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Questions About Oceans, Space-Time, and Impact Craters
In this engaging Q&A episode of Space Nuts, host Andrew Dunkley and the ever-knowledgeable Professor Fred Watson tackle a variety of intriguing listener questions. From the depths of Earth's oceans to the mysteries of space-time and the latest in astronomical discoveries, they provide insights and fascinating discussions.
Episode Highlights:
- Exploring Earth's Oceans: Listener Pete sparks a discussion on the origins and depth of Earth's oceans. Andrew and Fred Watson delve into theories about water's presence during Earth's formation and the intriguing idea of what our planet would look like without its vast oceans.
- The Stiffness of Space-Time: Doug's question leads to a deep dive into the concept of space-time stiffness, comparing it to steel and exploring how scientists measure this property. Fred Watson explains the relationship between mass and the distortion of space-time, shedding light on this complex topic.
- New Antenna Array Developments: John in New Mexico asks about the Next Generation Very Large Array (NGVLA), prompting a discussion on its significance in the astronomy community and how it compares to other major arrays like the Square Kilometre Array. Andrew and Fred Watson highlight the advancements and potential scientific contributions of these new technologies.
- Impact Craters in the Solar System: Rusty raises questions about the largest impact crater on Ganymede and its comparison to the Aitken Basin on the Moon. The duo explores the implications of these findings and the fascinating history behind these celestial features.
For more Space Nuts, including our continually updating newsfeed and to listen to all our episodes, visit our website. (https://www.spacenutspodcast.com/) Follow us on social media at SpaceNutsPod on Facebook, X, YouTube Music, Tumblr, Instagram, and TikTok. We love engaging with our community, so be sure to drop us a message or comment on your favourite platform.
If you’d like to help support Space Nuts and join our growing family of insiders for commercial-free episodes and more, visit spacenutspodcast.com/about (https://www.spacenutspodcast.com/about)
Stay curious, keep looking up, and join us next time for more stellar insights and cosmic wonders. Until then, clear skies and happy stargazing.
(00:00) Welcome to Space Nuts with Andrew Dunkley and Fred Watson Watson
(01:20) Discussion on the origins and depth of Earth's oceans
(15:00) Exploring the stiffness of space-time
(25:30) Updates on the Next Generation Very Large Array
(35:00) The largest impact craters in the solar system
For commercial-free versions of Space Nuts, join us on Patreon, Supercast, Apple Podcasts, or become a supporter here: 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) .
Episode link: https://play.headliner.app/episode/27070753?utm_source=youtube
00:00:00 --> 00:00:01 Hi there. Thanks for joining us again.
00:00:01 --> 00:00:05 This is Space Nuts, a Q&A edition. Uh my
00:00:05 --> 00:00:06 name is Andrew Dunley, your host. It's
00:00:06 --> 00:00:08 good to have your company. Uh questions
00:00:08 --> 00:00:11 today coming from Matt, who wants to
00:00:11 --> 00:00:13 talk about the oceans on Earth. Doug is
00:00:13 --> 00:00:16 asking about the stiffness of spaceime.
00:00:16 --> 00:00:17 We have talked about that before, but
00:00:17 --> 00:00:20 he's got a different idea. Uh John is
00:00:20 --> 00:00:23 asking questions about a new antenna
00:00:23 --> 00:00:26 array, and Rusty is honing in on
00:00:26 --> 00:00:28 something we talked about uh late last
00:00:28 --> 00:00:31 year. the largest impact crater, but he
00:00:31 --> 00:00:33 wants to go further than the surface of
00:00:33 --> 00:00:35 the Earth. So, we'll talk about all of
00:00:35 --> 00:00:39 that on this episode of Space Nuts. 15
00:00:39 --> 00:00:43 seconds. Guidance is internal. 10 9
00:00:43 --> 00:00:47 Ignition sequence start. Space Nuts. 5 4
00:00:47 --> 00:00:52 3 2 1 2 3 4 5 5 4 3 2 1 Space Nuts.
00:00:52 --> 00:00:55 Astronauts report. It feels good. And
00:00:55 --> 00:00:57 he's done all his homework. He's ready
00:00:57 --> 00:00:58 to go. It's Professor Fred Watson,
00:00:58 --> 00:01:01 astronomer at large. Hello, Fred. I've
00:01:01 --> 00:01:03 just um realized there was one bit of
00:01:03 --> 00:01:05 homework that I didn't do, which uh
00:01:05 --> 00:01:08 never mind. It'll be all right. There's
00:01:08 --> 00:01:10 this thing called guessing. We can do
00:01:10 --> 00:01:13 that. We can do that. Yeah, that'll
00:01:13 --> 00:01:16 solve it. Uh shall we just get straight
00:01:16 --> 00:01:18 into it? I think we ought to. Yes, I
00:01:18 --> 00:01:19 think that would be a very good uh thing
00:01:19 --> 00:01:22 to do. All right. Our first question is
00:01:22 --> 00:01:24 a text question from Matt. Hi, Andrew
00:01:24 --> 00:01:26 and Fred. I have a question for you.
00:01:26 --> 00:01:27 That's good because this is the Q&A
00:01:27 --> 00:01:30 segment. So, it's good that you've got a
00:01:30 --> 00:01:31 question. I was thinking about what the
00:01:32 --> 00:01:34 Earth's surface would look like as a
00:01:34 --> 00:01:37 rocky planet without any water. Imagine
00:01:37 --> 00:01:39 if you happen to live by the sea and
00:01:39 --> 00:01:41 could stand on the surface, how
00:01:41 --> 00:01:44 different your part of the world would
00:01:44 --> 00:01:46 suddenly look. You'd probably fall a
00:01:46 --> 00:01:49 long way too in some parts of um of the
00:01:49 --> 00:01:52 world. Uh that started me thinking uh
00:01:52 --> 00:01:55 what is it that determines how far our
00:01:55 --> 00:01:58 oceans got filled up? Uh why for
00:01:58 --> 00:02:02 instance aren't there much smaller and
00:02:02 --> 00:02:04 um or why aren't they much smaller and
00:02:04 --> 00:02:06 only a max of say a few hundred meters
00:02:06 --> 00:02:08 deep? What's the physics that governs
00:02:08 --> 00:02:12 how much total water we ended up having
00:02:12 --> 00:02:14 um on Earth? Uh and if you can share
00:02:14 --> 00:02:16 some wisdom on that it would be grand.
00:02:16 --> 00:02:18 Thank you. I love the podcast. been
00:02:18 --> 00:02:21 listening for a few years. Um, but this
00:02:21 --> 00:02:23 is my first question. Uh, keep up the
00:02:23 --> 00:02:25 good work. Thanks, Matt. Well, thanks
00:02:25 --> 00:02:26 for sending in the question. Uh, we
00:02:26 --> 00:02:29 we've talked about how water ended up on
00:02:29 --> 00:02:31 Earth and there are all sorts of
00:02:31 --> 00:02:33 initially the the thought was it's, you
00:02:33 --> 00:02:35 know, carried by asteroids, but then
00:02:35 --> 00:02:36 they started thinking no that they it
00:02:36 --> 00:02:39 wouldn't carry enough. And the latest
00:02:39 --> 00:02:43 theory is that um when the accretion of
00:02:43 --> 00:02:45 the planet happened, the water was
00:02:45 --> 00:02:48 already there, which would probably go a
00:02:48 --> 00:02:50 long way to answering Matt's question
00:02:50 --> 00:02:52 about how come there's this much. But
00:02:52 --> 00:02:55 yes, maybe that's right. Um in fact, you
00:02:55 --> 00:02:57 probably answered it in that regard.
00:02:57 --> 00:03:00 Although, uh I think the asteroid and
00:03:00 --> 00:03:04 comet theory still carries weight and
00:03:04 --> 00:03:07 yeah, holds water. It holds water. Yes.
00:03:07 --> 00:03:09 So I was avoiding that uh
00:03:09 --> 00:03:12 term. The the the thing that put doubt
00:03:12 --> 00:03:15 on that was the the mixture between
00:03:15 --> 00:03:18 heavy water and normal water, the the
00:03:18 --> 00:03:21 isotope ratio. Uh because the that
00:03:21 --> 00:03:23 mixture on in the Earth's oceans doesn't
00:03:23 --> 00:03:26 really match what we find in comets
00:03:26 --> 00:03:28 because we can analyze the vapors that
00:03:28 --> 00:03:31 they give off when when they get near
00:03:31 --> 00:03:33 the sun. Um and and in fact we we
00:03:33 --> 00:03:35 brought samples back from from certainly
00:03:35 --> 00:03:40 from asteroids. Uh so um but you're
00:03:40 --> 00:03:43 right. I think the the prevalent idea is
00:03:43 --> 00:03:46 that the water was intrinsic to the
00:03:46 --> 00:03:48 earth's formation and maybe it just got
00:03:48 --> 00:03:51 topped up a bit by asteroids and comets.
00:03:51 --> 00:03:54 Um so that does to some extent answer
00:03:54 --> 00:03:57 the question. It's uh to do with the uh
00:03:57 --> 00:04:00 you know with the inherent mix uh
00:04:00 --> 00:04:04 molecular mix of the constituents of the
00:04:04 --> 00:04:06 cloud of gas and dust from which the
00:04:06 --> 00:04:08 earth uh and the sun and the solar
00:04:08 --> 00:04:10 system were formed.
00:04:10 --> 00:04:14 Um I uh I think
00:04:14 --> 00:04:16 um it it it's not
00:04:16 --> 00:04:19 necessarily
00:04:19 --> 00:04:23 a a done deal though because
00:04:23 --> 00:04:26 uh we think about some of the ice moons
00:04:26 --> 00:04:29 of the solar system which are
00:04:29 --> 00:04:31 effectively covered in water. Uh they
00:04:31 --> 00:04:33 have far more water than the earth has
00:04:33 --> 00:04:35 in its oceans. And I'm talking now about
00:04:35 --> 00:04:38 places like Europa, like Titan, uh
00:04:38 --> 00:04:40 Saturn's moon Titan, Jupiter's moon
00:04:40 --> 00:04:43 Europa. Uh these are ice worlds. They've
00:04:43 --> 00:04:46 got a a liquid water ocean, uh with a
00:04:46 --> 00:04:49 covering of solid ice on top of that. So
00:04:49 --> 00:04:52 they're basically global water worlds,
00:04:52 --> 00:04:56 except they're covered with ice. Um so
00:04:56 --> 00:05:00 uh a bigger world of that kind could
00:05:00 --> 00:05:02 have a global ocean. And we when we're
00:05:02 --> 00:05:06 talking about um K218b that uh planet
00:05:06 --> 00:05:09 whose atmosphere has shown some possible
00:05:09 --> 00:05:12 biomarker chemicals uh one of the
00:05:12 --> 00:05:16 possible uh scenarios on K218b is a
00:05:16 --> 00:05:19 world that is actually covered in water
00:05:19 --> 00:05:21 that it's a global ocean that it's got a
00:05:21 --> 00:05:23 thick enough atmosphere that the
00:05:23 --> 00:05:25 atmospheric pressure balances out the
00:05:25 --> 00:05:27 water surface. So you've got a situation
00:05:27 --> 00:05:29 like we have on Earth where you've got
00:05:29 --> 00:05:31 equilibrium between the the liquid and
00:05:31 --> 00:05:35 the atmosphere. Um so it may be that you
00:05:35 --> 00:05:38 know uh our earth could have had more
00:05:38 --> 00:05:41 water. Uh maybe some of it's evaporated,
00:05:41 --> 00:05:43 maybe some of it has dissociated into
00:05:43 --> 00:05:47 its component chemicals um uh component
00:05:47 --> 00:05:49 elements hydrogen and oxygen uh and the
00:05:50 --> 00:05:51 and which have been lost into space as
00:05:51 --> 00:05:53 we think has happened on the planet
00:05:53 --> 00:05:57 Mars. Um so maybe you know um there is
00:05:57 --> 00:05:59 certainly snowball earth is one of the
00:05:59 --> 00:06:01 things that we think happened in the
00:06:01 --> 00:06:03 history of our planet that it was
00:06:03 --> 00:06:06 covered with ice with an icy surface. Uh
00:06:06 --> 00:06:09 it's a great question that Matt asks
00:06:09 --> 00:06:12 though uh about um you know what the
00:06:12 --> 00:06:14 earth would be like if you imagined it
00:06:14 --> 00:06:17 without the ocean oceans. Uh there'd be
00:06:17 --> 00:06:18 those trenches. What's the deepest one?
00:06:18 --> 00:06:20 8 kilometers or something like that.
00:06:20 --> 00:06:23 Yes. San Andreas I think which Yes.
00:06:23 --> 00:06:25 which would be pretty impressive. Yeah.
00:06:26 --> 00:06:28 Oh, can you imagine the Earth without
00:06:28 --> 00:06:32 water? Yes. San Andreas. Um, no, it's
00:06:32 --> 00:06:35 not San Andreas. The It's the um Oh,
00:06:35 --> 00:06:37 what's it called? Pacific Trench. Yes,
00:06:37 --> 00:06:39 it's a Pacific one.
00:06:39 --> 00:06:41 Um, can't remember either. Never mind.
00:06:41 --> 00:06:44 The Marinara trench. That's the one.
00:06:44 --> 00:06:50 Yeah, it's um it's incredibly deep. Uh
00:06:50 --> 00:06:54 it's about 8 kilometers. Yeah, I'm just
00:06:54 --> 00:06:55 trying to find it now. Check it out,
00:06:55 --> 00:06:57 Andrew. But uh yeah, if you imagine
00:06:57 --> 00:07:00 Earth without water, uh you could do
00:07:00 --> 00:07:02 some incredible skydiving there, I
00:07:02 --> 00:07:06 reckon, without having to catch a plane.
00:07:06 --> 00:07:08 Yeah. Yeah. Um but getting out, that
00:07:08 --> 00:07:11 would be the fun part, I imagine. But um
00:07:11 --> 00:07:13 yeah, it's Yeah. I can't find the depth
00:07:13 --> 00:07:15 of it, but it is it is something
00:07:15 --> 00:07:18 massive. But they have sent um
00:07:18 --> 00:07:21 submarines down deep into it. Yes.
00:07:21 --> 00:07:23 Without other people on board. Yeah.
00:07:23 --> 00:07:24 Here it is.
00:07:24 --> 00:07:27 26 ft or
00:07:27 --> 00:07:31 8 m deep. What I said. Yeah. Doing
00:07:31 --> 00:07:34 all right. You're doing very well. So,
00:07:34 --> 00:07:36 um, Matt, if if the Earth did not have
00:07:36 --> 00:07:40 oceans, uh, it would look very very
00:07:40 --> 00:07:42 different. It would be it'd be quite
00:07:42 --> 00:07:45 spectacular in places to say the least
00:07:45 --> 00:07:46 because there are mountain ranges under
00:07:46 --> 00:07:49 the Yes. The ocean which we can't see.
00:07:49 --> 00:07:51 Yeah. And I mean you got you got things
00:07:51 --> 00:07:53 like Hawaii which is a super volcano but
00:07:53 --> 00:07:56 you can only see the tip of it. Yes.
00:07:56 --> 00:08:00 Yes. I I I do wonder though um so you
00:08:00 --> 00:08:02 know there are significant differences.
00:08:02 --> 00:08:05 So plate tectonics is is the the key
00:08:05 --> 00:08:07 thing here. Uh the ocean plates are
00:08:08 --> 00:08:10 different from the continental plates
00:08:10 --> 00:08:12 and possibly a lot of that is the fact
00:08:12 --> 00:08:13 that they're being weighed down by the
00:08:13 --> 00:08:16 water on them. So so without the water
00:08:16 --> 00:08:18 they might bounce up a bit and you might
00:08:18 --> 00:08:20 get a much more level playing field
00:08:20 --> 00:08:22 compared with what um what it's like
00:08:22 --> 00:08:25 now. Well, you you see evidence of that
00:08:25 --> 00:08:28 uh around New Zealand where the you know
00:08:28 --> 00:08:29 Milford Sound and all the other and
00:08:29 --> 00:08:31 Dusty Sound and all those beautiful
00:08:31 --> 00:08:33 areas are uh they're still lifting after
00:08:33 --> 00:08:36 the ice age where where the glaciers
00:08:36 --> 00:08:37 compress the ground and you can see
00:08:37 --> 00:08:40 evidence of the of the the rebound
00:08:40 --> 00:08:42 effect. So, yeah, you're right. Uh
00:08:42 --> 00:08:45 because the water weighs
00:08:45 --> 00:08:46 I don't know how you'd measure it, but
00:08:46 --> 00:08:49 it's incredibly heavy. It's um and
00:08:49 --> 00:08:51 putting a lot of pressure on those uh on
00:08:51 --> 00:08:53 those areas. Uh yeah, the earth could
00:08:53 --> 00:08:55 look very different uh if all the water
00:08:55 --> 00:08:57 disappeared and it' probably bounce back
00:08:57 --> 00:08:59 pretty quickly. Yes, I think so. In the
00:08:59 --> 00:09:01 scheme of in geological time. That's
00:09:01 --> 00:09:04 right. Yes. Yes, absolutely. Uh thanks
00:09:04 --> 00:09:06 for the question, Matt. Hope we
00:09:06 --> 00:09:09 adequately answered that for you. Uh our
00:09:09 --> 00:09:11 next question is an audio question from
00:09:11 --> 00:09:15 Doug. Hi, this is Doug and Hazel the
00:09:15 --> 00:09:17 Wonder Doodle calling from Whippy,
00:09:17 --> 00:09:20 Ontario, Canada. Second time caller.
00:09:20 --> 00:09:23 Thanks very much for the show. Uh the
00:09:23 --> 00:09:26 question today from Hazel is we've heard
00:09:26 --> 00:09:30 people talk about the stiffness of
00:09:30 --> 00:09:33 spaceime being something like a 100
00:09:33 --> 00:09:37 billion billion times stiffer than steel
00:09:38 --> 00:09:40 and we're wondering how that can be when
00:09:40 --> 00:09:44 spacetime isn't matter so to speak. Uh,
00:09:44 --> 00:09:47 how can you measure the stiffness of
00:09:47 --> 00:09:50 spacetime and what exactly are you
00:09:50 --> 00:09:53 measuring? Thank you.
00:09:53 --> 00:09:56 Um, how long's a piece of string?
00:09:56 --> 00:09:59 Um, it's it's a great question and I
00:09:59 --> 00:10:00 appreciate that one because this is one
00:10:00 --> 00:10:03 that has always fascinated me. So what
00:10:03 --> 00:10:06 you do is
00:10:06 --> 00:10:12 you you look at the way matter distorts
00:10:12 --> 00:10:17 space and we know that very very well
00:10:17 --> 00:10:19 from Einstein's general theory of
00:10:19 --> 00:10:21 relativity. We we know what the
00:10:21 --> 00:10:23 distortion is for a given amount of mass
00:10:23 --> 00:10:26 and a given size. It's why we understand
00:10:26 --> 00:10:28 black holes because of the fact that the
00:10:28 --> 00:10:31 space is so highly distorted. So, so
00:10:32 --> 00:10:33 what you do, you look at the way matter
00:10:33 --> 00:10:37 distorts space and from that you can
00:10:37 --> 00:10:39 determine a property called the Young's
00:10:39 --> 00:10:42 modulus of space which is a kind of
00:10:42 --> 00:10:45 geometrical property. Um, it's usually
00:10:46 --> 00:10:49 applied to solids as uh exactly as Doug
00:10:49 --> 00:10:51 has said, you know, when how can you
00:10:51 --> 00:10:52 measure its stiffness when it's not a
00:10:52 --> 00:10:55 solid? Um, so what you do is you you
00:10:55 --> 00:10:57 know that it's flexible. You can see the
00:10:57 --> 00:11:01 way matter flexes it and you go from
00:11:01 --> 00:11:04 there to saying if it was a solid it
00:11:04 --> 00:11:06 would have this property and the
00:11:06 --> 00:11:07 property we measure is something called
00:11:07 --> 00:11:10 Young's modulus. Uh I remember doing
00:11:10 --> 00:11:12 Young's modulus as a physics experiment
00:11:12 --> 00:11:14 at school. You hang weights on a bit of
00:11:14 --> 00:11:17 wire and that gives you the amount of
00:11:17 --> 00:11:19 stretch the stiffness of the wire uh
00:11:20 --> 00:11:23 with the weights hanging on it. And so
00:11:23 --> 00:11:25 you can do an equivalent thing and it's
00:11:25 --> 00:11:27 exactly the number actually that uh that
00:11:27 --> 00:11:30 Doug has said. It's uh uh 100 billion
00:11:30 --> 00:11:33 billion times uh stiffer than steel. Uh
00:11:33 --> 00:11:36 10 to the^ 20. Uh there is a there's a
00:11:36 --> 00:11:38 paper it's pretty easy to find it on the
00:11:38 --> 00:11:42 web. Uh it was um written by let me see
00:11:42 --> 00:11:46 if I can bring it up. Uh it is by Kirk
00:11:46 --> 00:11:49 T. Macdonald who's uh at Princeton
00:11:49 --> 00:11:51 University. So this is probably the you
00:11:51 --> 00:11:53 know the almost the headquarters of
00:11:53 --> 00:11:55 gravity because that's where where
00:11:55 --> 00:11:59 Einstein did a lot of his work. Um he's
00:11:59 --> 00:12:01 uh he's got a little paper that you can
00:12:01 --> 00:12:03 find online. What is the stiffness of
00:12:03 --> 00:12:05 space time? And the answer I've given is
00:12:05 --> 00:12:09 the the classical answer the 10 the^ 20.
00:12:09 --> 00:12:12 Uh he's got a quantum answer as well. Uh
00:12:12 --> 00:12:15 and uh you can throw in something about
00:12:15 --> 00:12:16 cosmological sound waves and
00:12:16 --> 00:12:19 electromagnetic waves. uh and enjoy
00:12:19 --> 00:12:20 yourself with some of the equations
00:12:20 --> 00:12:22 there. But that's basically uh where
00:12:22 --> 00:12:23 that number comes from. It comes from
00:12:23 --> 00:12:25 that paper. Yeah. And it's not so much
00:12:25 --> 00:12:29 about the physical attributes of the
00:12:29 --> 00:12:31 universe. It's about the fabric of space
00:12:31 --> 00:12:34 time itself and and and the way it
00:12:34 --> 00:12:37 behaves. Yeah. Yes. Yeah. Cuz we have
00:12:37 --> 00:12:40 talked about it before and um I think
00:12:40 --> 00:12:42 when we first talked about it, I was
00:12:42 --> 00:12:45 quite astonished by how
00:12:45 --> 00:12:49 um stiff space is. Yes, in the scheme of
00:12:49 --> 00:12:51 things. But when you compare it to
00:12:51 --> 00:12:54 steel, um I I guess it puts you in a
00:12:54 --> 00:12:57 mindset of a physical thing. Yeah,
00:12:57 --> 00:12:59 that's right. Like an object, but that's
00:12:59 --> 00:13:03 not really what it's about. Yeah.
00:13:03 --> 00:13:06 All right. Um short answer, but there's
00:13:06 --> 00:13:09 Yeah, that it's pretty well documented
00:13:09 --> 00:13:11 and uh yeah, go you can you can
00:13:11 --> 00:13:13 certainly look that um that article up,
00:13:13 --> 00:13:16 Doug, and and learn more about it. And
00:13:16 --> 00:13:18 thanks for the question. and thanks for
00:13:18 --> 00:13:20 introducing us to your puppy dog. This
00:13:20 --> 00:13:23 is Space Nuts. Andrew Dunley with
00:13:23 --> 00:13:26 Professor Fred Watson, a Q&A
00:13:26 --> 00:13:28 edition. If you're heading overseas soon
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00:16:02 --> 00:16:06 SY here. Also Spacenuts. Our next
00:16:06 --> 00:16:09 question comes from John. I live in
00:16:09 --> 00:16:11 Cloudcraftoft, New Mexico in the United
00:16:11 --> 00:16:14 States. Today's Albuquerque, New Mexico
00:16:14 --> 00:16:16 newspaper reported on
00:16:16 --> 00:16:20 NGVLA. Uh it will replace an existing 27
00:16:20 --> 00:16:24 antenna array with 192. Each new
00:16:24 --> 00:16:27 foundation 430 tons. Each new antenna
00:16:27 --> 00:16:31 generating 1.5 terabytes per second. And
00:16:32 --> 00:16:36 each 18 m tall uh uh structure weighing
00:16:36 --> 00:16:39 130 tons. How will this new antenna fit
00:16:39 --> 00:16:43 into the astronomy community? uh and he
00:16:43 --> 00:16:46 he makes a reference to um the square
00:16:46 --> 00:16:49 kilometer array and mircat arrays that
00:16:49 --> 00:16:50 are being set up in Australia and South
00:16:50 --> 00:16:52 Africa. Thank you, John. Uh I didn't
00:16:52 --> 00:16:55 know about this one. Yeah, it's been in
00:16:55 --> 00:16:58 the pipeline quite a while. So the VA is
00:16:58 --> 00:17:02 uh the very large array. It's uh in New
00:17:02 --> 00:17:04 Mexico. We visited it a few years ago. A
00:17:04 --> 00:17:08 very impressive set of antennas. Uh and
00:17:08 --> 00:17:13 um um essentially uh it's been a really
00:17:13 --> 00:17:16 productive um uh machine for research,
00:17:16 --> 00:17:20 the VA back to going back to the 1970s.
00:17:20 --> 00:17:22 Uh and there's a note on their website
00:17:22 --> 00:17:23 that says it's been used for more than
00:17:23 --> 00:17:27 11 different observing projects. Um
00:17:27 --> 00:17:28 and had an impact on nearly every branch
00:17:28 --> 00:17:32 of astronomy. So uh what has happening
00:17:32 --> 00:17:35 what is happening now is an upgrade uh
00:17:35 --> 00:17:38 to make it the next generation very
00:17:38 --> 00:17:40 large array the NGVLA
00:17:40 --> 00:17:45 uh and um exactly as John says it's got
00:17:45 --> 00:17:48 similarities to uh actually to the mid
00:17:48 --> 00:17:50 frequency component of the square
00:17:50 --> 00:17:52 kilometer array which is a in South
00:17:52 --> 00:17:55 Africa and is a basically an extension
00:17:55 --> 00:17:57 of Mircat which is an existing array in
00:17:58 --> 00:18:02 in South Africa. Um, so, uh, that also
00:18:02 --> 00:18:05 will have, uh, antennas about 200, much
00:18:05 --> 00:18:08 the same as the, uh, NGVLA will have.
00:18:08 --> 00:18:10 Uh, what I was looking for, and this is
00:18:10 --> 00:18:11 the bit of homework that I didn't
00:18:11 --> 00:18:15 actually do, uh, it's, um, it's it's
00:18:15 --> 00:18:19 going to have uh, a frequency range,
00:18:19 --> 00:18:22 which uh, I I'm not sure about. It's
00:18:22 --> 00:18:27 probably quite similar. 1.2 2 GHz or 21
00:18:27 --> 00:18:32 cm to 116 GHz. Okay. Uh that's uh rather
00:18:32 --> 00:18:34 more I think than the um than the
00:18:34 --> 00:18:38 mid-frequency of the uh of the square
00:18:38 --> 00:18:41 kilometer observatory. Um I think though
00:18:41 --> 00:18:46 the other thing is that the NG VALA will
00:18:46 --> 00:18:53 have uh a much wider spacing of the
00:18:53 --> 00:18:56 antennas. They're talking about over
00:18:56 --> 00:18:59 nearly 9 kilometers. So this is
00:18:59 --> 00:19:01 continentwide stuff. Uh and that's
00:19:02 --> 00:19:05 certainly bigger than the array uh in
00:19:05 --> 00:19:08 South Africa. Uh and so it will probably
00:19:08 --> 00:19:09 be used for different science. So the
00:19:09 --> 00:19:11 answer to to John's question is that yes
00:19:12 --> 00:19:15 these things dovetail together uh m
00:19:15 --> 00:19:19 maybe in frequency and in um and in in
00:19:19 --> 00:19:23 spacing in antenna spacing. Uh it's the
00:19:23 --> 00:19:26 sort of thing that astronomers you know
00:19:26 --> 00:19:28 you they don't tend to work in
00:19:28 --> 00:19:30 isolation. Uh they have complimentary
00:19:30 --> 00:19:32 things and it's a bit like the three
00:19:32 --> 00:19:35 ELTs that are currently being planned or
00:19:35 --> 00:19:37 built extremely large telescopes. These
00:19:37 --> 00:19:40 are optical telescopes in the 20 to 30
00:19:40 --> 00:19:43 meter class. Uh and um well there's only
00:19:43 --> 00:19:45 one of them that's anywhere near
00:19:45 --> 00:19:46 completion and that's the European
00:19:46 --> 00:19:49 extremely large telescope 39 m
00:19:49 --> 00:19:50 instrument. But there are two others
00:19:50 --> 00:19:53 that are still on the stocks. I don't
00:19:53 --> 00:19:55 know how the current funding situation
00:19:55 --> 00:19:56 in the US will affect them because
00:19:56 --> 00:19:59 they've they require a huge component of
00:20:00 --> 00:20:01 US funding even though they're
00:20:01 --> 00:20:03 international projects. there the the
00:20:03 --> 00:20:05 giant Mellan telescope and the and the
00:20:05 --> 00:20:09 TMT the 30 meter telescope in Hawaii. So
00:20:09 --> 00:20:11 that that it's it's a similar situation.
00:20:11 --> 00:20:13 I think you've got differences. There
00:20:13 --> 00:20:15 are nuances of differences between them.
00:20:15 --> 00:20:18 They will um have different strengths um
00:20:18 --> 00:20:20 in terms of their capabilities. Uh and
00:20:20 --> 00:20:22 the astronomical community throughout
00:20:22 --> 00:20:24 the world will be glad to have them. Uh
00:20:24 --> 00:20:25 because the one thing that we're always
00:20:26 --> 00:20:29 short of is is astronomical facilities.
00:20:29 --> 00:20:32 uh telescopes are rare things when it
00:20:32 --> 00:20:34 comes to this you know things of this
00:20:34 --> 00:20:37 size of this stature. So uh great to to
00:20:37 --> 00:20:41 welcome the NG VALA into the uh you know
00:20:41 --> 00:20:43 into the mix. Yeah. They say the array
00:20:43 --> 00:20:46 will achieve uh high surface brightness
00:20:46 --> 00:20:48 sensitivity and high fidelity imaging on
00:20:48 --> 00:20:51 angular scales down to the uh mill arc
00:20:51 --> 00:20:55 second. Yeah. Um and it will uh extend
00:20:55 --> 00:20:58 out to 1 kilometers and uh it'll
00:20:58 --> 00:21:00 have longer baselines reaching across
00:21:00 --> 00:21:03 North America and Hawaii. Yeah. It's
00:21:03 --> 00:21:05 pretty long comes from. Yeah. Yeah.
00:21:05 --> 00:21:07 Yeah. Incredible. I mean we we've seen
00:21:07 --> 00:21:09 this already with the you know the event
00:21:09 --> 00:21:12 horizon telescope which goes over
00:21:12 --> 00:21:14 basically the diameter of the earth is
00:21:14 --> 00:21:17 the is the baseline for that but it's
00:21:17 --> 00:21:19 it's only that I think that's only nine
00:21:19 --> 00:21:20 telescopes or something like that or
00:21:20 --> 00:21:23 nine observatories. Yeah. I mean, I
00:21:23 --> 00:21:25 think it's great that they can integrate
00:21:25 --> 00:21:27 so much hardware over such vast
00:21:27 --> 00:21:29 distances to make them, you know, super
00:21:29 --> 00:21:32 telescopes basically. And y they're so
00:21:32 --> 00:21:35 much more powerful and uh yeah, the data
00:21:35 --> 00:21:36 will um be very interesting. I'm sure
00:21:36 --> 00:21:38 we'll be talking about it uh at some
00:21:38 --> 00:21:42 stage, John. So, keep your ear to the
00:21:42 --> 00:21:45 podcast platform that you use and there
00:21:45 --> 00:21:47 will be more. Thanks for the question.
00:21:47 --> 00:21:49 Let's take a little break from the show
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00:24:10 --> 00:24:12 only. And if you want more information,
00:24:12 --> 00:24:14 check out our show notes, but uh just
00:24:14 --> 00:24:17 remember the URL
00:24:17 --> 00:24:20 store.insta360.com and the promo code
00:24:20 --> 00:24:23 space nuts. Now, back to the show. Okay,
00:24:23 --> 00:24:25 we checked all four systems and being
00:24:25 --> 00:24:27 with the girls. Space nuts. One final
00:24:27 --> 00:24:30 question. This one comes from, you'll
00:24:30 --> 00:24:33 never guess, Rusty and Donny Brook.
00:24:33 --> 00:24:35 Hi Fred and Andrew. It's Rusty and Donny
00:24:35 --> 00:24:37 Brook. Andrew, it's good to have you
00:24:37 --> 00:24:39 back, but didn't Heidi do a great job in
00:24:39 --> 00:24:42 your absence. How did you find
00:24:42 --> 00:24:45 her? Questions about
00:24:45 --> 00:24:48 uh the largest
00:24:48 --> 00:24:51 uh crater in the solar system. I presume
00:24:51 --> 00:24:53 that the one you spoke about last
00:24:53 --> 00:24:57 September on Ganymede at 1600 kilometer
00:24:57 --> 00:25:00 diameter is larger than the one on the
00:25:00 --> 00:25:03 moon, the Aken basin. So the the title
00:25:03 --> 00:25:06 of largest would then change to the one
00:25:06 --> 00:25:09 on Ganymede. Does it have a name yet?
00:25:09 --> 00:25:12 And I'm just wondering about
00:25:12 --> 00:25:17 Triton. Um it's its odd shape would have
00:25:17 --> 00:25:20 to have come from an impact decision uh
00:25:20 --> 00:25:23 collision. And uh I'm wondering if that
00:25:23 --> 00:25:26 qualifies as a crater. It's about it
00:25:26 --> 00:25:28 took away about a third of the moon uh
00:25:28 --> 00:25:33 that impact. And uh was that impact with
00:25:33 --> 00:25:37 the planet or did it acquire its odd
00:25:37 --> 00:25:40 shape by hitting something else? Thanks
00:25:40 --> 00:25:44 guys. Cheers. Thanks Rusty. Always good
00:25:44 --> 00:25:46 to hear from you chucking us curve
00:25:46 --> 00:25:49 balls. Uh yeah, I'll answer his first
00:25:49 --> 00:25:51 question. How did we find Heidi? Heidi
00:25:51 --> 00:25:55 found us. Um, Heidi was a Space Nuts
00:25:55 --> 00:25:58 listener and she came to us to say,
00:25:58 --> 00:26:01 "Look, I got an idea and I just want to
00:26:01 --> 00:26:03 sort of go to school off you guys to
00:26:03 --> 00:26:05 find out how I can get my idea out
00:26:05 --> 00:26:08 there." And her idea was a podcast about
00:26:08 --> 00:26:11 the relationship between real life and
00:26:11 --> 00:26:14 science fiction. And I said, "Well, why
00:26:14 --> 00:26:16 don't I introduce you to Hugh in the
00:26:16 --> 00:26:19 studio, if you can find him, and see
00:26:19 --> 00:26:22 what happens?" And voila, uh Heidi's
00:26:22 --> 00:26:26 podcast became one of the byes.com
00:26:26 --> 00:26:29 stable, uh reality check, the science of
00:26:29 --> 00:26:31 fiction podcast. So that's how it
00:26:31 --> 00:26:33 happened. Uh Heidi just sort of wanted
00:26:33 --> 00:26:35 to find out how she could get her idea
00:26:35 --> 00:26:39 out there and we um we took her on.
00:26:39 --> 00:26:41 Simple as that. So, uh, yeah, it turned
00:26:41 --> 00:26:43 out to be a really great podcast series,
00:26:43 --> 00:26:45 too, if you want to look it up, uh, and
00:26:45 --> 00:26:47 and listen to some of the great, uh,
00:26:48 --> 00:26:51 concepts that science fiction can give
00:26:51 --> 00:26:54 to real life situations or vice versa.
00:26:54 --> 00:26:55 Sometimes they're a little bit out there
00:26:55 --> 00:26:58 and it would never be real, but uh, it's
00:26:58 --> 00:27:00 a and she speaks to experts in the field
00:27:00 --> 00:27:03 uh, about the ideas of science fiction
00:27:03 --> 00:27:04 and whether or not they're feasible in
00:27:04 --> 00:27:06 real life. Brilliant. Brilliant. But
00:27:06 --> 00:27:08 yes, she did a fabulous job while I was
00:27:08 --> 00:27:11 away. very pleased to uh be able to take
00:27:11 --> 00:27:13 a break and not have to have any worries
00:27:13 --> 00:27:19 at all about um Fred's behavior. Uh now
00:27:19 --> 00:27:22 um now the largest impact crater, we did
00:27:22 --> 00:27:25 talk about that recently and um I I've
00:27:25 --> 00:27:27 forgotten the nuts and bolts of Rusty's
00:27:27 --> 00:27:29 question now, but u I'm sure you've done
00:27:29 --> 00:27:32 your homework, Fred. I have. Two two
00:27:32 --> 00:27:35 parts to Rusty's question. one is uh he
00:27:35 --> 00:27:37 talks about and I had to go back to our
00:27:37 --> 00:27:41 um uh our podcast of the 4th of
00:27:41 --> 00:27:44 September last year to to find out what
00:27:44 --> 00:27:47 we actually said. Uh but yes it was a
00:27:47 --> 00:27:50 story uh that there is evidence on uh
00:27:50 --> 00:27:52 Jupiter's moon Ganymede the biggest moon
00:27:52 --> 00:27:56 in the solar system uh that uh sometime
00:27:56 --> 00:27:58 in the past it was hit by an asteroid
00:27:58 --> 00:28:01 probably a big one 300 kilometers in
00:28:01 --> 00:28:04 diameter uh which would have created a
00:28:04 --> 00:28:07 crater about somewhere between 1
00:28:07 --> 00:28:10 and600 kilometers wide on Ganymede
00:28:10 --> 00:28:13 that's a very very big chunk of Ganymede
00:28:14 --> 00:28:16 now that crater doesn't no longer
00:28:16 --> 00:28:19 exists. It's long gone. Uh Ganymede has
00:28:19 --> 00:28:21 a surface that's probably icy and is
00:28:21 --> 00:28:25 being renewed uh all the time um by
00:28:25 --> 00:28:29 probably you know the the the activity
00:28:29 --> 00:28:32 maybe even geysers of ice as we see on
00:28:32 --> 00:28:36 um on Europa and Enceladus. Uh so that
00:28:36 --> 00:28:38 crater isn't there anymore. And the
00:28:38 --> 00:28:41 reason why we did that story and what
00:28:41 --> 00:28:43 what has led to the idea that there was
00:28:43 --> 00:28:46 this clout of of Ganymede back in the in
00:28:46 --> 00:28:48 in the distant past about 4 billion
00:28:48 --> 00:28:51 years ago was what they were saying um
00:28:51 --> 00:28:55 was concentric circles uh which are in
00:28:55 --> 00:28:59 the surface of Ganymede. So the these
00:28:59 --> 00:29:01 concentric circles which are all
00:29:01 --> 00:29:04 centered on a point which is where that
00:29:04 --> 00:29:06 impact is thought to have taken place.
00:29:06 --> 00:29:09 So there's no crater but there are these
00:29:09 --> 00:29:12 uh ancient pieces of evidence of uh
00:29:12 --> 00:29:15 there having been uh an impact these
00:29:15 --> 00:29:17 concentric circular features which have
00:29:17 --> 00:29:19 which which are quite prominent on
00:29:19 --> 00:29:25 Ganymede's surface. Um so so I I think
00:29:25 --> 00:29:27 the Aken South Pole basin still has the
00:29:27 --> 00:29:31 record uh for the biggest crater
00:29:31 --> 00:29:33 certainly one of the biggest craters uh
00:29:34 --> 00:29:35 in the solar system. It's 2 and a half
00:29:35 --> 00:29:38 thousand kilometers in diameter. So it's
00:29:38 --> 00:29:40 actually bigger than what the Ganymede
00:29:40 --> 00:29:42 crater would have been had it still been
00:29:42 --> 00:29:46 there. Yeah, that's amazing. Yes. So, so
00:29:46 --> 00:29:48 it's a big a big dip in the southern
00:29:48 --> 00:29:52 polar region of the moon. Uh and again
00:29:52 --> 00:29:53 thought to be due to an asteroid impact
00:29:53 --> 00:29:56 perhaps in the very earliest history of
00:29:56 --> 00:30:00 the moon 4 billion years ago or so. Now,
00:30:00 --> 00:30:03 um, can they can they glean as to how
00:30:03 --> 00:30:05 large that asteroid would have been that
00:30:05 --> 00:30:08 hit the moon? Uh, yes. I I can't
00:30:08 --> 00:30:09 remember what the figure is, though.
00:30:09 --> 00:30:12 It's it's uh it's a sort of almost like
00:30:12 --> 00:30:14 a planetary body. It's almost a
00:30:14 --> 00:30:16 protolanet or something like that. So,
00:30:16 --> 00:30:18 several hundred kilometers across
00:30:18 --> 00:30:21 probably. Yeah. Okay.
00:30:21 --> 00:30:24 Uh the second part of uh of Russ's
00:30:24 --> 00:30:26 question has me very puzzled because he
00:30:26 --> 00:30:31 talks about Triton uh which is uh the
00:30:31 --> 00:30:34 biggest moon of Neptune
00:30:34 --> 00:30:40 uh and it um it is
00:30:40 --> 00:30:42 uh
00:30:42 --> 00:30:47 it's it's just well what the the the
00:30:47 --> 00:30:49 what what um Rossy is saying is that
00:30:49 --> 00:30:50 it's got a
00:30:50 --> 00:30:52 impact crater on it to make it a very
00:30:52 --> 00:30:55 odd shape. But actually, Triton's almost
00:30:55 --> 00:30:57 perfectly spherical. So, I'm not quite
00:30:57 --> 00:31:00 sure where what he's thinking of here
00:31:00 --> 00:31:02 and whether he and I are cross purposes
00:31:02 --> 00:31:04 here, whether he's thinking of another
00:31:04 --> 00:31:07 object, but Triton is a very well-
00:31:07 --> 00:31:09 behaved moon. It's in terms of its
00:31:09 --> 00:31:11 shape, it's pretty spherical. It's a
00:31:11 --> 00:31:14 large moon. It It's unusual in that it
00:31:14 --> 00:31:18 orbits uh Neptune backwards. It's what's
00:31:18 --> 00:31:19 called a retrograde orbit. It's
00:31:19 --> 00:31:22 clockwise as seen from above the north
00:31:22 --> 00:31:23 pole which is backwards compared with
00:31:23 --> 00:31:25 the rest of the solar system. And so
00:31:25 --> 00:31:29 it's it's probably uh was once a dwarf
00:31:29 --> 00:31:31 planet in the Kyper belt. So it's
00:31:31 --> 00:31:34 something that's been captured uh by the
00:31:34 --> 00:31:37 gravity of Neptune. U but it is nicely
00:31:37 --> 00:31:41 circular, nicely spherical. So not sure
00:31:41 --> 00:31:43 about the impact crater. We might talk
00:31:43 --> 00:31:46 to Rusty again about that. Yeah. Oh, he
00:31:46 --> 00:31:49 he he's not I I'm not sure he'll ever
00:31:49 --> 00:31:50 send a question in again, but if he
00:31:50 --> 00:31:52 does, he
00:31:52 --> 00:31:56 can he can uh he can follow us up and
00:31:56 --> 00:31:59 um provide more clarity, I think we'll
00:31:59 --> 00:32:01 say. Uh I just looked it up. Uh the
00:32:01 --> 00:32:04 South Pole Aken Basin on the moon impact
00:32:04 --> 00:32:07 crater. Um yeah, you said 2 and a half
00:32:08 --> 00:32:09 thousand kilometers, so biggest in the
00:32:09 --> 00:32:11 solar system. Uh the object they think
00:32:11 --> 00:32:14 was about 200 km in diameter. Okay.
00:32:14 --> 00:32:16 Right. Yeah, that's a big hit on a small
00:32:16 --> 00:32:19 moon type of situation.
00:32:19 --> 00:32:21 Yeah, made a bit of a mess by the sound
00:32:21 --> 00:32:24 of it. Rusty, thank you. If you want to
00:32:24 --> 00:32:26 um kind of come back to us, uh yeah, by
00:32:26 --> 00:32:29 all means um send us a bit more info so
00:32:29 --> 00:32:32 that we can um uh revisit that question.
00:32:32 --> 00:32:34 And don't forget, if you've got a
00:32:34 --> 00:32:35 question for us, send us in because we
00:32:35 --> 00:32:37 are a bit short because I I did a bit of
00:32:38 --> 00:32:41 a clean out when I got back and uh we um
00:32:41 --> 00:32:44 we need some fresh material. So send the
00:32:44 --> 00:32:47 questions into us via our website
00:32:47 --> 00:32:50 spacenutspodcast.com or spacenuts.io and
00:32:50 --> 00:32:53 just that little um AMA link at the top
00:32:53 --> 00:32:55 is where you can send text and audio
00:32:55 --> 00:32:57 questions. Uh which is pretty easy if
00:32:57 --> 00:33:00 you've got a device with a microphone um
00:33:00 --> 00:33:02 whether that's a smartphone or a tablet
00:33:02 --> 00:33:05 or or a computer. Um send it into us.
00:33:05 --> 00:33:07 Don't forget forget as always to tell us
00:33:07 --> 00:33:09 who you are and where you're from. We're
00:33:09 --> 00:33:12 all done, Fred. Thank you so much. Oh,
00:33:12 --> 00:33:14 it's uh been a pleasure as always and
00:33:14 --> 00:33:16 it's always stimulating and good to
00:33:16 --> 00:33:18 chat. It is. I love it. All right, we'll
00:33:18 --> 00:33:20 see you soon. Professor Fred Watson,
00:33:20 --> 00:33:22 astronomer at large and thanks to Hugh
00:33:22 --> 00:33:25 in the studio who couldn't be with us
00:33:25 --> 00:33:27 today because that's his preferred
00:33:27 --> 00:33:30 state. He just doesn't want to be with
00:33:30 --> 00:33:33 us. Thanks, Hugh. Uh, and from me,
00:33:33 --> 00:33:34 Andrew Dunley, thanks for your company.
00:33:34 --> 00:33:35 See you on the very next episode of
00:33:36 --> 00:33:39 Space Nuts. Bye-bye. Space Nuts. You've
00:33:39 --> 00:33:43 been listening to the Space Nuts podcast
00:33:43 --> 00:33:46 available at Apple Podcasts, Spotify,
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00:33:54 --> 00:33:58 podcast production from byes.com.