:02
  accelerated expansion of the universe back in
• 17:04
  the early universe. So I think all those
• 17:06
  things are well and truly understood and
• 17:09
  kept fairly separate by the scientists
• 17:12
  looking at them. And by that I mean time and
• 17:14
  dark energy. So that's a long, complicated
• 17:16
  move.
• 17:18
  Andrew Dunkley: Yeah, yeah. okay. Daniel
• 17:21
  Winfred says, I think these things have been
• 17:23
  long understood. That's his way of saying,
• 17:25
  you're way off, way, way
• 17:28
  off the mark.
• 17:29
  Professor Fred Watson: Go on.
• 17:33
  Andrew Dunkley: But it's worth asking because otherwise,
• 17:35
  obviously this is something people are
• 17:37
  thinking about. So it's worth asking,
• 17:40
  these different questions
• 17:43
  to, just see if it's a
• 17:46
  possibility. Thanks, Daniel. Appreciate that.
• 17:49
  Professor Fred Watson: Great question.
• 17:49
  Andrew Dunkley: if you've got questions for us, please send
• 17:52
  them in because we could always use them.
• 17:54
  just go, to our website, spacenutspodcast.com
• 17:57
  spacenuts IO and click on the various links.
• 18:00
  The AMA link will give you, access to,
• 18:03
  text and voice, audio. Or you
• 18:06
  can click on the little. It's not purple,
• 18:08
  it's green. When did they change the color of
• 18:10
  that? send us your. Oh, no, it's. It's purple
• 18:13
  when you hover on it. There you, go. send us
• 18:15
  your questions, on the right hand side of our
• 18:17
  homepage. And don't forget to tell us who you
• 18:19
  are and where you're from. Fred, we're done.
• 18:21
  Again, thank you so much.
• 18:23
  Professor Fred Watson: always a pleasure, Andrew, and I hope we'll
• 18:25
  see you then very, very soon.
• 18:28
  Andrew Dunkley: It's a distinct, possibility. Could
• 18:31
  be within 13.8 billion years, in fact.
• 18:34
  Professor Fred Watson: Yes.
• 18:35
  Andrew Dunkley: Thanks, Fred. See you soon. Fred Watson,
• 18:37
  astronomer at large. And, thanks to Huw in
• 18:39
  the studio for making our lives so much more
• 18:41
  difficult with these split episodes. But, no,
• 18:44
  it's okay. and from me, Andrew Dunkley, thank
• 18:46
  you so much for joining us. Looking forward
• 18:48
  to your company on the next episode of Space
• 18:51
  Nuts. See you then, Space Nuts.
• 18:53
  Generic: You've been listening to the Space Nuts
• 18:55
  Podcast. Available at
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  Apple Podcasts, Spotify,
• 19:01
  iHeartRadio, or your favorite podcast
• 19:03
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• 19:06
  bitesz.com This has been another quality
• 19:08
  podcast production from Bitesz.com