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