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