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Stellar Evolutions, Dark Energy Mysteries & Your Questions Answered · Space Nuts: Astronomy Insights & Cosmic Discoveries

• 0:00
  Speaker 1: Hi there, thanks for joining us. This is a Q
• 0:02
  Speaker 1: and A edition of Space Nuts. We talk astronomy in
• 0:05
  Speaker 1: space science, and in the Q and A episode we
• 0:08
  Speaker 1: answer questions from our audience. We've got a whole bunch. Today.
• 0:13
  Speaker 1: We're going to hear from Jeff, who wants to discuss
• 0:17
  Speaker 1: the effect when the sun goes red giant, which is
• 0:20
  Speaker 1: going to happen in a couple of weeks. No, No,
• 0:23
  Speaker 1: it's not blue. Is asking about accretion discs, Julian about
• 0:27
  Speaker 1: the expansion of the universe, and one of our old
• 0:30
  Speaker 1: favorite topics from Peter, dark energy. That's all coming up
• 0:34
  Speaker 1: in this episode of Space Nuts. Fifteen seconds guidance in
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  Speaker 1: Channel ten nine ignition sequence Space Nuts NY four three
• 0:45
  Speaker 1: two more red one Space Nuts as the night record it.
• 0:50
  Speaker 2: Bill's good.
• 0:53
  Speaker 1: And back again to furnish us with his wisdom or
• 0:55
  Speaker 1: just to have a couple of lucky guesses. Is Professor
• 0:57
  Speaker 1: Fred Watson, Astronomer at Large. Hello, Fred, Oh you doing,
• 1:01
  Speaker 1: Andrew good to see you good and you yes.
• 1:04
  Speaker 2: Sir, firing on all cylinders as far as I.
• 1:06
  Speaker 1: Know, that's all right. Back then they only made them
• 1:10
  Speaker 1: with three sel Oh gosh, I mean wicked mood today. Sorry,
• 1:16
  Speaker 1: about that. Yep, Okay, we better get on with it now.
• 1:21
  Speaker 1: I will put it out an appeal like I did
• 1:23
  Speaker 1: at the end of the last episode for audio questions.
• 1:26
  Speaker 1: Questions in general, but audio questions particularly. We are desperately
• 1:30
  Speaker 1: short and we don't know why. It's just a weird
• 1:33
  Speaker 1: quirk of fate, I suppose. But if you would like
• 1:36
  Speaker 1: to send us some audio questions, you can do that
• 1:38
  Speaker 1: on our website space nuts dot io and click on
• 1:41
  Speaker 1: the AMA ask Me Anything tab at the top and
• 1:45
  Speaker 1: send us the message. Don't forget to tell us who
• 1:48
  Speaker 1: you are and where you're from. Our first question, Fred,
• 1:51
  Speaker 1: comes from Jeff in Fayetteville, Arkansas in the United States. Hello, gentlemen,
• 1:56
  Speaker 1: Oh he's wrong for a start. Come on. I happy
• 2:00
  Speaker 1: upon your podcast several months ago and enjoy it very much.
• 2:04
  Speaker 1: Last month, you discussed the thought experiment having to do
• 2:07
  Speaker 1: with what would happen if the rest to the rest
• 2:10
  Speaker 1: of the Solar system if the Sun suddenly disappeared. My
• 2:13
  Speaker 1: question is a little bit more concrete. In five billion
• 2:17
  Speaker 1: years or so, our Sun is expected to swell into
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  Speaker 1: a red giant before perhaps collapsing into a white dwarf.
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  Speaker 1: What will this do to our son's total mass and
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  Speaker 1: what effect will it have on the outer planets that
• 2:29
  Speaker 1: survive being engulfed, Earth not being one of them, as
• 2:32
  Speaker 1: it turns out. A follow up question, are other sons
• 2:37
  Speaker 1: dying throughout our galaxy responsible for the rogue planets far
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  Speaker 1: out in space between stars that I've read about. Thank
• 2:44
  Speaker 1: you for your time and the stimulating discussions you allow
• 2:47
  Speaker 1: me to listen into. Thank you. Jeff's lovely a few
• 2:51
  Speaker 1: questions in there. Fred. So, Yes, our sun, which we
• 2:55
  Speaker 1: have talked about, going you know, ballistic about five billion
• 3:01
  Speaker 1: or so years, what happens to the outer planets?
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  Speaker 3: That's yes, it is a great question, and I think
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  Speaker 3: the sort of implicit assumption is that is that the
• 3:15
  Speaker 3: inner planets are not going to be around, which probably
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  Speaker 3: will include the Earth and possibly even Mars.
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  Speaker 1: So the.
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  Speaker 3: Yes, the process towards the end of the Sun's life
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  Speaker 3: and somewhere in the region of three to five billion years.
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  Speaker 3: I think the process starts about three billion years hence,
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  Speaker 3: so it's a little bit earlier than Jeff says, so
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  Speaker 3: that's not a cause for alarm.
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  Speaker 2: Three billion leads years.
• 3:43
  Speaker 1: That he's watched, so he's going to have to rese
• 3:44
  Speaker 1: it back and that's alway. The pain is such a right.
• 3:48
  Speaker 2: Yeah.
• 3:50
  Speaker 3: I the other day set dutifully set the timer to
• 3:53
  Speaker 3: time down on my phone because I had to take
• 3:56
  Speaker 3: things out of the oven, and it got to the
• 4:00
  Speaker 3: end of the time and didn't do anything. Just how
• 4:04
  Speaker 3: you stopped.
• 4:05
  Speaker 2: I did too.
• 4:06
  Speaker 1: My phone suddenly decided to put all calls through the
• 4:09
  Speaker 1: voicemail before I can even before I even know it's ringing.
• 4:13
  Speaker 1: Picked it up the other day and thought, why is
• 4:15
  Speaker 1: it vibrating? And then I realized my sister was ringing me,
• 4:18
  Speaker 1: but it was making no sound. There was no indication.
• 4:20
  Speaker 1: It just filtered, And when I pushed a couple of
• 4:23
  Speaker 1: buttons eventually found her and she said, ah, yeah, I
• 4:27
  Speaker 1: was just listening to your message. There you go voicemails,
• 4:32
  Speaker 1: which is not a problem.
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  Speaker 2: Will be really worried about intry, not just time.
• 4:36
  Speaker 1: But if anyone knows the answer to that, please let
• 4:38
  Speaker 1: me know.
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  Speaker 3: Well, I can tell you the answer. You have a
• 4:42
  Speaker 3: smart watch and the wings as well.
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  Speaker 1: Well, yeah, I don't think I had it on at
• 4:47
  Speaker 1: the time.
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  Speaker 3: Anyway, So so yes, the inner planet's get swallowed up
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  Speaker 3: as the sun swells. It doesn't happen suddenly. It is
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  Speaker 3: as a leisurely process. There is a collapse of the
• 5:02
  Speaker 3: core down to a white dwarf star, which is the
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  Speaker 3: end product. Is this white dwarf star, which is the
• 5:10
  Speaker 3: size of the Earth, but with quite a lot of
• 5:12
  Speaker 3: the mass of the Sun still tucked in there an
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  Speaker 3: outer shell of expanding gas, and if we were looking
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  Speaker 3: at that from the outside, we'd call it a planet
• 5:21
  Speaker 3: chair nebula. So that outer shell of gas is hot.
• 5:27
  Speaker 3: It's hot enough to basically vaporize the inner planets.
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  Speaker 2: But Jeff's questions not about.
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  Speaker 3: That, it's about how do things look from the outside,
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  Speaker 3: and so the outer planets. Interestingly, their orbits will be perturbed,
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  Speaker 3: which means changed, but maybe not as dramatically as you
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  Speaker 3: might think because that swelling. What it's doing is if
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  Speaker 3: you look at the center of gravity of all that,
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  Speaker 3: it's still at the center of the Solar System, even
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  Speaker 3: though the outer layers of the star and a significant
• 6:03
  Speaker 3: amount of mass in that. Even though most of the
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  Speaker 3: mass are going to be concentrated in the white dwarf star,
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  Speaker 3: but the outer layers are expanding, you're outside that zone.
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  Speaker 3: So to you, the center of gravity, center of mass
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  Speaker 3: of the Solar System remains where the sun is now,
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  Speaker 3: and so the effect on the orbits of the planets
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  Speaker 3: might not be as dramatic as propelling one of them
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  Speaker 3: out to become a rogue planet. So it could be
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  Speaker 3: a lot gentler than I mean, a super and ova
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  Speaker 3: is different. If it explodes, then you're talking about dramatic
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  Speaker 3: and cataclysmic events that would certainly disturb the orbits of planets,
• 6:43
  Speaker 3: although some planets seem to be able to survive that.
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  Speaker 3: We can see supernerova eminence with planets chugging around anyway, this.
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  Speaker 2: Scene.
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  Speaker 3: The scenario is that there may still be planets which
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  Speaker 3: will be outside the you know, the envelope of the
• 7:02
  Speaker 3: of the white of the red Giant. Now, eventually that
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  Speaker 3: envelope is going to pass the past the outer planets
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  Speaker 3: and may evaporate them as well, depending on what sort
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  Speaker 3: of temperature it is. But the so the red giant phase,
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  Speaker 3: the outer planets might be still okay and still say
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  Speaker 3: it's stable. But once it progresses beyond that, and you
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  Speaker 3: get to the planetary nebulus stage, where the outer layer
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  Speaker 3: is light years in diameter rather than rather than just
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  Speaker 3: a few hundred million kilometers in diameter, truly in kilometers
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  Speaker 3: in diameter. Then you're you're you're probably in trouble if
• 7:44
  Speaker 3: you're on the outer planets as well.
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  Speaker 1: Okay, how long does that process take to reach that
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  Speaker 1: nibula stage.
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  Speaker 3: It's it's relatively slow. You're talking about billions of years. Yeah,
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  Speaker 3: so I mean there must be there must be a
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  Speaker 3: collapse phase for the nucleus. I'm not an expert on
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  Speaker 3: these what we call highly evolved stars, but as it
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  Speaker 3: goes from red giant to a planetary nebula, that's when
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  Speaker 3: you change into a white dwarf. In the middle, you've
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  Speaker 3: got the nucleus of the star collapsing. So these are
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  Speaker 3: the end products of normal stars. Actually, a normal star
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  Speaker 3: will go through this phase, a massive star will become
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  Speaker 3: a super and ova will explode.
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  Speaker 2: Wow.
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  Speaker 1: Okay, so you pretty well answered everything in one hit.
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  Speaker 1: The white dwarf will have the same mess as our
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  Speaker 1: Sun at the moment, more or less, so it won't
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  Speaker 1: really have an impact on the out of planets until
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  Speaker 1: after the halo effect for billions of years, and probably
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  Speaker 1: not enough effect to cause rogue planets.
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  Speaker 3: I think that's right, Yes, I mean I think if
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  Speaker 3: operated planets is more likely, so rogue planets are most
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  Speaker 3: likely formed either just formed in gus clouds collapsing into stars.
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  Speaker 3: These are things that are big enough to collapse into
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  Speaker 3: stars so they become little planets on their own, or
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  Speaker 3: by being ejected because of a gravitational influence. You know,
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  Speaker 3: if you get two planets that pass very close to
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  Speaker 3: each other or something like that, one of them might
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  Speaker 3: get booted out of their solar system.
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  Speaker 1: There you go, Jeff, Hopefully that answered all of your questions.
• 9:24
  Speaker 1: We like multifaceted questions. It text us in all sorts
• 9:28
  Speaker 1: of strange directions. Sometimes great to hear from you. Hope
• 9:31
  Speaker 1: all is well in Arkansas. Fred. Our next question comes
• 9:34
  Speaker 1: from Blue is from London. I have a question about
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  Speaker 1: accretion disks. Given that gravitational time dilation causes time to
• 9:42
  Speaker 1: pass much slower near a black hole relative to Earth,
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  Speaker 1: why does the disc appear to move at high speeds
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  Speaker 1: to us? I would have expected the material to look
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  Speaker 1: like it's moving at extreme slow motion or even stop
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  Speaker 1: moving the closer you get to the event horizon. Love
• 10:00
  Speaker 1: the show, guys. Thanks Blue. Okay, now you're going to
• 10:04
  Speaker 1: know the answer to this one, because I think we've
• 10:06
  Speaker 1: had a similar question before, But it seems to be
• 10:09
  Speaker 1: an ongoing theme with black holes. Why do we see
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  Speaker 1: things that we don't think we should see.
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  Speaker 3: So, yes, the accretion disc is actually quite a long
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  Speaker 3: way from the black hole, and a lot of that
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  Speaker 3: swirling material is ejected from the black hole rather than
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  Speaker 3: getting sucked in by the magnetic fields that the black
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  Speaker 3: hole generates. It sort of projects the accretion disc material
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  Speaker 3: at very high velocities to the sort of north and
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  Speaker 3: south of.
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  Speaker 2: The accretion disc.
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  Speaker 3: So there will be a time dilation effect.
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  Speaker 2: I should check this as to how much it would.
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  Speaker 3: Be, but I think the overarching point is that far
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  Speaker 3: enough away from the event horizon that time dilation in
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  Speaker 3: the accretion disk is not great. It's not high enough.
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  Speaker 3: I think it's all a matter of scale rather than
• 11:08
  Speaker 3: being a matter of the phenomenon, which I think Blue
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  Speaker 3: is right. I think is you know, anything that gets
• 11:13
  Speaker 3: close to the to the black hole's event horizon is
• 11:17
  Speaker 3: going to show up a time dilation phenomenon.
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  Speaker 1: I suppose it would also depend on what kind of
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  Speaker 1: black hole it is. I mean some of them are
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  Speaker 1: massively Yes.
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  Speaker 2: That's right, that's correct.
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  Speaker 3: So a super massive black hole will produce a bigger phenomenon.
• 11:38
  Speaker 3: I'm just going to try looking something up to see
• 11:42
  Speaker 3: if I can put any detail on that.
• 11:50
  Speaker 1: I'm helping you a lot here.
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  Speaker 3: Yeah, okay, all right, here you are. Here's a number
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  Speaker 3: for a ten thousand and solar mass black hole, and
• 12:01
  Speaker 3: that's a bit. I mean, that's the kind of limit.
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  Speaker 2: Of what we call an.
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  Speaker 3: Intermediate mass black hole, something measured in tens of thousands
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  Speaker 3: of solar masses. For a ten thousand solar mass black hole,
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  Speaker 3: the time dilation of the increase the accretion disc inner
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  Speaker 3: edge is only twenty two percent. So it's what I've said,
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  Speaker 3: it's the scale of the process that makes makes the difference.
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  Speaker 1: Fair enough, okay, simple answer.
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  Speaker 2: Really, yeah, it seems to be.
• 12:34
  Speaker 1: All right, Thank you Blue. Hope you're going well. Love London.
• 12:38
  Speaker 1: Only been there twice I think twice, yes, and yeah,
• 12:42
  Speaker 1: I really enjoyed my time. It's a beautiful city. Really
• 12:45
  Speaker 1: love that place. So I'd go back tomorrow for could.
• 12:49
  Speaker 1: Thank you Blue. And this is space Nuts. You're listening
• 12:53
  Speaker 1: to it with Andrew Dunkley and Professor Fred what's an.
• 12:58
  Speaker 3: We choose to Golden Moon and this decay and do
• 13:01
  Speaker 3: the other thing not because they are easy, but because.
• 13:05
  Speaker 1: They are are these nuts. Next question Fred hey nutters
• 13:13
  Speaker 1: Julian from Brampton, Ontario, Canada. Here, what is causing the
• 13:18
  Speaker 1: expansion of the universe? Oh? That old chestnut? I mean,
• 13:22
  Speaker 1: are we a black hole eating outside matter? Or are
• 13:28
  Speaker 1: other fundamental forces responsible? Or are the forces actually keeping
• 13:33
  Speaker 1: us together? Part two? I think we're up to part four. Actually,
• 13:36
  Speaker 1: part two of this question would be Fred mentioned the
• 13:38
  Speaker 1: universe is expanding slower. Does that mean we know exactly
• 13:43
  Speaker 1: how fast the universe is expanding? And does that mean
• 13:46
  Speaker 1: speeds faster than light? I hope you all got that.
• 13:49
  Speaker 1: Love the show, thanks, Julian. Oh, he's packed in a
• 13:52
  Speaker 1: lot there in three or four sentences. What's causing the
• 13:58
  Speaker 1: expansion of the union of a spread? And I know
• 14:01
  Speaker 1: the answer to this one.
• 14:05
  Speaker 3: I think, well, you know, the way we usually interpret
• 14:08
  Speaker 3: the Big Bang is in the beginning, there was nothing,
• 14:14
  Speaker 3: and then it exploded and that's kind of more or
• 14:20
  Speaker 3: less what it was. And so we're still seeing the
• 14:24
  Speaker 3: aftermath or the effect of that explosion in the expansion.
• 14:28
  Speaker 3: So it's driven by by a you know, some fundamental
• 14:35
  Speaker 3: injection of energy at the start of the universe. We
• 14:38
  Speaker 3: can kind of quantify how much it was. It's a
• 14:40
  Speaker 3: very large number that set the expansion in motion, and
• 14:44
  Speaker 3: it's still going on now. The second bit of the
• 14:51
  Speaker 3: question is the is the interesting bit part two? So
• 14:56
  Speaker 3: so let me just yes that there are of parts here.
• 15:00
  Speaker 3: Are we a black hole eating outside material? Some scientists
• 15:06
  Speaker 3: have suggested that we are within the event horizon of
• 15:08
  Speaker 3: a brook ball, and that's what I've heard what's causing
• 15:12
  Speaker 3: the expansion of the universe. It's a very speculative idea.
• 15:16
  Speaker 3: It's not one I'm very fond of because I you know,
• 15:20
  Speaker 3: I think I think we need a bit more hard
• 15:22
  Speaker 3: evidences to that black hole's there. Are we a black
• 15:27
  Speaker 3: hole eating outside material? Probably not?
• 15:30
  Speaker 2: Or are there other fundamental forces responsible?
• 15:34
  Speaker 1: Well?
• 15:34
  Speaker 3: Yes, maybe, And that comes to the second bit of
• 15:37
  Speaker 3: the question. It says Fred mentioned the universe is expanding slower.
• 15:42
  Speaker 3: That's actually not the case. It's expanding faster all the time.
• 15:48
  Speaker 3: But that acceleration is reducing, reducing. Yes, so the exposure of.
• 15:53
  Speaker 1: Conundrum, isn't it right? It is us expanding at a
• 15:55
  Speaker 1: faster rate. Now it's expanding faster, slower.
• 16:00
  Speaker 3: Faster, slower, that's right. I mean, before we used to
• 16:03
  Speaker 3: think it was expanding at a slower rate. We used
• 16:05
  Speaker 3: to think in the seventies and eighties that it was
• 16:08
  Speaker 3: slowing down, the expansion was slowing down, and one day
• 16:11
  Speaker 3: they'd be perhaps a reversal of the expansion and a
• 16:14
  Speaker 3: big crunch. Then in nineteen ninety eight, along Cane, Branchmidt
• 16:17
  Speaker 3: and saw Perl Muta, and between them they figured out
• 16:20
  Speaker 3: and Adam Reice, of course the three Nobel Prize winners
• 16:23
  Speaker 3: in twenty eleven, they figured out that actually the expansion
• 16:27
  Speaker 3: is accelerating. And that's still the case today. That is
• 16:32
  Speaker 3: the situation we have. The expansion is still is accelerating,
• 16:35
  Speaker 3: but there is now new evidence that suggests that the
• 16:42
  Speaker 3: acceleration is reducing. So it's not that the expansion of
• 16:47
  Speaker 3: the universe is slowing down. It's that the acceleration of
• 16:50
  Speaker 3: the expansion of the universe is slowing down, and that's
• 16:53
  Speaker 3: a different matter. So it is still it's still accelerating
• 16:57
  Speaker 3: in its expansion, and we tribute to dark energy. That
• 17:04
  Speaker 3: is something that the new results that suggest that the
• 17:10
  Speaker 3: acceleration is slowing down actually throw a spanner in the
• 17:14
  Speaker 3: works because we thought we understood dark energy as what's
• 17:18
  Speaker 3: called a cosmological constant, a force that basically is proportional
• 17:23
  Speaker 3: to the size of space. The more space you have,
• 17:25
  Speaker 3: the more expansion force. There is a kind of pressure,
• 17:28
  Speaker 3: if you like, off space itself springing us of space.
• 17:33
  Speaker 3: The fact that as time goes on that expansion seems
• 17:36
  Speaker 3: to be the acceleration of the expansion seems to be reducing.
• 17:41
  Speaker 3: Is it's actually suggestive of new physics, which might mean
• 17:46
  Speaker 3: higher dimensions and all the other good stuff that we
• 17:49
  Speaker 3: love talking about on space nuts.
• 17:50
  Speaker 2: Yes, indeed.
• 17:52
  Speaker 3: So his last bit of the question, does that mean
• 17:57
  Speaker 3: speeds faster than light? There will be a limit beyond
• 18:01
  Speaker 3: which we can't see the universe because it's expanding from
• 18:06
  Speaker 3: us faster than light can get to us. That's already
• 18:10
  Speaker 3: the case, but we don't see that because we see
• 18:13
  Speaker 3: the cosmic microwave background radiation first.
• 18:16
  Speaker 2: That's the nearer phenomenon.
• 18:18
  Speaker 3: So yeah, So it's an interesting set of questions which
• 18:25
  Speaker 3: I guess highlighting some of the mysteries that we face
• 18:28
  Speaker 3: with with our current understanding of cosmology.
• 18:33
  Speaker 1: In truth. In truth, though we do not know how
• 18:36
  Speaker 1: fast the expansion rate currently is. We can't put a
• 18:38
  Speaker 1: number on that, can we?
• 18:40
  Speaker 2: Yes, we can.
• 18:41
  Speaker 3: Okay, that's the Hubble constant, which is, yeah, we have
• 18:46
  Speaker 3: we talked about that before. We've yeah, because because there's
• 18:49
  Speaker 3: this tension that between the Hubble constant as we measure
• 18:52
  Speaker 3: it now and the Hubble constant as we determine it
• 18:57
  Speaker 3: from the cosmic microwave background radiation called Hubble tension, which
• 19:01
  Speaker 3: may be something that really is just to do with measurements.
• 19:05
  Speaker 3: So the Hubble constance in odd units in it's in
• 19:08
  Speaker 3: kilometers per second per mega parsek, which is basically a
• 19:13
  Speaker 3: fancy way of saying we do no health.
• 19:16
  Speaker 1: LASTI sex badis Yeah, the answer is seventy to seventy
• 19:19
  Speaker 1: four kilometers per second per megaparsic.
• 19:23
  Speaker 2: Yep, give a take. Well that's right.
• 19:28
  Speaker 3: You know, when I was a young astronomer keep saying
• 19:31
  Speaker 3: this back in the seventies, there were two The estimates
• 19:36
  Speaker 3: of that number were out by a factor of two.
• 19:39
  Speaker 3: There was one group said it's fifty kilometers per second
• 19:42
  Speaker 3: per mega parsec and other group said it's one hundred
• 19:44
  Speaker 3: kilometers per second megaparsec. And look what we've got with
• 19:47
  Speaker 3: the Hubble telescope and other instruments. We've got basically the
• 19:50
  Speaker 3: average of those two, which is quite neat really, but
• 19:54
  Speaker 3: we still got some uncertainty.
• 19:55
  Speaker 1: There was also this conflict, wasn't they that they were
• 20:00
  Speaker 1: I couldn't figure out the answer for. But we did
• 20:02
  Speaker 1: a story about them, figuring out that the conflict was
• 20:05
  Speaker 1: actually normal, and we you know, that's within acceptable parameters.
• 20:10
  Speaker 1: I think it did. Yeah, Okay, do we answer all
• 20:14
  Speaker 1: this question? I think we did. Yeah. Oh, I did
• 20:18
  Speaker 1: look up something else. How powerful was the Big Bang?
• 20:21
  Speaker 1: Greater than ten to the sixty eight rules?
• 20:25
  Speaker 2: Okay, that's what you call a bag.
• 20:29
  Speaker 1: That's a big, big, big, big, big big bang. But
• 20:32
  Speaker 1: we just shouldn't it a big bangs? Good number?
• 20:35
  Speaker 2: Turned to the sixty eight duels?
• 20:37
  Speaker 1: Yes, yeah, put that on your calculator and see what happens.
• 20:43
  Speaker 1: Thank Louid Julian, I hope you will. Let's answer one
• 20:47
  Speaker 1: more question before we finish up today, and this is
• 20:49
  Speaker 1: a question with forty seven parts. Hi Professor Fred and
• 20:53
  Speaker 1: Andrew Peter here from San Diego, California. I have a
• 20:57
  Speaker 1: dual question about dark energy. Under standing is that dark
• 21:01
  Speaker 1: energy is causing our universe to expand also, we have
• 21:05
  Speaker 1: an observable part of the universe where light is able
• 21:08
  Speaker 1: to reach us, and an unobservable part of the universe. Funny,
• 21:11
  Speaker 1: have we already talked about this, but all these questions
• 21:15
  Speaker 1: kind of dovetailed. Question one, is it feasible that the
• 21:19
  Speaker 1: unobservable part of the universe contains enough matter to act
• 21:22
  Speaker 1: gravitationally on the observable universe, thus causing the expansion? And
• 21:27
  Speaker 1: question two, which we'll get back to, same question. Within
• 21:30
  Speaker 1: the context of the multi sphere, could universes other than
• 21:34
  Speaker 1: our own be gravitationally impacting the expansion of our universe?
• 21:38
  Speaker 1: Love your show, keep up the great work, Thank you, Peter.
• 21:42
  Speaker 1: Question one, is it feasible that the unobservable part of
• 21:46
  Speaker 1: our universe contains enough matter to act gravitationally on the
• 21:50
  Speaker 1: observa observable universe, thus causing the expansion.
• 21:55
  Speaker 3: Yes, once again we've got to unpick what we mean
• 21:59
  Speaker 3: by the explod So Peter says, my understanding is that
• 22:04
  Speaker 3: dark energy is causing our universe to expand, and that's
• 22:07
  Speaker 3: not the case as we've just described. It's the Big
• 22:09
  Speaker 3: Bang that caused the universe to expand, but dark energy
• 22:12
  Speaker 3: is what's causing the expansion to accelerate to get faster.
• 22:17
  Speaker 1: It's EASi it confused now, isn't it, Because it is
• 22:19
  Speaker 1: absolutely not. This is an event with a lot of
• 22:22
  Speaker 1: moving parts.
• 22:24
  Speaker 2: Yes, as you'd expect. It's a universe after all.
• 22:27
  Speaker 3: But what Peter says is correct because we, as we've
• 22:33
  Speaker 3: just said, there are you know, there are parts of
• 22:35
  Speaker 3: the universe well beyond thirteen point eight billion light years
• 22:40
  Speaker 3: which we can't see because what we run into is
• 22:42
  Speaker 3: the cosmic microwave background radiation the flash of the Big Bang,
• 22:45
  Speaker 3: So we know there's universe beyond that.
• 22:47
  Speaker 2: But we can't see it.
• 22:49
  Speaker 3: And Peter's suggestion is it feasible that the unobservable part
• 22:54
  Speaker 3: of the universe contains enough matter to act gravitationally on
• 22:57
  Speaker 3: the observable universe and thus causing the expansion. It's actually
• 23:02
  Speaker 3: thus causing the acceleration of the expansion. That is one
• 23:06
  Speaker 3: of the theories that people have looked at exactly that
• 23:08
  Speaker 3: that are we in a kind of local bubble where
• 23:12
  Speaker 3: the density is low compared with what is outside the
• 23:17
  Speaker 3: boundary that we can see where the density might be higher,
• 23:21
  Speaker 3: and hence having a gravitational effect on our local bubble.
• 23:25
  Speaker 3: It's certainly a you know, a conjecture that is raised
• 23:29
  Speaker 3: by by astrophysicists and cosmologists.
• 23:32
  Speaker 2: So pieces on the right.
• 23:34
  Speaker 3: Track there and then question two, the same question within
• 23:37
  Speaker 3: the context of the multiverse. Could universes other than our
• 23:40
  Speaker 3: own gravitationally be gravitationally impacting the expansion of our universe?
• 23:45
  Speaker 3: And I think that is also something that's considered. One
• 23:50
  Speaker 3: of the reasons why people think there might be multiverses.
• 23:55
  Speaker 3: It is that gravity itself is compared with the other
• 24:02
  Speaker 3: three fundamental forces in nature.
• 24:06
  Speaker 2: It is incredibly weak.
• 24:08
  Speaker 3: So the fundamental forces are the strong and weak nuclear forces,
• 24:12
  Speaker 3: things that ald atoms together, the electromagnetic force causes chemical reactions,
• 24:16
  Speaker 3: and photons so that we can talk to each other.
• 24:19
  Speaker 3: Those are the three which are best known. Gravity is
• 24:23
  Speaker 3: the fourth fundamental force, but it is gazillions of times
• 24:27
  Speaker 3: weaker than the other three. Some people suggest that maybe
• 24:32
  Speaker 3: that is because it is leaking into other universes. Hence
• 24:36
  Speaker 3: the idea of a multiverse scenario. That is very speculative.
• 24:40
  Speaker 3: We don't have any hard evidence that points towards a multiverse.
• 24:44
  Speaker 3: But yes, once again, maybe there are gravitational influences coming
• 24:49
  Speaker 3: from the outside of our universe, whatever that means, because
• 24:51
  Speaker 3: of the universe by definition means everything you can observe
• 24:54
  Speaker 3: or understand, so it is possible.
• 24:57
  Speaker 2: So I think pieces.
• 24:59
  Speaker 3: You know, is questions are well well directed. He's on
• 25:02
  Speaker 3: the right track.
• 25:04
  Speaker 1: Yeah, I think, as you said, there's no direct evidence
• 25:08
  Speaker 1: whatsoever of multiverses. But we've said it before. Mathematically it's plausible, it's.
• 25:15
  Speaker 2: Possible, that's right.
• 25:16
  Speaker 3: Yeah, a lot of things are mathematically possible that you
• 25:20
  Speaker 3: don't see in reality.
• 25:22
  Speaker 1: And how much of the universe can we not see?
• 25:24
  Speaker 1: Is it like seventy five percent or something? No idea,
• 25:28
  Speaker 1: We don't know.
• 25:29
  Speaker 2: We don't know how big ideas could be infinite, We
• 25:32
  Speaker 2: don't know. Ye, all we know is what we can see.
• 25:36
  Speaker 1: It's crazy town, isn't it when it is?
• 25:39
  Speaker 2: Yeah, it is, that's right. It's keeps you in a job,
• 25:46
  Speaker 2: yes it does.
• 25:48
  Speaker 1: It keeps me at a job, that's yeah. But that's yeah.
• 25:52
  Speaker 1: That's when the critics come out. We've got all you
• 25:54
  Speaker 1: blokes trying to figure out and ladies, what's going on.
• 25:57
  Speaker 1: You've been working on it for hundreds of years and
• 25:59
  Speaker 1: you still don't know the answer.
• 26:00
  Speaker 2: So we still don't know.
• 26:01
  Speaker 3: The good news is that notice paying me now, so
• 26:05
  Speaker 3: that's all right, so you don't have to worry about that.
• 26:09
  Speaker 1: It's a cost free analysis. Now there you go.
• 26:11
  Speaker 2: You get it. All free. That's right, ladies, and job
• 26:13
  Speaker 2: this all comes to you free.
• 26:15
  Speaker 1: Yes, it does, all right. So I think we covered
• 26:19
  Speaker 1: everything there, Thank you, Peter. A great set of questions
• 26:23
  Speaker 1: all up. Some really intrigue in some of those as well,
• 26:27
  Speaker 1: which is really good. But as I've said many times,
• 26:30
  Speaker 1: we need some more questions. So if you can get
• 26:33
  Speaker 1: online to our website and click on the ask Me
• 26:35
  Speaker 1: Anything tab at the top of our page, send us
• 26:39
  Speaker 1: text or audio questions. We certainly could use some more
• 26:42
  Speaker 1: audio questions. We get a lot from people who might
• 26:45
  Speaker 1: ask ten at a time. Obviously we can't run them
• 26:48
  Speaker 1: all consecutively otherwise no one else gets a bite. But
• 26:51
  Speaker 1: if you've thought about asking a question and you haven't
• 26:54
  Speaker 1: got around to it yet, don't be scared. We don't
• 26:57
  Speaker 1: buy what we do bite, but don't worry about that.
• 26:59
  Speaker 1: It's harmless. We're not venomous. But you can send it
• 27:03
  Speaker 1: in through space Nuts podcast dot com or space nuts
• 27:06
  Speaker 1: dot io and click on that tab and send us
• 27:10
  Speaker 1: your question or just a comment. I mean, if you
• 27:12
  Speaker 1: want to add a comment, we can throw that into
• 27:15
  Speaker 1: the show. It's nice to have all these different voices
• 27:17
  Speaker 1: on the air, so yes, send him into a stamt
• 27:21
  Speaker 1: forage to tell us who you are and where you're from.
• 27:23
  Speaker 1: I think I've already said that. We are done, Fred,
• 27:25
  Speaker 1: Thank you so very very much.
• 27:27
  Speaker 2: It's a great pleasure. Andrew and I will do it
• 27:30
  Speaker 2: again sometime.
• 27:31
  Speaker 1: I hope so too, maybe in a week, maybe more,
• 27:33
  Speaker 1: maybe less. You just now it's all to do with
• 27:37
  Speaker 1: scheduling and availability and what our wives are doing at
• 27:42
  Speaker 1: any particular time. That's the most significant factor. Thanks Fred,
• 27:45
  Speaker 1: will see us soon. Cheers for no Bubba, Professor Fred Watson,
• 27:50
  Speaker 1: Astronomer at Large. And thanks to Hue in the studio
• 27:52
  Speaker 1: who couldn't be with us today because he's unobservable. And
• 27:57
  Speaker 1: from me Andrew Duntry, thanks to your company for you
• 28:00
  Speaker 1: on the next episode of Space Nuts. Bye bye Spacenuts.
• 28:04
  Speaker 1: You'll be listening to the Space Nuts podcast available at
• 28:09
  Speaker 1: Apple Podcasts, Spotify, iHeartRadio, or your favorite podcast player.
• 28:14
  Speaker 2: You can also stream on demand at bites dot com.
• 28:17
  Speaker 1: This has been another quality podcast production from nights dot Com.