In this engaging Q&A edition of Space Nuts, hosts Andrew Dunkley and Professor Fred Watson tackle intriguing listener questions that delve into the mysteries of space. From the visibility of Voyager 1 in the depths of the solar system to the challenges of shielding astronauts from cosmic radiation, this episode is a treasure trove of cosmic knowledge.
Episode Highlights:
- Light in Space: Lee from New York City poses a thought-provoking question about how much light exists in space. Andrew and Fred explore the visibility of Voyager 1 and the implications of being far from the Sun, shedding light on human eye sensitivity and the ambient light from stars.
- Shielding Astronauts: Fenton from St. Paul, Minnesota, raises an important question about protecting astronauts from radiation beyond the Van Allen Belt. The hosts discuss potential technologies, including superconducting electromagnets and the surprising effectiveness of hydrogen-rich materials like water as radiation shields.
- Moon Comparisons: Robert from Vienna, Austria, wonders how our understanding of the solar system would differ if Earth had a moon like Europa or Titan, rather than our heavily cratered moon. The discussion highlights the significance of craters in understanding planetary history and the feasibility of landing on such moons.
- Ice Giants Explained: Duncan from Weymouth, UK, questions why Uranus and Neptune are termed "ice giants" instead of "rock giants." Andrew and Fred clarify the definitions and characteristics that distinguish these planets from their gas giant counterparts, emphasizing the unique atmospheric compositions.
For more Space Nuts, including our continuously updating newsfeed and to listen to all our episodes, visit our website. Follow us on social media at SpaceNutsPod on Facebook, X, YouTube Music Music, Tumblr, Instagram, and TikTok. We love engaging with our community, so be sure to drop us a message or comment on your favorite platform.
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Stay curious, keep looking up, and join us next time for more stellar insights and cosmic wonders. Until then, clear skies and happy stargazing.
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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
00:25:29 --> 00:25:31 your question. That's audio questions only.
00:25:31 --> 00:25:33 Uh, or you can send us text and audio
00:25:33 --> 00:25:36 questions via the AMA M tab up the top. It's
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00:25:46 --> 00:25:49 can subscribe just by pressing the subscribe
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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