#456: Safeguarding the Moon, Titan's Liquid Sounds & Dark Matter Drifts

[00:00:00] [SPEAKER_02]: Hi there, thanks for joining us yet again on Space Nuts. This is a Q&A episode where we answer

[00:00:06] [SPEAKER_02]: your questions. You ask the questions we, as in the Royal Wee, as in Fred answers them.

[00:00:12] [SPEAKER_02]: We should do it the other way around one day. We ask you the questions. Why don't you get a job

[00:00:18] [SPEAKER_02]: for a starter? But anyway, coming up on this episode, we're going to answer questions about

[00:00:26] [SPEAKER_02]: protecting the Moon, the sound of liquids on other worlds. Interesting. Dark Matter movement,

[00:00:33] [SPEAKER_02]: shocker, Dark Matter question, and how atmospheres are formed. That's all coming up on this episode of

[00:00:39] [SPEAKER_02]: Space Nuts.

[00:00:57] [SPEAKER_02]: One man who's got a job is Professor Fred Watson, Astronomer at Large. Unlike me, I don't work

[00:01:03] [SPEAKER_02]: anymore. I've chucked it all in. This is not a job. This is fun. This is a hobby. Hi, Fred.

[00:01:10] [SPEAKER_01]: Yeah, it's fun for me. Excuse me. It's fun for me too. But you're right. I do have a job and

[00:01:15] [SPEAKER_02]: there we go. Yes. Now, we have got a lot to get through. So I think we'll just plow

[00:01:23] [SPEAKER_02]: straight into it. And our first question comes from a regular sender-innera. His name is Mikey.

[00:01:31] [SPEAKER_03]: Hey, Fred and Andrew. It's Mikey once again from Way Too Hot Illinois. Got a question for you

[00:01:39] [SPEAKER_03]: guys. I know we have like a planetary protection for incoming asteroids that threaten Earth,

[00:01:48] [SPEAKER_03]: but do we have the same thing for the Moon? Like what if a ginormous asteroid were to hit the Moon

[00:01:56] [SPEAKER_03]: and blow it to smithereens or knock it off course or alter it in some huge way? Because the Moon

[00:02:03] [SPEAKER_03]: is very important to the life on Earth, right? So I guess first of all, what would happen

[00:02:10] [SPEAKER_03]: if something happened to the Moon when we still have a good chance of surviving? And secondly,

[00:02:16] [SPEAKER_03]: is there a protection plan in place like there is for the Earth for the Moon? Thanks, guys. Love

[00:02:21] [SPEAKER_02]: about it, Gast. Thanks, Mikey. Always ask interesting questions. The answer's no and yes.

[00:02:29] [SPEAKER_02]: Well, it is, yeah. Yeah. We've had questions about the loss of the Moon before and what might

[00:02:36] [SPEAKER_02]: happen to us. And I do believe that we have discussed maybe once or twice

[00:02:42] [SPEAKER_02]: that the protection of the planet includes the Moon. We realize that, yeah, we can't just

[00:02:48] [SPEAKER_02]: protect ourselves. We've got to protect the Moon. Otherwise, you know, if it gets obliterated,

[00:02:54] [SPEAKER_01]: we're in big trouble. Yeah, okay. So, but obliterated, that would have to be a huge object.

[00:03:00] [SPEAKER_01]: That's the point. There's nothing, there's no scenario that we can envisage at the moment

[00:03:07] [SPEAKER_01]: that would involve such a collision. So we're talking about asteroids, you know, even something

[00:03:16] [SPEAKER_01]: measured in kilometers hitting the Moon would be of concern to us because the Moon's very

[00:03:24] [SPEAKER_01]: close to the Earth and, you know, that's one of the things that we need to know about.

[00:03:29] [SPEAKER_01]: So the bottom line is that our protection of Earth in terms of it's not actually

[00:03:35] [SPEAKER_01]: planetary protection is something slightly different. That's a biological thing. Planetary

[00:03:40] [SPEAKER_01]: defense is what we're talking about. And defending the Earth effectively means we defend the Moon

[00:03:45] [SPEAKER_01]: as well in the sense that if we are looking for hazardous objects, and that's, you know,

[00:03:51] [SPEAKER_01]: that's a well-established technology which we're doing, we think we've discovered most of the

[00:03:56] [SPEAKER_01]: objects that might threaten Earth and the Moon, which are more than a kilometer in size.

[00:04:02] [SPEAKER_01]: It's the objects of a few hundred meters that we're looking at now. Now, the detection of those

[00:04:09] [SPEAKER_01]: is part and parcel of modern astronomy and we find them with regularity. If one was on a

[00:04:18] [SPEAKER_01]: collision course with the Earth then we'd do something about it and we've discussed that before

[00:04:23] [SPEAKER_01]: many times Andrew. If one of these... We test as a theory of deflection.

[00:04:28] [SPEAKER_01]: Yes indeed, it was a dark mission. That's right. But if one of them was shown to impact the Moon,

[00:04:36] [SPEAKER_01]: we wouldn't do anything about it. I think we would let it happen because it's just part of

[00:04:42] [SPEAKER_01]: the natural cycle of events and unless there were... There was a threat to humans on the Moon,

[00:04:49] [SPEAKER_01]: you wouldn't do anything about it. And in fact, if you knew enough about such an object,

[00:04:54] [SPEAKER_01]: going to hit the Moon, you'd bring humans back. You'd get them off the Moon because that's a lot

[00:05:00] [SPEAKER_01]: easier than trying to deflect an asteroid. So it's... The lunar defense is basically wrapped up

[00:05:10] [SPEAKER_01]: within planetary defense of the Earth with the one exception that we would not try and

[00:05:17] [SPEAKER_01]: deflect an asteroid if one of any particular size was shown to be targeting the Moon.

[00:05:25] [SPEAKER_01]: It gets hit a lot anyway, doesn't it? It does, that's right. Yes, getting... And because there's no

[00:05:30] [SPEAKER_01]: atmosphere on the Moon, they get clouded. The Moon gets clouded much more forcefully

[00:05:37] [SPEAKER_01]: than the Earth does by these incoming objects. So yes, it's a work in progress. It's happening

[00:05:44] [SPEAKER_01]: all the time. And sometimes there's interesting physics involved. If you can see the flash of an

[00:05:53] [SPEAKER_01]: impacting meteor or asteroid, then you've got new data to look at and to work with.

[00:06:03] [SPEAKER_02]: If something was big enough to destroy the Moon, we probably wouldn't have a prayer

[00:06:08] [SPEAKER_02]: stopping it anyway, would we? No, we wouldn't. And there isn't anything. So it's okay. No.

[00:06:16] [SPEAKER_02]: Yeah, well not within our solar system but maybe something... Yeah, that's right.

[00:06:21] [SPEAKER_02]: Extra solar might come through. We've had a couple of those over the years.

[00:06:25] [SPEAKER_01]: Yeah. The thing is, the bigger the object is, the easier it is to detect. And

[00:06:31] [SPEAKER_01]: you know, there's just nothing on the horizon even of that kind of the Moon.

[00:06:37] [SPEAKER_01]: Although the Moon being made of cheese would absorb an impact quite easily.

[00:06:44] [SPEAKER_01]: Unless it was a particularly hard cheddar, that might...

[00:06:48] [SPEAKER_02]: Yes, so that's a point. Yeah. All right, I can think of a few cheese puns but let's move on.

[00:06:56] [SPEAKER_02]: Thanks, Mikey. Good to hear from you. Our next question comes from somebody else and I've actually

[00:07:03] [SPEAKER_02]: managed to lose it. Here we go. Don't know how that happened. Thank you, Windows.

[00:07:09] [SPEAKER_02]: G'day, Fred and Andrew. As a native Minnetonan, Minnesota. All right, Minnesotan.

[00:07:17] [SPEAKER_02]: I quite enjoy taking holiday time along the North Shore of Lake Superior. I love

[00:07:22] [SPEAKER_02]: the sound of the waves washing onto the shore and that got me to thinking about lakes and rivers

[00:07:27] [SPEAKER_02]: on Titan. Would they sound comparable to what we have on Earth or because it's not water,

[00:07:33] [SPEAKER_02]: would there be some kind of distinctive difference to the sound of the liquid

[00:07:37] [SPEAKER_02]: ethane-methane interacting with its surroundings? I realize this is probably out of Fred's area

[00:07:42] [SPEAKER_02]: of expertise but that's half of the course here on Space Nuts. Thanks very much guys

[00:07:48] [SPEAKER_02]: from James Greenfield. Yeah, James asks an interesting question because we've talked in

[00:07:54] [SPEAKER_02]: the past about different types of suns and if life existed on worlds surrounding those suns,

[00:08:01] [SPEAKER_02]: the trees might have different colored leaves and things like that but I would imagine also

[00:08:07] [SPEAKER_02]: that sounds on other planets and other moons would vary depending on the conditions, would they not?

[00:08:20] [SPEAKER_01]: It's yes, they would and there's two things at play here. First of all, there's the liquid

[00:08:27] [SPEAKER_01]: which may be quite viscous. We don't really know. It's sort of oily. It's hydrocarbon.

[00:08:37] [SPEAKER_01]: We know what liquid hydrocarbons are like here on Earth but there might be

[00:08:42] [SPEAKER_01]: compounds within it that make it a bit more viscous. We think

[00:08:46] [SPEAKER_01]: we covered a story not long ago that suggested that if you look at the shape of the lakes

[00:08:52] [SPEAKER_01]: on Titan, you can tell that there are waves there, windblown waves. Yeah, that's right.

[00:09:00] [SPEAKER_01]: But the likelihood is they're not very high because radar reflections from Titan's

[00:09:08] [SPEAKER_01]: seas are very, very smooth indeed and so I mean I've read some papers that suggest that

[00:09:13] [SPEAKER_01]: the waves are only millimeters high which probably wouldn't make much noise. The other thing though

[00:09:21] [SPEAKER_01]: is the atmosphere which is at a different pressure from our atmosphere on planet Earth.

[00:09:29] [SPEAKER_01]: 1.5 bars is the atmospheric pressure there and so it's basically is 50% higher than our

[00:09:40] [SPEAKER_01]: atmospheric pressure here. So that's going to change the speed of sound, it's going to change the way

[00:09:44] [SPEAKER_01]: things sound. It's really hard to imagine what the waves on Titan might sound like and I think

[00:09:51] [SPEAKER_01]: James poses a really interesting question. There'd probably be a way of working it out though

[00:09:57] [SPEAKER_01]: if you're really needed to know that. Somebody will do a simulation if needed but theory

[00:10:05] [SPEAKER_02]: would help as well. It would also change the pitch of your voice wouldn't it?

[00:10:11] [SPEAKER_02]: Yeah, that's right. Probably. Hello Andrew joining you. Yeah well you'd probably be going

[00:10:18] [SPEAKER_02]: help and that'll be the end of that. That'll be the end of that. That's right. But yeah everything

[00:10:24] [SPEAKER_02]: would probably be different in one way or another so yeah definitely James you would

[00:10:31] [SPEAKER_02]: have a different sounding liquid scenario on somewhere like Titan and any other place with

[00:10:37] [SPEAKER_02]: liquid surfaces. Good to get your question. Thank you James this is SpaceNuts,

[00:10:42] [SPEAKER_02]: Andrew Dunkley with Professor Fred Watson. Let's take a quick break from the show to

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[00:13:19] [SPEAKER_02]: To our next question an audio question this one Fred comes from Bill. Hi this is Bill

[00:13:27] [SPEAKER_00]: San Francisco Bay area. My question is could dark matter travel through space? So dark matter apparently

[00:13:38] [SPEAKER_00]: doesn't interact with other things other than through gravity so could dark matter get thrown

[00:13:46] [SPEAKER_00]: around or out of a galaxy due to other gravitational events kind of like planets and other stuff does?

[00:13:54] [SPEAKER_00]: Oh that's my question. Love the show. Thanks. Thank you Bill. Bill's from a very watery part

[00:14:01] [SPEAKER_02]: of the world as well San Francisco Bay it would have some sloshy sounds around it indeed.

[00:14:08] [SPEAKER_02]: Dark matter we did talk about it recently in light of the fact that they discovered that

[00:14:14] [SPEAKER_02]: it may well interact with itself but that's not what he's asking he's asking about dark

[00:14:19] [SPEAKER_02]: matter movement can it move around? We also I think discussed that it seems to concentrate around

[00:14:28] [SPEAKER_02]: galaxies and in places of saturation I suppose of other objects so it's an interesting question.

[00:14:39] [SPEAKER_01]: That's right so dark matter basically is where normal matter is and we think that's no accident

[00:14:45] [SPEAKER_01]: we think that the dark matter cosmic web provided basically gravitational centers for

[00:14:53] [SPEAKER_01]: normal matter to collect and turn into stars and galaxies but you've highlighted one of the crucial

[00:15:00] [SPEAKER_01]: aspects of this that we did talk a couple of weeks ago I think it was about the idea that dark

[00:15:07] [SPEAKER_01]: matter might interact with itself some evidence that seemed to suggest that although I think

[00:15:13] [SPEAKER_01]: the common view is still that it doesn't and the evidence for that comes from something that

[00:15:25] [SPEAKER_01]: directly answers Bill's question. Dark matter move and the answer is yes there is

[00:15:34] [SPEAKER_01]: if I remember rightly I think it's called the Pandora cluster it's a cluster of galaxies

[00:15:40] [SPEAKER_01]: which is actually two galaxy clusters colliding and what you can see there is the material of the

[00:15:53] [SPEAKER_01]: galaxies themselves the gas and dust that we can see sort of piles up in this collision

[00:16:01] [SPEAKER_01]: and so you've got a galaxy cluster that's made up of two galaxy clusters in the act of colliding

[00:16:09] [SPEAKER_01]: but the dark matter which is around them and we can detect that by means of gravitational

[00:16:17] [SPEAKER_01]: lensing the dark matter just carries on so what you've got is this galaxy cluster it's two galaxies

[00:16:25] [SPEAKER_01]: that have collided and they've wound up together but then on either side of them

[00:16:31] [SPEAKER_01]: on each side is a blob of dark matter the dark matter has passed through itself

[00:16:38] [SPEAKER_01]: the two dark matter halos of each of the two clusters has gone through itself and not interacted

[00:16:44] [SPEAKER_01]: and that's why people think dark matter does not interact with itself but it does prove

[00:16:51] [SPEAKER_01]: the answer to Bill's question that dark matter can move. It can move okay we don't know a lot

[00:16:57] [SPEAKER_02]: about it Bill and we're trying to find out what we can there's studies into it but

[00:17:03] [SPEAKER_02]: it's elusive because it's dark matter it doesn't interact. It's not of our realm technically

[00:17:10] [SPEAKER_01]: speaking does it? Yeah that's a nice way to put it it is not of our realm that's right yeah yeah

[00:17:17] [SPEAKER_02]: thank you Bill I'm great to hear from you too and our final question today comes from Brady

[00:17:24] [SPEAKER_02]: hello from the great state of Florida I just well I have a question Fred why does everyone who

[00:17:30] [SPEAKER_02]: lives in Florida call it the great state of Florida most of the questions we get say hey I'm

[00:17:36] [SPEAKER_02]: from the great state of Florida are they just saying Florida abbreviated is it actually called

[00:17:41] [SPEAKER_01]: the great state of Florida? I'm being a bit coy here a bit I think it's local pride I think it is

[00:17:50] [SPEAKER_01]: from other states as well everybody's you know happy about where they live which is great

[00:17:59] [SPEAKER_02]: well I can get it I mean they've got 50 states to sort of talk about we've only got

[00:18:07] [SPEAKER_02]: you know half a dozen but when we all we're one country split into states but during the football

[00:18:15] [SPEAKER_02]: season New South Wales and Queensland hate each other so just a temporary thing yes other than

[00:18:21] [SPEAKER_02]: that we're really good friends so from the great state of Florida Brady asks I was wondering how

[00:18:30] [SPEAKER_02]: atmospheres are formed how do they go from a ball of rock and lava to having an atmosphere

[00:18:35] [SPEAKER_02]: good good question yeah I have never pondered that and glad you asked it is a good question so

[00:18:44] [SPEAKER_01]: you know if you've got a world at the temperature at which the volatile material the stuff that easily

[00:18:50] [SPEAKER_01]: turns into gas is gas then you're going to have a gas envelope around a planet it's a good it's a

[00:18:59] [SPEAKER_01]: great question and you know when you when you think of the way planets are formed they start off

[00:19:08] [SPEAKER_01]: as dust and gas and so you've got this kind of bedding down process where the dust turns into

[00:19:15] [SPEAKER_01]: planet ismals and they all bash into each other and that probably heats up everything so that the

[00:19:20] [SPEAKER_01]: temperature gets exceeds where things like nitrogen and oxygen and carbon dioxide are gas

[00:19:28] [SPEAKER_01]: then what you end up with is a solid world because the the other things the silicates

[00:19:35] [SPEAKER_01]: and things like that are temperatures that are solid you know within the places like the goldilocks

[00:19:41] [SPEAKER_01]: zone and so you've you end up with this natural natural scenario of a solid rocky body with a

[00:19:52] [SPEAKER_01]: gas envelope and it that's turned on its head when we get out to the to the giant planets because

[00:19:58] [SPEAKER_01]: the rocky body there is very small and probably has quite a lot of water ice in it because you'd be on

[00:20:06] [SPEAKER_01]: the frost line and the gas is the the main part of the of the the body so so the atmosphere of a

[00:20:16] [SPEAKER_01]: gas giant is formed in a rather different way from the atmosphere of a rocky planet yeah i in fact

[00:20:25] [SPEAKER_02]: yeah gas giants are very different because you're basically looking at well depending on the size

[00:20:31] [SPEAKER_02]: but you're getting on towards star formation some some of those gas giants are actually failed

[00:20:36] [SPEAKER_01]: stars aren't they effectively yeah jupiter's often described as a failed star it would have to be

[00:20:41] [SPEAKER_01]: about 90 times bigger i think if i remember rightly to be a star if it was only 13 times

[00:20:47] [SPEAKER_01]: bigger though it would be a brown dwarf star which is which is a different kind of category

[00:20:51] [SPEAKER_02]: star but yeah yeah yeah so it's got a lot to do with proximity to the star golly lock zone

[00:21:01] [SPEAKER_02]: um all those things come into play although you get you get gas giants that are close to their

[00:21:07] [SPEAKER_02]: parent star too which is seemingly yeah so far fairly normal in the discovery of exoplanets

[00:21:13] [SPEAKER_01]: yeah and you get them a long way from planets as well sorry a long way from their stars like

[00:21:18] [SPEAKER_02]: yeah like the planets and gas giants in the solar system okay so um it's just part of a process

[00:21:27] [SPEAKER_01]: yes that's i think that's the way to put it that's thank you brady um you've kind of highlighted my

[00:21:35] [SPEAKER_01]: thinking about uh these planets and their atmospheres and uh it is a process that's the

[00:21:40] [SPEAKER_02]: way to put it all right good question brady um look i don't think it'll happen but one day

[00:21:46] [SPEAKER_02]: someone might send a question in where i go that's just not interesting and it's a bad question

[00:21:52] [SPEAKER_02]: no it hasn't happened yet it hasn't happened yet i'm gonna have it adrew it's all right

[00:21:57] [SPEAKER_02]: definitely not but if you do have questions for us go to our website because that's where

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[00:22:35] [SPEAKER_02]: platform that you prefer we're all done fred thank you very much again it's a pleasure um i'm

[00:22:42] [SPEAKER_01]: always happy to be on space nuts thank you andrew i'm glad you are otherwise you probably would

[00:22:48] [SPEAKER_02]: have left eight years ago yeah professor fred what's an astronomer at large and thanks to

[00:22:55] [SPEAKER_02]: here in the studio who's uh busily making lunch i think yeah i can't see him he's not on the

[00:23:02] [SPEAKER_02]: camera no no it's a brush turkey sandwich by the look of it good on it and for me andrew

[00:23:08] [SPEAKER_02]: thanks for your company as always catch you on the very next episode of space nuts bye bye