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.
(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
00:00:00 --> 00:00:02 Andrew Dunkley: Hello again and thank you for joining us on
00:00:02 --> 00:00:04 another episode of Space Nuts. This is a Q
00:00:04 --> 00:00:06 and A edition where we take audience
00:00:06 --> 00:00:09 questions. We put them on paper and then we
00:00:09 --> 00:00:11 put them on a roll that goes on a little
00:00:11 --> 00:00:14 thing in a bathroom. Or we could
00:00:14 --> 00:00:16 answer them. We can do that. Uh, coming up
00:00:16 --> 00:00:19 today we have questions, uh, uh,
00:00:19 --> 00:00:22 from John about Martian days. The length
00:00:22 --> 00:00:25 of a Martian day. It's close, but is it
00:00:25 --> 00:00:28 close enough to Earth standard? We'll discuss
00:00:28 --> 00:00:31 that. Uh, the growth of a black
00:00:31 --> 00:00:33 hole has been, uh, brought up again.
00:00:34 --> 00:00:36 Uh, we've got a, um, a question, uh,
00:00:36 --> 00:00:39 from an 11 year old named Thomas. Hi, Thomas.
00:00:39 --> 00:00:41 He wants to talk about the galactic centre.
00:00:42 --> 00:00:44 And Paul is asking our, uh, about
00:00:44 --> 00:00:47 our galactic location. So we'll deal with
00:00:47 --> 00:00:50 all of that today on this episode of Space
00:00:50 --> 00:00:51 Nuts.
00:00:51 --> 00:00:53 Professor Fred Watson: 15 seconds. Guidance is internal.
00:00:54 --> 00:00:56 10, 9. Ignition
00:00:56 --> 00:00:57 sequence start.
00:00:58 --> 00:00:59 Professor Fred Watson: Space Nuts.
00:00:59 --> 00:01:01 Professor Fred Watson: 5, 4, 3. 2. 1. 2, 3, 4,
00:01:02 --> 00:01:04 5, 5, 4, 3. Space
00:01:04 --> 00:01:07 Nuts astronauts report it feels good.
00:01:08 --> 00:01:11 Andrew Dunkley: Joining us again to sort all that out is
00:01:11 --> 00:01:13 Professor Fred Watson Watson, astronomer at
00:01:13 --> 00:01:14 large. Hello, Fred Watson.
00:01:14 --> 00:01:16 Professor Fred Watson: Hello, Andrew. Good to see you again.
00:01:16 --> 00:01:17 Andrew Dunkley: Uh, good to see you too.
00:01:18 --> 00:01:20 Professor Fred Watson: Yes. Despite the hole in my head.
00:01:20 --> 00:01:23 Andrew Dunkley: Yeah, yeah. It doesn't look any better than
00:01:23 --> 00:01:23 last time.
00:01:24 --> 00:01:25 Professor Fred Watson: It doesn't, does it?
00:01:26 --> 00:01:28 Andrew Dunkley: No, I mean, you know, it's only been
00:01:28 --> 00:01:30 minutes. You'd think it would have improved
00:01:30 --> 00:01:31 by now.
00:01:32 --> 00:01:34 Professor Fred Watson: That's what happens when you walk into a,
00:01:34 --> 00:01:36 when you walk into a closed screen door.
00:01:36 --> 00:01:37 Andrew Dunkley: Yeah.
00:01:37 --> 00:01:39 Professor Fred Watson: In the dark it hurts.
00:01:40 --> 00:01:43 Andrew Dunkley: Now that's why they have stuff, um, on,
00:01:43 --> 00:01:46 on glass sliding doors, you know,
00:01:46 --> 00:01:48 uh, that, 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 Professor Fred Watson: Yeah.
00:01:52 --> 00:01:54 Andrew Dunkley: But when it's nighttime and it's a screen
00:01:54 --> 00:01:56 door. Not, not many excuses left there,
00:01:56 --> 00:01:57 Fred Watson.
00:01:57 --> 00:02:00 Professor Fred Watson: Really only stupidity, I think is the,
00:02:00 --> 00:02:02 is the last one. But that's, that's
00:02:02 --> 00:02:04 my excuse many, many times.
00:02:05 --> 00:02:08 Andrew Dunkley: Yeah, well, we've all done it.
00:02:09 --> 00:02:11 Shall we try and answer these questions?
00:02:11 --> 00:02:12 Professor Fred Watson: We should.
00:02:12 --> 00:02:14 Andrew Dunkley: Okay, let's go to question one. This one
00:02:14 --> 00:02:16 comes from John.
00:02:16 --> 00:02:19 Uh, we know that the Martian Day is 39
00:02:19 --> 00:02:22 minutes longer than an Earth Day. That's
00:02:22 --> 00:02:25 about four and a half hours a week. Uh, when
00:02:25 --> 00:02:27 and if Mars is populated with humans,
00:02:28 --> 00:02:31 how would we work with the longer
00:02:31 --> 00:02:33 day, week? Would human
00:02:33 --> 00:02:36 biology tend to keep to the 24 hour
00:02:36 --> 00:02:38 day or would we adapt to a longer day,
00:02:38 --> 00:02:41 Night. Cycle. Cycle. Thanks. Love the show
00:02:41 --> 00:02:43 and have been a listener since you started.
00:02:43 --> 00:02:46 Wow, you've got a lot of spare time, John.
00:02:47 --> 00:02:49 Thank you so much, uh, for sending your
00:02:49 --> 00:02:52 question in and hope all is well. Uh,
00:02:52 --> 00:02:54 I love this question because
00:02:55 --> 00:02:58 you've got a planet that is close enough for
00:02:58 --> 00:03:00 us to get to in the not too distant future.
00:03:00 --> 00:03:03 Probably not a
00:03:03 --> 00:03:04 permanent settlement, but a rotating
00:03:04 --> 00:03:07 settlement of some kind will be the initial
00:03:07 --> 00:03:10 stages of humans being on Mars.
00:03:11 --> 00:03:14 And yet you've got an extra 39
00:03:14 --> 00:03:17 minutes a day to deal with what
00:03:17 --> 00:03:19 is going to be the impact.
00:03:20 --> 00:03:22 Professor Fred Watson: Um, I think we've already, we have
00:03:23 --> 00:03:25 um, a lot of data on this
00:03:25 --> 00:03:28 Andrew Dunkley: because the, we've already talked about this
00:03:28 --> 00:03:30 once before in the deep dark past. Quite a
00:03:30 --> 00:03:31 lot came up again.
00:03:31 --> 00:03:33 Professor Fred Watson: Yeah, yeah, because of the, the um,
00:03:34 --> 00:03:36 rover, um, drivers, they,
00:03:38 --> 00:03:41 the people who are uh, in command of,
00:03:41 --> 00:03:42 if I can put it that way, because they don't
00:03:42 --> 00:03:45 actually drive them directly but in command
00:03:45 --> 00:03:48 of the rovers on Mars and the two active
00:03:48 --> 00:03:50 NASA ones at the moment are Curiosity. Uh,
00:03:50 --> 00:03:53 and perseverance. Uh, they
00:03:53 --> 00:03:54 Adapt to uh,
00:03:56 --> 00:03:58 24 hours, 39 minutes day,
00:03:59 --> 00:04:02 and do it quite successfully
00:04:02 --> 00:04:05 as far as I've been able to work out.
00:04:06 --> 00:04:09 Andrew Dunkley: Well I hope so, yeah.
00:04:09 --> 00:04:11 Professor Fred Watson: Otherwise there might be a pile up on Mars.
00:04:11 --> 00:04:14 Um, and in fact the reason why I said they
00:04:14 --> 00:04:16 don't actually drive them is because the
00:04:16 --> 00:04:19 rovers themselves have got to be to some
00:04:19 --> 00:04:22 extent autonomous because of the delay
00:04:22 --> 00:04:25 in signal time to get between Mars and
00:04:26 --> 00:04:28 the Earth. You can't have video coming back
00:04:28 --> 00:04:30 from your rover and a steering wheel so that
00:04:30 --> 00:04:32 you respond to that because you'd have a sort
00:04:32 --> 00:04:35 of 20 or 30 minute delay probably before
00:04:36 --> 00:04:38 uh, before um, you turn, before
00:04:38 --> 00:04:41 the wheels turned on the rover.
00:04:41 --> 00:04:44 Andrew Dunkley: I would imagine that the manual
00:04:44 --> 00:04:47 driving of a rover from Earth
00:04:47 --> 00:04:50 on Mars would be damn near impossible because
00:04:51 --> 00:04:53 even your images would be out of sync with.
00:04:53 --> 00:04:54 Professor Fred Watson: Everything's out of sync. That's right.
00:04:54 --> 00:04:56 Andrew Dunkley: So you say, oh, there's a rock coming up.
00:04:56 --> 00:04:59 That was 40 minutes ago, I'll turn
00:04:59 --> 00:05:00 left now.
00:05:01 --> 00:05:02 Martin Berman Gorvine: Oops.
00:05:03 --> 00:05:03 Andrew Dunkley: Yeah.
00:05:03 --> 00:05:05 Professor Fred Watson: Ah, um,
00:05:06 --> 00:05:09 so the rovers drive themselves basically,
00:05:09 --> 00:05:12 uh, with a lot of assistance, um,
00:05:12 --> 00:05:15 and monitoring from Earth, uh, in order
00:05:15 --> 00:05:18 to see what's coming up and see what
00:05:19 --> 00:05:21 the onboard computers are doing in terms of
00:05:21 --> 00:05:23 what route they're taking through the rocks
00:05:23 --> 00:05:26 and debris on Mars. Ah, uh,
00:05:27 --> 00:05:29 um, but those people, as I understand
00:05:29 --> 00:05:32 it, do go on to uh, this 24
00:05:32 --> 00:05:35 hours and 39 minutes day length.
00:05:35 --> 00:05:37 Uh, I think it's nearing enough to our 24
00:05:37 --> 00:05:39 hours that I think they adapt quite quickly.
00:05:39 --> 00:05:41 From my recollection of our previous
00:05:41 --> 00:05:43 conversation about this Andrew.
00:05:44 --> 00:05:47 Andrew Dunkley: Yeah, if I remember rightly, we were talking
00:05:47 --> 00:05:49 about the fact that if you're going to stay
00:05:49 --> 00:05:51 on Mars long term you would
00:05:51 --> 00:05:53 have to adapt.
00:05:54 --> 00:05:57 Um, you wouldn't adapt naturally
00:05:58 --> 00:06:01 at all you'd have to take catnaps
00:06:01 --> 00:06:04 or something like that to catch up. Um,
00:06:05 --> 00:06:07 or something to that effect.
00:06:08 --> 00:06:11 Professor Fred Watson: Well, yes. So your circadian rhythms
00:06:11 --> 00:06:13 would, they'd be under stress, they'd change
00:06:15 --> 00:06:18 and I suppose you'd have a permanent feeling
00:06:18 --> 00:06:20 of jet lag. Probably what it feels like.
00:06:20 --> 00:06:23 Andrew Dunkley: It would be tough. I read an article, uh,
00:06:23 --> 00:06:26 last weekend which I found fascinating
00:06:26 --> 00:06:29 and it was, um, detailing how
00:06:29 --> 00:06:32 the eight hour night cycle
00:06:32 --> 00:06:34 that humans have, like going to bed for eight
00:06:34 --> 00:06:36 hours, is a myth.
00:06:36 --> 00:06:37 Professor Fred Watson: Yes.
00:06:37 --> 00:06:40 Andrew Dunkley: And that, um, it was actually
00:06:40 --> 00:06:42 something invented by a mattress company back
00:06:42 --> 00:06:45 in 1938. Have you heard this?
00:06:45 --> 00:06:48 Professor Fred Watson: No. Yes, I do know that
00:06:48 --> 00:06:50 we used to sleep twice in the night.
00:06:50 --> 00:06:53 Andrew Dunkley: That's right. So you go to bed at like 9 o'
00:06:53 --> 00:06:55 clock and you'd sleep for four hours
00:06:56 --> 00:06:58 and then you'd get up for two hours and you'd
00:06:58 --> 00:07:00 do stuff like, stuff we can't talk about on
00:07:00 --> 00:07:03 this podcast, but other stuff like,
00:07:03 --> 00:07:05 um, they cited a couple of,
00:07:07 --> 00:07:10 um, famous people, um, whose names have
00:07:10 --> 00:07:12 dropped straight out of my head. Um,
00:07:13 --> 00:07:15 William Shakespeare apparently wrote
00:07:16 --> 00:07:18 a lot of his famous works between
00:07:18 --> 00:07:21 1 and 3 in the morning when he got up and
00:07:21 --> 00:07:24 then he'd go back to bed for four hours. And,
00:07:24 --> 00:07:26 uh, Beethoven did the same thing with some of
00:07:26 --> 00:07:28 his symphonies. He wrote some of the
00:07:29 --> 00:07:31 best works that he ever created
00:07:32 --> 00:07:35 at 3 o' clock in the morning, um,
00:07:35 --> 00:07:37 during his wake time between his two sleeps.
00:07:38 --> 00:07:40 So the eight hour sleep
00:07:41 --> 00:07:44 that we have at night was an invention
00:07:44 --> 00:07:47 apparently, to sell mattresses. That's
00:07:47 --> 00:07:49 what I'm told. Look, I haven't confirmed or
00:07:49 --> 00:07:52 denied that, but it seems
00:07:52 --> 00:07:53 possible, I suppose.
00:07:54 --> 00:07:56 Professor Fred Watson: Well, yes, I think we have,
00:07:58 --> 00:08:00 uh, I think, um, there's been evidence
00:08:00 --> 00:08:02 from the earliest times,
00:08:04 --> 00:08:06 uh, the times when people truly were ancient
00:08:06 --> 00:08:08 peoples back thousands of years ago,
00:08:09 --> 00:08:10 uh, that that's how they lived their lives.
00:08:10 --> 00:08:13 Exactly as you've said. And maybe the last
00:08:13 --> 00:08:16 vestiges of that were keeping
00:08:16 --> 00:08:17 going in Shakespeare's time and then in
00:08:17 --> 00:08:20 Beethoven's time. Um, there
00:08:20 --> 00:08:22 weren't that many clocks around then. There
00:08:22 --> 00:08:24 were some, but not that many. It wasn't like
00:08:24 --> 00:08:27 you had a smart watch by your bedside or
00:08:27 --> 00:08:30 anything like that. So, uh, it would be a
00:08:30 --> 00:08:33 natural rhythm that they would use, uh,
00:08:34 --> 00:08:35 to sleep and wake up.
00:08:36 --> 00:08:38 Andrew Dunkley: Yes. Modernization certainly
00:08:38 --> 00:08:40 messed us up, hasn't it?
00:08:40 --> 00:08:41 Professor Fred Watson: Yeah, yeah, that's right. I think in that
00:08:41 --> 00:08:42 case it has.
00:08:42 --> 00:08:44 Andrew Dunkley: And I think, uh, on Mars, um,
00:08:45 --> 00:08:47 it will be a pretty difficult thing,
00:08:47 --> 00:08:49 Professor Fred Watson: I imagine it may be.
00:08:50 --> 00:08:53 So maybe I can just sidestep here slightly,
00:08:53 --> 00:08:56 Andrew, um, because I would very much like to
00:08:56 --> 00:08:58 know uh, what
00:08:58 --> 00:09:01 answer one of our listeners would give to
00:09:01 --> 00:09:03 that, and that's Dr. Heidi DeBlock who's
00:09:03 --> 00:09:06 I think based in Houston, if I remember
00:09:06 --> 00:09:09 rightly, who is basically a space medic.
00:09:09 --> 00:09:12 Uh, and um, uh, it will be very interesting
00:09:12 --> 00:09:15 to hear her take on how humans will adapt
00:09:15 --> 00:09:18 to that. And if I may, she was in touch with
00:09:18 --> 00:09:20 us recently to comment on one of our earlier
00:09:20 --> 00:09:23 questions. Would it be all right if I. Yeah.
00:09:23 --> 00:09:26 Andrew Dunkley: And that was when we were talking about how
00:09:26 --> 00:09:28 people deal with um, gravity when they
00:09:28 --> 00:09:30 get back on Earth after being out in space
00:09:30 --> 00:09:32 for a while, correct?
00:09:32 --> 00:09:35 Professor Fred Watson: Yes, that's right. Uh, she
00:09:35 --> 00:09:38 says, um, I just finished the July
00:09:38 --> 00:09:40 5th space nuts and wanted to help answer the
00:09:40 --> 00:09:42 question about how the astronauts feel when
00:09:42 --> 00:09:44 they land back on Earth. Of course I haven't
00:09:44 --> 00:09:47 experienced it in person, but have worked
00:09:47 --> 00:09:49 with plenty of astronauts at landing. In
00:09:49 --> 00:09:51 particular, all of our, uh, 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 the
00:09:58 --> 00:10:00 shuttle and in space. For short time.
00:10:01 --> 00:10:04 Sorry, for a short time. Some had significant
00:10:04 --> 00:10:07 problems. They stemmed from the orthostatic
00:10:07 --> 00:10:10 hypotension as a result from the
00:10:10 --> 00:10:13 cardiovascular changes, some of the changes
00:10:13 --> 00:10:15 in the inner ear with balance and knowing
00:10:15 --> 00:10:17 where you physically are, some mild
00:10:17 --> 00:10:20 weaknesses, et cetera. These changes are more
00:10:20 --> 00:10:23 exaggerated with long duration flight in the
00:10:23 --> 00:10:25 International Space Station. The vision
00:10:25 --> 00:10:28 problems are called SANS S A N S
00:10:28 --> 00:10:30 which is an acronym for Spaceflight
00:10:30 --> 00:10:32 Associated Neuro Ocular
00:10:33 --> 00:10:36 Syndrome. Our lab is studying that
00:10:36 --> 00:10:38 as well. That's a whole other fascinating
00:10:38 --> 00:10:41 issue. I could tell you some
00:10:41 --> 00:10:43 fun storeys about astronauts and how weird
00:10:43 --> 00:10:46 some of them feel when they get back. Maybe
00:10:46 --> 00:10:48 we need to get Heidi on the show. Maybe we
00:10:48 --> 00:10:50 do. Yeah, no, that's um,
00:10:51 --> 00:10:53 uh, she has another interesting comment
00:10:53 --> 00:10:56 actually about the, about the uh,
00:10:56 --> 00:10:58 Voyager Golden Record. But we might talk
00:10:58 --> 00:11:00 about that another time. Fair enough.
00:11:00 --> 00:11:02 Andrew Dunkley: Yeah. All right. Thank you, Heidi. That was
00:11:02 --> 00:11:02 fascinating.
00:11:02 --> 00:11:03 Professor Fred Watson: Yeah.
00:11:03 --> 00:11:06 Andrew Dunkley: Um, what an amazing job working with all
00:11:06 --> 00:11:09 those incredible people trying to
00:11:09 --> 00:11:11 figure out how to deal with the zero G
00:11:11 --> 00:11:13 problem. But uh, on Mars the gravity will
00:11:13 --> 00:11:16 also be an issue. So, um, there's
00:11:16 --> 00:11:19 a heck of a lot that needs to be sorted out
00:11:19 --> 00:11:22 before we um, put people down
00:11:22 --> 00:11:25 there. Because it's such a long trip to
00:11:25 --> 00:11:26 get there. It's not like you can go, uh, ah,
00:11:26 --> 00:11:28 no, this is no good and come straight back.
00:11:28 --> 00:11:30 Professor Fred Watson: It's not going to be that simple. That's
00:11:30 --> 00:11:32 right. Once you're on your way. On your way.
00:11:32 --> 00:11:34 And the only way back is to keep going.
00:11:34 --> 00:11:37 Andrew Dunkley: Yeah, exactly. Thanks for the question, John.
00:11:37 --> 00:11:40 Uh, well asked. And yeah, it's not
00:11:40 --> 00:11:43 going to be a snack, that's for sure. Let's,
00:11:43 --> 00:11:45 uh, move on to our, uh, next question from
00:11:45 --> 00:11:46 Dan.
00:11:47 --> 00:11:49 Martin Berman Gorvine: Hello gentlemen. Dan from the Gold coast
00:11:49 --> 00:11:51 here. Uh, now I know you've been
00:11:52 --> 00:11:55 asked a million questions about black holes,
00:11:55 --> 00:11:57 uh, but I do have a quick two parter and I'm
00:11:57 --> 00:11:59 hoping that's something you've never had to
00:11:59 --> 00:12:02 answer before. Really quickly, from the
00:12:02 --> 00:12:05 point when a black hole is born,
00:12:05 --> 00:12:07 birth, created, whatever you want to call it,
00:12:07 --> 00:12:10 uh, how quickly is that growing to become a,
00:12:10 --> 00:12:12 let's say, supermassive black hole or just
00:12:12 --> 00:12:13 something a lot bigger? Um,
00:12:14 --> 00:12:17 or is that not how black holes work and I'm
00:12:17 --> 00:12:19 not understanding it properly? Two,
00:12:21 --> 00:12:23 Hypothetically, uh, if there's no matter or
00:12:23 --> 00:12:25 energy or anything surrounding
00:12:26 --> 00:12:29 the black hole to take in and let's say
00:12:29 --> 00:12:32 eat, uh, is the black hole still going to
00:12:32 --> 00:12:34 grow? Is there more to the black hole growing
00:12:34 --> 00:12:36 than I understand?
00:12:37 --> 00:12:39 Um, yeah. Hopefully that made sense and
00:12:39 --> 00:12:41 hopefully it's worth answering. Love the
00:12:41 --> 00:12:44 show. Love you guys. Work. Cheers,
00:12:44 --> 00:12:45 bye.
00:12:45 --> 00:12:47 Andrew Dunkley: Thank you, Dan. Uh, nice to hear from you.
00:12:48 --> 00:12:50 Uh, yeah, a couple of questions in that one.
00:12:51 --> 00:12:53 Um, we never talk about black holes, but we
00:12:53 --> 00:12:56 will today. Ah, speed of growth.
00:12:56 --> 00:12:58 Um, that's an interesting one. Um,
00:12:59 --> 00:13:02 given that we're starting to think that there
00:13:02 --> 00:13:04 were some absolutely
00:13:04 --> 00:13:07 enormous, um, black holes in the
00:13:07 --> 00:13:09 early universe. Um,
00:13:10 --> 00:13:13 and, and they're looking
00:13:13 --> 00:13:14 for more and more evidence to see what was
00:13:14 --> 00:13:17 going on early on. Um, but we've got some
00:13:17 --> 00:13:19 gargantuan ones still around. Uh,
00:13:20 --> 00:13:22 so how fast did they get that big? And
00:13:22 --> 00:13:25 I, um, I'm starting to think, Fred Watson,
00:13:25 --> 00:13:27 it wouldn't be a stock standard approach.
00:13:28 --> 00:13:31 Professor Fred Watson: Maybe not, maybe not. Uh, but I mean,
00:13:31 --> 00:13:33 Dan's asking, uh, one of the
00:13:33 --> 00:13:35 fundamental questions of astrophysics at the
00:13:35 --> 00:13:38 moment. This is a very hot topic. Uh, and
00:13:38 --> 00:13:40 what set the cat among the pigeons and made
00:13:40 --> 00:13:42 it a hot topic is the James Webb Space
00:13:42 --> 00:13:45 Telescope. Because, um, until
00:13:45 --> 00:13:48 that came along, the idea was
00:13:48 --> 00:13:51 that as basically as Daniel suggests,
00:13:51 --> 00:13:54 black holes were formed in
00:13:54 --> 00:13:56 the early universe by exploding stars that,
00:13:56 --> 00:13:59 um, collapsed at the end of their lives
00:13:59 --> 00:14:02 to form a black hole. The core would collapse
00:14:02 --> 00:14:04 to a black hole and that then
00:14:05 --> 00:14:07 over billions of years that black hole would
00:14:07 --> 00:14:10 grow. And eventually in our own epoch
00:14:10 --> 00:14:13 today, 13.8 billion years after the
00:14:13 --> 00:14:16 Big Bang, uh, you have supermassive black
00:14:16 --> 00:14:19 holes at the centre of every galaxy. That
00:14:19 --> 00:14:21 was the old wisdom. But the James Webb
00:14:21 --> 00:14:23 telescope has turned that completely on its
00:14:23 --> 00:14:25 head because we have serious
00:14:25 --> 00:14:28 evidence of supermassive black holes
00:14:29 --> 00:14:31 within the first 500 million years
00:14:32 --> 00:14:34 of the universe's existence. And that's
00:14:34 --> 00:14:37 too quick for, or too
00:14:37 --> 00:14:40 short a time for this, um, you
00:14:40 --> 00:14:42 know, this slow accretion of
00:14:43 --> 00:14:46 stuff, uh, as being the, um,
00:14:46 --> 00:14:49 the growth mechanism for black holes. Uh,
00:14:49 --> 00:14:51 it's too short a time for that to be the
00:14:51 --> 00:14:53 case. Uh, so
00:14:53 --> 00:14:56 either our ideas of how fast they gobble
00:14:56 --> 00:14:59 up matter is wrong. And they
00:14:59 --> 00:15:01 gobble up matter a lot faster than we
00:15:01 --> 00:15:03 thought. And we actually covered a storey on
00:15:03 --> 00:15:06 this, I think, about four or five episodes
00:15:06 --> 00:15:08 ago, because there are some scientists who
00:15:09 --> 00:15:11 came to conclusion that one of the things
00:15:11 --> 00:15:14 that we thought limited how fast a
00:15:14 --> 00:15:17 black hole can gobble stuff up, uh, was
00:15:17 --> 00:15:19 actually invalid under certain circumstances.
00:15:20 --> 00:15:23 So that's that one avenue of
00:15:23 --> 00:15:25 research that's come from the James Webb
00:15:25 --> 00:15:27 Telescope showing us that, ah, we've got
00:15:27 --> 00:15:29 these supermassive black holes in the early
00:15:29 --> 00:15:31 universe. But the other one is the idea of
00:15:31 --> 00:15:34 the little pink dots or the little red dots
00:15:34 --> 00:15:37 as they're called. And these are thought to
00:15:37 --> 00:15:39 be, uh, basically just
00:15:39 --> 00:15:42 clouds of gas, hydrogen gas,
00:15:42 --> 00:15:45 which are directly feeding a black hole
00:15:45 --> 00:15:48 that may have been formed in the Big Bang. In
00:15:48 --> 00:15:50 other words, you didn't have to have star
00:15:50 --> 00:15:53 formation and then stars blowing up to
00:15:53 --> 00:15:55 create black holes in order to kick this
00:15:55 --> 00:15:58 process off. The Big Bang itself might have
00:15:58 --> 00:15:59 kicked off the process of black hole
00:15:59 --> 00:16:02 formation by producing these things that we
00:16:02 --> 00:16:05 call primordial black holes. Um, and
00:16:05 --> 00:16:08 they may have turned out to be able
00:16:08 --> 00:16:10 to grow very quickly, um, by
00:16:10 --> 00:16:13 immersing themselves simply in big
00:16:13 --> 00:16:16 clouds of hydrogen and gobbling it all up.
00:16:16 --> 00:16:19 Andrew Dunkley: Yeah, of course, um,
00:16:19 --> 00:16:22 when they run out of stuff, they can't grow.
00:16:22 --> 00:16:22 Is that right?
00:16:23 --> 00:16:25 Professor Fred Watson: That's right. So that's part two of, uh,
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 and
00:16:29 --> 00:16:31 they become what we call quiescent black
00:16:31 --> 00:16:34 holes? They don't do anything. They're
00:16:34 --> 00:16:36 there, uh, and they're still, uh,
00:16:37 --> 00:16:39 things that, um, if a cloud of hydrogen
00:16:39 --> 00:16:42 strayed by, they might seize it
00:16:42 --> 00:16:45 by their own gravity and pull it in. But,
00:16:45 --> 00:16:47 um, they're not going to go out,
00:16:49 --> 00:16:51 um, roaming through the universe looking for
00:16:51 --> 00:16:53 stuff to accrete. In other words, looking for
00:16:53 --> 00:16:53 a snack.
00:16:54 --> 00:16:54 Professor Fred Watson: Yeah.
00:16:54 --> 00:16:57 Andrew Dunkley: Ah, I used to work with a guy whose nickname
00:16:57 --> 00:16:58 was quiescent black hole. He was there, but
00:16:58 --> 00:16:59 he didn't do anything.
00:17:03 --> 00:17:04 Professor Fred Watson: Yes, I think I know who you mean.
00:17:08 --> 00:17:10 Yeah. Anyway, quiescent black holes, uh, are,
00:17:10 --> 00:17:13 uh, basically what, uh, Dan has
00:17:13 --> 00:17:14 described. But the first part of his question
00:17:14 --> 00:17:17 is absolutely asking the same questions
00:17:17 --> 00:17:20 that today's astrophysicists are. Uh, it's
00:17:20 --> 00:17:22 one whose answer we don't know. But the
00:17:22 --> 00:17:24 consensus will emerge over the next. Probably
00:17:24 --> 00:17:26 not very long because we're getting so much
00:17:26 --> 00:17:29 data from the James Webb telescope that I
00:17:29 --> 00:17:31 think it'll be quite soon before this whole
00:17:31 --> 00:17:34 issue is resolved, I would think. Sorry,
00:17:34 --> 00:17:36 I was just going to say when, when there is
00:17:36 --> 00:17:38 hard evidence of a primordial black hole
00:17:38 --> 00:17:41 being discovered, one that was created in the
00:17:41 --> 00:17:43 Big Bang, then that'll be Nobel
00:17:43 --> 00:17:45 Prize winning science when we get to that
00:17:45 --> 00:17:48 stage. But it won't be us.
00:17:48 --> 00:17:50 Andrew Dunkley: Indeed, I was going to suggest that black um,
00:17:50 --> 00:17:53 holes are probably like humans. Consumption
00:17:53 --> 00:17:54 will decide how big they get.
00:17:55 --> 00:17:58 Professor Fred Watson: Maybe that's right, yeah, yeah, we'll have
00:17:58 --> 00:18:01 Andrew Dunkley: to wait and see. All right Dan. Hopefully uh,
00:18:02 --> 00:18:04 we covered that for you adequately. Thanks
00:18:04 --> 00:18:06 for sending in the question. This is Space
00:18:06 --> 00:18:08 Nuts with Andrew Dunkley and Professor
00:18:08 --> 00:18:09 Fred Watson Watson.
00:18:12 --> 00:18:14 Professor Fred Watson: Three, two, one.
00:18:15 --> 00:18:16 Andrew Dunkley: Space Nuts.
00:18:17 --> 00:18:19 Our next question, Fred Watson, comes from
00:18:19 --> 00:18:22 Thomas Reid. Thomas is 11 years old.
00:18:22 --> 00:18:24 He says something has been troubling me. In
00:18:24 --> 00:18:27 books I've read they say that the centres of
00:18:27 --> 00:18:30 galaxies are very big black holes and I
00:18:30 --> 00:18:32 have a few questions about them but uh, I'm
00:18:32 --> 00:18:34 only an 11 year old kid so the questions
00:18:34 --> 00:18:36 might sound silly but here they are. Now
00:18:36 --> 00:18:38 we've got five questions Fred Watson, so we
00:18:38 --> 00:18:41 can be brief on on them. Unless you wanted to
00:18:41 --> 00:18:43 sit here for another couple of hours. Um, if
00:18:43 --> 00:18:45 Jonty was here we would be a couple of hours.
00:18:46 --> 00:18:49 Um, can the galactic centre swallow all the
00:18:49 --> 00:18:52 stars and planets in the galaxy? How big are
00:18:52 --> 00:18:54 the galactic centres or do we not know,
00:18:55 --> 00:18:57 uh, if they can swallow up all the stars and
00:18:57 --> 00:19:00 planets. Is there a limit? If there is a
00:19:00 --> 00:19:02 limit, what is it? And if there is a
00:19:02 --> 00:19:05 limit happens when the limit is reached.
00:19:05 --> 00:19:07 Thank you for taking the time to read this
00:19:07 --> 00:19:09 and I would love it if you could reply. Well
00:19:09 --> 00:19:12 we are going to reply right now Thomas. Um,
00:19:13 --> 00:19:16 yeah, it's great that somebody, uh, so
00:19:16 --> 00:19:19 young is taking a keen interest in something
00:19:19 --> 00:19:22 so mysterious as a black hole. Uh,
00:19:22 --> 00:19:24 we want to start at the top. Can the galactic
00:19:24 --> 00:19:26 centre swallow all the stars and planets in
00:19:26 --> 00:19:26 the galaxy?
00:19:27 --> 00:19:30 Professor Fred Watson: Well so the answer is no. Um, so the
00:19:30 --> 00:19:33 galaxies are very big. Ours is about 100
00:19:33 --> 00:19:35 light years across. Uh, black holes
00:19:35 --> 00:19:38 have ah, 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 by
00:19:43 --> 00:19:45 the time you get there the gravity of the
00:19:45 --> 00:19:48 black hole is very, very weak indeed. And
00:19:48 --> 00:19:51 so it's only in the central region of a
00:19:51 --> 00:19:54 galaxy where you could get material
00:19:54 --> 00:19:57 being swallowed up uh, to create this
00:19:57 --> 00:19:58 activity that we talk about when we Talk
00:19:58 --> 00:20:01 about active black holes, uh, where
00:20:01 --> 00:20:03 there's, uh, an accretion disc, a disc of
00:20:03 --> 00:20:06 material swirling around it. And these jets,
00:20:07 --> 00:20:09 uh, point basically at right angles to the
00:20:09 --> 00:20:10 accretion disc, jets of material travelling
00:20:10 --> 00:20:12 at nearly the speed of light. Quite
00:20:12 --> 00:20:15 extraordinary. So, um, that's all
00:20:15 --> 00:20:17 great and black holes, like a factory or a
00:20:17 --> 00:20:20 furnace doing that, but its stretch is not
00:20:20 --> 00:20:23 very far. Uh, it's measured
00:20:23 --> 00:20:25 in light years, but not in hundreds of
00:20:25 --> 00:20:27 thousands of light years, which would have to
00:20:27 --> 00:20:29 be to grab everything in the galaxy. So the
00:20:29 --> 00:20:32 answer is no. The, uh, galactic centre, uh,
00:20:32 --> 00:20:34 black hole cannot swallow all the stars and
00:20:34 --> 00:20:35 planets in the galaxy.
00:20:36 --> 00:20:39 Andrew Dunkley: Uh, so Thomas can sleep well tonight. Um, how
00:20:39 --> 00:20:42 big are the galactic centres? Do we know how
00:20:42 --> 00:20:42 big?
00:20:42 --> 00:20:45 Professor Fred Watson: M. We do. Yes, we do, because
00:20:47 --> 00:20:50 we can measure the speed
00:20:50 --> 00:20:52 of rotation of stuff
00:20:52 --> 00:20:55 swirling around a black hole, if it's an
00:20:55 --> 00:20:58 active one. And that directly tells you
00:20:58 --> 00:21:01 the mass of the black hole. Um, because
00:21:01 --> 00:21:03 the bigger the black hole, the faster the
00:21:03 --> 00:21:06 stuff is going. And so, um, in terms
00:21:06 --> 00:21:09 of if, the if by
00:21:09 --> 00:21:12 big, Thomas means what's their mass?
00:21:12 --> 00:21:15 Uh, we can measure them quite accurately
00:21:15 --> 00:21:18 now because we can measure their mass. We can
00:21:18 --> 00:21:20 also work out their event horizon
00:21:20 --> 00:21:23 diameter or radius. The event horizon
00:21:23 --> 00:21:26 is 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 --> 00:21:34 sphere. So the event horizon is the
00:21:34 --> 00:21:37 point of no return for anything going into a
00:21:37 --> 00:21:40 black hole. And it's also the point of no
00:21:40 --> 00:21:42 escape for light waves. Uh,
00:21:42 --> 00:21:45 so we can, knowing the mass of a black hole,
00:21:45 --> 00:21:48 we can calculate how big that event
00:21:48 --> 00:21:50 horizon would be. And some of the
00:21:50 --> 00:21:52 supermassive ones, ah, 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 supermassive
00:21:56 --> 00:21:57 black holes.
00:21:57 --> 00:22:00 Andrew Dunkley: Yeah. It's a level of enormity
00:22:00 --> 00:22:01 that you just struggle to get your head
00:22:01 --> 00:22:02 around.
00:22:02 --> 00:22:03 Professor Fred Watson: Yeah, yeah, I suppose.
00:22:03 --> 00:22:05 Andrew Dunkley: In terms of the rest of Thomas's questions,
00:22:05 --> 00:22:07 you've basically answered it with the answer
00:22:07 --> 00:22:10 to first question, because he's asking if
00:22:10 --> 00:22:11 they can swallow up all the stars and
00:22:11 --> 00:22:13 planets. Is there a limit? If there is a
00:22:13 --> 00:22:16 limit, what is it? Uh, and if there is a
00:22:16 --> 00:22:18 limit, what happens when the limit is
00:22:18 --> 00:22:20 reached? Well, the limit is probably
00:22:21 --> 00:22:24 the local area of the centre of the galaxy
00:22:24 --> 00:22:26 and what's available to eat.
00:22:26 --> 00:22:29 Professor Fred Watson: Yes, that's right. So the limiting factor,
00:22:29 --> 00:22:31 uh, is, um,
00:22:32 --> 00:22:34 basically what you might call the grasp of
00:22:34 --> 00:22:37 the black hole, how far it can reach to
00:22:37 --> 00:22:40 pull something in. And that is
00:22:40 --> 00:22:43 dependent on how fast the objects are moving.
00:22:43 --> 00:22:45 So you can have some stars and there are
00:22:45 --> 00:22:47 some. We've observed them, uh, with infrared
00:22:47 --> 00:22:50 radiation that are comfortably in
00:22:50 --> 00:22:52 orbit, uh, around
00:22:53 --> 00:22:55 the black hole at the centre of our own
00:22:55 --> 00:22:57 galaxy, which are not being pulled in,
00:22:57 --> 00:22:59 they're orbiting. And that's because their
00:22:59 --> 00:23:02 speed is enough to keep them out of the grasp
00:23:02 --> 00:23:05 of the black hole. Um, their distances from
00:23:05 --> 00:23:08 the black hole are measured in not two
00:23:08 --> 00:23:11 dissimilar units from the solar system. Sort
00:23:11 --> 00:23:13 of half a light day or something like that,
00:23:13 --> 00:23:16 you know, light day, that's
00:23:16 --> 00:23:18 the sort of measures that we're talking
00:23:18 --> 00:23:21 about. Um, which probably
00:23:21 --> 00:23:23 denies what I just said a few minutes ago
00:23:23 --> 00:23:26 about, um, some black hole event horizons
00:23:26 --> 00:23:28 being tens of light years. I don't think they
00:23:28 --> 00:23:30 are. I think they're smaller than that.
00:23:30 --> 00:23:30 Joe: Okay.
00:23:30 --> 00:23:33 Andrew Dunkley: I thought of a way to explain it to Thomas.
00:23:33 --> 00:23:35 So, uh, Thomas, you've won a competition
00:23:35 --> 00:23:37 kitchen and you can go to
00:23:37 --> 00:23:39 McDonald's and eat everything you want.
00:23:40 --> 00:23:43 Absolutely. Just keep eating until, you know,
00:23:43 --> 00:23:46 the cows come home. However, you aren't
00:23:46 --> 00:23:48 allowed to move from wherever you're standing
00:23:48 --> 00:23:50 and you can only eat 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 the
00:23:57 --> 00:23:59 way. How's that for an analogy?
00:23:59 --> 00:24:01 Professor Fred Watson: It's a nice one. I like it. Yes. Yeah,
00:24:01 --> 00:24:03 because your reach is the sort of
00:24:03 --> 00:24:06 gravitational force that you can exert. It's
00:24:06 --> 00:24:06 a good way of putting it.
00:24:07 --> 00:24:07 Professor Fred Watson: It.
00:24:07 --> 00:24:08 Andrew Dunkley: Andrew, well done.
00:24:08 --> 00:24:09 Professor Fred Watson: You should be on the I try
00:24:09 --> 00:24:11 Andrew Dunkley: to think on 11 year old level, but I'm
00:24:11 --> 00:24:13 thinking Thomas was probably much brighter at
00:24:13 --> 00:24:15 11 than I was struggle
00:24:15 --> 00:24:17 Professor Fred Watson: to get to 11. So do I.
00:24:17 --> 00:24:20 Andrew Dunkley: Yes, thanks Thomas. That was really terrific.
00:24:20 --> 00:24:22 Thanks for sending it in and uh, keep on
00:24:22 --> 00:24:22 listening.
00:24:26 --> 00:24:29 Professor Fred Watson: Tranquilly Base here. The eagle has landed.
00:24:29 --> 00:24:30 Professor Fred Watson: Space nets.
00:24:31 --> 00:24:34 Andrew Dunkley: Final question, Fred Watson, comes from Paul.
00:24:35 --> 00:24:36 Joe: Hello, Space Nights. Paul here from
00:24:36 --> 00:24:38 Sunnybris, Vegas, where it's currently
00:24:38 --> 00:24:41 bucketing down in what is being described
00:24:41 --> 00:24:44 as a rare rain occurrence.
00:24:45 --> 00:24:47 Anyway, I
00:24:48 --> 00:24:51 am currently looking through a very old book
00:24:51 --> 00:24:54 of mine. Guess it's old compared to
00:24:54 --> 00:24:56 these students I teach. It was published back
00:24:56 --> 00:24:59 in 1978. I think I got it in 1980 from
00:25:00 --> 00:25:02 uh, an uncle of mine, Uncle Jim. Thank you
00:25:02 --> 00:25:04 very much. It's called Stars and Planets and
00:25:04 --> 00:25:06 it's probably what got me into
00:25:07 --> 00:25:10 the whole field of astronomy in the first
00:25:10 --> 00:25:12 place. At least my interest in astronomy.
00:25:12 --> 00:25:13 Obviously
00:25:15 --> 00:25:17 Andrew Dunkley: very, uh, very grateful.
00:25:17 --> 00:25:20 Joe: I'm on the page where it's talking about
00:25:20 --> 00:25:22 how the American astronomer Carlo
00:25:22 --> 00:25:25 Shapley used
00:25:25 --> 00:25:28 the 1.5 metre reflector on
00:25:28 --> 00:25:30 top of Matt Wilson in California
00:25:31 --> 00:25:34 to work out that our sun is
00:25:34 --> 00:25:36 not at the centre of our galaxy. As was
00:25:36 --> 00:25:39 previously thought, but is about two thirds
00:25:39 --> 00:25:42 of the way to the edge. Could you
00:25:42 --> 00:25:45 please give us some idea how
00:25:45 --> 00:25:47 he actually managed to do that?
00:25:48 --> 00:25:50 Was it something about the
00:25:50 --> 00:25:53 density of stars? I mean, how many
00:25:53 --> 00:25:55 stars in the field of view?
00:25:56 --> 00:25:57 Andrew Dunkley: Uh, when you point it one way
00:25:57 --> 00:25:59 Joe: compared to the other other. How did you do
00:25:59 --> 00:26:01 it? I'm really curious and I know I could
00:26:01 --> 00:26:04 Google it, but I'd rather hear it from you
00:26:04 --> 00:26:07 guys. So thanks in advance. Love
00:26:07 --> 00:26:10 the show and dare I
00:26:10 --> 00:26:12 say, keep up the good work. Cheers.
00:26:13 --> 00:26:13 Professor Fred Watson: Cheers.
00:26:13 --> 00:26:15 Andrew Dunkley: Paul, thanks for sending that in. Uh,
00:26:16 --> 00:26:18 sending the question in and uh, we don't know
00:26:18 --> 00:26:21 the answer, so. But
00:26:21 --> 00:26:24 we're going to Google it. No, um, uh,
00:26:24 --> 00:26:26 1978, stars and planets. Uh,
00:26:27 --> 00:26:29 I tried to look it up. There are umpteen
00:26:29 --> 00:26:31 books named Stars and Planets.
00:26:31 --> 00:26:32 Professor Fred Watson: Yeah.
00:26:32 --> 00:26:34 Andrew Dunkley: So I haven't been able to, you know,
00:26:34 --> 00:26:36 distinguish one from the other as yet. So,
00:26:36 --> 00:26:39 um. Uh, yeah, you'll have to do some
00:26:39 --> 00:26:41 fishing to find the book that, uh, Paul was
00:26:41 --> 00:26:42 talking about.
00:26:42 --> 00:26:44 But he wanted to know about
00:26:45 --> 00:26:47 the man who decided or
00:26:47 --> 00:26:50 discovered that the sun was not the centre of
00:26:50 --> 00:26:53 everything. Uh, which was a common
00:26:53 --> 00:26:54 belief back in the day.
00:26:55 --> 00:26:58 Professor Fred Watson: It was, um, it was actually 1919 when that
00:26:58 --> 00:26:59 discovery was made.
00:27:00 --> 00:27:00 Andrew Dunkley: Was it that recent?
00:27:01 --> 00:27:04 Professor Fred Watson: Yeah. Wow. Uh, it's one of my favourite
00:27:04 --> 00:27:06 astronomical discoveries, which is why I
00:27:06 --> 00:27:08 didn't need to go to Google to look it up.
00:27:08 --> 00:27:11 Um, so it goes back to the time
00:27:11 --> 00:27:14 of William Herschel, uh, who was
00:27:14 --> 00:27:17 a German turned British
00:27:17 --> 00:27:20 astronomer, worked late in
00:27:20 --> 00:27:23 the 18th century and early in the 19th
00:27:23 --> 00:27:25 century, discovered the planet Uranus in
00:27:25 --> 00:27:27 1780. But what he was doing when
00:27:27 --> 00:27:30 he discovered Uranus was actually mapping the
00:27:30 --> 00:27:33 Milky Way. He was observing, um,
00:27:33 --> 00:27:36 the Milky Way in a very systematic way with a
00:27:36 --> 00:27:39 relatively small telescope. So sort of
00:27:39 --> 00:27:42 counting stars in the
00:27:42 --> 00:27:44 field of view of his telescope and then
00:27:44 --> 00:27:46 moving the telescope a bit further along the
00:27:46 --> 00:27:48 Milky Way, counting stars again, how many he
00:27:48 --> 00:27:51 could see in the field of view and doing that
00:27:51 --> 00:27:53 and doing it. He couldn't do it all the way
00:27:53 --> 00:27:54 around the Milky Way. Cause there's parts of
00:27:54 --> 00:27:56 it that he could never see because they're in
00:27:56 --> 00:27:58 the southern hemisphere. But he'd got round
00:27:58 --> 00:28:01 most of it. And what he discovered was that
00:28:02 --> 00:28:05 the star counts are pretty even all the way
00:28:05 --> 00:28:07 around. And so that led
00:28:08 --> 00:28:11 him to build the hypothesis that
00:28:11 --> 00:28:13 the stars are in a sort of flattened disc,
00:28:13 --> 00:28:16 which is correct. Uh, but that we're very
00:28:16 --> 00:28:18 near the middle, which is not correct.
00:28:18 --> 00:28:21 And the reason why he got that
00:28:21 --> 00:28:23 erroneous answer was that, uh, when you look
00:28:23 --> 00:28:26 through, I think it was a 7 inch telescope,
00:28:26 --> 00:28:28 if I remember right, a telescope of that
00:28:28 --> 00:28:31 size at, uh, the Milky Way, the stars that
00:28:31 --> 00:28:34 you see are all relatively
00:28:34 --> 00:28:36 nearby. They're perhaps 1000
00:28:36 --> 00:28:38 light years away or something like that,
00:28:38 --> 00:28:41 maybe a bit more, maybe a couple of thousand
00:28:41 --> 00:28:43 light years away in the plane of the Milky
00:28:43 --> 00:28:45 Way. And, uh, that's partly because the Milky
00:28:45 --> 00:28:48 Way is very dusty. Uh, there's a lot of dust
00:28:48 --> 00:28:50 everywhere. It's probably better described as
00:28:50 --> 00:28:53 smoke, but we call it dust in the world of
00:28:53 --> 00:28:55 astronomy. And so that dust limits how far
00:28:55 --> 00:28:58 you can see. And so when you look at the
00:28:58 --> 00:29:01 Milky Way, it does look generally relatively
00:29:01 --> 00:29:03 even. There's one bit in the constellation of
00:29:03 --> 00:29:06 Sagittarius where it's brighter and that's
00:29:06 --> 00:29:07 because you are looking towards, as we now
00:29:07 --> 00:29:10 know, the galactic centre. But, um, Herschel,
00:29:11 --> 00:29:13 um, he couldn't see that very well from the
00:29:13 --> 00:29:15 Northern hemisphere anyway. But he did sort
00:29:15 --> 00:29:18 of discount that. Uh, he said, by and large,
00:29:18 --> 00:29:21 it's the same count all the way around, so we
00:29:21 --> 00:29:24 must be in the middle, uh, roll
00:29:24 --> 00:29:27 on the years. And in 1919, Harlow
00:29:27 --> 00:29:29 Shapley, a very gifted American astronomer,
00:29:29 --> 00:29:31 although he did get one thing, one big thing
00:29:31 --> 00:29:34 wrong, uh, but what he did was
00:29:35 --> 00:29:37 he was interested in objects that we call
00:29:37 --> 00:29:39 globular clusters. And so these are, uh, in
00:29:39 --> 00:29:41 fact they were named by William Herschel. He
00:29:41 --> 00:29:43 gave them that name. Uh, clusters of stars
00:29:43 --> 00:29:46 that appear like a globe. Uh, and
00:29:47 --> 00:29:50 Harlow Shapley was, uh,
00:29:51 --> 00:29:53 he was interested in globular clusters. He
00:29:53 --> 00:29:56 noticed there were a lot of them in our, uh,
00:29:56 --> 00:29:59 skies. Uh, they tended
00:29:59 --> 00:30:02 to be different sizes. Uh,
00:30:02 --> 00:30:04 and he didn't know whether that was because
00:30:04 --> 00:30:06 they were all the same size and some were
00:30:06 --> 00:30:08 nearer than others or whether they were
00:30:08 --> 00:30:10 intrinsically different sizes. But what he
00:30:10 --> 00:30:13 did notice was that there's a concentration
00:30:13 --> 00:30:15 of them in the southern
00:30:15 --> 00:30:18 hemisphere sky. Uh, he was
00:30:18 --> 00:30:20 observing from California, so he could see,
00:30:20 --> 00:30:22 see a fair swath of the southern hemisphere
00:30:22 --> 00:30:25 sky. But he noticed that they were
00:30:25 --> 00:30:28 concentrated in that direction and that made
00:30:28 --> 00:30:30 him wonder if that
00:30:31 --> 00:30:33 was where the centre of the galaxy lay,
00:30:33 --> 00:30:36 rather than us being near the centre. Uh,
00:30:36 --> 00:30:38 but then his other step was that he
00:30:38 --> 00:30:41 recognised that within these globular
00:30:41 --> 00:30:44 clusters was something called, they
00:30:44 --> 00:30:47 called them cluster variables, stars that
00:30:47 --> 00:30:49 varied in a certain way with a
00:30:49 --> 00:30:52 periodicity of about a day. Uh, today
00:30:52 --> 00:30:55 we call them RR liry variables. And I
00:30:55 --> 00:30:56 actually started my astronomical research
00:30:56 --> 00:30:59 back in the 70s studying these things,
00:30:59 --> 00:31:02 uh, RR variables. Uh, and
00:31:03 --> 00:31:06 they are good because they've
00:31:06 --> 00:31:09 got basically a known distance.
00:31:09 --> 00:31:12 Uh, if you can see an RR
00:31:12 --> 00:31:15 variable and identify it as one, you know how
00:31:15 --> 00:31:18 intrinsically bright it is, uh, and then from
00:31:18 --> 00:31:20 that you can work out how far away it is.
00:31:21 --> 00:31:24 And so he found these variable stars in the
00:31:24 --> 00:31:27 globular clusters and recognised that he
00:31:27 --> 00:31:29 could draw a chart with the globular
00:31:29 --> 00:31:32 clusters all at their correct distance on it,
00:31:32 --> 00:31:35 make a kind of three dimensional map of the
00:31:35 --> 00:31:37 sky and sure enough, um, they
00:31:37 --> 00:31:40 concentrated around the galactic
00:31:40 --> 00:31:42 centre around a point. Uh, he actually got
00:31:42 --> 00:31:45 the answer wrong because his magnitude, his
00:31:45 --> 00:31:47 brightness that he had for the, uh, cluster
00:31:47 --> 00:31:50 variables was incorrect. And I can't remember
00:31:50 --> 00:31:53 what answer he got, but in my modern PARLANCE
00:31:54 --> 00:31:56 it's about 25 light years.
00:31:57 --> 00:32:00 The globular clusters themselves cluster
00:32:00 --> 00:32:03 around a point about 25 light years
00:32:03 --> 00:32:05 away, which is deeply hidden by the dust
00:32:05 --> 00:32:08 clouds in Sagittarius. So he
00:32:08 --> 00:32:10 figured out that that's where the centre of
00:32:10 --> 00:32:12 the galaxy was. A brilliant piece of
00:32:12 --> 00:32:15 detective work. We know he was right. Uh,
00:32:15 --> 00:32:18 what he was wrong about was, uh, he had a big
00:32:18 --> 00:32:21 discussion, I think in 1923,
00:32:21 --> 00:32:24 just before Hubble recogn that
00:32:24 --> 00:32:27 galaxies were big things a long way away. Uh,
00:32:27 --> 00:32:29 Shapley was arguing that galaxies lie within
00:32:29 --> 00:32:32 our own Milky Way, that they're small objects
00:32:32 --> 00:32:34 in our own Milky Way. And he was, um,
00:32:35 --> 00:32:37 arguing. It was a public debate actually,
00:32:37 --> 00:32:39 between Shapley and a guy called Heber
00:32:39 --> 00:32:42 Curtis. Uh, Curtis had the answer right. He
00:32:42 --> 00:32:44 said they're big and a long way off. Uh,
00:32:44 --> 00:32:46 Shapley said, no, they're small and nearby.
00:32:47 --> 00:32:49 And it was very soon after that that Hubble
00:32:49 --> 00:32:51 produced that they're big and a long way. Uh,
00:32:51 --> 00:32:53 uh, proved that they're big and a long way
00:32:53 --> 00:32:55 off. So Shapley was wrong in that, but he was
00:32:55 --> 00:32:57 right about galactic centre.
00:32:57 --> 00:33:00 Andrew Dunkley: Fantastic. Gee whiz. Um, great
00:33:00 --> 00:33:03 question, Paul. And, um, yeah, uh,
00:33:03 --> 00:33:05 if people are looking for that, uh, book
00:33:06 --> 00:33:08 Stars and Planets, uh, it is out there. Uh,
00:33:08 --> 00:33:11 look, I've found a couple that were actually
00:33:11 --> 00:33:13 published around that time that Paul
00:33:13 --> 00:33:15 mentioned, but not, um, sure if they're the
00:33:15 --> 00:33:18 ones. I can't remember the author now, um,
00:33:18 --> 00:33:19 that he said, but I don't think
00:33:19 --> 00:33:21 Professor Fred Watson: anyway, mentioned an author.
00:33:21 --> 00:33:22 Andrew Dunkley: I thought he did, but, uh, he might have
00:33:22 --> 00:33:23 mentioned it.
00:33:23 --> 00:33:23 Joe: Uncle.
00:33:24 --> 00:33:25 Professor Fred Watson: It was his uncle he mentioned.
00:33:25 --> 00:33:25 Andrew Dunkley: Uncle.
00:33:25 --> 00:33:26 Professor Fred Watson: Uncle Jim.
00:33:27 --> 00:33:28 Andrew Dunkley: Right. But, um,
00:33:30 --> 00:33:32 um, so, yeah, thanks, Paul. Thanks for the
00:33:32 --> 00:33:35 question. And, um, yeah, it's a fascinating,
00:33:35 --> 00:33:38 um, history in astronomy as we discover these
00:33:38 --> 00:33:40 things. I think one of my favourite
00:33:40 --> 00:33:43 moments, I suppose, in astronomical history
00:33:43 --> 00:33:46 was when they discovered that our sun was a
00:33:46 --> 00:33:46 star.
00:33:48 --> 00:33:50 Professor Fred Watson: M. That was a long time ago. Yeah,
00:33:51 --> 00:33:51 yeah.
00:33:51 --> 00:33:54 Andrew Dunkley: But for a while there we didn't think of It.
00:33:54 --> 00:33:55 Professor Fred Watson: I thought it was something else. That's
00:33:55 --> 00:33:58 right. Something a bit special. Yeah.
00:33:58 --> 00:34:01 Andrew Dunkley: Um, and I saw that on a BBC documentary
00:34:01 --> 00:34:03 many years ago and I sat there and went,
00:34:04 --> 00:34:06 wow. I never thought about that because I've
00:34:06 --> 00:34:09 always known it to be a star, but for
00:34:09 --> 00:34:10 generations they didn't.
00:34:12 --> 00:34:15 Quite intriguing. And why would you. It
00:34:15 --> 00:34:16 doesn't look like a star.
00:34:17 --> 00:34:20 Professor Fred Watson: That's right. Uh, uh, it's
00:34:20 --> 00:34:22 clearly quite different from a star. Uh,
00:34:23 --> 00:34:24 Andrew Dunkley: incredible.
00:34:24 --> 00:34:26 Thanks, Paul. Thanks for sending that in. And
00:34:26 --> 00:34:29 if you have a question for. Thanks to all our
00:34:29 --> 00:34:31 sender innerers, 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, spacenutspodcast.com or
00:34:37 --> 00:34:40 spacenuts IO and there's a little
00:34:40 --> 00:34:43 AMA M tab at the top, which stands for Ask
00:34:43 --> 00:34:45 me anything. Not me personally, it's the
00:34:45 --> 00:34:48 rookie royal me. And, um,
00:34:48 --> 00:34:50 just put your, uh, question in there. It can
00:34:50 --> 00:34:53 be text or audio. Don't forget to tell us who
00:34:53 --> 00:34:54 you are and where you're from and have a look
00:34:54 --> 00:34:56 around. While you're there, don't forget to
00:34:56 --> 00:34:59 leave a review at your favourite podcasting
00:34:59 --> 00:35:01 platform. We're all done. Thanks,
00:35:01 --> 00:35:01 Fred Watson.
00:35:02 --> 00:35:04 Professor Fred Watson: A great pleasure, Andrew. Um, we, uh,
00:35:04 --> 00:35:07 continue to get great questions from great
00:35:07 --> 00:35:09 listeners and long may it continue. Thank
00:35:09 --> 00:35:09 you.
00:35:09 --> 00:35:12 Andrew Dunkley: Yes, indeed, we continue to solve and evolve.
00:35:13 --> 00:35:14 Um, maybe not.
00:35:15 --> 00:35:16 Professor Fred Watson: I'm not evolving.
00:35:18 --> 00:35:21 Andrew Dunkley: Once you reach a certain age, evolving
00:35:21 --> 00:35:23 just is not part of the programme. That's
00:35:23 --> 00:35:23 right.
00:35:23 --> 00:35:24 Professor Fred Watson: Yeah.
00:35:24 --> 00:35:26 Andrew Dunkley: Ask my mum on the Internet. Uh, thanks,
00:35:26 --> 00:35:27 Fred Watson. We'll see you soon.
00:35:28 --> 00:35:29 Professor Fred Watson: Sounds great. Thanks, Andrea.
00:35:29 --> 00:35:31 Andrew Dunkley: Professor Fred Watson Watson, astronomer at
00:35:31 --> 00:35:33 large. And thanks to Huw in the studio. He's
00:35:33 --> 00:35:35 just turned up. Um, we started 39
00:35:35 --> 00:35:38 minutes ago and, um, Huw set his
00:35:38 --> 00:35:41 clock to a Martian day, so that's why he's
00:35:41 --> 00:35:42 39 minutes late.
00:35:42 --> 00:35:43 Professor Fred Watson: Boom, boom.
00:35:43 --> 00:35:45 Andrew Dunkley: And from me, Andrew Dunkley, thanks for your
00:35:45 --> 00:35:47 company. We'll see you on the next episode of
00:35:47 --> 00:35:48 Space Nuts.
00:35:48 --> 00:35:48 Professor Fred Watson: Bye. Bye.
00:35:49 --> 00:35:52 Joe: You've been listening to the Space Nuts
00:35:52 --> 00:35:55 Andrew Dunkley: podcast, available at
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00:35:57 --> 00:35:59 iHeartRadio or your favourite podcast
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00:36:04 --> 00:36:06 quality podcast production from
00:36:06 --> 00:36:07 bytes.com.