Martian Meteorites, Gas Giants & The Search for Alien Life | Q&A | Space Nuts: Astronomy...

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Language: en

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Hello again. Thanks for joining us. This


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is a Q&A episode of Space Nuts, where we


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answer astronomy and space science


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questions from our audience. Today,


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David wants to know about Mars meteor


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showers. Penny is asking about fly


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through missions for Saturn and Jupiter.


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That could be messy. Uh Andy is asking


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about the gravitational effect of


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Jupiter on its uh moons, particularly


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Europa. And Duncan wants to talk about


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alien civilizations. We will deal with


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all of that and more on this episode of


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Space Nuts.


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>> 15 seconds. Guidance is internal. 10 9


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Ignition sequence start.


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>> Space Nuts.


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>> 5 4 3 2 1 2 3 4 5 4 3 2 1


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>> Space Nuts.


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>> Astronauts report. It feels good.


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>> This is Fred Watson's favorite segment.


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He's back again for more. Professor Fred


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Watson, astronomer at large. Hello.


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Hello, Andrew. How are you?


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>> I am quite well. It's been a long time,


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like I don't know, two or three minutes.


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>> Hope nobody's guessed that we record


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these in pairs. But never mind. Never


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mind.


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>> If they haven't figured it out by now,


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they probably never will.


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>> That's right.


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>> I'm pretty sure most people know how it


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works. I mean, they just have to look at


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the shirts we're wearing every week.


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That's if they do it on the YouTube


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channel. Although I don't know if I


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don't know if they put the video on


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anymore because um it could be could be


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a bit bit of a turnoff. So I don't know.


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Um anyway, uh all is well with you. I


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trust


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>> it is. Thank you. Yes. All good.


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>> I already knew the answer, but we have


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to ask because you know this is just to


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be bal.


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>> Yes, that's it. Exactly. Um what why


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don't we try and answer some questions?


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>> Oh, all right. If you must.


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>> Well, you do it. I'm just going to push


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him in there. Uh, let's go to our first


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question. It comes from David


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>> David Thompson here from Spring in the


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UK. Back to Mars. As a child of the 50s


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and 60s,


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uh, reading the comics


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at the time, there was always a risk of


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meteor showers. I'm just wondering given


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that Mars atmosphere is not as dense as


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the Earth's


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whether smaller meteorites would be able


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to


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hit the surface of Mars and be a real


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hazard to anybody putting a house there.


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Find the podcast absolutely amazing.


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Everybody have a great day. Bye.


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Thank you, David. Thanks for those kind


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words. I'm glad you're enjoying the the


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podcast. Uh so, we're back to Mars. I


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didn't push him there. I didn't. Um


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everyone knows I love Mars, but uh yeah,


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meteor showers. Uh he makes up He brings


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up an interesting point. It's got a much


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less significant atmosphere than Earth.


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So, does that mean smaller things can


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get through?


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>> It does. Yes, it does. Uh David's


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absolutely right. Uh I'm delighted we've


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got a listener in Horton Lispring. I um


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used to drive past there very very


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frequently. It's between Durham and


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Sunderland in the north of England. And


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I was a very very regular user of the


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A1M which goes right past Horton the


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spring. Uh and it's lovely to hear your


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voice, David, and hear that lovely North


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Durham accent there. Um the answer is


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yes. Uh uh so because the atmosphere you


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know the atmospheric pressure on Mars is


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I think it's 6% of our atmospheric


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pressure which means that meteorites


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coming in are going to have a lot less


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resistance. Um we know of meteorites on


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Mars. Many have been identified by both


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Curiosity and Perseverance uh usually by


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their but by their color, but both those


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um rovers were equipped with laser


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zappers that could give us an idea of


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their content. And some of those


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meteorites have been found to be


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metallic. Uh so meteorites on Mars are


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something that happens. And yes, there's


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probably a higher risk of uh of damage


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from an incoming meteorite on Mars than


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on Earth. um because uh the likelihood


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is that their terminal velocity uh the


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sort of final velocity after they've


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passed through the atmosphere will be


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much higher than it will be on Earth


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just because of that lower pressure.


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>> Uh and so yes um me meteorite protection


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might turn out to be quite an important


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aspect of putting humans on Mars. We


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haven't had any reports of you know


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there's how many rovers have been on


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Mars now? I can think of one, two,


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three, four, five, six.


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>> At least six, probably more like seven


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or eight. Uh they are um Andrew is


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googling it as we speak.


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>> Yeah.


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>> Six.


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>> Six rovers. Sojourer, Spirit,


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Opportunity, Curiosity, Perseverance,


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and uh Jirong, the Chinese mission.


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>> The Chinese one. That's right. Yeah,


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that So I did get the right answer. Six.


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>> Yeah. Uh yeah, it's um so uh none of


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those as to the best of our knowledge


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has suffered any kind of meteoritic


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impact. So at least so far so good in


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terms of our understanding of the


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meteorite hazard on Mars. But a good


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question to raise David and gives us


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always always gives us a chance to talk


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about Mars. He he did ask about the


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danger to housing


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on Mars. They probably won't build


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houses on Mars like they do on Earth and


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and the because of the radiation issues,


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they're probably going to have to go


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underground which would um protect them


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from anything like that. But there will


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be surface something or other there one


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day.


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>> So that's infrastructure.


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>> Yeah. Perhaps domes that they could be


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susceptible maybe. Yeah, it looks like I


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mean what what we imagine is something


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like White Cliffs in uh Western New


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South Wales where people live


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underground.


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>> They do.


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>> And that's just to get out of the heat.


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Um


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>> so


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>> that's that's radiation.


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>> Yes, it is solar radiation. That's


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right.


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>> Yeah, indeed.


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>> Yeah. I thought of another question. Um


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we Yeah, here it is. Uh we are


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constantly monitoring for big objects


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that could be threatening to Earth,


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things that could destroy cities or


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regions or god forbid the planet itself


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as we know it. Uh what about Mars? Do we


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keep an eye on anything that might hit


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that? Um so yes to some extent if you


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you know if you can identify near-Earth


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objects uh and look at their orbits you


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would certainly find out um from the


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analysis very quickly if there was any


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risk of one of those hitting the planet


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Mars but there's probably many small


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objects in the vicinity of Mars because


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it's closer to the asteroid belt than we


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are uh which are undetectable from the


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distance of Earth. Uh, you know, objects


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that might even be as big as Phobos,


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Mars's biggest moon.


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>> Uh, we we we would be able to detect


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that from Earth quite easily. But, um,


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as we obviously can, it was discovered


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in the 1800s. Uh but you know if you had


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something that was only a few tens of


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meters across uh which could pose a


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hazard uh to houses on Mars um that uh


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would be hard to detect from the


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distance of Earth unless it be unless it


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was also a near-Earth object. So it was


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coming uh close to closer to our


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telescopes.


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>> Yeah. Uh there'd be nothing much we


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could do about a big thing hitting Mars


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anyway is there? Or there'd be a good


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experiment if we wanted to test our


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capabilities. Well, that's right. If


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there was, you know, the the bigger ones


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are the the ones that we know more


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about, uh, because they're easier to


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see. Uh, if something like that was


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looking as though it might collide with


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Mars,


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>> yes, it might be a good time to test out


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the theories that were put into place


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with the Dart mission a few years ago,


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see whether it'll actually work on


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something a bit bigger than that.


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One can only wonder, but um hopefully we


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don't ever have to put it to the test


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for for ourselves. But uh yeah, you just


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never know. There's always something


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going on out there. There's so much


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stuff bumping into it. There's something


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else out there. It's it's only a matter


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of time before one of them carines into


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our sector and becomes a potential


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threat. Although we seem to be finding


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them more and more now, don't we


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>> with with and that's the the good news


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part of this story. two good news sides


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of this story. One is that the big ones


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are the easiest to find and the other is


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that we've been finding these things now


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for the last 40 years and have a good


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idea of what the Earth's environments


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like.


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>> Yeah, great to hear from you, David.


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Great question and uh thanks for sending


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it in. Our next question comes from


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Penny. It's a short quick one. I think I


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know where this one might go too in


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terms of an answer. As Saturn and


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Jupiter are gas giants, are there any


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plans to fly a spacecraft through the


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middle of one or both of them?


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Interesting question, Penny. Uh I do


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recall um when you're talking about u


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comet or asteroid impacts, the um the


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impact with Jupiter uh many many years


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ago that we we almost got footage of. It


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was just quite not quite the right


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angle, but we did see the aftermath of


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it.


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That's Schumaci the second one Jupiter


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back


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>> can't remember what year 94 I think it


00:09:53.839 --> 00:09:59.190
might have been um so uh the issue is


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that um the gas giant aspect of these


00:10:03.839 --> 00:10:05.829
planets is really just their outer


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envelope that's gassy u and we don't


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really know what's underneath that. Uh


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the likelihood is there will be a solid


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core there. Uh it may be rocky. Some


00:10:16.640 --> 00:10:19.509
have suggested that it will be made of


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metallic hydrogen which is hydrogen in a


00:10:22.640 --> 00:10:25.190
very unusual form. Uh so you've got a


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core of something called metallic


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hydrogen. So um flying through is not


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anything that's planned because it would


00:10:32.959 --> 00:10:36.150
be impossible. But even if these gas


00:10:36.160 --> 00:10:38.470
giants were sort of gaseous all the way


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through, it still would be a very hard


00:10:41.760 --> 00:10:44.389
thing to achieve because you're entering


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an atmosphere that you'd have to slow


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the rocket the spacecraft down


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enormously in order to prevent it from


00:10:52.640 --> 00:10:54.550
just melting by friction with the


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atmosphere, which is what happened to


00:10:56.240 --> 00:10:58.790
Cassini. Cassini was plunged into


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Saturn's atmosphere at the end of its


00:11:00.320 --> 00:11:03.190
mission in 2017. uh it didn't burn up


00:11:03.200 --> 00:11:05.430
because there's no oxygen in Saturn's


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atmosphere, but the friction made it


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melt. Basically, it just melted and fell


00:11:09.200 --> 00:11:12.230
to pieces. In fact, NASA produced uh


00:11:12.240 --> 00:11:14.230
some real tearjerker footage of what


00:11:14.240 --> 00:11:16.150
that might have looked like,


00:11:16.160 --> 00:11:19.269
>> which we saw uh often at the end of the


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Cassini mission. uh you know this thing


00:11:23.120 --> 00:11:25.509
which had performed valiantly for the


00:11:25.519 --> 00:11:28.230
previous 13 years and done a marvelous


00:11:28.240 --> 00:11:30.389
job at revolutionizing our knowledge not


00:11:30.399 --> 00:11:31.990
just of Saturn and its rings and moons


00:11:32.000 --> 00:11:34.150
but also the way planets form and things


00:11:34.160 --> 00:11:37.509
like that. Uh this footage of uh Cassini


00:11:37.519 --> 00:11:39.590
hitting the top of Saturn's atmosphere


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and having its antennas ripped off and


00:11:41.760 --> 00:11:44.310
eventually just melting into becoming


00:11:44.320 --> 00:11:46.870
part of the atoms of the atmosphere of


00:11:46.880 --> 00:11:50.310
Saturn. And that is you, you know, any


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mission to try and penetrate down


00:11:52.640 --> 00:11:54.710
through the atmosphere would would


00:11:54.720 --> 00:11:58.389
struggle uh because of the the rapid


00:11:58.399 --> 00:11:59.750
increase in density, the fact that


00:11:59.760 --> 00:12:01.190
you've got to slow the spacecraft down


00:12:01.200 --> 00:12:03.269
in order to stop it just burning up by


00:12:03.279 --> 00:12:07.350
friction. Um, I think one of the Jupiter


00:12:07.360 --> 00:12:11.269
missions, I can't remember which one,


00:12:11.279 --> 00:12:14.150
might have been Galileo, um, actually


00:12:14.160 --> 00:12:17.590
sensed as it hits Jupiter's atmosphere


00:12:17.600 --> 00:12:21.030
to burn up again or to to melt. I think


00:12:21.040 --> 00:12:22.949
there were sensors on board that were


00:12:22.959 --> 00:12:24.550
giving us some readings of what the


00:12:24.560 --> 00:12:26.710
conditions were like.


00:12:26.720 --> 00:12:28.870
>> Yeah. Um,


00:12:28.880 --> 00:12:30.790
I I think the other big problem would be


00:12:30.800 --> 00:12:32.470
pressure, wouldn't it? if you tried to


00:12:32.480 --> 00:12:33.670
fly through.


00:12:33.680 --> 00:12:37.030
>> Yeah. So, the pressure just goes up um


00:12:37.040 --> 00:12:39.590
probably exponentially at some level.


00:12:39.600 --> 00:12:41.990
>> Yeah. Uh and Penny might be interested


00:12:42.000 --> 00:12:44.790
to know that there are some missions


00:12:44.800 --> 00:12:48.790
slated for um the near future. Uh Europa


00:12:48.800 --> 00:12:52.470
Clipper uh which will launch in or it's


00:12:52.480 --> 00:12:56.230
already launched should be 20 yeah 2030.


00:12:56.240 --> 00:12:58.230
Uh there's the juice mission which


00:12:58.240 --> 00:13:02.150
launched in 2023 which arrives in 2031


00:13:02.160 --> 00:13:04.310
and Dragonfly


00:13:04.320 --> 00:13:07.350
um with with the um with the helicopter


00:13:07.360 --> 00:13:07.670
um


00:13:07.680 --> 00:13:08.949
>> off to Titan.


00:13:08.959 --> 00:13:12.230
>> Yeah, we'll launch in 2028. So they


00:13:12.240 --> 00:13:15.190
they're more interested in some of the


00:13:15.200 --> 00:13:18.870
um moons around those gas giants, but um


00:13:18.880 --> 00:13:22.550
yes, they are fascinating. And of


00:13:22.560 --> 00:13:24.550
course, we're most interested in Europa


00:13:24.560 --> 00:13:26.629
Clipper because we want to know if


00:13:26.639 --> 00:13:29.750
anything's living in the ocean.


00:13:29.760 --> 00:13:32.150
And maybe there is, maybe there isn't.


00:13:32.160 --> 00:13:34.470
Who knows? It could just be made of


00:13:34.480 --> 00:13:36.790
jelly. We we don't really know. Uh


00:13:36.800 --> 00:13:38.230
although the juice mission is more


00:13:38.240 --> 00:13:40.310
likely to figure all that out. Uh boom


00:13:40.320 --> 00:13:42.389
boom. Um thank you, Penny. Lovely to


00:13:42.399 --> 00:13:44.629
hear from you. This is Space Nuts Q&A


00:13:44.639 --> 00:13:47.110
edition with Andrew Dunley and Professor


00:13:47.120 --> 00:13:49.829
Fred Watson.


00:13:49.839 --> 00:13:51.350
Let's take a break from the show to tell


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00:15:23.600 --> 00:15:25.910
>> Okay, we checked all four systems and


00:15:25.920 --> 00:15:26.470
with the go.


00:15:26.480 --> 00:15:30.710
>> Space nuts. And speaking of uh Europa


00:15:30.720 --> 00:15:33.030
and Jupiter, we've got a a question now


00:15:33.040 --> 00:15:35.430
from Andy. This is Andy, the train


00:15:35.440 --> 00:15:37.670
driver from London. Uh just got a


00:15:37.680 --> 00:15:39.990
question about Europa. I know Europa


00:15:40.000 --> 00:15:42.069
erupts because it's being sort of


00:15:42.079 --> 00:15:45.350
squeezed by the gravity of Jupiter,


00:15:45.360 --> 00:15:48.949
but what I don't understand is if Europa


00:15:48.959 --> 00:15:51.430
is being affected by Jupiter's gravity,


00:15:51.440 --> 00:15:53.350
why is it not just being pulled closer


00:15:53.360 --> 00:15:57.430
to Jupiter? I thought gravity pulls


00:15:57.440 --> 00:15:59.269
things down. Like when you throw a ball


00:15:59.279 --> 00:16:02.069
in the air, gravity pulls it back down.


00:16:02.079 --> 00:16:04.629
I don't understand how Europa is being


00:16:04.639 --> 00:16:07.590
squeezed. Uh that suggests to me that


00:16:07.600 --> 00:16:09.990
it's being affected by gravity from all


00:16:10.000 --> 00:16:12.710
directions. So I squeeze it like a like


00:16:12.720 --> 00:16:14.710
you could squeeze a tennis ball. Maybe


00:16:14.720 --> 00:16:17.350
you can shed some light on this or tell


00:16:17.360 --> 00:16:19.509
me that I'm barking up the wrong tree.


00:16:19.519 --> 00:16:21.430
Anyway, thanks for the podcast, guys.


00:16:21.440 --> 00:16:23.910
Really interesting. Uh and see you on


00:16:23.920 --> 00:16:26.470
the next one. It's Jord's job to bark up


00:16:26.480 --> 00:16:30.949
the wrong tree. But um that


00:16:30.959 --> 00:16:32.470
>> nicely done, Andrew.


00:16:32.480 --> 00:16:35.269
>> Um your point is well taken, Andy. Uh


00:16:35.279 --> 00:16:37.030
it's not just Europa, though. Uh there


00:16:37.040 --> 00:16:39.430
are several moons orbiting the gas


00:16:39.440 --> 00:16:41.749
giants that that do get that squeeze


00:16:41.759 --> 00:16:43.829
effect. Titan, I think, is is one of


00:16:43.839 --> 00:16:47.350
them. And um oh, look, probably all of


00:16:47.360 --> 00:16:49.590
them to some degree, but Europa, yeah,


00:16:49.600 --> 00:16:53.509
it's it's it's in a difficult position.


00:16:53.519 --> 00:16:55.110
Uh, it's a good question though. Why


00:16:55.120 --> 00:16:57.430
don't they just get sucked in? Like our


00:16:57.440 --> 00:17:00.629
moon doesn't, but we're not a gas giant.


00:17:00.639 --> 00:17:02.389
>> No. Same thing happens to our moon,


00:17:02.399 --> 00:17:04.630
though. Um, so, uh, it's actually


00:17:04.640 --> 00:17:06.710
probably I think the moon that Andy's


00:17:06.720 --> 00:17:09.110
thinking of is Io, which is the


00:17:09.120 --> 00:17:12.230
innermost of the of the moons, the the


00:17:12.240 --> 00:17:14.710
big moon, big four moons of Jupiter. And


00:17:14.720 --> 00:17:15.990
it is the one that gets the most


00:17:16.000 --> 00:17:19.189
squeezing and squashing u because of its


00:17:19.199 --> 00:17:23.110
uh proximity to to Jupiter. Europa


00:17:23.120 --> 00:17:25.029
probably also has the same phenomenon


00:17:25.039 --> 00:17:28.150
and there there may be eruptions of it


00:17:28.160 --> 00:17:32.710
on Europa that possibly um a bit like


00:17:32.720 --> 00:17:34.470
Enceladus where you've got stuff


00:17:34.480 --> 00:17:36.150
streaming out through the cracks in the


00:17:36.160 --> 00:17:37.510
in the ice.


00:17:37.520 --> 00:17:40.070
>> Uh but the the genuine volcanic


00:17:40.080 --> 00:17:42.150
eruptions which they really are it's hot


00:17:42.160 --> 00:17:45.750
lava uh is what take place on Eio the


00:17:45.760 --> 00:17:48.549
innermost of those moons. So um the way


00:17:48.559 --> 00:17:52.870
to understand this uh is to real


00:17:52.880 --> 00:17:56.390
recognize that if you've got an object


00:17:56.400 --> 00:17:58.470
in a very strong gravitational field


00:17:58.480 --> 00:18:00.789
first of all let me just clarify the


00:18:00.799 --> 00:18:03.510
reason why objects in orbit around other


00:18:03.520 --> 00:18:05.669
objects don't just get pulled in. They


00:18:05.679 --> 00:18:07.830
are getting pulled in but they've got a


00:18:07.840 --> 00:18:10.470
forward motion that compensates for the


00:18:10.480 --> 00:18:13.350
for the pull. So basically the the


00:18:13.360 --> 00:18:16.070
motion of the object through space uh is


00:18:16.080 --> 00:18:19.270
what balances out the gravity of a giant


00:18:19.280 --> 00:18:22.230
like Jupiter. And so that you know the


00:18:22.240 --> 00:18:25.190
the greater the gravity of a of a planet


00:18:25.200 --> 00:18:27.270
the faster it satellites have to orbit


00:18:27.280 --> 00:18:30.470
in order not to not to fall in. Um and


00:18:30.480 --> 00:18:33.909
so that's that's the mechanism that


00:18:33.919 --> 00:18:35.990
stops these things just immediately


00:18:36.000 --> 00:18:38.070
being sucked in to Jupiter. They're


00:18:38.080 --> 00:18:40.150
already moving and that comes about. Why


00:18:40.160 --> 00:18:41.590
are they moving? Because they were


00:18:41.600 --> 00:18:44.070
formed that way with the the way the,


00:18:44.080 --> 00:18:45.590
you know, the planets and their


00:18:45.600 --> 00:18:48.070
satellites evolved, the way they formed.


00:18:48.080 --> 00:18:50.310
They're basically swirling around right


00:18:50.320 --> 00:18:52.549
from the start. And that swirling motion


00:18:52.559 --> 00:18:55.510
is what stops which is fossilized in the


00:18:55.520 --> 00:18:57.590
in the planets themselves and and the


00:18:57.600 --> 00:18:59.590
moons of the planets and stops them


00:18:59.600 --> 00:19:02.630
falling into their parent object. But


00:19:02.640 --> 00:19:04.710
the the squeezing and squashing comes


00:19:04.720 --> 00:19:07.430
from what we call a tidal effect. And it


00:19:07.440 --> 00:19:09.190
is actually exactly the same thing that


00:19:09.200 --> 00:19:11.909
gives rise to tides on the earth. Uh but


00:19:11.919 --> 00:19:13.909
let's concentrate for a minute on Io.


00:19:13.919 --> 00:19:16.310
Here's this little world


00:19:16.320 --> 00:19:19.590
right next to gas giant Jupiter. One


00:19:19.600 --> 00:19:22.789
side of EO is feeling the gravitational


00:19:22.799 --> 00:19:25.510
pull of Jupiter. The other side is as


00:19:25.520 --> 00:19:27.750
well, but it's feeling slightly less


00:19:27.760 --> 00:19:30.310
because it's further away because the


00:19:30.320 --> 00:19:33.270
gravitational pull falls off as as the


00:19:33.280 --> 00:19:35.029
distance squared. One over the distance


00:19:35.039 --> 00:19:38.470
squared. So um further on the farther


00:19:38.480 --> 00:19:40.789
side of EO from Jupiter it's going to


00:19:40.799 --> 00:19:43.990
feel less force and that is what con


00:19:44.000 --> 00:19:45.830
contributes to this tension that there


00:19:45.840 --> 00:19:49.350
is uh and basically elongates the planet


00:19:49.360 --> 00:19:51.990
slightly in the direction of Jupiter.


00:19:52.000 --> 00:19:53.669
Now


00:19:53.679 --> 00:19:55.110
why we talk about squashing and


00:19:55.120 --> 00:19:57.350
squeezing is that throughout the orbit


00:19:57.360 --> 00:19:59.750
of Vo which is not a planet it's a


00:19:59.760 --> 00:20:02.390
satellite but around the orbit of Vo as


00:20:02.400 --> 00:20:05.110
it goes around is not circular. So


00:20:05.120 --> 00:20:07.270
sometimes that force is greater than


00:20:07.280 --> 00:20:08.789
others that tension that's trying to


00:20:08.799 --> 00:20:11.590
pull it apart. Uh it's greater than at


00:20:11.600 --> 00:20:15.110
other times and and basically it's that


00:20:15.120 --> 00:20:17.750
squashing uh stretching really is the


00:20:17.760 --> 00:20:20.230
best word for it. As it goes round as it


00:20:20.240 --> 00:20:22.789
goes around Jupiter uh that change in


00:20:22.799 --> 00:20:25.190
the stretch force that's being applied


00:20:25.200 --> 00:20:27.830
is what generates the heat that causes


00:20:27.840 --> 00:20:30.230
these eruptions to continually take


00:20:30.240 --> 00:20:32.630
place. So and that's called the tidal


00:20:32.640 --> 00:20:34.630
effect. the fact that one side of a body


00:20:34.640 --> 00:20:36.230
feels a different gravitational force


00:20:36.240 --> 00:20:38.390
from the other. It's what makes us


00:20:38.400 --> 00:20:40.630
susceptible if we fall into a black hole


00:20:40.640 --> 00:20:42.390
to spaghettification.


00:20:42.400 --> 00:20:44.390
Spaghettification is just a nicer word


00:20:44.400 --> 00:20:46.310
than tidal effects.


00:20:46.320 --> 00:20:48.230
>> Yeah. So, you've got a real combination


00:20:48.240 --> 00:20:49.669
of of factors.


00:20:49.679 --> 00:20:50.950
>> Yeah, that's right. You you've got the


00:20:50.960 --> 00:20:52.870
the the gravitational effect, you've got


00:20:52.880 --> 00:20:54.390
orbital dynamics.


00:20:54.400 --> 00:20:54.710
>> Yep.


00:20:54.720 --> 00:20:57.830
>> Um all sort of coinciding to keep these


00:20:57.840 --> 00:20:59.510
things from falling into the planet, but


00:20:59.520 --> 00:21:01.270
there's a tug of war going on.


00:21:01.280 --> 00:21:03.830
>> Yeah. Uh I I saw a really good


00:21:03.840 --> 00:21:06.470
demonstration online oh probably three


00:21:06.480 --> 00:21:09.830
or four weeks ago on on how the tides


00:21:09.840 --> 00:21:12.470
work on Earth. And of course most people


00:21:12.480 --> 00:21:15.990
and I must confess guilt here assume


00:21:16.000 --> 00:21:18.470
that the moon causes the water to rise


00:21:18.480 --> 00:21:20.950
and then fall. But it's not. It's the


00:21:20.960 --> 00:21:22.870
fact that the Earth is rotating, the


00:21:22.880 --> 00:21:25.270
moon is orbiting, and there's always a


00:21:25.280 --> 00:21:27.909
wave. It's just always there. And it's


00:21:27.919 --> 00:21:30.149
just that when it um when the moon


00:21:30.159 --> 00:21:33.590
reaches your vicinity that that lump of


00:21:33.600 --> 00:21:35.830
water comes up.


00:21:35.840 --> 00:21:36.549
>> Yeah.


00:21:36.559 --> 00:21:38.630
>> And goes down again. It's it's not the


00:21:38.640 --> 00:21:40.630
water so much rising. It's just it's


00:21:40.640 --> 00:21:43.510
always risen in proximity to the moon.


00:21:43.520 --> 00:21:44.710
>> Am I right?


00:21:44.720 --> 00:21:47.669
>> Uh you are. You're partly right because


00:21:47.679 --> 00:21:48.390
it's a bit more


00:21:48.400 --> 00:21:49.830
>> I knew I missed something.


00:21:49.840 --> 00:21:52.070
>> Yeah. And the that doesn't explain the


00:21:52.080 --> 00:21:54.549
bulge on the other side because as you


00:21:54.559 --> 00:21:57.110
know you get a high tide every every 20


00:21:57.120 --> 00:21:58.870
hours not every 24 hours.


00:21:58.880 --> 00:22:01.590
>> And that's because um again it's the


00:22:01.600 --> 00:22:04.390
tidal effect. So the moon's pulling on


00:22:04.400 --> 00:22:07.110
the ocean on the near side. It's also


00:22:07.120 --> 00:22:10.390
pulling on the earth itself and that


00:22:10.400 --> 00:22:12.310
leaves behind the water on the other


00:22:12.320 --> 00:22:14.789
side. So you get a bulge


00:22:14.799 --> 00:22:18.070
on each side. That's works.


00:22:18.080 --> 00:22:19.750
>> Fascinating. Yeah. Yeah, it's worth


00:22:19.760 --> 00:22:22.070
looking up that demo. Um I didn't read


00:22:22.080 --> 00:22:23.750
the fine print obviously, but uh yeah,


00:22:23.760 --> 00:22:25.909
that that makes sense. So the water's


00:22:25.919 --> 00:22:28.710
being pulled, sort of dragging with it,


00:22:28.720 --> 00:22:30.470
and then the water is being left behind


00:22:30.480 --> 00:22:31.830
on the other side. So you got two


00:22:31.840 --> 00:22:32.470
bulges.


00:22:32.480 --> 00:22:34.230
>> Two bulges. Exactly. So


00:22:34.240 --> 00:22:35.590
>> it's fascinating.


00:22:35.600 --> 00:22:36.070
>> So


00:22:36.080 --> 00:22:38.070
>> um and that's what's happening to all


00:22:38.080 --> 00:22:41.190
these these moons in various ways. If


00:22:41.200 --> 00:22:42.630
they have not water, something else is


00:22:42.640 --> 00:22:43.270
being


00:22:43.280 --> 00:22:44.789
>> Well, that's right. It's the rock. The


00:22:44.799 --> 00:22:46.390
rock does it as well. The same is true


00:22:46.400 --> 00:22:48.710
on Earth. We the rock goes up and down


00:22:48.720 --> 00:22:50.470
as well. I've got a question for Andy,


00:22:50.480 --> 00:22:53.990
though. Um if he's um ever getting back


00:22:54.000 --> 00:22:55.270
to us, I'd like to know what sort of


00:22:55.280 --> 00:22:56.710
trains he drives.


00:22:56.720 --> 00:22:59.350
>> Uh because um yeah, I'm a bit of a train


00:22:59.360 --> 00:23:00.950
nerd myself.


00:23:00.960 --> 00:23:03.750
>> Train train drivers are my heroes.


00:23:03.760 --> 00:23:06.070
>> Yeah. I live next door to a retired


00:23:06.080 --> 00:23:07.590
train driver. So


00:23:07.600 --> 00:23:10.789
>> yeah. Um but when we flew into do the


00:23:10.799 --> 00:23:14.230
other day, I looked down at the rail


00:23:14.240 --> 00:23:16.230
maintenance facility. It's it's a brand


00:23:16.240 --> 00:23:18.470
new system uh facility that's just been


00:23:18.480 --> 00:23:20.710
built in do and they're fitting out all


00:23:20.720 --> 00:23:22.870
the new regional trains and you can see


00:23:22.880 --> 00:23:25.909
them all lined up bright red all


00:23:25.919 --> 00:23:27.750
>> getting ready to go. They're putting all


00:23:27.760 --> 00:23:30.390
the furniture in them and uh uh the


00:23:30.400 --> 00:23:33.110
Wi-Fi systems and yeah uh they'll be


00:23:33.120 --> 00:23:35.510
rolled out pretty soon. Not not exactly


00:23:35.520 --> 00:23:38.470
sure when, but um the plan is soon.


00:23:38.480 --> 00:23:39.830
That's the answer to the question


00:23:39.840 --> 00:23:43.110
officially. Have you um have you ridden


00:23:43.120 --> 00:23:45.990
on um new metro trains here in Sydney?


00:23:46.000 --> 00:23:47.110
>> Yes, I have. Yes.


00:23:47.120 --> 00:23:49.110
>> So, you'll know that they drive 100


00:23:49.120 --> 00:23:50.950
kilometer now with no driver. You can


00:23:50.960 --> 00:23:52.390
stand at the front, look out the front


00:23:52.400 --> 00:23:54.630
window, and pretend you're driving it.


00:23:54.640 --> 00:23:56.710
>> Yeah. And I've done that in a taxi in


00:23:56.720 --> 00:23:57.669
San Francisco.


00:23:57.679 --> 00:23:58.549
>> Oh, yes, you have.


00:23:58.559 --> 00:23:59.830
>> Drives driverless taxis.


00:23:59.840 --> 00:24:00.870
>> Driverless taxi.


00:24:00.880 --> 00:24:02.950
>> That's next level. That's just amazing.


00:24:02.960 --> 00:24:03.990
But yeah. Yeah.


00:24:04.000 --> 00:24:05.750
>> Pretty incredible stuff.


00:24:05.760 --> 00:24:08.070
>> Thanks, Sandy. Um really enjoyed that


00:24:08.080 --> 00:24:10.149
question. And uh yeah, if you want to


00:24:10.159 --> 00:24:11.669
tell us what sort of train you drive,


00:24:11.679 --> 00:24:13.430
send us another message. We'd um we'd


00:24:13.440 --> 00:24:16.710
love to find out.


00:24:16.720 --> 00:24:20.630
>> I'm going to step off the land now.


00:24:20.640 --> 00:24:25.990
That's one small step for man,


00:24:26.000 --> 00:24:28.950
one lead for mankind.


00:24:28.960 --> 00:24:30.789
>> Space nuts.


00:24:30.799 --> 00:24:33.669
>> Our final question today, Fred, comes


00:24:33.679 --> 00:24:36.149
from Duncan. He said, "I've heard that a


00:24:36.159 --> 00:24:38.390
group of astrophysicists have calculated


00:24:38.400 --> 00:24:41.750
that there are an estimated 1,000 alien


00:24:41.760 --> 00:24:43.590
civilizations spread across the Milky


00:24:43.600 --> 00:24:46.549
Way, but the Milky Way is 100,000 light


00:24:46.559 --> 00:24:49.110
years across. How far away would an


00:24:49.120 --> 00:24:51.430
advanced civilization have to be in


00:24:51.440 --> 00:24:54.549
practical terms to be uncontactable?"


00:24:54.559 --> 00:24:56.630
Uh, in other words, uh, are we


00:24:56.640 --> 00:24:59.190
realistically given the distances


00:24:59.200 --> 00:25:02.230
involved effectively alone?


00:25:02.240 --> 00:25:04.470
Uh yes is the answer.


00:25:04.480 --> 00:25:04.870
>> Yeah.


00:25:04.880 --> 00:25:08.390
>> Uh and it's not just about the distance.


00:25:08.400 --> 00:25:10.390
It's also about the time.


00:25:10.400 --> 00:25:13.750
>> Um because a thousand civilizations


00:25:13.760 --> 00:25:16.070
with a in a galaxy that's 12 billion


00:25:16.080 --> 00:25:18.710
years old. Uh they might well have


00:25:18.720 --> 00:25:21.190
turned up and gone long ago or still be


00:25:21.200 --> 00:25:22.950
in the future.


00:25:22.960 --> 00:25:25.190
>> Assume that we all coexist.


00:25:25.200 --> 00:25:27.430
>> That's right. And we probably don't.


00:25:27.440 --> 00:25:30.310
There's actually um a really nice piece


00:25:30.320 --> 00:25:32.470
now. Let me see if I can find it. Uh to


00:25:32.480 --> 00:25:37.190
direct uh Duncan to it. Uh it's um on


00:25:37.200 --> 00:25:40.149
one of the um SP the science media came


00:25:40.159 --> 00:25:43.990
in today. So actually I think is where


00:25:44.000 --> 00:25:47.830
is it? Sorry, I've lost it. Uh yeah. Uh


00:25:47.840 --> 00:25:49.830
it's it's basically a summary of


00:25:49.840 --> 00:25:52.950
thinking by the likes of uh Richard


00:25:52.960 --> 00:25:56.789
Fineman uh and other great minds. Um and


00:25:56.799 --> 00:25:59.029
the bottom line is it's exactly what


00:25:59.039 --> 00:26:00.310
I've been saying. It's not just the


00:26:00.320 --> 00:26:04.630
distances, it's the time uh that you're


00:26:04.640 --> 00:26:07.750
the era in which you live. And it's very


00:26:07.760 --> 00:26:11.909
unlikely that we'd find communicable


00:26:11.919 --> 00:26:13.750
civilizations


00:26:13.760 --> 00:26:16.390
um within the same time zone that we're


00:26:16.400 --> 00:26:18.149
living in, if I can put it that way.


00:26:18.159 --> 00:26:20.789
It's actually on uh it is on again on


00:26:20.799 --> 00:26:23.830
the brighter side of news. Uh and the


00:26:23.840 --> 00:26:25.830
headline is a really very very


00:26:25.840 --> 00:26:27.909
thoughtful article, well worth a read.


00:26:27.919 --> 00:26:29.990
Interstellar travel is impossible and


00:26:30.000 --> 00:26:31.590
aliens haven't visited the earth,


00:26:31.600 --> 00:26:33.510
physicists say. And it's because the


00:26:33.520 --> 00:26:36.230
laws of physics basically make any kind


00:26:36.240 --> 00:26:39.110
of travel uh or or even communication


00:26:39.120 --> 00:26:41.110
extremely difficult. The laws of physics


00:26:41.120 --> 00:26:43.510
are very rigid uh worth having a look


00:26:43.520 --> 00:26:44.230
at.


00:26:44.240 --> 00:26:46.149
>> Yeah. Yeah. Indeed. Uh although there's


00:26:46.159 --> 00:26:48.230
this new book that I know that's been


00:26:48.240 --> 00:26:50.549
written that kind of is counter to all


00:26:50.559 --> 00:26:52.149
that, but you can do that in science


00:26:52.159 --> 00:26:54.789
fiction


00:26:54.799 --> 00:26:57.190
>> quite. So yeah, that's that's why it's


00:26:57.200 --> 00:26:59.510
called science fiction.


00:26:59.520 --> 00:27:02.070
>> Yes, that's that's what it is. Uh by by


00:27:02.080 --> 00:27:05.110
way of example though, if I may, um


00:27:05.120 --> 00:27:09.190
Duncan, uh if you were to be aware of a


00:27:09.200 --> 00:27:11.909
an advanced communicative civilization


00:27:11.919 --> 00:27:14.630
on a rocky planet orbiting Alpha


00:27:14.640 --> 00:27:17.830
Centator, for example,


00:27:17.840 --> 00:27:21.269
um and you sent them a message, it would


00:27:21.279 --> 00:27:25.990
take, I'm just trying to remember, 4.37


00:27:26.000 --> 00:27:28.710
years to get there. And that means a


00:27:28.720 --> 00:27:30.630
return message if they answered you


00:27:30.640 --> 00:27:32.390
immediately


00:27:32.400 --> 00:27:33.990
would mean that you would not get a


00:27:34.000 --> 00:27:38.630
reply for 8.74 years. Yep. Give or take.


00:27:38.640 --> 00:27:40.310
But let's round that out to a decade


00:27:40.320 --> 00:27:41.750
because you know what the bureaucracy is


00:27:41.760 --> 00:27:43.510
like around Alphasi. They're not going


00:27:43.520 --> 00:27:45.110
to you know they're going to they're


00:27:45.120 --> 00:27:46.310
going to take a couple of years to


00:27:46.320 --> 00:27:50.070
figure out what they want to say.


00:27:50.080 --> 00:27:51.750
>> But that's the reality of it, isn't it?


00:27:51.760 --> 00:27:54.710
And that's our nearest potential


00:27:54.720 --> 00:27:55.110
>> y


00:27:55.120 --> 00:27:56.789
>> neighbor.


00:27:56.799 --> 00:28:00.630
It's it's it's true and um I mean the


00:28:00.640 --> 00:28:03.830
point that this article makes is uh you


00:28:03.840 --> 00:28:06.549
know we we live in a bubble of radio


00:28:06.559 --> 00:28:08.230
radiation which are all the trans


00:28:08.240 --> 00:28:10.950
transmissions from earth that's now


00:28:10.960 --> 00:28:14.149
basically 100 uh light years in rad in


00:28:14.159 --> 00:28:16.870
radius because we've been sending radio


00:28:16.880 --> 00:28:19.510
transmissions for about 100 years. Um


00:28:19.520 --> 00:28:22.310
and all right what's that 100 divided by


00:28:22.320 --> 00:28:24.230
it's a thousandth of the diameter of the


00:28:24.240 --> 00:28:27.029
galaxy. Uh and so you know it's hardly


00:28:27.039 --> 00:28:32.149
any distance at all. Uh so yeah it's


00:28:32.159 --> 00:28:35.430
it's an unc in a way an uncomfortable


00:28:35.440 --> 00:28:38.389
reality. Uh to all intents and purposes


00:28:38.399 --> 00:28:40.310
we're alone. We're uncontable. We are


00:28:40.320 --> 00:28:42.630
alone. That's it. Good side cuz we're


00:28:42.640 --> 00:28:44.630
unlikely to be picked on by any


00:28:44.640 --> 00:28:48.630
voracious uh aliens. But Yep.


00:28:48.640 --> 00:28:51.590
>> Yeah. Um yeah. I think we got to be


00:28:51.600 --> 00:28:53.590
realistic about it. Even if there are a


00:28:53.600 --> 00:28:56.149
thousand alien civilizations with


00:28:56.159 --> 00:29:01.510
advanced technology in our our galaxy,


00:29:01.520 --> 00:29:03.590
we are probably never going to be in a


00:29:03.600 --> 00:29:06.070
position to communicate with them or and


00:29:06.080 --> 00:29:07.909
and certainly not be able to travel to


00:29:07.919 --> 00:29:12.789
them in any um meaningful way. And so


00:29:12.799 --> 00:29:15.909
even if we're not alone, we are alone.


00:29:15.919 --> 00:29:19.110
>> Yes, that's right. Exactly. um you know


00:29:19.120 --> 00:29:22.149
that of that uh thousand civilizations


00:29:22.159 --> 00:29:24.149
maybe 500 of them have been and gone and


00:29:24.159 --> 00:29:28.230
500 of them are yet to evolve.


00:29:28.240 --> 00:29:31.430
>> Do do you um concur with that estimation


00:29:31.440 --> 00:29:32.870
or you don't think it's


00:29:32.880 --> 00:29:36.070
>> um I look uh I have seen similar figures


00:29:36.080 --> 00:29:38.789
being quoted uh not that there's that


00:29:38.799 --> 00:29:40.710
number of civilizations but that there


00:29:40.720 --> 00:29:41.830
might be that sort of number of


00:29:41.840 --> 00:29:43.830
habitable planets that might be


00:29:43.840 --> 00:29:45.350
earthlike.


00:29:45.360 --> 00:29:46.470
Um,


00:29:46.480 --> 00:29:48.470
>> we don't know whether being Earthlike


00:29:48.480 --> 00:29:50.149
necessarily means you evolve an


00:29:50.159 --> 00:29:52.310
intelligent species.


00:29:52.320 --> 00:29:54.389
>> Of course, it has done it once, but


00:29:54.399 --> 00:29:55.909
>> but the only time


00:29:55.919 --> 00:29:57.830
>> could be and because the circumstances


00:29:57.840 --> 00:29:59.830
have to be perfectly right. Although we,


00:29:59.840 --> 00:30:02.389
you know, we're assuming humanoid type


00:30:02.399 --> 00:30:04.230
carbon based life forms, but there could


00:30:04.240 --> 00:30:06.470
be others out there that were created a


00:30:06.480 --> 00:30:08.070
completely different way.


00:30:08.080 --> 00:30:09.990
>> Yeah. So,


00:30:10.000 --> 00:30:11.590
yeah, that's that's the stuff of


00:30:11.600 --> 00:30:13.269
imagination at the moment, but it's a


00:30:13.279 --> 00:30:15.350
possibility, I suppose. Uh, and of


00:30:15.360 --> 00:30:17.350
course we'll look like deals next week


00:30:17.360 --> 00:30:20.870
when a massive alien mother ship sets


00:30:20.880 --> 00:30:22.789
itself down on top of the White House.


00:30:22.799 --> 00:30:24.230
And


00:30:24.240 --> 00:30:26.950
>> yeah, to rescue us all.


00:30:26.960 --> 00:30:28.549
>> Maybe,


00:30:28.559 --> 00:30:31.590
maybe. Oh gosh. Thanks, Duncan. Thanks


00:30:31.600 --> 00:30:33.190
to everybody who sent in questions.


00:30:33.200 --> 00:30:35.350
Please send them in to us. Oh, I I do


00:30:35.360 --> 00:30:37.190
have a bit of homework sort of. Um, we


00:30:37.200 --> 00:30:39.669
got a question twice now. I've received


00:30:39.679 --> 00:30:42.630
it from Mike in New York. Uh Mike, you


00:30:42.640 --> 00:30:44.470
you sent us a question in about black


00:30:44.480 --> 00:30:47.350
holes, uh an audio question. The whole


00:30:47.360 --> 00:30:49.909
guts of the question got cut off somehow


00:30:49.919 --> 00:30:52.310
and so we got the the first we got your


00:30:52.320 --> 00:30:54.310
preamble, then you started asking the


00:30:54.320 --> 00:30:55.990
question, then there was about 5 hours


00:30:56.000 --> 00:30:58.630
of nothing, probably about four, you


00:30:58.640 --> 00:31:01.029
know, 20 seconds, and then we heard you


00:31:01.039 --> 00:31:02.870
say goodbye. So, we don't actually have


00:31:02.880 --> 00:31:05.110
the question. So, if you'd like to send


00:31:05.120 --> 00:31:07.669
it again, uh please do. Uh, I don't know


00:31:07.679 --> 00:31:09.669
what happened there, but um, you know,


00:31:09.679 --> 00:31:11.430
it's the internet, so that's what that's


00:31:11.440 --> 00:31:14.230
what happened there. Uh, but yeah, Mike


00:31:14.240 --> 00:31:16.149
um would love to get that question so we


00:31:16.159 --> 00:31:17.990
can run with it. And any questions you


00:31:18.000 --> 00:31:20.230
want to send in via the ask me anything


00:31:20.240 --> 00:31:21.590
tab at the top of our website,


00:31:21.600 --> 00:31:23.269
spacenutspodcast.com,


00:31:23.279 --> 00:31:25.909
spacenuts.io.


00:31:25.919 --> 00:31:27.269
And don't forget to tell us who you are


00:31:27.279 --> 00:31:29.110
and where you're from. Thank you, Fred,


00:31:29.120 --> 00:31:31.269
as always. It's been a lot of fun.


00:31:31.279 --> 00:31:33.110
>> Absolutely. It's great questions. Good


00:31:33.120 --> 00:31:35.110
to hear everybody's voice and um, nice


00:31:35.120 --> 00:31:36.470
to see their questions. Thank you.


00:31:36.480 --> 00:31:39.029
Indeed. Uh that's Professor Fred Watson,


00:31:39.039 --> 00:31:40.789
astronomer at large. And thanks to Hugh


00:31:40.799 --> 00:31:43.750
in the studio. Um couldn't be with us


00:31:43.760 --> 00:31:46.230
today. He got stopped by border security


00:31:46.240 --> 00:31:48.710
and they realized he was an alien. He


00:31:48.720 --> 00:31:50.310
comes from New Zealand. It made sense.


00:31:50.320 --> 00:31:52.470
So he's been arrested. Uh he might be


00:31:52.480 --> 00:31:53.830
back next week. And from me, Andrew


00:31:53.840 --> 00:31:55.269
Dunley. Thanks for your company. We'll


00:31:55.279 --> 00:31:57.590
catch you on the next episode of Space


00:31:57.600 --> 00:31:58.870
Nuts. Bye-bye.


00:31:58.880 --> 00:32:01.190
>> Space Nuts. You've been listening to the


00:32:01.200 --> 00:32:04.230
Space Nuts podcast


00:32:04.240 --> 00:32:07.190
>> available at Apple Podcasts, Spotify,


00:32:07.200 --> 00:32:09.830
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00:32:09.840 --> 00:32:12.230
player. You can also stream on demand at


00:32:12.240 --> 00:32:15.110
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