April 19, 2026

Planetary Orbits, Cosmic Expansion & The Nature of Nothing | Space Nuts Q&A

Show Notes
Transcript

Planetary Orbits, Cosmic Expansion, and the Nature of Nothingness In this thought-provoking Q&A episode of Space Nuts, hosts Andrew Dunkley and Professor Fred Watson tackle a diverse array of listener questions that delve into the intricacies of our universe. From the stability of planetary orbits to the enigmatic concept of nothingness before the Big Bang, this episode promises to enlighten and intrigue.
Episode Highlights:
- Planetary Orbits vs. Energy: Justin from Melbourne asks how planets maintain stable orbits around the sun without spiraling inwards. Andrew and Fred explore the negligible forces at play in interplanetary space, discussing the stability of planetary dynamics and the historical migrations of planets within the solar system.
- Expansion of Earth: Larry questions whether the Earth is expanding along with the universe. The hosts clarify that while space itself is expanding, the forces that hold the Earth together, such as gravity, prevent any significant changes at a local scale.
- The Concept of Nothingness: Mike from the UK raises a philosophical query about what existed before the Big Bang. Andrew and Fred discuss the implications of time and existence, examining the idea that time itself may have begun with the Big Bang and the theories surrounding this profound mystery.
- Projectiles in Space: Giles presents a fascinating "what if" scenario regarding the accuracy of firing solid metal projectiles from orbit. The hosts analyze the challenges of targeting and the influence of atmospheric conditions, drawing parallels with historical warfare and modern technology.

For more Space Nuts, including our continuously updating newsfeed and to listen to all our episodes, visit our website. Follow us on social media at SpaceNutsPod on Facebook, Instagram, and more. We love engaging with our community, so be sure to drop us a message or comment on your favorite platform.
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Stay curious, keep looking up, and join us next time for more stellar insights and cosmic wonders. Until then, clear skies and happy stargazing.

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WEBVTT

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Hi there, Thanks again for joining us. This is Space

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Nuts a Q and A Edition. My name is Andrew Dunkley,

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your host. It's good to have your company. A Q

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and A edition means that people ask us questions and

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we don't do anything about it except try to answer them.

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Justin has sent a question in about planetary orbits versus energy.

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He doesn't quite get what's going on there. Larry is

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asking about whether or not the Earth is expanding in

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relation to the universe expanding. Giles wants to talk about

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solid metal projectiles in a what if question, and Mike

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wants to talk about nothing for fifteen seconds. Guidance is

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in channel ten nine ignition sequence Space Nuts Guy or

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three two one spacenutes as can I report it? Bill's

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good and back to share his wealth of knowledge with

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us is Professor Fred Watson, an astronomer at large. Hello Fred, Hello,

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an't true?

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That's a nice word.

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Is wealth?

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Isn't it wealth?

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Yes?

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Yes, the knowledge is fine, but do make you wealthy?

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No, it doesn't does it does not unless you know

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what to use it for. Yes, that's right, Yes, never mind,

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Let's let's get some questions sorted out because we've got

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a batch of really really good ones again today, and

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our first question comes from Justin.

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Hello, Fred and Andrew, it's Justin down in Melbourne. Thank

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you for answering my first question earlier this year. I

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have another question now, which relates to the Solar System.

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We're told that classical physics can't explain the existence of

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the assom because negatively charged particles orbiting a positive nucleus

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would lose energy and spiral in towards a nucleus. And

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of course we need quantum mechanics to explain the atom stability.

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But by extension, I was thinking about the Solar system.

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How is it that the planets maintain orbits around the

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Sun without losing energy and spiraling in towards the Sun.

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If you think about that classic demonstration with the rubber

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sheet and the bowling ball with some marbles, the marbles

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will orbit the bowling ball, but then very quickly lose

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energy and find themselves next to the bowling ball. And

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of course that's due to the friction of the rubber sheet.

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But I'm assuming there's a frictional component even in interplanetary space.

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But is it the fact that that really is negligible

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even on geological time scales and wouldn't cause the planets

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to lose energy. So perhaps you can walk us through

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how that works. And my second question is to do

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with the fact that the planets themselves obviously gravitationally interact,

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and perhaps there are some resins and is there as

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well which can cause planets to move either further away

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from the Sun, as Jupiter is supposed to have done

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in its lifespan. So, given that the Sun is at

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the halfway point in its life, do we foresee any

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radical restructuring or reshuffling of the planets in the Solar

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System in the Sun's second half of life. I love

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the podcast and I hope you can share some insights

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on that one.

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Thank you. We will do our very best. Actually I

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won't do anything, thank you, justin I'll end it all

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over to Fred. So two questions really interesting, both of

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them planetary orbits versus energy. Why don't they sort of

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slow down and fall in like you do with the

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old bowling ball on a rubber mat trick and the

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planet's reshuffling as the Sun gets older? Will do them separately?

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It's a good question. I don't know if we've had

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this one recently. We might have had it before. But

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what keeps them keeping on for it?

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Well, they do, They just keep on keeping on. So

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just Justin's right in that, Yes, the thing that sends

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the marble down to the bowling ball on the rubber

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sheet is the friction of the of the rolling phenomenon.

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All sorts of frictions come in. There's a bit of

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air braking as well with that, not much, but and

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that that's what leads to that situation. In the Solar System,

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there's very little to provide any kind of friction, if

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at all. The I mean, the outward pressure of the

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solar wind is in terms of planetary dynamics, exerts a

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negligible force that the force actually does affect small objects

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like asteroids. We've discussed recently how the Sun's red can

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speed up the spin of asteroids. That's an effect to

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his name, I can't remember, but that's the case.

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So it's.

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Essentially a situation where you've you've set these things in

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motion and the speed of rotation determined or revolution determined

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how far away they are from the Sun's We are

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in a very stable era in the Solar System, and

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I mean, notwithstanding the fact that it seems counterintuitive that

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they should just be able to go on forever rotating

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in their orbits to sort of lurch towards the second

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part of Justin's question. Yes, there probably have been migrations,

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we believe of planets from one orb bit to another.

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Things are very very stable, as they are now, incredibly

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stable we have, yeah, and probably for the second half

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of the Sun's life, things will remain much as they

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are now. The Moon's drifting away from the Earth, we

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know about that. That's because it's losing energy or gaining

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it sorry, gaining energy from the slow down of the

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s rotation that pushes it further and further out. But

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in terms of the planets, there isn't anything really similar

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going on. The Sun's mass is by far the biggest component,

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by a huge amount, of the mass of the Solar System,

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and Jupiter's mass is by a huge amount the biggest

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component of the mass of the planets. So Jupiter certainly

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calls the shots, and that's why we've got an asteroid

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belt where we have, because it probably Jupiter's gravitational interaction

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with the debris disk from which the planets formed probably

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sort of stymied the idea of things sticking together. Well,

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as soon as protoplanets stuck together, they or as planet

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Isi wal stuck together, that they got blasted apart by

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the gravitational pull of Jupiter and probably collisions as well.

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So the history of the Solar System is probably dominated

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in its early era by planetary orbits evolving, and that's

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just because the density of material. There's still a lot

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of debris left in the dust disk, there's a lot

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of collisions carrying taking place, and perhaps some gravitational instabilities

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that just needed to get themselves sorted out. Justin mentioned resonances,

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and there are many situations like that in the Solar System.

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There's a group of asteroids called the Hilda asteroids, which

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are in the main asteroid belt, but they have a

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resonance with Jupiters. So for every three orbits of a

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Hilda asteroid, you get two orbits of Jupiter. So every

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three a filled and two of Jupiter.

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There. Yes, we talked about this before and that didn't

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we find some weird ex planet that had like eight planets.

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Yes, that's right, Yes, that's one. I think that's the Trappist.

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I think it's one of the trappest planetary systems. Yes,

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and it's got that they're all in neat orders because

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they're all in resonance, and that that's something that's evolved,

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you know, probably quite early on in the history of

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that planetary system. You've got this array of planets that

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do pull themselves into resonant orbits. Now resident there aren't

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really resonances between the planets except that Pluto is in

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resonance with Neptune. I can't remember. That might be three

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to two as well, for every three orbits of Neptune

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two of Pluto. You might need to check what those

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numbers are. But it is a resonance. It's called a

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resonant object, and so that's come about over time. Neptune

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is much more dominant than Pluto in its gravitational pool, so.

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It is a three it's a three to two resonance. Yeah.

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Yeah, so that's a fairly common one. So, yes, it

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does happen. But the way things are now is they're

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very stable. They've evolved over four point seven billion years,

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and they're pretty happy with the way things are.

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I think. Yeah, it's fascinating, isn't it. You mentioned that

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effect of the Sun on asteroids. There's actually two effects.

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There's the yorp effect. Yeah, that's the sport in four

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names four yes, and the Yarkovsky effect, which is where

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the Sun heats the asteroid up, which causes it to

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emit heat, which acts as a tiny thruster which accelerates

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its orbital speed. Yeah.

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But these are you know, these are the tiny bodies

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of the Solar System. So they're they're orbits are evolving,

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that suggests, but they very much the you know, they're

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not planets.

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No, definitely not. So there's basically nothing stopping the planets

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from just doing what they're doing forever until the Sun

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gives up and says all right, I've had enough of

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you lot and gets too big for itselves. Yes, so

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nothing to worry about. Justin, you can go to work tomorrow.

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Oh I heard him say, thanks for the question. Justin.

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Lovely to hear from you. Our next question comes from Larry.

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I know we've been down this road before, actually, but

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it's a great question. Larry asks, is space. If space

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is expanding, then is the Earth also expanding? By how much?

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And would it be measurable?

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Now?

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I seem to remember a conversation we had a long

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time ago about the fact that as the universe expands,

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everything's expanding with it and moving further and further away,

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and we're going to reach a point where it will

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expand so much that we won't be able to see

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anything because everything we're just too far away for the

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light to reach us. But I think I did ask

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you the question as to whether or not my next

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door neighbor's house will be moving away from me, and

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the answer was yes, wasn't it.

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No, it's no, it's no right, you stuck with them,

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I'm afraid. Yeah, so you're right that the space occupied

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by the Earth is expanding, but it's you know, it's

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not even microscopic, it's a sub atomic level over even

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geological lifetimes, probably because it's such a small distance. The

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universe is very, very big and might long way to

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the exactly chemist shop. Yeah, that's twice we've had Douglas

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Adams been worth quoting. Yes, in recent weeks. I was

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going to say, yes, they are worth quoting. So it's

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it's you only really see the expansion when you start

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looking out millions of light years. Then you do, as

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discovered back in nineteen twenty nine. But the reason why

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the Earth is not participating in that expansion. Is that

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the forces that hold atoms together and that holds the

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Earth together, which is certainly gravity in terms of keeping

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the Earth together, is by far the dominant force. So

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the Earth's self gravity is easily enough to basically to

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overcome any tendency of the space within which the Earth

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sits to expands. On the scale of the Solar System,

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you can forget the cosmic expansion. In fact, on the

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scale of our galaxy, you can forget it.

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Basically.

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It's only when you start looking at more distant galaxies

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that you start seeing any measurable velocity change.

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Okay, so yep, gravity overcomes all. Yes, So sorry, Larry,

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You're stuck with your neighbors as I am with mine.

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It's just just the way it is. Earth will hold

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itself together. We are tough. Good question, though, good question,

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and is I was going to say, yeah, if you

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do want to said his questions, you can do so

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on our website and I'll tell you about that at

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the end of the show. This is Space Nuts with

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Andrew Dunkley and Professor Fred Watson. The crew of.

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Artemis two now bound for the Moon, Humanity's next Great

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Voyage begins space Nuts.

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Our next question, Fred is going to be a quick

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one because basically it's about nothing.

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No.

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This is Mike from Cromer in the UK. You had

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a question, Well, i'm podcast, I'm listening to the beginning

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of the universe as in the Big Bang, referred to

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it as being nothing before it, Shirley, from a non

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science point of view, it be better to say there

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was something before the Big Bang, but you don't know

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what it was. Why do you refer it refer to

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it as nothing before the Big Bang? It was trans question,

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but I thought i'd ask cheers.

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Thank you, Mike. I think it was me that said

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that we thought there was nothing before the Big Bang,

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and I think your answer was now it wasn't nothing,

226
00:14:27.440 --> 00:14:29.879
it's we don't know. Is that right? Or am I

227
00:14:30.919 --> 00:14:32.200
getting crossed up with something?

228
00:14:32.200 --> 00:14:35.639
And I mean that's right as well?

229
00:14:36.120 --> 00:14:39.679
That the issue, yes, so that.

230
00:14:39.720 --> 00:14:43.200
The standard line is in the beginning there was nothing

231
00:14:43.240 --> 00:14:48.799
and then it exploded. That's you know, that's a standard line,

232
00:14:48.840 --> 00:14:52.360
and that's very glib. The issue I have with trying

233
00:14:52.360 --> 00:14:55.440
to explain this is not with the word nothing or

234
00:14:55.480 --> 00:14:59.200
even with the word something, which is what Mike would

235
00:14:59.200 --> 00:15:02.679
prefer something, but we don't know what it was. But

236
00:15:02.759 --> 00:15:06.440
the issue I have is with the word before, because

237
00:15:07.840 --> 00:15:11.879
our understanding of the universe, certainly as far as relativity,

238
00:15:11.919 --> 00:15:15.120
informs us the models that you can build that you

239
00:15:15.159 --> 00:15:19.759
can build Time started with the Big Bang. Now, that

240
00:15:19.919 --> 00:15:23.559
is the prevalent, prevalent theory, but it is only one theory.

241
00:15:23.759 --> 00:15:26.240
There are others that do suggest that there was something

242
00:15:26.279 --> 00:15:29.639
before the Big Bang. Roger Penrose is one of the

243
00:15:29.639 --> 00:15:32.600
proponents of that sort of thing. But the kind of

244
00:15:32.639 --> 00:15:37.879
classical relativistic theory of the origin of the universe is

245
00:15:37.960 --> 00:15:43.039
that it's not that there was nothing before the Big Bang,

246
00:15:43.600 --> 00:15:46.120
it's that there was no time, and so before is

247
00:15:46.200 --> 00:15:51.960
not defined. Before has no meaning if you've before, only

248
00:15:52.000 --> 00:15:55.600
has meaning if you're in a time domain, and time

249
00:15:56.840 --> 00:15:59.519
the start of the universe may be created time as

250
00:15:59.519 --> 00:16:03.720
well as space. And that sort of ties in with

251
00:16:03.799 --> 00:16:06.600
some of the theories that are upcoming now from which

252
00:16:06.639 --> 00:16:09.039
you and I have talked about. The idea that time

253
00:16:09.120 --> 00:16:12.919
is an illusion really is an illusion that emerges from

254
00:16:13.000 --> 00:16:17.919
a much deeper level by quantum entanglement. That's the thinking.

255
00:16:18.360 --> 00:16:20.360
I'm not clear in my own head how these things

256
00:16:20.399 --> 00:16:25.879
link together, but it's certainly a very interesting possibility. And

257
00:16:25.960 --> 00:16:30.240
so that you know the idea that before the Big Bang, that.

258
00:16:31.440 --> 00:16:32.799
There was no before.

259
00:16:34.039 --> 00:16:37.360
Before the Big Bank because time didn't exist, then that

260
00:16:37.639 --> 00:16:40.399
would seem to be a possibility, given that we're looking

261
00:16:40.440 --> 00:16:44.279
for a deeper theory that explains the existence of the universe,

262
00:16:45.039 --> 00:16:47.799
in which time is not really a player. Time comes

263
00:16:47.840 --> 00:16:52.879
up as an illusion rather than a real thing. It's

264
00:16:52.960 --> 00:16:56.759
fascinating stuff. A lot of it's, as Mike says, it's

265
00:16:56.799 --> 00:17:01.440
almost into philosophy rather than rather and science. But the

266
00:17:01.480 --> 00:17:04.359
scientists are working hard on it. I'm really interested in

267
00:17:04.400 --> 00:17:09.279
this stuff because I think you know, Einstein himself was

268
00:17:09.319 --> 00:17:13.119
convinced that times in illusion, and he wrote something to

269
00:17:13.160 --> 00:17:16.359
that effect to a widow of one of his best

270
00:17:16.359 --> 00:17:19.960
friends who just died. It said time is a stubbor.

271
00:17:20.480 --> 00:17:20.839
It wasn't.

272
00:17:20.880 --> 00:17:24.759
He said, the idea of past, present, and future is

273
00:17:24.799 --> 00:17:26.559
a stubbornly persistent illusion.

274
00:17:27.440 --> 00:17:28.480
That was that.

275
00:17:28.480 --> 00:17:29.920
Those were his words in his letter.

276
00:17:30.400 --> 00:17:34.240
Yeah, I've read a theory a while back that suggested

277
00:17:34.359 --> 00:17:40.680
that all of time overlaps and that everything we know

278
00:17:41.079 --> 00:17:42.400
exists simultaneously.

279
00:17:42.519 --> 00:17:46.200
Yeah, that's that's what comes out of relativity. That's the

280
00:17:46.240 --> 00:17:51.119
Einstein view exactly that, and it comes from the fact

281
00:17:51.200 --> 00:17:57.039
that we realized very shortly after Hubbell, sorry, after Einstein

282
00:17:57.359 --> 00:18:00.519
developed his special theory of relativity in ninety one hundred

283
00:18:00.519 --> 00:18:04.960
and five, there was a mathematician who kind of unpicked

284
00:18:05.000 --> 00:18:07.920
the details, and it was from there that we realized

285
00:18:08.160 --> 00:18:12.680
that time is actually a dimension which behaves a little

286
00:18:12.680 --> 00:18:16.519
bit like space, because you can bend time. Relativity bends time,

287
00:18:17.119 --> 00:18:18.839
and that's one of the things that tells you that

288
00:18:18.880 --> 00:18:22.759
it's probably not a very deep and fundamental thing. And

289
00:18:23.319 --> 00:18:27.119
so Einstein's view of the universe was exactly what you've

290
00:18:27.160 --> 00:18:32.519
just elucidated, the idea of that everything back, past, present,

291
00:18:32.519 --> 00:18:37.119
and future all exists in some way, and our sort

292
00:18:37.160 --> 00:18:41.440
of gradual progress through them from past to future is

293
00:18:41.599 --> 00:18:44.599
the bit that's an illusion. It has a name that

294
00:18:44.759 --> 00:18:47.400
is called the block time theory of the universe. It's

295
00:18:47.440 --> 00:18:50.640
sort of time is all is in a single block,

296
00:18:51.000 --> 00:18:52.279
if I can put it that way, and we just

297
00:18:52.319 --> 00:18:55.039
stepped through it from moment to moment, but it all exists.

298
00:18:55.640 --> 00:18:59.480
Yeah. There's another element to that, which we've also talked

299
00:18:59.480 --> 00:19:04.119
about before, and that is that our existence is a

300
00:19:04.200 --> 00:19:10.079
manifestation of our own what our lives are what our

301
00:19:10.119 --> 00:19:13.240
world is, what our planet, what our universe is, is

302
00:19:13.279 --> 00:19:17.920
a manifestation of ours we I don't know how they

303
00:19:18.160 --> 00:19:22.440
come to that concept, but that's another theory that's been

304
00:19:22.480 --> 00:19:25.160
put forward, that none of this is real. We've just

305
00:19:25.240 --> 00:19:27.599
created it in our minds.

306
00:19:27.960 --> 00:19:31.440
Yeah, which tells you that a consciousness might be a

307
00:19:31.480 --> 00:19:35.440
fundamental part of the universe. And if it took the

308
00:19:35.559 --> 00:19:40.799
universe several billion years to evolve creatures that had consciousness

309
00:19:41.200 --> 00:19:45.039
and what was happening before that.

310
00:19:44.400 --> 00:19:47.200
Maybe we were just living a giant mind. We just

311
00:19:47.279 --> 00:19:49.559
made it all up or a big black hole. That's

312
00:19:49.599 --> 00:19:51.000
another ye.

313
00:19:52.119 --> 00:19:55.400
But thanks for that, Mike, trying to get these things

314
00:19:55.720 --> 00:19:58.119
sorted out in our heads. And yeah, chrome is quite

315
00:19:58.119 --> 00:19:59.839
a nice part of the world if I remember rightly,

316
00:20:00.119 --> 00:20:01.680
a bit to the Isle of Wight, but that's where

317
00:20:01.680 --> 00:20:02.400
it is.

318
00:20:02.680 --> 00:20:05.680
Wonderful. Thank you, Mike. Very thought provoking. We love those

319
00:20:05.759 --> 00:20:09.559
kinds of questions.

320
00:20:09.640 --> 00:20:13.519
Three space nuts.

321
00:20:14.400 --> 00:20:19.559
Our final question today comes from Giles. This is really

322
00:20:19.599 --> 00:20:21.839
interesting as well. This is a what if high from

323
00:20:21.880 --> 00:20:25.279
England Andrew and fred. A popular idea in science fiction

324
00:20:25.359 --> 00:20:28.559
when dealing with objects in fixed orbits, such as space

325
00:20:28.599 --> 00:20:32.319
stations or planetary targets, is simply to fire big rocks

326
00:20:32.400 --> 00:20:35.400
at them from a ship elsewhere in the system. What

327
00:20:35.599 --> 00:20:39.519
sort of accuracy could we currently hope to achieve with

328
00:20:39.599 --> 00:20:44.680
a simple shaped, solid metal projectile fired from low earth orbit,

329
00:20:45.079 --> 00:20:50.759
dropping through the atmosphere, assuming no corrective adjustments after launch,

330
00:20:51.599 --> 00:20:56.480
Could we, for instance, landscape London or would we be

331
00:20:56.680 --> 00:21:00.240
lucky to hit something in the city of England. Ume

332
00:21:00.359 --> 00:21:04.559
hitting a target in orbit would be much easier to achieve. Giles, Now,

333
00:21:05.240 --> 00:21:08.119
before you answer this, Fred, it's really interesting that he

334
00:21:08.160 --> 00:21:12.319
brings that up because I am currently reading a John

335
00:21:12.319 --> 00:21:17.759
Birmingham series called World War three point two and it's

336
00:21:17.759 --> 00:21:22.759
called subtitle The Access of Time. John Birmingham's from the UK,

337
00:21:22.920 --> 00:21:26.920
but he's living in Australia, up in Queensland.

338
00:21:28.000 --> 00:21:29.599
What's did a gig with him? Yeah?

339
00:21:29.680 --> 00:21:33.720
A lovely guy and he writes beautifully. I love his books,

340
00:21:33.880 --> 00:21:39.039
highly recommend them if you're into science fiction. And in

341
00:21:39.079 --> 00:21:41.559
this series there were three books and he enjoyed writing

342
00:21:41.599 --> 00:21:44.119
them so much he wrote three more books, which were

343
00:21:44.200 --> 00:21:48.200
just novel atts and then he announced, look, I'm going

344
00:21:48.240 --> 00:21:50.519
to keep going. This is just too much fun. And

345
00:21:50.559 --> 00:21:52.920
he's written three more books and he's now announced he's

346
00:21:52.960 --> 00:21:56.960
going to keep going again on this series. It's got

347
00:21:56.960 --> 00:21:59.720
some great characters in it, including Prince Harry, who's actually

348
00:21:59.799 --> 00:22:02.599
one of the main characters of the story. You've got

349
00:22:02.599 --> 00:22:05.319
to remember that Prince Harry was thrust back in time

350
00:22:05.400 --> 00:22:07.599
to World War Two with the rest of a fleet

351
00:22:07.680 --> 00:22:09.680
and so on and so forth. There's time travel in

352
00:22:09.720 --> 00:22:13.079
and all that. But what's interesting is in those novelettes

353
00:22:13.119 --> 00:22:17.960
in between, they were trying to rescue a scientist, a

354
00:22:18.039 --> 00:22:22.640
rocket scientist or a nuclear scientist, to try and stop

355
00:22:22.759 --> 00:22:25.759
Russia from getting a nuclear weapon, and et cetera, et cetera.

356
00:22:26.720 --> 00:22:31.440
As a part of that, Stalin decides to lash out

357
00:22:31.599 --> 00:22:37.759
against the Allies in Europe and attacks them with tungsten

358
00:22:37.880 --> 00:22:42.519
spears fired from a weapons platform in orbit and obliterates

359
00:22:42.599 --> 00:22:49.119
the NATO forces. So that's exactly what Giles is talking about. Yeah,

360
00:22:50.359 --> 00:22:53.559
and they even though it's not a nuclear weapon, the effect,

361
00:22:54.599 --> 00:22:58.240
from what John writes in his novels, the effect is

362
00:22:58.279 --> 00:23:01.279
the same it probably was.

363
00:23:01.359 --> 00:23:04.319
Yeah, I mean, it's you know, just turling things down,

364
00:23:05.519 --> 00:23:09.359
whether it's got explosive in it or not.

365
00:23:10.279 --> 00:23:10.720
That's right.

366
00:23:10.920 --> 00:23:15.920
You've got enough enough momentum in order to when you

367
00:23:15.960 --> 00:23:19.039
convert that to energy in order to make a big impact,

368
00:23:19.079 --> 00:23:22.279
which is why we lost the dinosaurs back in the day,

369
00:23:22.680 --> 00:23:26.720
same explosion, explosion from that, so, I think Giles's question

370
00:23:26.839 --> 00:23:30.440
is how well you could control that, and he's right

371
00:23:30.640 --> 00:23:34.319
in that from you know, firing an object from orbit

372
00:23:34.799 --> 00:23:39.960
from one place to another is straightforward because the dominant

373
00:23:40.200 --> 00:23:45.000
feature there is the interaction of the object with gravity,

374
00:23:45.119 --> 00:23:48.000
and it's the you know, gravity generally in the Solar

375
00:23:48.079 --> 00:23:51.480
System from the Sun and the planets, and that's highly predictable.

376
00:23:51.559 --> 00:23:55.519
And of course we had a dead on bulls eye

377
00:23:55.599 --> 00:24:01.160
hit with the Dart spacecraft on Dimorphous back in twenty

378
00:24:01.240 --> 00:24:03.359
twenty two that I think I can't remember. It was

379
00:24:03.359 --> 00:24:05.640
within just a few meters of the target, and that's

380
00:24:05.680 --> 00:24:09.279
because it's easy to do that with high precision. I

381
00:24:09.319 --> 00:24:12.480
guess when you're putting something down to the Earth's surface

382
00:24:12.519 --> 00:24:16.880
from orbit, you've got the vagaries of the atmosphere to

383
00:24:16.920 --> 00:24:20.759
deal with, and so you've got winds which are probably

384
00:24:21.319 --> 00:24:25.400
having some influence at different levels. You're still talking about

385
00:24:25.519 --> 00:24:28.759
very high velocities though, so they would you know, for

386
00:24:28.799 --> 00:24:32.400
your descending object, the winds would have some effect, but

387
00:24:32.519 --> 00:24:36.880
maybe not as much as you would think. We're now

388
00:24:37.400 --> 00:24:42.960
entering an era of hypersonic missile technology which could be

389
00:24:43.039 --> 00:24:48.799
launched from orbit, and those things are very high speed

390
00:24:48.960 --> 00:24:52.559
vehicles that can be steered in atmosphere. That's why they're

391
00:24:52.599 --> 00:24:56.559
different from ballistic missiles, which followed just the laws of

392
00:24:56.599 --> 00:25:01.480
gravity and a bit of atmospheric interaction, so you can

393
00:25:01.799 --> 00:25:03.519
kind of work out where they're going to land or

394
00:25:03.559 --> 00:25:06.319
where they're going to come in and intercept them. With

395
00:25:06.519 --> 00:25:09.880
defensive missiles. That doesn't hold true for hypersonics because they

396
00:25:09.880 --> 00:25:12.680

Planetary Orbits, Cosmic Expansion & The Nature of Nothing | Space Nuts Q&A

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