00:00:00 --> 00:00:02 Andrew Dunkley: Space Nuts is taking a bit of a break at the
00:00:02 --> 00:00:05 moment, Fred. Uh, and I will be back, uh, in
00:00:05 --> 00:00:06 the not too distant future with fresh
00:00:06 --> 00:00:09 episodes. In the meantime, enjoy some of, uh,
00:00:09 --> 00:00:12 the key episodes that we have presented over
00:00:12 --> 00:00:14 the years. Major events in
00:00:14 --> 00:00:17 astronomy and space science. And
00:00:17 --> 00:00:18 we'll see you real soon.
00:00:19 --> 00:00:20 Generic: Space Nuts.
00:00:20 --> 00:00:23 Andrew Dunkley: Hi there. Thanks for joining us on a Q and A
00:00:23 --> 00:00:25 edition of Space Nuts. I'm Andrew Dunkley,
00:00:25 --> 00:00:28 your host. Once again. Uh, thanks for joining
00:00:28 --> 00:00:31 us and, um, good to have your company. On
00:00:31 --> 00:00:32 this edition, we're, uh, answering some
00:00:32 --> 00:00:35 questions about light in space. Um, this
00:00:35 --> 00:00:38 one comes from Lee. He's asked a very
00:00:38 --> 00:00:39 interesting question. I've never actually
00:00:39 --> 00:00:41 thought about this particular
00:00:42 --> 00:00:45 concept, but, uh, it's a question that I
00:00:45 --> 00:00:47 think is worth answering for sure. That's why
00:00:47 --> 00:00:50 we included it. Fenton wants to know about,
00:00:50 --> 00:00:52 um, shielding astronauts in the
00:00:52 --> 00:00:54 outer reaches of the solar system. And he's
00:00:54 --> 00:00:57 got an idea on how to do that. Uh,
00:00:57 --> 00:00:59 Robert wants to, uh, talk about things we
00:00:59 --> 00:01:01 learned from the moon. And what if our moon
00:01:01 --> 00:01:04 wasn't the same as the moon is now?
00:01:04 --> 00:01:06 Would our learnings be different? That's a
00:01:06 --> 00:01:09 really interesting question. And Duncan wants
00:01:09 --> 00:01:11 to talk about ice giants. And why are they
00:01:11 --> 00:01:13 ice giants? Why don't we call them something
00:01:13 --> 00:01:15 else? That's all coming up shortly on this
00:01:15 --> 00:01:17 edition of Space Nuts.
00:01:18 --> 00:01:20 Generic: 15 seconds. Guidance is internal.
00:01:20 --> 00:01:23 10, 9. Ignition
00:01:23 --> 00:01:24 sequence start.
00:01:24 --> 00:01:25 Professor Fred Watson: Space Nuts.
00:01:25 --> 00:01:27 Generic: 5, 4, 3, 2.
00:01:27 --> 00:01:27 Duncan: 1.
00:01:27 --> 00:01:30 Generic: 2, 3, 4, 5, 5, 4, 3, 2,
00:01:30 --> 00:01:30 1.
00:01:30 --> 00:01:33 Professor Fred Watson: Space Nuts astronauts report at Beales.
00:01:33 --> 00:01:33 Good.
00:01:34 --> 00:01:37 Andrew Dunkley: Once again we welcome the one and only Fred
00:01:37 --> 00:01:39 Watson, astronomer at large. Hello, Fred.
00:01:39 --> 00:01:41 Professor Fred Watson: Hello, Andrew. How have you been since we
00:01:41 --> 00:01:42 last spoke?
00:01:43 --> 00:01:46 Andrew Dunkley: I haven't moved from this seat in all that
00:01:46 --> 00:01:46 time.
00:01:47 --> 00:01:50 Professor Fred Watson: Well, it's. I know. It's, uh. I can see
00:01:50 --> 00:01:52 you're glued to your chair there. Um,
00:01:53 --> 00:01:55 very much so. Uh, yes.
00:01:55 --> 00:01:57 Andrew Dunkley: Uh, shall we get, um, straight into it and
00:01:57 --> 00:02:00 answer some questions from our audience?
00:02:01 --> 00:02:03 Professor Fred Watson: Uh, that's a good idea.
00:02:03 --> 00:02:05 Andrew Dunkley: Yeah, it is. That's what we're here for.
00:02:05 --> 00:02:07 This first one, Fred, comes from Lee. He
00:02:07 --> 00:02:10 lives in New York City. Uh,
00:02:10 --> 00:02:13 he's asking how much light is in space.
00:02:14 --> 00:02:17 He'll qualify that question. For example, if
00:02:17 --> 00:02:19 you were to visit Voyager 1, where Voyager 1
00:02:19 --> 00:02:22 is today, would you be able to see. See it?
00:02:22 --> 00:02:25 Would you see just a silhouette? Would you be
00:02:25 --> 00:02:28 able to make out, uh, details and colors, if
00:02:28 --> 00:02:31 there are any colors on it? Uh, what about
00:02:31 --> 00:02:34 if, uh, you and Voyager were midway between
00:02:34 --> 00:02:36 the sun and Alpha Centauri? Uh, can we
00:02:37 --> 00:02:39 know a reasonably accurate answer,
00:02:39 --> 00:02:42 or is it pure speculation? Thanks. Love the
00:02:42 --> 00:02:45 show. Lee, from New York. I've never
00:02:45 --> 00:02:47 thought about that. I mean, we take for
00:02:47 --> 00:02:49 granted light on Earth because we're
00:02:49 --> 00:02:51 illuminated by the sun. But it's a bit
00:02:51 --> 00:02:54 different in other parts of the solar system
00:02:54 --> 00:02:56 and the universe in general. So, yeah, if we
00:02:56 --> 00:02:59 could just go, snap, we're out there next to
00:02:59 --> 00:03:02 Voyager 1. Could we actually see it? Is it
00:03:02 --> 00:03:04 illuminated in any way? Is it being
00:03:04 --> 00:03:06 illuminated by something? What would it be
00:03:06 --> 00:03:07 like?
00:03:08 --> 00:03:11 Professor Fred Watson: Uh, the answer is yes, you'd see it. Um, and
00:03:12 --> 00:03:14 so we're talking really now about the
00:03:14 --> 00:03:17 sensitivity of the human eye. Um, because,
00:03:17 --> 00:03:20 uh, with a camera, uh, you know,
00:03:20 --> 00:03:23 with long exposure settings and things you'd
00:03:23 --> 00:03:25 be able to see in great detail
00:03:25 --> 00:03:28 but thinking about the human eye. So,
00:03:29 --> 00:03:32 um, I used
00:03:32 --> 00:03:34 to work, as you know, at Siding Spring
00:03:34 --> 00:03:36 Observatory. Uh, I spent
00:03:36 --> 00:03:39 many hours, uh, outside at
00:03:39 --> 00:03:41 night. There it is a place that is truly
00:03:41 --> 00:03:44 dark. There's no interference from street
00:03:44 --> 00:03:47 lights. Uh, there are a few blobs of
00:03:47 --> 00:03:49 light on the horizon, but nothing that
00:03:49 --> 00:03:51 affects the pristine darkness of the night
00:03:51 --> 00:03:54 sky. And on a starry night
00:03:54 --> 00:03:57 with the sun not in the sky, you can see
00:03:57 --> 00:03:59 quite clearly. Um, there's enough
00:03:59 --> 00:04:02 light from the stars themselves to let
00:04:02 --> 00:04:05 you see where you're going. Uh, let
00:04:05 --> 00:04:08 you, you know, walk around and be
00:04:08 --> 00:04:10 quite confident that you're not going to fall
00:04:10 --> 00:04:12 off the mountain, as I nearly did one night
00:04:12 --> 00:04:15 when it was, uh, cloudy. I went out without
00:04:15 --> 00:04:16 my torch. I thought, oh, yeah, I'll see by
00:04:16 --> 00:04:18 the stars. But fortunately, unfortunately,
00:04:18 --> 00:04:20 the cloud had come in, I couldn't see
00:04:20 --> 00:04:22 anything and I nearly fell off the mountain.
00:04:23 --> 00:04:25 Uh, I didn't in the end. But, um.
00:04:25 --> 00:04:27 Andrew Dunkley: It's a long drop free.
00:04:27 --> 00:04:29 Professor Fred Watson: Yes, it is. Yes. It's quite a long drop
00:04:29 --> 00:04:31 anyway, uh, if you, uh, you know,
00:04:32 --> 00:04:34 normally on a starry night, you will see,
00:04:35 --> 00:04:38 um, by the light of the stars. Now,
00:04:38 --> 00:04:41 where voyager is Voyager 1, I
00:04:41 --> 00:04:44 just looked it up. Uh, it is, uh,
00:04:44 --> 00:04:46 at a distance from the sun
00:04:47 --> 00:04:49 in astronomical units, which is
00:04:49 --> 00:04:52 163 astronomical units. That's
00:04:52 --> 00:04:55 163 times the number
00:04:55 --> 00:04:58 of times the distance between the Earth and
00:04:58 --> 00:05:01 the sun. So that's 150 million
00:05:01 --> 00:05:04 kilometers. Multiply that by 163
00:05:04 --> 00:05:06 and you will get,
00:05:07 --> 00:05:10 uh. What do you get? I was looking for it in
00:05:10 --> 00:05:12 kilometers, but it's not there. I'll have to
00:05:12 --> 00:05:14 do the numbers anyway. It doesn't matter. The
00:05:14 --> 00:05:16 bad thing is, um, Its distance is
00:05:16 --> 00:05:19 22.55 light hours away.
00:05:19 --> 00:05:22 That's how long it takes, uh, the signal to
00:05:22 --> 00:05:25 get from Voyager to Earth. It's almost a day.
00:05:25 --> 00:05:28 It's almost a light day away. Um,
00:05:28 --> 00:05:31 so at that distance from the Sun,
00:05:31 --> 00:05:33 160 odd astronomical units,
00:05:34 --> 00:05:36 there's still significant light coming from
00:05:36 --> 00:05:38 the sun, not to mention Venus,
00:05:39 --> 00:05:42 uh, and um, you know, Jupiter and
00:05:42 --> 00:05:45 uh, the other planets. Mostly the sun though,
00:05:45 --> 00:05:47 you'd, you're being illuminated by the sun,
00:05:47 --> 00:05:50 so that's certainly opposite, uh, as
00:05:50 --> 00:05:53 compared with just being illuminated by the
00:05:53 --> 00:05:55 starry sky, which is what I was just talking
00:05:55 --> 00:05:57 about. So you'd see it really clearly. You
00:05:57 --> 00:05:59 uh, wouldn't have any problem making it out,
00:05:59 --> 00:06:01 assuming your eye was dark adapted.
00:06:03 --> 00:06:06 Andrew Dunkley: So, um, it's fairly bright out
00:06:06 --> 00:06:06 there.
00:06:06 --> 00:06:08 We talked about the sensitivity of the human
00:06:08 --> 00:06:11 eye as uh, you referred to
00:06:12 --> 00:06:14 how sort of small amount of light can we see
00:06:14 --> 00:06:15 as human beings?
00:06:16 --> 00:06:19 Professor Fred Watson: Um, I think there were some
00:06:19 --> 00:06:22 experiments. Let me think, was
00:06:22 --> 00:06:23 it one photon.
00:06:23 --> 00:06:25 Andrew Dunkley: Or one pixel like that?
00:06:25 --> 00:06:28 Professor Fred Watson: There was. That's right. We might have talked
00:06:28 --> 00:06:30 about this. There were experiments done that
00:06:30 --> 00:06:32 showed that the human eye is capable of
00:06:32 --> 00:06:35 detecting single photons. Uh, it was
00:06:35 --> 00:06:38 under special circumstances, but uh,
00:06:38 --> 00:06:41 and that is just extraordinary, um,
00:06:41 --> 00:06:44 when you think that the human eye can also
00:06:44 --> 00:06:47 cope with broad daylight. That's the
00:06:47 --> 00:06:49 amazing thing about the human eye. It can,
00:06:49 --> 00:06:52 you know, it's quite happy, uh, to see
00:06:53 --> 00:06:55 light, uh, one brightness and then
00:06:55 --> 00:06:58 a light that's only a millionth of as bright.
00:06:58 --> 00:07:01 Um, it's fine. You can deal with that. Ah.
00:07:01 --> 00:07:03 And that's a combination of what's called
00:07:03 --> 00:07:06 retinal bleaching and the iris of
00:07:06 --> 00:07:08 your eye opening and closing. It's all those
00:07:08 --> 00:07:10 things come together to give you this
00:07:11 --> 00:07:14 unbelievably versatile and sensitive
00:07:14 --> 00:07:16 tool with which we can look at the uh, our
00:07:16 --> 00:07:19 surroundings. Whether it's uh, the rock face
00:07:19 --> 00:07:21 I'm looking at now because that's what our
00:07:21 --> 00:07:24 backyard consists of, or whether it's uh,
00:07:24 --> 00:07:26 you know, the night sky where you're looking
00:07:26 --> 00:07:28 at faint objects, uh, in the sky.
00:07:29 --> 00:07:30 It's quite amazing.
00:07:31 --> 00:07:33 Andrew Dunkley: So even if you went deeper into space, way
00:07:33 --> 00:07:36 beyond our solar system, you, you would
00:07:36 --> 00:07:39 probably still see objects that you were
00:07:39 --> 00:07:39 near.
00:07:40 --> 00:07:41 Professor Fred Watson: There'd be enough light from the stars. The
00:07:41 --> 00:07:44 Milky Way is bright. Uh, it
00:07:44 --> 00:07:47 would, it would. You know, even if, as uh,
00:07:47 --> 00:07:50 Lee says, even if you were halfway between
00:07:51 --> 00:07:53 sun and Alpha Centauri, you'd still see it
00:07:53 --> 00:07:56 because of the ambient light, um,
00:07:56 --> 00:07:59 that's coming from, from the stars. Yeah.
00:07:59 --> 00:08:01 Andrew Dunkley: And you'd still see color because that's
00:08:01 --> 00:08:03 what. Well, it's dark enough, it might turn
00:08:03 --> 00:08:04 into the grays, which happens.
00:08:04 --> 00:08:06 Professor Fred Watson: That's right. Yeah. And I think that's
00:08:06 --> 00:08:08 likely. I think, I don't Think you would see
00:08:08 --> 00:08:11 color? Um, you. You would. Where it is now,
00:08:11 --> 00:08:12 there's enough light coming from the sun that
00:08:12 --> 00:08:15 you'd see color. But I think, uh, when you
00:08:15 --> 00:08:17 got further out, you would start to just see
00:08:17 --> 00:08:20 the. You know, as you said, that
00:08:21 --> 00:08:23 sort of pale gray appearance. Where you're
00:08:23 --> 00:08:25 looking at very low light. Low light levels
00:08:25 --> 00:08:27 indeed. Where the color cells aren't
00:08:27 --> 00:08:28 receptive.
00:08:29 --> 00:08:30 Andrew Dunkley: There you go. Lee, uh, the answer to your
00:08:30 --> 00:08:32 question's yes to all of the above,
00:08:32 --> 00:08:33 Basically.
00:08:33 --> 00:08:34 Duncan: Yeah.
00:08:34 --> 00:08:36 Andrew Dunkley: Great question. Excellent question.
00:08:37 --> 00:08:39 All right, let's move on. This is from
00:08:39 --> 00:08:40 Fenton.
00:08:40 --> 00:08:43 Duncan: Yeah. Hello, Fred and Andrew. This is
00:08:43 --> 00:08:46 Fenton contacting you from St.
00:08:46 --> 00:08:48 Paul, Minnesota, in the U.S.
00:08:49 --> 00:08:52 um, I sort of have a different type of
00:08:52 --> 00:08:54 astrophysical question for you.
00:08:55 --> 00:08:58 And this is on how to
00:08:58 --> 00:09:00 shield astronauts from
00:09:00 --> 00:09:03 radiation outside of the Van Allen Belt.
00:09:04 --> 00:09:07 Um, I was curious if you know of any pending
00:09:07 --> 00:09:10 technologies. That would allow this
00:09:10 --> 00:09:13 obvious choice would some people would say is
00:09:13 --> 00:09:16 lead. But I can think of several reasons why
00:09:16 --> 00:09:18 this is not a good idea. How about
00:09:18 --> 00:09:21 a miniature Van Allen Belt
00:09:21 --> 00:09:24 which could surround a
00:09:24 --> 00:09:27 spacecraft? How does that sound? How
00:09:27 --> 00:09:29 could this become, uh, reality?
00:09:30 --> 00:09:32 Thank you very much. I hope you like the
00:09:32 --> 00:09:34 question. Bye now.
00:09:34 --> 00:09:36 Andrew Dunkley: Thanks, Fenton. Fenton always has these
00:09:36 --> 00:09:39 intriguing thoughts. I've noticed in the
00:09:39 --> 00:09:41 Times that we've heard from him. Um, maybe we
00:09:41 --> 00:09:43 should start by explaining what the Van Allen
00:09:43 --> 00:09:45 Belt is. For those of us who just can't
00:09:45 --> 00:09:46 remember, like me.
00:09:48 --> 00:09:50 Professor Fred Watson: Um, it's, uh.
00:09:51 --> 00:09:53 So the Van Allen belts are the. Basically
00:09:53 --> 00:09:56 the. You know, the magnetic shielding
00:09:56 --> 00:09:59 around the Earth, uh, which is,
00:09:59 --> 00:10:02 uh. Caused by
00:10:02 --> 00:10:04 the magnetism of the Earth. It's caused by,
00:10:05 --> 00:10:08 uh, the fact that we've got an iron core. And
00:10:09 --> 00:10:11 basically, uh, it's in two parts. It's solid
00:10:11 --> 00:10:14 and liquid. So it acts like a dynamo. It's
00:10:14 --> 00:10:16 rotating. And that gives us this, uh.
00:10:16 --> 00:10:18 Exactly the protection that, um.
00:10:19 --> 00:10:21 Um. Um. Fenton is talking about.
00:10:22 --> 00:10:22 Andrew Dunkley: Um.
00:10:22 --> 00:10:25 Professor Fred Watson: Yeah, I was gonna refer.
00:10:25 --> 00:10:27 I'm a bit annoyed actually, because I've lost
00:10:27 --> 00:10:30 it. Uh, there is a very
00:10:30 --> 00:10:32 nice article on, um.
00:10:33 --> 00:10:35 Uh, it's actually on the, um.
00:10:35 --> 00:10:38 BBC's website. Uh,
00:10:38 --> 00:10:41 their sky at Night website. There's a lovely
00:10:41 --> 00:10:44 article on exactly this. Here it is. I found
00:10:44 --> 00:10:47 it. I hadn't lost it. How astronauts can hide
00:10:47 --> 00:10:49 from radiation on Mars. And it goes into,
00:10:50 --> 00:10:53 uh. Exactly the problem that,
00:10:53 --> 00:10:55 uh, Fenton's talking about. How do you
00:10:55 --> 00:10:58 present. How do you prevent, um, astronauts
00:10:59 --> 00:11:01 basically becoming irradiated.
00:11:02 --> 00:11:04 Uh, and over time it's
00:11:04 --> 00:11:07 basically lethal. Uh, because
00:11:07 --> 00:11:10 of the cosmic radiation that's coming down
00:11:10 --> 00:11:12 through space. Uh, and
00:11:14 --> 00:11:16 the cell damage, uh, in your
00:11:16 --> 00:11:19 body. Uh, and it can actually trigger cancer.
00:11:20 --> 00:11:23 So, um, the whole study of
00:11:23 --> 00:11:26 this is. Sorry,
00:11:26 --> 00:11:29 the thrust of this article, BBC sky at
00:11:29 --> 00:11:31 Night magazine, uh, is to
00:11:32 --> 00:11:34 discuss how you might protect astronauts,
00:11:35 --> 00:11:37 uh, from the radiation. Uh, and that's not
00:11:37 --> 00:11:40 just on Mars, but on route. Uh,
00:11:40 --> 00:11:42 okay, uh, the
00:11:43 --> 00:11:46 solution that Fenton has suggested
00:11:46 --> 00:11:48 is covered in a paragraph. I'm going to read
00:11:48 --> 00:11:51 it because we quoted where the source is. Uh,
00:11:51 --> 00:11:54 for example. All right,
00:11:54 --> 00:11:57 let me go back a paragraph. One method of
00:11:57 --> 00:11:59 helping astronauts to avoid the radiation on
00:11:59 --> 00:12:02 Mars is active shielding. For
00:12:02 --> 00:12:05 example, superconducting electromagnets could
00:12:05 --> 00:12:07 be used to create a powerful magnetic field
00:12:08 --> 00:12:10 to deflect the incoming charged radiation
00:12:10 --> 00:12:12 particles away, just as the Earth's field
00:12:12 --> 00:12:15 does. That's the Van Allen Belt. The problem
00:12:15 --> 00:12:17 is that such solutions can demand a lot of
00:12:17 --> 00:12:20 power to run, and the technology is a long
00:12:20 --> 00:12:23 way from being fully developed. An easier
00:12:23 --> 00:12:25 alternative is passive shielding. Simply
00:12:25 --> 00:12:28 placing a thick bulk of shielding material
00:12:28 --> 00:12:30 between the crew habitat and the sky.
00:12:31 --> 00:12:34 Uh, and then they go on to consider different
00:12:34 --> 00:12:37 materials. Aluminium, AKA
00:12:37 --> 00:12:40 aluminum, the metal that spacecraft are
00:12:40 --> 00:12:42 constructed from is actually a pretty bad
00:12:42 --> 00:12:45 radiation shield. Um, and
00:12:45 --> 00:12:47 they say when hit by an energetic cosmic
00:12:47 --> 00:12:50 ray, its atoms can shatter and fly onwards to
00:12:50 --> 00:12:52 create even more radiation particles.
00:12:53 --> 00:12:55 And Martian soil, the regolith, uh, which if
00:12:55 --> 00:12:58 you're on Mars, you might think about digging
00:12:58 --> 00:13:00 a hole there. Uh, it's got the same problem,
00:13:00 --> 00:13:03 but it's actually, uh, you know,
00:13:03 --> 00:13:06 abundant. Um, and so you
00:13:06 --> 00:13:09 could use that to dig a pole. If you
00:13:09 --> 00:13:12 put a 2 to 3 meter layer on top of
00:13:12 --> 00:13:14 your habitat, uh, then you'll,
00:13:14 --> 00:13:17 you'll get some protection. But, uh, the
00:13:17 --> 00:13:20 thing that surprised me, Andrew, uh, is once
00:13:20 --> 00:13:23 again, it comes from this same article. Uh,
00:13:23 --> 00:13:25 hydrogen is the best shielding material
00:13:26 --> 00:13:28 as it's light atoms. Yeah, it's light
00:13:28 --> 00:13:31 atoms. Uh, and by light I mean
00:13:31 --> 00:13:34 not heavy. Its light atoms don't create as
00:13:34 --> 00:13:37 much secondary radiation. And so tanks of
00:13:37 --> 00:13:39 rocket fuel or water, which is
00:13:39 --> 00:13:42 rich in hydrogen, placed over crew quarters
00:13:42 --> 00:13:44 could double up as effective radiation
00:13:44 --> 00:13:47 shields. I've heard that before that, um,
00:13:47 --> 00:13:49 one way of protecting your spacecraft as it
00:13:49 --> 00:13:52 flies to Mars is put it in a tank of water.
00:13:53 --> 00:13:55 Uh, it's the last thing you'd expect to do,
00:13:55 --> 00:13:57 but water is a good shielding material.
00:13:58 --> 00:14:01 And they also, uh, point out the
00:14:01 --> 00:14:03 alternative of hydrogen rich plastics like
00:14:03 --> 00:14:05 polyethylene could be used to cement
00:14:06 --> 00:14:08 regolith grains together. This is on Mars.
00:14:08 --> 00:14:11 And improve their shielding effect. Um,
00:14:11 --> 00:14:13 so, uh, if you want to read more about this,
00:14:13 --> 00:14:16 it's an article that originally appeared in
00:14:16 --> 00:14:19 the August 2022 issue of BBC
00:14:19 --> 00:14:21 sky at Night magazine. And it covers pretty
00:14:21 --> 00:14:23 well most of the ideas, uh, that have been,
00:14:23 --> 00:14:26 that have been suggested for this radiation
00:14:26 --> 00:14:28 issue. It's one that's got to, you know, it's
00:14:28 --> 00:14:31 got to find an answer soon because, uh,
00:14:31 --> 00:14:34 good old Elon and his starship, uh,
00:14:34 --> 00:14:36 is getting nearer to thinking about going to
00:14:36 --> 00:14:37 Mars. I don't think it's ever going to
00:14:37 --> 00:14:40 happen, but, uh, that's something he'll
00:14:40 --> 00:14:41 definitely be thinking about.
00:14:42 --> 00:14:45 Andrew Dunkley: Yes, indeed. He's too busy dealing with the
00:14:45 --> 00:14:46 Australian government at the moment.
00:14:47 --> 00:14:48 Professor Fred Watson: That's right.
00:14:48 --> 00:14:50 Andrew Dunkley: Some of the content on Twitter that the
00:14:50 --> 00:14:53 government wants to get rid of simply because
00:14:53 --> 00:14:55 of its, um, volatility. But anyway, that's a
00:14:55 --> 00:14:57 different story. Um, but there's plenty of
00:14:57 --> 00:15:00 water on Mars, so maybe, maybe creating those
00:15:00 --> 00:15:03 water barriers is probably the simplest thing
00:15:03 --> 00:15:05 to do. You've already got the material there.
00:15:05 --> 00:15:07 Professor Fred Watson: If you've landed in the right spot where
00:15:07 --> 00:15:09 you've got permafrost or whatever.
00:15:09 --> 00:15:11 Andrew Dunkley: That's the question. Yes, indeed. Uh, well
00:15:11 --> 00:15:14 done, Fenton. You actually happened across
00:15:14 --> 00:15:16 some of, uh, the answers too in, uh, asking
00:15:16 --> 00:15:19 your question. Uh, this is Space
00:15:19 --> 00:15:21 Nuts Andrew Dunkley here with Professor Fred
00:15:21 --> 00:15:22 Watson.
00:15:25 --> 00:15:27 Generic: Three, two, one.
00:15:28 --> 00:15:29 Andrew Dunkley: Space Nuts.
00:15:29 --> 00:15:32 Now, Fred, uh, our next question comes from
00:15:32 --> 00:15:34 Robert. Hi guys. Love your show. Sorry for
00:15:34 --> 00:15:36 the long question, but feel free to
00:15:36 --> 00:15:39 paraphrase, uh, or shorten it. Our
00:15:39 --> 00:15:42 moon is heavily crated and has given
00:15:42 --> 00:15:44 us a lot of insight into the history of the
00:15:44 --> 00:15:46 solar system and perhaps how the planets
00:15:46 --> 00:15:48 formed. But what if we had a moon
00:15:49 --> 00:15:51 like the icy moon Europa or the
00:15:51 --> 00:15:54 shrouded in, uh, haze Titan, both of
00:15:54 --> 00:15:56 which don't show immediate evidence of
00:15:56 --> 00:15:59 cratering? Would our theory about, uh, how
00:15:59 --> 00:16:02 the planets developed would, uh, be
00:16:02 --> 00:16:04 different? What other insights about our
00:16:04 --> 00:16:07 solar system would be missing or would
00:16:07 --> 00:16:10 we be missing? And lastly, uh, would we have
00:16:10 --> 00:16:12 spent, uh, or would we have sent people to
00:16:12 --> 00:16:14 land on such moons, that is, uh,
00:16:15 --> 00:16:18 would they be more dangerous for
00:16:18 --> 00:16:19 astronauts? Cheers.
00:16:19 --> 00:16:22 Robert in Vienna, Austria. Wow. I don't think
00:16:22 --> 00:16:24 we've had a question from Vienna before, have
00:16:24 --> 00:16:26 we? Lovely to hear from you, Robert.
00:16:27 --> 00:16:28 Professor Fred Watson: I think, I think Robert might have been in
00:16:28 --> 00:16:29 touch once before.
00:16:29 --> 00:16:32 Andrew Dunkley: Oh, I might have been too. It's very rare to
00:16:32 --> 00:16:33 hear from Vienna.
00:16:34 --> 00:16:35 Professor Fred Watson: Yeah, I was in Vienna at the beginning of
00:16:35 --> 00:16:37 last year and I think, I think we got
00:16:37 --> 00:16:39 something around about the same time. And I
00:16:39 --> 00:16:41 was waxing lyrical about being in Vienna at
00:16:41 --> 00:16:44 the UN when I was at, uh, the copywritten
00:16:44 --> 00:16:46 meeting. Anyway, that's another, another
00:16:46 --> 00:16:49 issue. Uh, what if we had a. Yeah, it's a
00:16:49 --> 00:16:51 really interesting question. Um,
00:16:52 --> 00:16:55 what would we not know about
00:16:55 --> 00:16:57 the solar system. If our moon
00:16:58 --> 00:17:00 was basically one
00:17:01 --> 00:17:03 that had been resurfaced in recent years
00:17:03 --> 00:17:06 or even millennia, because that's what makes
00:17:06 --> 00:17:09 the surface smooth. That's how we
00:17:09 --> 00:17:11 recognize, um, the
00:17:11 --> 00:17:14 fact that the universe. Sorry, that the.
00:17:15 --> 00:17:17 It's how we recognize the age of a surface is
00:17:17 --> 00:17:20 by how many craters it's got. The older, the
00:17:20 --> 00:17:22 older the surface, the more craters it has.
00:17:23 --> 00:17:25 And so the Moon's southern region, which is
00:17:25 --> 00:17:28 heavily cratered, as is the backside, tell
00:17:28 --> 00:17:31 uh, us that, uh, early on in the solar
00:17:31 --> 00:17:33 system's history, it was a very, um, wild and
00:17:33 --> 00:17:36 woolly place with things charging about all
00:17:36 --> 00:17:38 over and causing these craters. Now if we
00:17:38 --> 00:17:41 had a moon that was like Europa, that had,
00:17:41 --> 00:17:43 um, you know, icy, uh,
00:17:43 --> 00:17:46 geysers on it that basically covered up the
00:17:46 --> 00:17:49 craters, would we have known about that? My
00:17:49 --> 00:17:52 guess is yes, we would, because we'd
00:17:52 --> 00:17:54 see other bodies within the solar solar
00:17:54 --> 00:17:56 system, uh, like, you know, other moons,
00:17:56 --> 00:17:59 like, um, places like,
00:18:00 --> 00:18:02 um, Ceres, um, the biggest of the
00:18:02 --> 00:18:04 asteroids, the dwarf planet that dominates
00:18:04 --> 00:18:06 the asteroid belt that's heavily cratered.
00:18:07 --> 00:18:09 Uh, parts of Pluto are heavily cratered.
00:18:10 --> 00:18:10 Duncan: Um.
00:18:11 --> 00:18:14 Professor Fred Watson: Uh, Mimas, uh, one of Saturn's
00:18:15 --> 00:18:18 moons is heavily cratered too. So we'd
00:18:18 --> 00:18:20 know about it by looking at other objects.
00:18:20 --> 00:18:23 Even if our own moon was smoothly, uh,
00:18:23 --> 00:18:26 surfaced, um, it's, it's, uh.
00:18:26 --> 00:18:29 But the. Robert's last point, uh, on,
00:18:29 --> 00:18:31 um, this would, uh. We have sent
00:18:31 --> 00:18:34 people to land on such a moon. I,
00:18:34 --> 00:18:37 uh, think, um. I don't know. That's a really
00:18:37 --> 00:18:39 good question. I mean, we have sent people to
00:18:39 --> 00:18:42 land on our moon as it stands, uh, with an
00:18:42 --> 00:18:45 ancient surface. In fact, where they landed
00:18:45 --> 00:18:48 were more recent, uh, than the heavily
00:18:48 --> 00:18:49 cratered surfaces because they were
00:18:49 --> 00:18:52 principally in the maria, the basalt plains.
00:18:52 --> 00:18:55 Yeah, so maybe that
00:18:55 --> 00:18:58 suggests that we would have landed people on
00:18:58 --> 00:19:00 Europa as well, uh, because I think we
00:19:00 --> 00:19:01 probably.
00:19:01 --> 00:19:03 Andrew Dunkley: Yeah, we probably would because it would have
00:19:03 --> 00:19:06 a solid surface. There'd be places because it
00:19:06 --> 00:19:08 would be so close to us, we'd be able to
00:19:08 --> 00:19:11 examine and find the right landing points.
00:19:12 --> 00:19:15 Might be a bit more difficult with a moon
00:19:15 --> 00:19:17 that's shrouded in land gas.
00:19:17 --> 00:19:20 Professor Fred Watson: Yeah, yeah, that's right. And
00:19:20 --> 00:19:22 especially in places, um, like Titan.
00:19:23 --> 00:19:26 Uh, I still think
00:19:26 --> 00:19:28 we'd have done it actually. I think, um, you
00:19:28 --> 00:19:31 know, the JFK's, uh, promise
00:19:31 --> 00:19:33 to put astronauts on the moon would have
00:19:33 --> 00:19:35 still held good even if it had been a very
00:19:35 --> 00:19:38 different place. If it had been like IO, uh,
00:19:38 --> 00:19:40 it might have been a different story where,
00:19:40 --> 00:19:42 you know, you've got the most volcanically
00:19:42 --> 00:19:45 active body in the entire solar system with
00:19:45 --> 00:19:47 stuff going off all over the place, I think
00:19:47 --> 00:19:48 we might have been a bit more reluctant to
00:19:49 --> 00:19:49 land on eo.
00:19:49 --> 00:19:52 Andrew Dunkley: Uh, yes, possibly. So, uh,
00:19:52 --> 00:19:54 it would be interesting to have something
00:19:54 --> 00:19:57 different. But then if we'd always
00:19:57 --> 00:19:59 had an ice moon, we probably would have
00:19:59 --> 00:20:02 caught a question from, uh, Robert asking,
00:20:02 --> 00:20:04 what if we had a rocky moon now.
00:20:04 --> 00:20:07 Professor Fred Watson: Would we look, would we have
00:20:07 --> 00:20:07 a.
00:20:07 --> 00:20:10 Andrew Dunkley: Different interpretation of the formations of
00:20:10 --> 00:20:11 the planets if there was a rocky moon next to
00:20:11 --> 00:20:14 us instead of an ice moon? Yes. Um, in an
00:20:14 --> 00:20:16 alternative universe, Robert, you would have
00:20:16 --> 00:20:18 flipped your question. Good to hear from you.
00:20:18 --> 00:20:21 Hope all is well in Austria.
00:20:21 --> 00:20:23 Our final question for this episode comes
00:20:23 --> 00:20:24 from Duncan.
00:20:25 --> 00:20:27 Duncan: Hello, Duncan here from
00:20:27 --> 00:20:29 Weymouth in the uk.
00:20:30 --> 00:20:32 Again, a quick question.
00:20:34 --> 00:20:37 Just looking was doing some reading and I
00:20:37 --> 00:20:39 noticed that Uranus and Neptune
00:20:39 --> 00:20:42 are often referred to as ice
00:20:42 --> 00:20:44 giants. Now
00:20:45 --> 00:20:47 given that ice is
00:20:48 --> 00:20:50 basically just sort of like a rock form of
00:20:50 --> 00:20:53 water or CO2
00:20:53 --> 00:20:56 or whatever else, but basically just
00:20:56 --> 00:20:59 a solid form of it, why are they not just
00:20:59 --> 00:21:01 called rock giants? Why do we
00:21:02 --> 00:21:05 make the definition of ice rather than just
00:21:05 --> 00:21:08 calling them rock? It just seems
00:21:08 --> 00:21:11 odd because the little planets in the
00:21:11 --> 00:21:13 inner solar system are referred to as rocky
00:21:13 --> 00:21:16 planets. So given that they're also
00:21:17 --> 00:21:19 apparently rocky, why are they not called
00:21:19 --> 00:21:22 rocky giants? Okay,
00:21:22 --> 00:21:24 thank you, Bye.
00:21:24 --> 00:21:27 Andrew Dunkley: Thanks, Duncan. Appreciate your questions as
00:21:27 --> 00:21:30 always. Uh, yeah, why do we call them ice
00:21:30 --> 00:21:32 giants? Just for the sake of the exercise?
00:21:32 --> 00:21:35 Because there's gas giants and ice giants.
00:21:36 --> 00:21:39 Professor Fred Watson: Yeah, except one is a subset of the other.
00:21:39 --> 00:21:42 And so all four of the outer
00:21:42 --> 00:21:44 planets, Jupiter, Saturn, Neptune, sorry,
00:21:44 --> 00:21:47 Uranus, Neptune, they're all gas giants
00:21:47 --> 00:21:50 because they have, uh, high mass.
00:21:51 --> 00:21:54 Uh, um, you know, much more,
00:21:54 --> 00:21:56 um, in the case of Jupiter certainly, than,
00:21:56 --> 00:21:59 uh, our own planet. Um,
00:21:59 --> 00:22:02 the. They've got their giants, they're big,
00:22:02 --> 00:22:05 they've got high mass, and they don't
00:22:05 --> 00:22:07 have a visible surface,
00:22:08 --> 00:22:10 which is why they call gas giants, because
00:22:10 --> 00:22:12 all we see is a gassy envelope.
00:22:12 --> 00:22:15 Um, just to go to the last of
00:22:15 --> 00:22:17 Duncan's questions there, we wouldn't call
00:22:17 --> 00:22:20 the inner planets rocky giants because
00:22:20 --> 00:22:22 they're not giants. They're, uh, kind of
00:22:22 --> 00:22:23 normal planet size. You know, if you, if you
00:22:23 --> 00:22:25 think of the Earth as being your standard
00:22:25 --> 00:22:27 planet, then, uh, Mercury,
00:22:28 --> 00:22:31 Venus and Mars are similar, ah, in size.
00:22:31 --> 00:22:33 They're, uh, all smaller. Venus is about the
00:22:33 --> 00:22:35 same size, but Mercury and Mars of course are
00:22:35 --> 00:22:38 smaller. Uh, so it's only when you
00:22:38 --> 00:22:40 compare with the size of Earth that you'd
00:22:40 --> 00:22:42 start talking about giants because they are
00:22:42 --> 00:22:45 much, much bigger than Earth. And so that's
00:22:45 --> 00:22:47 the gas giants. So why Are, uh,
00:22:48 --> 00:22:50 Uranus and Neptune called ice giants
00:22:51 --> 00:22:53 because they have
00:22:53 --> 00:22:56 hazes of ice in their atmosphere.
00:22:57 --> 00:23:00 So. And that's the trick. It's not
00:23:00 --> 00:23:02 a solid surface. It's not rock.
00:23:03 --> 00:23:06 It's a haze. It's kind of like, uh, a dust
00:23:06 --> 00:23:08 of ice which permeates their atmosphere.
00:23:08 --> 00:23:11 And it's water ice, in fact, uh,
00:23:11 --> 00:23:14 mostly. Uh, so that's why they
00:23:14 --> 00:23:17 called ice giants, because unlike Saturn and
00:23:17 --> 00:23:20 Jupiter, which don't have these hazes,
00:23:20 --> 00:23:20 uh,
00:23:23 --> 00:23:25 the two outer planets, Uranus and
00:23:25 --> 00:23:28 Neptune, do they have ice hazes in their
00:23:28 --> 00:23:29 atmosphere. Hence the name.
00:23:30 --> 00:23:33 Andrew Dunkley: Okay. Yeah. And of course, the last episode
00:23:33 --> 00:23:35 we learned there wasn't much water in
00:23:35 --> 00:23:36 Jupiter's atmosphere.
00:23:36 --> 00:23:37 Professor Fred Watson: That's right.
00:23:38 --> 00:23:41 Andrew Dunkley: In the two outer gas giants. Yeah,
00:23:41 --> 00:23:43 it sounds like there is. Is that why they're
00:23:43 --> 00:23:43 a different color?
00:23:44 --> 00:23:47 Professor Fred Watson: Yes, yes, I think that's right. Um,
00:23:48 --> 00:23:50 and also their atmospheric constituents are,
00:23:50 --> 00:23:53 uh, different. They don't have the same belt
00:23:53 --> 00:23:56 structure that Saturn and Jupiter do. It may
00:23:56 --> 00:23:58 be that that's because any belts that exist
00:23:58 --> 00:24:00 are, uh, much lower in the atmosphere, and so
00:24:00 --> 00:24:03 you don't see them. Um, yeah, I
00:24:03 --> 00:24:06 mean, uh, there's a strong body of,
00:24:07 --> 00:24:10 uh, advocacy within the space
00:24:10 --> 00:24:12 fraternity to get
00:24:14 --> 00:24:16 more spacecraft out to Uranus and
00:24:16 --> 00:24:19 Neptune because they're the two planets about
00:24:19 --> 00:24:22 which we know least. Um, and, uh, will
00:24:22 --> 00:24:23 be good to know more.
00:24:24 --> 00:24:25 Duncan: Yeah.
00:24:25 --> 00:24:27 Andrew Dunkley: Well, if you sit down in snow for long
00:24:27 --> 00:24:30 enough, Uranus turns into a nice giant.
00:24:32 --> 00:24:33 I couldn't help it.
00:24:33 --> 00:24:35 Professor Fred Watson: Sorry. Uh, yeah,
00:24:36 --> 00:24:39 which is why we call it Uranus in politics.
00:24:39 --> 00:24:40 I know, I know.
00:24:41 --> 00:24:43 Andrew Dunkley: Yeah. But it's just a joke.
00:24:43 --> 00:24:43 Duncan: Got to tell.
00:24:43 --> 00:24:44 Professor Fred Watson: It's just.
00:24:44 --> 00:24:45 Andrew Dunkley: You have to.
00:24:46 --> 00:24:49 Professor Fred Watson: Yes, I. I blame Johannes Boda, who is
00:24:49 --> 00:24:52 the person who chose the name. He's fine in
00:24:52 --> 00:24:54 German. There's nothing wrong with
00:24:55 --> 00:24:57 German ruins. All the jokes
00:24:57 --> 00:24:58 there.
00:24:59 --> 00:25:01 Andrew Dunkley: All right, so, yes, uh, they're ice giants
00:25:01 --> 00:25:03 for a very good reason, Duncan. Because
00:25:03 --> 00:25:05 they've got ice in them in, uh, the
00:25:05 --> 00:25:07 atmosphere. But, uh, technically speaking,
00:25:07 --> 00:25:09 they are, in fact, gas giants. But, yes,
00:25:10 --> 00:25:11 you differentiate them because of their
00:25:12 --> 00:25:14 substantially different atmospheres. There
00:25:14 --> 00:25:14 you are.
00:25:15 --> 00:25:15 Professor Fred Watson: Thanks, Duncan.
00:25:15 --> 00:25:17 Andrew Dunkley: Great to hear from you. Great to, uh, hear
00:25:17 --> 00:25:18 from everybody. Thanks for sending in your
00:25:18 --> 00:25:20 questions. Don't forget, you can send in
00:25:20 --> 00:25:22 questions via our website, spacenuts
00:25:22 --> 00:25:25 podcast.com spacenuts IO
00:25:25 --> 00:25:26 and all you have to do is click on the
00:25:26 --> 00:25:29 various links on the right hand side, send us
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00:25:31 --> 00:25:33 Uh, or you can send us text and audio
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00:25:49 --> 00:25:52 button below. Which, yes, it's down
00:25:52 --> 00:25:55 there somewhere. I don't know one of those
00:25:55 --> 00:25:57 places. Fred, as always, thank you so much.
00:25:58 --> 00:25:59 Professor Fred Watson: Pleasure, Andrew. See you soon.
00:26:00 --> 00:26:03 Andrew Dunkley: Okay. Fred Watson, astronomer at large. We'll
00:26:03 --> 00:26:04 catch him on the next episode of Space Nuts.
00:26:04 --> 00:26:07 We might catch Huw then as well because, um,
00:26:09 --> 00:26:11 not here today. Didn't even call in sick. I
00:26:11 --> 00:26:14 need a note. And from me, Andrew Dunkley.
00:26:14 --> 00:26:16 Thanks very much for your company. We'll see
00:26:16 --> 00:26:18 you again soon on the next episode of Space
00:26:18 --> 00:26:19 Nuts. Bye. Bye.
00:26:20 --> 00:26:22 Generic: You've been listening to the Space Nuts
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