In this engaging Q&A episode of Space Nuts, join host Andrew Dunkley and astronomer Fred Watson Watson as they tackle a variety of fascinating questions from listeners. From the peculiarities of Martian days to the mysteries of black holes and the galactic centre, this episode is filled with enlightening discussions that are sure to spark curiosity about the cosmos.
In this episode:
- John asks about the implications of Mars' longer day length on human biology and potential adaptations for future colonists.
- Dan inquires about the growth of black holes, exploring how quickly they can develop into supermassive entities and what happens when there’s nothing left to consume.
- Young Thomas, just 11 years old, poses several intriguing questions about the galactic centre, including whether it can swallow all stars and planets in the galaxy, and the limits of a black hole's gravitational reach.
- Paul reflects on historical discoveries in astronomy, specifically how Harlow Shapley determined our Sun's position within the Milky Way, challenging the long-held belief that it was at the centre.
Join Andrew and Fred Watson as they explore these thought-provoking questions and more, encouraging listeners to continue their journey of exploration and discovery in the universe.
Become a supporter of this podcast: https://www.spreaker.com/podcast/space-nuts-astronomy-insights-cosmic-discoveries--2631155/support (https://www.spreaker.com/podcast/space-nuts-astronomy-insights-cosmic-discoveries--2631155/support?utm_source=rss&utm_medium=rss&utm_campaign=rss) .
(00:00) This is a Q and A edition where we take audience questions
(02:16) When and if Mars is populated with humans, how would we work with longer day
(08:50) Andrew: How astronauts deal with gravity when they land on Earth
(11:47) Dan from the Gold coast has some questions about black holes
(12:51) Fred: How fast do black holes grow? Dan asks fundamental astrophysics question
(18:17) Fred asks five questions about black holes from Thomas Reid, 11
(22:03) Thomas asks if black holes can swallow up all stars and planets
(24:31) Final question comes from Paul from Las Vegas
(26:42) It was actually 1919 when that discovery was made
(34:24) We continue to receive great questions from great listeners and long may it continue
Episode link: https://play.headliner.app/episode/34693771?utm_source=youtube
00:00:00 --> 00:00:01 Hello again and thank you for joining us
00:00:02 --> 00:00:03 on another episode of Space Nuts. This
00:00:03 --> 00:00:06 is a Q&A edition where we take audience
00:00:06 --> 00:00:08 questions, we put them on paper, and
00:00:08 --> 00:00:11 then we put them on a roll that goes on
00:00:11 --> 00:00:14 a little thing in a bathroom.
00:00:14 --> 00:00:16 Or we could answer them. We can do that.
00:00:16 --> 00:00:19 Uh coming up today, we have uh questions
00:00:19 --> 00:00:22 uh from John about Martian days. The
00:00:22 --> 00:00:25 length of a Martian day. It's close, but
00:00:25 --> 00:00:27 is it close enough to Earth's standard?
00:00:27 --> 00:00:31 We'll discuss that. Uh, the growth of a
00:00:31 --> 00:00:34 black hole has been uh brought up again.
00:00:34 --> 00:00:37 Uh, we've got a um a uh question from an
00:00:37 --> 00:00:39 11-year-old named Thomas. Hi, Thomas. He
00:00:39 --> 00:00:42 wants to talk about the galactic center.
00:00:42 --> 00:00:45 And Paul is asking our uh about our
00:00:45 --> 00:00:47 galactic location. So, we'll deal with
00:00:47 --> 00:00:50 all of that today on this episode of
00:00:50 --> 00:00:51 Space Nuts.
00:00:51 --> 00:00:56 >> 15 seconds. Guidance is internal. 10 9
00:00:56 --> 00:00:59 ignition sequence start. Space Nuts.
00:00:59 --> 00:01:01 >> 5 4 3 2
00:01:01 --> 00:01:04 >> 1 2 3 4 5 5 4 3 2 1
00:01:04 --> 00:01:05 >> Space Nuts.
00:01:05 --> 00:01:08 >> Astronauts report. It feels good.
00:01:08 --> 00:01:10 >> Joining us again to sort all of that out
00:01:10 --> 00:01:13 is Professor Fred Watson, astronomer at
00:01:13 --> 00:01:14 large. Hello, Fred.
00:01:14 --> 00:01:16 >> Hello, Andrew. Good to see you again.
00:01:16 --> 00:01:18 >> Good to see you, too.
00:01:18 --> 00:01:20 >> Yes. Despite the hole in my head.
00:01:20 --> 00:01:23 >> Yeah. Yeah. It doesn't look any better
00:01:23 --> 00:01:24 than the last time I show you.
00:01:24 --> 00:01:26 >> It doesn't, does it?
00:01:26 --> 00:01:28 >> No. I mean, you know, it's only been
00:01:28 --> 00:01:30 minutes. You'd think it would have
00:01:30 --> 00:01:32 improved by now.
00:01:32 --> 00:01:34 >> That's what happens when you walk into a
00:01:34 --> 00:01:37 when you walk into a closed screen door.
00:01:37 --> 00:01:37 >> Yeah.
00:01:37 --> 00:01:38 >> In the dark,
00:01:38 --> 00:01:40 >> it hurts.
00:01:40 --> 00:01:44 >> Now, that's why they have stuff um on on
00:01:44 --> 00:01:46 glass sliding doors. You know, that
00:01:46 --> 00:01:48 that's a standard safety standard
00:01:48 --> 00:01:50 required these days so that you know the
00:01:50 --> 00:01:51 door is there.
00:01:51 --> 00:01:52 >> Yeah.
00:01:52 --> 00:01:54 But when it's nighttime and it's a
00:01:54 --> 00:01:56 screen door, not not many excuses left
00:01:56 --> 00:01:58 there, Fred. Really?
00:01:58 --> 00:02:00 >> Only stupidity, I think, is the is the
00:02:00 --> 00:02:03 last one. But that's that's my excuse
00:02:03 --> 00:02:05 many, many times.
00:02:05 --> 00:02:07 >> Yeah. Well, like I said before, we've
00:02:08 --> 00:02:09 all done it.
00:02:09 --> 00:02:11 >> Uh shall we try and answer these
00:02:11 --> 00:02:11 questions?
00:02:11 --> 00:02:12 >> We should.
00:02:12 --> 00:02:14 >> Okay, let's go to question one. This one
00:02:14 --> 00:02:18 comes from John. Uh we know that the
00:02:18 --> 00:02:20 Martian day is 39 minutes longer than an
00:02:20 --> 00:02:23 Earth Day. That's about 4 and 1/2 hours
00:02:23 --> 00:02:27 a week. Uh when and if Mars is populated
00:02:27 --> 00:02:30 with humans, how would we work with the
00:02:30 --> 00:02:32 longer day/week?
00:02:32 --> 00:02:35 Would human biology tend to keep to the
00:02:35 --> 00:02:38 24-hour day or would we adapt to a
00:02:38 --> 00:02:41 longer dayight cycle? Thanks. Love the
00:02:41 --> 00:02:43 show and have been a listener since you
00:02:43 --> 00:02:45 started. Wow, you've got a lot of spare
00:02:45 --> 00:02:49 time, John. Uh thank you so much uh for
00:02:49 --> 00:02:51 sending your question in and hope all is
00:02:51 --> 00:02:55 well. Uh I love this question because it
00:02:55 --> 00:02:58 you've got a planet that is close enough
00:02:58 --> 00:03:00 for us to get to in the not too distant
00:03:00 --> 00:03:02 future. Probably
00:03:02 --> 00:03:04 not a permanent settlement, but a
00:03:04 --> 00:03:07 rotating settlement of some kind will be
00:03:07 --> 00:03:09 the initial stages of humans being on
00:03:09 --> 00:03:11 Mars.
00:03:11 --> 00:03:15 and yet you've got an extra 39 minutes a
00:03:15 --> 00:03:18 day to deal with. What is going to be
00:03:18 --> 00:03:20 the impact?
00:03:20 --> 00:03:22 >> Um I think we've already
00:03:22 --> 00:03:26 >> have um a lot of data on this because
00:03:26 --> 00:03:27 the
00:03:27 --> 00:03:28 >> we've already talked about this once
00:03:28 --> 00:03:31 before in the dead dark past came up
00:03:31 --> 00:03:31 again. Yeah.
00:03:31 --> 00:03:34 >> Yeah. because of the the um um rover
00:03:34 --> 00:03:36 drivers.
00:03:36 --> 00:03:40 >> Uh they um people the people who are uh
00:03:40 --> 00:03:42 in command of if I can put it that way
00:03:42 --> 00:03:43 because they don't actually drive them
00:03:44 --> 00:03:46 directly but in command of the the
00:03:46 --> 00:03:48 rovers on Mars and the two active NASA
00:03:48 --> 00:03:51 ones at the moment are Curiosity and
00:03:51 --> 00:03:52 Perseverance.
00:03:52 --> 00:03:58 uh they adapt to a 20 to 24 hours 39
00:03:58 --> 00:04:01 minutes day uh and do it quite
00:04:02 --> 00:04:05 successfully as far as I've been able to
00:04:05 --> 00:04:06 work out.
00:04:06 --> 00:04:09 >> Well, I hope so.
00:04:09 --> 00:04:10 >> Yeah. Otherwise, there might be a pile
00:04:10 --> 00:04:13 up on Mars. Um, and in fact, the reason
00:04:13 --> 00:04:14 why I said they don't actually drive
00:04:14 --> 00:04:17 them is because the the rovers
00:04:17 --> 00:04:19 themselves have got to be to some extent
00:04:19 --> 00:04:22 autonomous because of the the the delay
00:04:22 --> 00:04:25 in in signal time to get between Mars
00:04:25 --> 00:04:28 and the Earth. You can't have video
00:04:28 --> 00:04:29 coming back from your rover and a
00:04:29 --> 00:04:31 steering wheel so that you respond to
00:04:31 --> 00:04:33 that because you'd have a sort of 20 or
00:04:33 --> 00:04:36 30 minute delay probably before
00:04:36 --> 00:04:39 >> uh before um you you turn before the
00:04:39 --> 00:04:41 wheels turned on on the rover.
00:04:41 --> 00:04:44 >> I would I would imagine that the the
00:04:44 --> 00:04:48 manual driving of a rover from Earth on
00:04:48 --> 00:04:50 Mars would be damn near impossible
00:04:50 --> 00:04:52 because even your images would be out of
00:04:52 --> 00:04:53 sync with
00:04:53 --> 00:04:54 >> everything's out of sync. That's right.
00:04:54 --> 00:04:56 So you see, oh, there's a rock coming
00:04:56 --> 00:04:58 up. That was 40 minutes ago.
00:04:58 --> 00:05:01 >> I'll turn left now.
00:05:01 --> 00:05:03 >> Oops.
00:05:03 --> 00:05:08 >> Yeah. Um so so the the rovers drive
00:05:08 --> 00:05:12 themselves basically uh with a lot of um
00:05:12 --> 00:05:15 assistance and monitoring from Earth uh
00:05:15 --> 00:05:18 in order to see what's coming up and see
00:05:18 --> 00:05:21 what the onboard computers are doing in
00:05:21 --> 00:05:23 terms of what route they're taking
00:05:23 --> 00:05:26 through the rocks and debris on Mars.
00:05:26 --> 00:05:29 uh and um so but those people as I
00:05:29 --> 00:05:32 understand it do go on to uh this 24
00:05:32 --> 00:05:36 hours and 39 minutes day length uh I
00:05:36 --> 00:05:38 think it's near enough to our 24 hours
00:05:38 --> 00:05:39 that I think they adapt quite quickly
00:05:39 --> 00:05:41 from my recollection of our previous
00:05:42 --> 00:05:44 conversation about this Andrew
00:05:44 --> 00:05:47 >> yeah I if I remember rightly we were
00:05:47 --> 00:05:48 talking about the fact that if you're
00:05:48 --> 00:05:51 going to stay on Mars long term you
00:05:51 --> 00:05:55 would have to adapt
00:05:55 --> 00:05:59 um you wouldn't adapt naturally
00:05:59 --> 00:06:01 at all. You you'd have to take catnaps
00:06:01 --> 00:06:05 or something like that to to catch up um
00:06:05 --> 00:06:08 or something to that effect.
00:06:08 --> 00:06:11 >> Well, it Yes. So, your circadian rhythms
00:06:11 --> 00:06:12 would they'd be under stress. They
00:06:12 --> 00:06:14 they'd change.
00:06:14 --> 00:06:17 >> Um um and I suppose you'd have a
00:06:17 --> 00:06:19 permanent feeling of jet lag probably.
00:06:19 --> 00:06:21 Probably what it feels like.
00:06:21 --> 00:06:23 >> It would be tough. I read an article uh
00:06:23 --> 00:06:26 last weekend which I I found fascinating
00:06:26 --> 00:06:30 and it was um detailing how the 8hour
00:06:30 --> 00:06:33 night cycle that humans have like going
00:06:33 --> 00:06:36 to bed for 8 hours is a myth.
00:06:36 --> 00:06:37 >> Yes.
00:06:37 --> 00:06:40 >> And that um it was it was actually
00:06:40 --> 00:06:42 something invented by a mattress company
00:06:42 --> 00:06:45 back in 1938. Have you heard this?
00:06:45 --> 00:06:46 >> No. Yes.
00:06:46 --> 00:06:49 >> I I I do know that we used to sleep
00:06:49 --> 00:06:50 twice in the night with it.
00:06:50 --> 00:06:52 >> That's right. So, you go to bed at like
00:06:52 --> 00:06:54 9:00
00:06:54 --> 00:06:56 >> and you'd sleep for 4 hours and then
00:06:56 --> 00:06:58 you'd get up for 2 hours and you'd do
00:06:58 --> 00:06:59 stuff
00:06:59 --> 00:07:01 >> like stuff we can't talk about on this
00:07:01 --> 00:07:04 podcast, but other stuff like um
00:07:04 --> 00:07:08 >> they cited a couple of um famous people
00:07:08 --> 00:07:10 um whose names have dropped straight out
00:07:10 --> 00:07:14 of my head. Um, William Shakespeare
00:07:14 --> 00:07:17 >> uh apparently wrote a lot of his famous
00:07:17 --> 00:07:20 works between 1 and 3 in the morning
00:07:20 --> 00:07:22 when he got up and then he go back to
00:07:22 --> 00:07:25 bed for 4 hours. And Bethovven did the
00:07:26 --> 00:07:27 same thing with some of his symphonies.
00:07:27 --> 00:07:30 He wrote some of the best works that he
00:07:30 --> 00:07:35 ever created at 3:00 in the morning um
00:07:35 --> 00:07:37 during his wake time between his two
00:07:37 --> 00:07:41 sleeps. Yeah. So the 8hour sleep
00:07:41 --> 00:07:44 that we have at night was an invention
00:07:44 --> 00:07:46 apparently to sell mattresses.
00:07:46 --> 00:07:48 That's what I'm told. I look I haven't
00:07:48 --> 00:07:52 confirmed or denied that but it seems it
00:07:52 --> 00:07:55 seems possible I suppose. Well, yes. I I
00:07:55 --> 00:08:00 think I think we have we've I think um
00:08:00 --> 00:08:02 there's been evidence from, you know,
00:08:02 --> 00:08:04 the earliest times,
00:08:04 --> 00:08:06 uh the times when people truly were
00:08:06 --> 00:08:08 ancient peoples back thousands of years
00:08:08 --> 00:08:10 ago, uh that that's how they lived their
00:08:10 --> 00:08:12 lives, exactly as you've said. And maybe
00:08:12 --> 00:08:14 there were the last vestigages of that
00:08:14 --> 00:08:15 were
00:08:15 --> 00:08:17 >> keeping going in Shakespeare's time and
00:08:17 --> 00:08:20 then in Beethoven's time. Um
00:08:20 --> 00:08:22 there weren't that many clocks around
00:08:22 --> 00:08:23 then. There were some, but not that
00:08:23 --> 00:08:25 many. It wasn't like you had a
00:08:26 --> 00:08:27 smartwatch by your bedside or anything
00:08:28 --> 00:08:30 like that. So, uh it would be a natural
00:08:30 --> 00:08:34 rhythm that they would use uh to, you
00:08:34 --> 00:08:36 know, to to sleep and wake up.
00:08:36 --> 00:08:37 >> Yes. And if you're natural,
00:08:37 --> 00:08:39 modernization certainly messed us up,
00:08:39 --> 00:08:40 hasn't it?
00:08:40 --> 00:08:41 >> Yeah. Yeah, that's right. I think in
00:08:41 --> 00:08:42 that case it has.
00:08:42 --> 00:08:45 >> And I think uh on Mars it will be um it
00:08:45 --> 00:08:48 will be a pretty difficult thing. I I
00:08:48 --> 00:08:48 imagine
00:08:48 --> 00:08:51 >> it may be. So, um maybe I can just
00:08:51 --> 00:08:54 sidestep here slightly, Andrew, because
00:08:54 --> 00:08:58 um I would very much like to know uh
00:08:58 --> 00:09:00 what answer one of our listeners would
00:09:00 --> 00:09:02 give to that. And that's Dr. Heidi
00:09:02 --> 00:09:05 Deblock, who's I think based in Houston,
00:09:05 --> 00:09:07 if I remember rightly, who is a
00:09:07 --> 00:09:11 basically a space medic. Uh and um it
00:09:11 --> 00:09:13 will be very interesting to hear her
00:09:13 --> 00:09:16 take on how humans will adapt to that.
00:09:16 --> 00:09:18 And if I may, she was in touch with us
00:09:18 --> 00:09:20 recently to comment on one of our
00:09:20 --> 00:09:22 earlier questions. Would it be all right
00:09:22 --> 00:09:23 if I read that?
00:09:23 --> 00:09:25 >> And that was when we were talking about
00:09:25 --> 00:09:28 how people deal with um gravity when
00:09:28 --> 00:09:30 they get back on Earth after being out
00:09:30 --> 00:09:31 in space for a while.
00:09:31 --> 00:09:33 >> Correct. Yes, that's right.
00:09:33 --> 00:09:37 >> Uh she says, um, "I just finished the
00:09:37 --> 00:09:40 July 5th Space Nuts and wanted to help
00:09:40 --> 00:09:41 answer the question about how the
00:09:41 --> 00:09:43 astronauts feel when they land back on
00:09:43 --> 00:09:45 Earth. Of course, I haven't experienced
00:09:45 --> 00:09:47 it in person, but have worked with
00:09:47 --> 00:09:49 plenty of astronauts at landing in
00:09:49 --> 00:09:51 particular. All of our physiology
00:09:51 --> 00:09:54 changes in space as we are designed for
00:09:54 --> 00:09:57 1G. Some astronauts are pretty good when
00:09:57 --> 00:09:58 they land, especially those who are on
00:09:58 --> 00:10:01 the shuttle and in space for short time
00:10:01 --> 00:10:04 for a sorry a 4A short time. Some had
00:10:04 --> 00:10:07 significant problems. They stem from the
00:10:07 --> 00:10:10 orthostatic hypotension as a result from
00:10:10 --> 00:10:12 the cardiovascular changes. Some of the
00:10:12 --> 00:10:14 changes in the inner ear with balance
00:10:14 --> 00:10:16 and knowing where you physically are,
00:10:16 --> 00:10:19 some mild weaknesses, etc. These changes
00:10:20 --> 00:10:22 are more exaggerated with long duration
00:10:22 --> 00:10:23 flight in the International Space
00:10:23 --> 00:10:26 Station. The vision problems are called
00:10:26 --> 00:10:30 SANS, SNS, which is an acronym for
00:10:30 --> 00:10:33 spaceflight associated neuroccular
00:10:33 --> 00:10:36 syndrome. Our lab is studying that as
00:10:36 --> 00:10:38 well. That's a whole other fascinating
00:10:38 --> 00:10:40 issue.
00:10:40 --> 00:10:42 I could tell you some fun stories about
00:10:42 --> 00:10:44 astronauts and how weird some of them
00:10:44 --> 00:10:46 feel when they get back. Maybe we need
00:10:46 --> 00:10:47 to get Heidi on the show.
00:10:48 --> 00:10:49 >> Maybe we do.
00:10:49 --> 00:10:52 >> Yeah. No, that's um that's uh she has
00:10:52 --> 00:10:54 another interesting comment actually
00:10:54 --> 00:10:57 about the uh about the uh Voyager Golden
00:10:57 --> 00:10:59 Record, but we might talk about that
00:10:59 --> 00:11:00 another time.
00:11:00 --> 00:11:01 >> Fair enough. Yeah. All right. Thank you,
00:11:01 --> 00:11:03 Heidi. That was fascinating. Yeah. Um
00:11:04 --> 00:11:05 what a what an amazing job working with
00:11:06 --> 00:11:08 all those incredible people
00:11:08 --> 00:11:10 trying to figure out how to deal with
00:11:10 --> 00:11:13 the zerog problem. But uh on Mars the
00:11:13 --> 00:11:15 gravity will also be an issue. So um
00:11:16 --> 00:11:17 there's there's a heck of a lot that
00:11:17 --> 00:11:21 needs to be sorted out before we um
00:11:21 --> 00:11:24 >> put people down there because it it it's
00:11:24 --> 00:11:25 so such a long trip to get there. It's
00:11:25 --> 00:11:27 not like you can go ah no this is no
00:11:27 --> 00:11:28 good and come straight back. It's not
00:11:28 --> 00:11:30 going to be that simple.
00:11:30 --> 00:11:31 >> No, that's right. Once you're on your
00:11:31 --> 00:11:33 way, you're on your way. And the only
00:11:33 --> 00:11:35 way back is to keep going.
00:11:35 --> 00:11:37 >> Yeah, exactly. Thanks for the question,
00:11:37 --> 00:11:40 John. Uh, well asked. And, uh, yeah,
00:11:40 --> 00:11:42 it's not going to be a snack, that's for
00:11:42 --> 00:11:44 sure. Let's, uh, move on to our next
00:11:44 --> 00:11:48 question from Dan. Hello, gentlemen. Dan
00:11:48 --> 00:11:50 from the Gold Coast here. Uh, now, I
00:11:50 --> 00:11:53 know you've been asked a million
00:11:53 --> 00:11:56 questions about black holes. Uh, but I
00:11:56 --> 00:11:57 do have a quick two-parter, and I'm
00:11:58 --> 00:11:59 hoping it's something you've never had
00:11:59 --> 00:12:02 to answer before. really quickly from
00:12:02 --> 00:12:05 the point when a black hole is born,
00:12:05 --> 00:12:06 birth, created, whatever you want to
00:12:06 --> 00:12:09 call it. Uh how quickly is that growing
00:12:09 --> 00:12:11 to become a let's say super massive
00:12:11 --> 00:12:12 black hole or just something a lot
00:12:12 --> 00:12:16 bigger? Um or is that not how black
00:12:16 --> 00:12:18 holes work and I'm not understanding it
00:12:18 --> 00:12:22 properly? two, uh, hypothetically, if
00:12:22 --> 00:12:24 there's no matter or energy or anything
00:12:24 --> 00:12:28 surrounding the black hole to take in
00:12:28 --> 00:12:31 and let's say eat, uh, is the black hole
00:12:31 --> 00:12:33 still going to grow? Is there more to
00:12:33 --> 00:12:36 the black hole growing than I
00:12:36 --> 00:12:39 understand? Um, yeah, hopefully that
00:12:39 --> 00:12:40 made sense and hopefully it's worth
00:12:40 --> 00:12:43 answering. Love the show. Love you guys
00:12:43 --> 00:12:45 work. Cheers. Bye.
00:12:45 --> 00:12:47 >> Thank you, Dan. Uh, nice to hear from
00:12:47 --> 00:12:50 you. Uh yeah, a couple of questions in
00:12:50 --> 00:12:52 that one. Um we never talk about black
00:12:52 --> 00:12:55 holes, but we will today. Uh speed of
00:12:55 --> 00:12:59 growth. Um that's an interesting one. Uh
00:12:59 --> 00:13:01 given that we're starting to think that
00:13:01 --> 00:13:06 there were some absolutely enormous
00:13:06 --> 00:13:09 um black holes in the early universe.
00:13:09 --> 00:13:13 Um and and that they're looking for more
00:13:13 --> 00:13:14 and more evidence to see what was going
00:13:14 --> 00:13:17 on early on. Um, but we've got some
00:13:17 --> 00:13:21 gargantuan ones still around. Uh, so how
00:13:21 --> 00:13:24 fast did they get that big? And I I I'm
00:13:24 --> 00:13:26 starting to think, Fred, it wouldn't be
00:13:26 --> 00:13:28 a stock standard approach.
00:13:28 --> 00:13:31 Maybe not. Maybe not. Uh, but well, I
00:13:31 --> 00:13:34 mean, Dan's asking uh one of the
00:13:34 --> 00:13:35 fundamental questions of astrophysics at
00:13:35 --> 00:13:37 the moment. This is a very hot topic.
00:13:37 --> 00:13:39 Yeah. And what set the cat among the
00:13:39 --> 00:13:41 pigeons and made it a hot topic is the
00:13:41 --> 00:13:44 James Web Space Telescope because um
00:13:44 --> 00:13:48 until that came along, the idea was that
00:13:48 --> 00:13:51 as basically as Dan suggests, black
00:13:51 --> 00:13:54 holes were formed in the early universe
00:13:54 --> 00:13:58 by exploding stars that um collapsed at
00:13:58 --> 00:14:00 the end of their lives to to form a
00:14:00 --> 00:14:02 black hole. the core would collapse to a
00:14:02 --> 00:14:05 black hole and that then over over
00:14:05 --> 00:14:07 billions of years that black hole would
00:14:08 --> 00:14:10 grow and eventually in our own epoch
00:14:10 --> 00:14:13 today 13.8 billion years after the after
00:14:13 --> 00:14:16 the big bang uh you have super massive
00:14:16 --> 00:14:17 black holes at the center of every
00:14:18 --> 00:14:21 galaxy. That was the old wisdom. But the
00:14:21 --> 00:14:22 James Webb telescope has turned that
00:14:22 --> 00:14:25 completely on its head because we have
00:14:25 --> 00:14:28 serious evidence of super massive black
00:14:28 --> 00:14:32 holes within the first 500 million years
00:14:32 --> 00:14:34 of the universe's existence. And that's
00:14:34 --> 00:14:39 too quick for or too short a time for
00:14:39 --> 00:14:42 this um you know the this slow accretion
00:14:42 --> 00:14:46 of of stuff uh as being the um the the
00:14:46 --> 00:14:49 the growth mechanism for black holes. Uh
00:14:49 --> 00:14:50 it's too too short a time for that to be
00:14:50 --> 00:14:55 the case. Uh so either our ideas of how
00:14:55 --> 00:14:59 fast they gobble up matter is wrong and
00:14:59 --> 00:15:01 they gobble up faster matter a lot
00:15:01 --> 00:15:02 faster than we thought. And we actually
00:15:02 --> 00:15:05 covered a story on this I think about
00:15:05 --> 00:15:07 four or five episodes ago because there
00:15:07 --> 00:15:10 are some scientists who came to
00:15:10 --> 00:15:11 conclusion that one of the things that
00:15:12 --> 00:15:15 we thought limited how fast a black hole
00:15:15 --> 00:15:17 can gobble stuff up uh was actually
00:15:17 --> 00:15:20 invalid under certain circumstances.
00:15:20 --> 00:15:23 >> So that's that's one avenue of research
00:15:23 --> 00:15:26 that's come from the James Web telescope
00:15:26 --> 00:15:28 showing us that we've got these super
00:15:28 --> 00:15:29 massive black holes in the early
00:15:29 --> 00:15:31 universe. But the other one is the the
00:15:31 --> 00:15:33 idea of the little pink dots or the
00:15:33 --> 00:15:35 little red dots as they're called. And
00:15:36 --> 00:15:39 these are thought to be basically just
00:15:39 --> 00:15:43 clouds of gas, hydrogen gas, which are
00:15:43 --> 00:15:46 directly feeding a black hole that may
00:15:46 --> 00:15:48 have been formed in the Big Bang. In
00:15:48 --> 00:15:49 other words, you didn't have to have
00:15:49 --> 00:15:52 star formation and then stars blowing up
00:15:52 --> 00:15:55 to create back black holes in order to
00:15:55 --> 00:15:57 kick this process off. the big bang
00:15:57 --> 00:15:59 itself might have kicked off the process
00:15:59 --> 00:16:00 of black hole formation by producing
00:16:00 --> 00:16:03 these things that we call primordial
00:16:03 --> 00:16:07 black holes. Um and they may have turned
00:16:07 --> 00:16:10 out to be able to grow very quickly uh
00:16:10 --> 00:16:13 by immersing themselves simply in big
00:16:13 --> 00:16:15 clouds of hydrogen and gobbling it all
00:16:16 --> 00:16:16 up.
00:16:16 --> 00:16:20 >> Yeah. Of course uh when they run out of
00:16:20 --> 00:16:23 stuff they can't grow. Is that right?
00:16:23 --> 00:16:25 >> That's right. So, that's part two of
00:16:25 --> 00:16:28 Dan's question. Uh, what happens when
00:16:28 --> 00:16:29 there's nothing there for them to eat?
00:16:29 --> 00:16:31 And they become what we call quiescent
00:16:31 --> 00:16:33 black holes. They they they don't do
00:16:33 --> 00:16:36 anything. They're there. Uh, and they're
00:16:36 --> 00:16:39 still things that um if if a cloud of
00:16:39 --> 00:16:42 hydrogen strayed by, they they might
00:16:42 --> 00:16:44 seize it by their own gravity and pull
00:16:44 --> 00:16:45 it in. Yeah.
00:16:45 --> 00:16:47 >> But, um, they're not going to go out
00:16:47 --> 00:16:49 roaming through the um roaming through
00:16:49 --> 00:16:51 the universe looking for stuff to
00:16:52 --> 00:16:53 accrete. In other words, looking for a
00:16:53 --> 00:16:54 snap.
00:16:54 --> 00:16:56 >> Yeah. I used to work with a guy whose
00:16:56 --> 00:16:58 nickname was queercent black hole. He
00:16:58 --> 00:17:03 was there, but he didn't do anything.
00:17:03 --> 00:17:08 >> Yes, I think I know who you mean.
00:17:08 --> 00:17:11 Yeah. Anyway, quent black holes are
00:17:11 --> 00:17:13 basically what what Dan has described.
00:17:13 --> 00:17:15 But the first part of his question is
00:17:15 --> 00:17:17 absolutely asking the same questions
00:17:17 --> 00:17:20 that today's astrophysicists are. It's
00:17:20 --> 00:17:22 one whose answer we don't know. But the
00:17:22 --> 00:17:24 contentus will emerge over the next
00:17:24 --> 00:17:26 probably not very long because we're
00:17:26 --> 00:17:28 getting so much data from the James Webb
00:17:28 --> 00:17:29 telescope
00:17:29 --> 00:17:30 >> uh that I think it'll be quite soon
00:17:30 --> 00:17:32 before this whole issue is resolved.
00:17:32 --> 00:17:34 >> I would think sorry
00:17:34 --> 00:17:36 >> I was just going to say when when there
00:17:36 --> 00:17:38 is hard evidence of a primordial black
00:17:38 --> 00:17:40 hole being discovered, one that was
00:17:40 --> 00:17:43 created in the Big Bang, then that'll be
00:17:43 --> 00:17:45 Nobel Prizewinning science when we get
00:17:45 --> 00:17:47 to that stage.
00:17:47 --> 00:17:48 >> But it won't be us.
00:17:48 --> 00:17:50 >> Indeed. I was going to suggest that um
00:17:50 --> 00:17:53 black holes are probably like humans.
00:17:53 --> 00:17:54 Consumption will decide how big they
00:17:54 --> 00:17:56 get.
00:17:56 --> 00:17:57 >> Maybe that's right.
00:17:57 --> 00:17:58 >> Yeah. Yeah.
00:17:58 --> 00:18:01 >> We'll have to wait and see. All right,
00:18:01 --> 00:18:03 Dan. Uh hopefully we covered that for
00:18:03 --> 00:18:05 you adequately. Thanks for sending in
00:18:05 --> 00:18:07 the question. This is Space Nuts with
00:18:07 --> 00:18:12 Andrew Dunley and Professor Fred Watson.
00:18:12 --> 00:18:15 >> Three, two, one.
00:18:15 --> 00:18:18 >> Space nuts. Our next question, Fred,
00:18:18 --> 00:18:21 comes from Thomas Reed. Thomas is 11
00:18:21 --> 00:18:23 years old. He says, "Something has been
00:18:23 --> 00:18:25 troubling me in books I've read. They
00:18:25 --> 00:18:28 say that the centers of galaxies are
00:18:28 --> 00:18:30 very big black holes, and I have a few
00:18:30 --> 00:18:32 questions about them, but I'm only an
00:18:32 --> 00:18:35 11year-old kid, so the questions might
00:18:35 --> 00:18:36 sound silly, but here they are. Now, we
00:18:36 --> 00:18:38 got five questions, Fred, so we can be
00:18:38 --> 00:18:41 brief on them on them, unless you want
00:18:41 --> 00:18:43 to sit here another couple of hours. Um,
00:18:43 --> 00:18:45 if Jy was here, we would be a couple of
00:18:45 --> 00:18:46 hours.
00:18:46 --> 00:18:49 Um, can the galactic centers swallow all
00:18:49 --> 00:18:51 the stars and planets in the galaxy? How
00:18:51 --> 00:18:54 big are the galactic centers or do we
00:18:54 --> 00:18:56 not know? Uh, if they can swallow up all
00:18:56 --> 00:18:59 the stars and planets, is there a limit?
00:18:59 --> 00:19:01 If there is a limit, what is it? And if
00:19:02 --> 00:19:04 there is a limit, what happens when the
00:19:04 --> 00:19:06 limit is reached? Thank you for taking
00:19:06 --> 00:19:08 the time to read this. And I would love
00:19:08 --> 00:19:09 it if you could reply. Well, we are
00:19:10 --> 00:19:13 going to reply right now, Thomas. Um,
00:19:13 --> 00:19:15 yeah, it's uh it's great that uh
00:19:15 --> 00:19:18 somebody so young is is taking a keen
00:19:18 --> 00:19:20 interest in something so mysterious as a
00:19:20 --> 00:19:23 as a black hole. Uh we want to start at
00:19:23 --> 00:19:25 the top. Can the galactic center swallow
00:19:25 --> 00:19:27 all the stars and planets in the galaxy?
00:19:27 --> 00:19:30 >> Well, so the answer is no. Um so the
00:19:30 --> 00:19:32 galaxies are very big. Um ours is about
00:19:32 --> 00:19:35 100 light years across. Uh, black
00:19:35 --> 00:19:38 holes have a a kind of sphere of
00:19:38 --> 00:19:41 influence um, which gravitationally
00:19:41 --> 00:19:43 stretches to the edge of the galaxy, but
00:19:43 --> 00:19:45 by the time you get there, the gravity
00:19:45 --> 00:19:47 of the black hole is very very weak
00:19:47 --> 00:19:50 indeed. Uh, and so it's only in the
00:19:50 --> 00:19:53 central region of a galaxy where you
00:19:53 --> 00:19:55 could get material being swallowed up
00:19:55 --> 00:19:58 uh, to create this activity that we talk
00:19:58 --> 00:19:59 about when we talk about active black
00:19:59 --> 00:20:03 holes. uh where there's uh an accretion
00:20:03 --> 00:20:05 disc, a disc of material swirling around
00:20:05 --> 00:20:08 it and these jets that point basically
00:20:08 --> 00:20:09 at right angles to the accretion disc.
00:20:09 --> 00:20:11 Jets of material traveling at nearly the
00:20:11 --> 00:20:13 speed of light. Quite extraordinary.
00:20:13 --> 00:20:16 >> So, um that's all great and a black hole
00:20:16 --> 00:20:18 is like a factory or a furnace doing
00:20:18 --> 00:20:20 that, but it's it stretch is not very
00:20:20 --> 00:20:24 far. Uh it's measured in light years,
00:20:24 --> 00:20:25 but not in hundreds of thousands of
00:20:25 --> 00:20:27 light years, which you'd have to be to
00:20:27 --> 00:20:29 to grab everything in the galaxy. So the
00:20:29 --> 00:20:32 answer is no. Uh the galactic center
00:20:32 --> 00:20:34 black hole cannot swallow all the stars
00:20:34 --> 00:20:36 and planets in the galaxy.
00:20:36 --> 00:20:39 >> So So Thomas can sleep well tonight. Um
00:20:39 --> 00:20:41 how big are the galactic centers? Do we
00:20:41 --> 00:20:43 know how big?
00:20:43 --> 00:20:47 >> We do. Yes, we do because we can measure
00:20:47 --> 00:20:50 we can measure the uh the speed of
00:20:50 --> 00:20:54 rotation of stuff swirling around a
00:20:54 --> 00:20:56 black hole if it's an active one.
00:20:56 --> 00:20:58 >> Yeah. And that directly tells you the
00:20:58 --> 00:21:01 mass of the black hole. Um because the
00:21:01 --> 00:21:03 bigger the black hole the faster the
00:21:03 --> 00:21:07 stuff is going. And so um in terms of
00:21:07 --> 00:21:10 you know if the if if by big Thomas
00:21:10 --> 00:21:13 means what's their mass uh we can we can
00:21:13 --> 00:21:16 measure them quite accurately. Now
00:21:16 --> 00:21:18 because we can measure their mass we can
00:21:18 --> 00:21:20 also work out their event horizon
00:21:20 --> 00:21:24 diameter or radius. The event horizon is
00:21:24 --> 00:21:26 that sort of imaginary sphere around a
00:21:26 --> 00:21:29 black hole beyond which light cannot
00:21:29 --> 00:21:32 escape and so it would appear as a dark
00:21:32 --> 00:21:35 sphere. Um so the event horizon is the
00:21:35 --> 00:21:36 point of no return for anything going
00:21:36 --> 00:21:39 into a black hole and it's also the
00:21:39 --> 00:21:42 point of no escape for for light waves.
00:21:42 --> 00:21:45 Uh so we can knowing the mass of a black
00:21:45 --> 00:21:48 hole we can calculate how big that event
00:21:48 --> 00:21:50 horizon would be. And some of the super
00:21:50 --> 00:21:52 massive ones are really very big.
00:21:52 --> 00:21:55 They're measured in light years, tens of
00:21:55 --> 00:21:56 light years perhaps for the super
00:21:56 --> 00:21:57 massive black holes.
00:21:57 --> 00:22:00 >> Yeah, that it's it's a level of enormity
00:22:00 --> 00:22:01 that you just struggle to get your head
00:22:02 --> 00:22:02 around.
00:22:02 --> 00:22:04 >> Yeah. I suppose in terms of the rest of
00:22:04 --> 00:22:06 Thomas's questions, you've basically
00:22:06 --> 00:22:08 answered it with the answer to the first
00:22:08 --> 00:22:10 question cuz he's asking if they can
00:22:10 --> 00:22:12 swallow all the stars and planets. Is
00:22:12 --> 00:22:14 there a limit? If there is a limit, what
00:22:14 --> 00:22:17 is it? Uh and if there is a limit, what
00:22:17 --> 00:22:19 happens when the limit is reached? Well,
00:22:19 --> 00:22:23 the limit is probably the local area of
00:22:23 --> 00:22:25 the center of the galaxy and what's
00:22:25 --> 00:22:27 available to eat.
00:22:27 --> 00:22:28 >> Yes, that's right. So the the limit the
00:22:28 --> 00:22:33 limiting factor is um basically the the
00:22:33 --> 00:22:35 what you might call the grasp of the
00:22:35 --> 00:22:37 black hole. How how far it can reach to
00:22:37 --> 00:22:40 pull something in. And that is dependent
00:22:40 --> 00:22:43 on how fast the objects are moving. So
00:22:43 --> 00:22:45 you can have some stars and there are
00:22:45 --> 00:22:47 some we've observed them uh with
00:22:47 --> 00:22:50 infrared radiation that are comfortably
00:22:50 --> 00:22:54 in orbit uh around the the black hole at
00:22:54 --> 00:22:56 the center of our own galaxy which are
00:22:56 --> 00:22:58 not being pulled in. They're orbiting
00:22:58 --> 00:23:00 and that's because their speed is enough
00:23:00 --> 00:23:02 to keep them out of the out of the grasp
00:23:02 --> 00:23:05 of the black hole. um their distances
00:23:05 --> 00:23:07 from the black hole are measured, you
00:23:07 --> 00:23:09 know, in not two dissimilar units from
00:23:09 --> 00:23:11 the from the solar system, sort of half
00:23:11 --> 00:23:14 a light day or something like that, you
00:23:14 --> 00:23:17 know, light light day. That's that's the
00:23:17 --> 00:23:18 sort of measures that we're talking
00:23:18 --> 00:23:19 about.
00:23:19 --> 00:23:22 >> Um which probably denies what I just
00:23:22 --> 00:23:25 said a few minutes ago about um some
00:23:25 --> 00:23:27 black hole event horizons being tens of
00:23:27 --> 00:23:29 light years. I don't think they are. I
00:23:29 --> 00:23:30 think they're smaller than that.
00:23:30 --> 00:23:32 >> Okay. I've thought of a way to explain
00:23:32 --> 00:23:34 it to Thomas. say, "Uh, Thomas, you've
00:23:34 --> 00:23:37 won a competition and you can go to
00:23:37 --> 00:23:40 McDonald's and eat everything you want."
00:23:40 --> 00:23:43 Absolutely. Just keep eating until you
00:23:43 --> 00:23:45 know the cows come home. However, you
00:23:45 --> 00:23:47 aren't allowed to move from wherever
00:23:47 --> 00:23:49 you're standing and you can only eat
00:23:49 --> 00:23:52 what's within reach.
00:23:52 --> 00:23:54 Once you run out of food, you stop
00:23:54 --> 00:23:57 growing. And you're the black hole, by
00:23:57 --> 00:23:59 the way. How's that for an analogy?
00:23:59 --> 00:24:00 >> It's a nice one. I like it.
00:24:00 --> 00:24:03 >> Yes. Yeah. Because the your reach is the
00:24:03 --> 00:24:04 sort of gravitational
00:24:04 --> 00:24:04 >> Yeah.
00:24:04 --> 00:24:06 >> force that you can exert. Yeah, it's a
00:24:06 --> 00:24:07 good way of putting it, Andrew. Well
00:24:07 --> 00:24:08 done. You should be on the reach.
00:24:08 --> 00:24:11 >> I try to think on 11y old level, but I'm
00:24:11 --> 00:24:12 I'm thinking Thomas was probably much
00:24:12 --> 00:24:15 brighter at 11 than I was.
00:24:15 --> 00:24:17 >> Struggle to get to 11. So do I.
00:24:17 --> 00:24:19 >> Yes. Thanks, Thomas. That was really
00:24:20 --> 00:24:21 terrific. Thanks for sending it in. And
00:24:21 --> 00:24:25 uh keep on listening.
00:24:25 --> 00:24:27 >> Swiftity
00:24:27 --> 00:24:30 base here. The angle has landed. Space
00:24:30 --> 00:24:31 Nuts.
00:24:31 --> 00:24:35 >> Final question, Fred, comes from Paul.
00:24:35 --> 00:24:37 Hello, Space Nuts. Paul here from sunny
00:24:37 --> 00:24:38 Bris Vegas, where it's currently
00:24:38 --> 00:24:40 bucketing down in what is being
00:24:40 --> 00:24:45 described as a rare rain occurrence.
00:24:45 --> 00:24:47 Anyway,
00:24:47 --> 00:24:50 I am currently looking through a very
00:24:50 --> 00:24:53 old book of mine. Guess it's old
00:24:53 --> 00:24:56 compared to the students I teach. It was
00:24:56 --> 00:24:58 published back in 1978. I think I got in
00:24:58 --> 00:25:01 in 1980 from uh an uncle of mine, Uncle
00:25:01 --> 00:25:03 Jim. Thank you very much. It's called
00:25:03 --> 00:25:05 Stars and Planets, and it's probably
00:25:05 --> 00:25:09 what got me into the whole field of
00:25:09 --> 00:25:11 astronomy in the first place, at least
00:25:11 --> 00:25:16 my interest in astronomy, obviously. Uh
00:25:16 --> 00:25:18 very very grateful. I'm on the page
00:25:18 --> 00:25:20 where it's talking about how the
00:25:20 --> 00:25:24 American astronomer Harlo Shepley
00:25:24 --> 00:25:28 used the 1.5 m reflector on top of Mount
00:25:28 --> 00:25:31 Wilson in California
00:25:31 --> 00:25:35 to work out that our sun is not at the
00:25:35 --> 00:25:37 center of our galaxy as was previously
00:25:37 --> 00:25:39 thought, but is about 2/3 of the way to
00:25:40 --> 00:25:43 the edge. Could you please give us some
00:25:43 --> 00:25:48 idea how he actually managed to do that?
00:25:48 --> 00:25:52 Was it something about the density of
00:25:52 --> 00:25:55 stars? I mean, how many stars in the
00:25:55 --> 00:25:57 field of view uh when you point it one
00:25:57 --> 00:25:59 way compared to the other? How did he do
00:25:59 --> 00:26:01 it? I'm really curious. And I know I
00:26:01 --> 00:26:03 could Google it, but I'd rather hear it
00:26:03 --> 00:26:07 from you guys. So, thanks in advance.
00:26:07 --> 00:26:10 love the show and dare I say, keep up
00:26:10 --> 00:26:13 the good work. Cheers.
00:26:13 --> 00:26:15 >> Cheers, Paul. Thanks for sending that
00:26:15 --> 00:26:18 in, uh, sending the question in and, uh,
00:26:18 --> 00:26:21 we don't know the answer. So,
00:26:21 --> 00:26:24 but we're going to Google it. No. Um,
00:26:24 --> 00:26:28 1978, Stars and Planets. Uh, I tried to
00:26:28 --> 00:26:30 look it up. There are teen books named
00:26:30 --> 00:26:31 Stars and Planets.
00:26:31 --> 00:26:32 >> Yeah.
00:26:32 --> 00:26:34 >> So, I haven't been able to, you know,
00:26:34 --> 00:26:36 distinguish one from the other as yet.
00:26:36 --> 00:26:39 So um uh yeah, you'll have to do some
00:26:39 --> 00:26:41 fishing to find the book that Paul was
00:26:41 --> 00:26:44 talking about. But he wanted to know
00:26:44 --> 00:26:48 about the man who decided or discovered
00:26:48 --> 00:26:50 that the sun was not the center of
00:26:50 --> 00:26:53 everything. Uh which was a common belief
00:26:54 --> 00:26:55 back in the day.
00:26:55 --> 00:26:58 >> It was um it was actually 1919 when that
00:26:58 --> 00:26:59 discovery was made. Um
00:26:59 --> 00:27:01 >> is it was it that recent?
00:27:01 --> 00:27:04 >> Yeah. Um I I it's one of my favorite
00:27:04 --> 00:27:06 astronomical discoveries, which is why I
00:27:06 --> 00:27:07 didn't need to go to Google to look it
00:27:07 --> 00:27:11 up. Um so it goes back to the time of
00:27:12 --> 00:27:16 William Hershel, uh who was a
00:27:16 --> 00:27:19 German turned British astronomer,
00:27:19 --> 00:27:22 worked late in the 18th century and
00:27:22 --> 00:27:23 early in the 19th century. He discovered
00:27:23 --> 00:27:26 the planet Uranus in 1781.
00:27:26 --> 00:27:28 But what he was doing when he discovered
00:27:28 --> 00:27:30 Uranus was actually mapping the Milky
00:27:30 --> 00:27:34 Way. He was observing uh the the Milky
00:27:34 --> 00:27:36 Way in a very systematic way with a
00:27:36 --> 00:27:39 relatively small telescope. So he sort
00:27:39 --> 00:27:42 of counting stars in the field of view
00:27:42 --> 00:27:44 of his telescope and then moving the
00:27:44 --> 00:27:46 telescope a bit further along the Milky
00:27:46 --> 00:27:48 Way. Counting stars again, how many he
00:27:48 --> 00:27:51 could see in the field of view and doing
00:27:51 --> 00:27:52 that and doing it. He couldn't do it all
00:27:52 --> 00:27:54 the way around the Milky Way because
00:27:54 --> 00:27:55 there's parts of it that he he could
00:27:55 --> 00:27:56 never see because they're in the
00:27:56 --> 00:27:58 southern hemisphere. But he got round
00:27:58 --> 00:28:01 most of it. And what he discovered was
00:28:01 --> 00:28:04 that the star counts are pretty even all
00:28:04 --> 00:28:06 the way around.
00:28:06 --> 00:28:09 >> And so that led him to build the
00:28:09 --> 00:28:12 hypothesis that the stars are in a sort
00:28:12 --> 00:28:15 of flattened disc, which is correct, uh,
00:28:15 --> 00:28:17 but that we're very near the middle,
00:28:17 --> 00:28:20 which is not correct. And the reason why
00:28:20 --> 00:28:23 he got that erroneous answer was that
00:28:23 --> 00:28:25 when you look through a I think it was a
00:28:25 --> 00:28:28 7-in telescope if I remember rightly a
00:28:28 --> 00:28:30 telescope of that size at the Milky Way,
00:28:30 --> 00:28:33 the stars that you see are all
00:28:33 --> 00:28:36 relatively nearby. They're perhaps a
00:28:36 --> 00:28:38 thousand light years away or something
00:28:38 --> 00:28:40 like that, maybe a bit more, maybe a
00:28:40 --> 00:28:42 couple of thousand light years away in
00:28:42 --> 00:28:44 the plane of the Milky Way. And that's
00:28:44 --> 00:28:46 partly because the Milky Way is very
00:28:46 --> 00:28:48 dusty. Uh there's a lot of dust
00:28:48 --> 00:28:50 everywhere. It's probably better
00:28:50 --> 00:28:52 described as smoke, but we call it dust
00:28:52 --> 00:28:54 in the world of astronomy. And so that
00:28:54 --> 00:28:57 dust limits how far you can see. And so
00:28:57 --> 00:28:59 when you look at the Milky Way, it does
00:28:59 --> 00:29:01 look generally relatively even. There's
00:29:01 --> 00:29:03 one bit in the constellation of
00:29:03 --> 00:29:05 Sagittarius where it's it's brighter and
00:29:05 --> 00:29:07 that's because you are looking towards
00:29:07 --> 00:29:09 as we now know the galactic center. But
00:29:09 --> 00:29:12 um Hershel um he couldn't see that very
00:29:12 --> 00:29:13 well from the northern hemisphere
00:29:14 --> 00:29:16 anyway. But he did sort of discount that
00:29:16 --> 00:29:19 uh he said by and large it's the same
00:29:20 --> 00:29:21 count all the way around. So we must be
00:29:21 --> 00:29:25 in the middle. Uh roll on the the years
00:29:25 --> 00:29:28 and in 1919 Harlo Shappley a very gifted
00:29:28 --> 00:29:30 American astronomer although he did get
00:29:30 --> 00:29:33 one thing one big thing wrong. Uh but
00:29:33 --> 00:29:36 what he did was he was interested in
00:29:36 --> 00:29:38 objects that we call globular clusters.
00:29:38 --> 00:29:40 And so these are in fact they were named
00:29:40 --> 00:29:42 by William Hershel. He gave them that
00:29:42 --> 00:29:44 name clusters of stars that appear like
00:29:44 --> 00:29:49 a globe. Uh and uh her halos Shappley
00:29:49 --> 00:29:52 was uh obser he like he was interested
00:29:52 --> 00:29:54 in globular clusters. He noticed there
00:29:54 --> 00:29:59 were a lot of them in our skies. Uh they
00:29:59 --> 00:30:02 tended to be different sizes.
00:30:02 --> 00:30:04 Uh and he didn't know whether that was
00:30:04 --> 00:30:06 cuz they were all the same size and some
00:30:06 --> 00:30:08 were nearer than others or whether they
00:30:08 --> 00:30:10 were intrinsically different sizes. But
00:30:10 --> 00:30:12 what he did notice was that there's a
00:30:12 --> 00:30:15 concentration of them in the southern
00:30:16 --> 00:30:19 hemisphere sky. Uh he was observing from
00:30:19 --> 00:30:21 California, so he could see a fair swath
00:30:21 --> 00:30:23 of the southern hemisphere sky. But he
00:30:23 --> 00:30:26 he noticed that they were concentrated
00:30:26 --> 00:30:28 in that direction and that made him
00:30:28 --> 00:30:32 wonder if that was where the center of
00:30:32 --> 00:30:34 the galaxy lay rather than us being near
00:30:34 --> 00:30:38 the center. Uh but then his other step
00:30:38 --> 00:30:41 was that he recognized that within these
00:30:41 --> 00:30:43 globular clusters were something called
00:30:43 --> 00:30:46 clust they called them cluster variables
00:30:46 --> 00:30:49 stars that varied in a certain way on a
00:30:49 --> 00:30:52 with a periodicity of about a day. Uh
00:30:52 --> 00:30:55 today we call them rli variables and I
00:30:55 --> 00:30:56 actually started my astronomical
00:30:56 --> 00:30:58 research back in the 70s studying these
00:30:58 --> 00:31:03 things. uh rlari variables uh and they
00:31:03 --> 00:31:07 they are good because they've got a
00:31:07 --> 00:31:11 basically a known distance uh if you if
00:31:11 --> 00:31:13 you can see an RLI variable and identify
00:31:13 --> 00:31:16 it as one you know how intrinsically
00:31:16 --> 00:31:19 bright it is uh and then from that you
00:31:19 --> 00:31:21 can work out how far away it is. And so
00:31:21 --> 00:31:24 he found these variable stars in the
00:31:24 --> 00:31:27 globular clusters and recognized that he
00:31:27 --> 00:31:29 could draw a chart with the the globular
00:31:29 --> 00:31:32 clusters all at their correct distance
00:31:32 --> 00:31:34 on it, make a kind of three-dimensional
00:31:34 --> 00:31:37 map of the sky. And sure enough, um they
00:31:37 --> 00:31:40 concentrated around the galactic center
00:31:40 --> 00:31:43 around a point. Uh he actually got the
00:31:43 --> 00:31:45 answer wrong because his magnitude, his
00:31:45 --> 00:31:47 brightness that he had for the uh
00:31:47 --> 00:31:50 cluster variables was incorrect. uh and
00:31:50 --> 00:31:51 I can't remember what answer he got, but
00:31:52 --> 00:31:55 in modern parliament it's about 25
00:31:55 --> 00:31:58 light years. The cluster, the globular
00:31:58 --> 00:32:00 clusters themselves cluster around a
00:32:00 --> 00:32:03 point about 25 light years away,
00:32:03 --> 00:32:05 which is deeply hidden by the dust
00:32:05 --> 00:32:08 clouds in Sagittarius. So
00:32:08 --> 00:32:10 >> he figured out that that's where the
00:32:10 --> 00:32:12 center of the galaxy was. A brilliant
00:32:12 --> 00:32:14 piece of detective work. We know he was
00:32:14 --> 00:32:17 right. Uh what he was wrong about was uh
00:32:17 --> 00:32:21 he had a big discussion I think in 1923
00:32:21 --> 00:32:24 just before Hubble recognized that
00:32:24 --> 00:32:26 galaxies were big things a long way
00:32:26 --> 00:32:28 away. Uh Shappley was arguing that
00:32:28 --> 00:32:31 galaxies lie within our own Milky Way
00:32:31 --> 00:32:32 that they're small objects in our own
00:32:32 --> 00:32:36 Milky Way. And he was um arguing it was
00:32:36 --> 00:32:37 a public debate actually between
00:32:38 --> 00:32:40 Chappley and a guy called Hea Curtis. Uh
00:32:40 --> 00:32:42 Curtis had the answer right. He said
00:32:42 --> 00:32:44 they're big and a long way off. Uh
00:32:44 --> 00:32:46 Shappley said, "No, they're small and
00:32:46 --> 00:32:48 nearby." And it was very soon after that
00:32:48 --> 00:32:50 that Hubble produced that they're big
00:32:50 --> 00:32:52 and a long way proved that they're big
00:32:52 --> 00:32:53 and a long way off.
00:32:53 --> 00:32:54 >> Yeah.
00:32:54 --> 00:32:55 >> So Shappley was wrong in that, but he
00:32:55 --> 00:32:57 was right about the Galactic Center.
00:32:57 --> 00:33:00 Fantastic. Gee whiz. Um great question,
00:33:00 --> 00:33:04 Paul. And um yeah, if people are looking
00:33:04 --> 00:33:06 for that uh that book, Stars and
00:33:06 --> 00:33:09 Planets, uh it is out there. Uh, look,
00:33:09 --> 00:33:10 I've I've found a couple that were
00:33:10 --> 00:33:13 actually published around that time that
00:33:13 --> 00:33:15 Paul mentioned, but um not sure if
00:33:15 --> 00:33:17 they're the ones I I can't remember the
00:33:17 --> 00:33:19 author now um that he said, but
00:33:19 --> 00:33:20 >> I don't think he mentioned an author,
00:33:20 --> 00:33:21 did he?
00:33:21 --> 00:33:22 >> I thought he did, but uh No, he might
00:33:22 --> 00:33:25 have mentioned an uncle
00:33:25 --> 00:33:27 mention
00:33:27 --> 00:33:28 it.
00:33:28 --> 00:33:30 >> But um
00:33:30 --> 00:33:32 um so yeah, thanks Paul. Thanks for the
00:33:32 --> 00:33:34 the question. And um yeah, it's it's a
00:33:34 --> 00:33:37 fascinating um history in astronomy as
00:33:37 --> 00:33:39 we discover these things. I think one of
00:33:39 --> 00:33:40 my favorite
00:33:40 --> 00:33:43 >> moments I suppose in in astronomical
00:33:43 --> 00:33:45 history was when they discovered that
00:33:45 --> 00:33:48 our sun was a star.
00:33:48 --> 00:33:50 >> Yeah, that was a long long time ago.
00:33:50 --> 00:33:51 >> Yeah.
00:33:51 --> 00:33:53 >> But for a while there we didn't think of
00:33:54 --> 00:33:54 it like that.
00:33:54 --> 00:33:55 >> Thought it was something else. That's
00:33:55 --> 00:33:57 right. Something bit special.
00:33:57 --> 00:34:00 >> Yeah. Um, and and I I saw that on a BBC
00:34:00 --> 00:34:02 documentary many years ago, and I sat
00:34:02 --> 00:34:05 there and went, "Wow, I never thought
00:34:05 --> 00:34:07 about that cuz I've always known it to
00:34:07 --> 00:34:10 be a star, but for generations, they
00:34:10 --> 00:34:12 didn't."
00:34:12 --> 00:34:14 Quite quite intriguing. And why would
00:34:14 --> 00:34:16 you? It doesn't look like a star.
00:34:16 --> 00:34:20 >> That's That's right. Uh, it's uh it's
00:34:20 --> 00:34:24 clearly quite different from a star.
00:34:24 --> 00:34:25 >> Incredible. Thanks, Paul. Thanks for
00:34:25 --> 00:34:27 sending that in. And if you have a
00:34:27 --> 00:34:29 question for a thanks to all our
00:34:29 --> 00:34:31 senderiners, I've always wanted to say
00:34:31 --> 00:34:33 that uh for their questions. And if you
00:34:33 --> 00:34:34 would like to send a question, go to our
00:34:34 --> 00:34:37 website spaceenutspodcast.com
00:34:37 --> 00:34:39 or spacenuts.io
00:34:39 --> 00:34:42 and there's a little AMA tab at the top
00:34:42 --> 00:34:44 which stands for ask me anything. Not me
00:34:44 --> 00:34:48 personally, it's the royal me. And um
00:34:48 --> 00:34:50 just put your uh question in there. It
00:34:50 --> 00:34:52 can be text or audio. Don't forget to
00:34:52 --> 00:34:53 tell us who you are and where you're
00:34:53 --> 00:34:55 from and have a look around while you're
00:34:55 --> 00:34:57 there. Don't forget to leave a review at
00:34:57 --> 00:35:00 your favorite podcasting platform. We're
00:35:00 --> 00:35:02 all done. Thanks, Fred.
00:35:02 --> 00:35:05 >> A great pleasure, Andrew. We um we uh
00:35:05 --> 00:35:07 continue to get great questions from
00:35:07 --> 00:35:09 great listeners and long may it
00:35:09 --> 00:35:09 continue. Thank you.
00:35:10 --> 00:35:12 >> Yes, indeed. We we continue to solve and
00:35:12 --> 00:35:13 evolve.
00:35:13 --> 00:35:15 Um maybe not.
00:35:15 --> 00:35:18 >> I'm not evolving.
00:35:18 --> 00:35:20 >> When once you reach a certain certain
00:35:20 --> 00:35:22 age, evolving just is not part of the
00:35:22 --> 00:35:23 program.
00:35:23 --> 00:35:24 >> That's right.
00:35:24 --> 00:35:26 >> Yeah. Ask my mom in the internet. Uh,
00:35:26 --> 00:35:28 thanks Fred. We'll see you soon.
00:35:28 --> 00:35:29 >> Sounds great. Thanks.
00:35:29 --> 00:35:31 >> Professor Fred Watson, astronomer at
00:35:31 --> 00:35:32 large. And thanks to Hugh in the studio.
00:35:32 --> 00:35:35 He's just turned up. Um, we started 39
00:35:36 --> 00:35:38 minutes ago. And and um, Hugh set his
00:35:38 --> 00:35:41 clock to a Martian day. So that's why
00:35:41 --> 00:35:43 he's 39 minutes late. Boom. Boom. And
00:35:43 --> 00:35:45 from me, Andrew Dunley, thanks for your
00:35:45 --> 00:35:46 company. We'll see you on the next
00:35:46 --> 00:35:48 episode of Space Nuts. Bye-bye.
00:35:48 --> 00:35:51 >> Space Nuts. You've been listening to the
00:35:51 --> 00:35:54 Space Nuts podcast. Missing complete
00:35:54 --> 00:35:57 >> available at Apple Podcasts, Spotify,
00:35:57 --> 00:35:59 iHeart Radio, or your favorite podcast
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00:36:05 --> 00:36:09 podcast production from byes.com.