Black Holes, Navigation, The Big Crunch & Re-Entry Speeds: Your Cosmic Questions Answered

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Andrew Dunkley: Hi there. Thanks for joining us. Once again,

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this is a Q and A edition of Space Nuts. My

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name is Andrew Dunkley. Great to have your

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company. Uh, we will be answering audience

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questions exclusively on this episode. We'll

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never do it again. Yes, we will. Uh, we're

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going to be, um, looking at

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a, uh, concept that Ross has put up about,

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uh, black holes equaling dark matter. Uh,

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we'll explain that. Or he will and we'll try

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and tear it apart. Uh, Sandy is

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asking about navigation in space.

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Uh, John is talking relativity, time,

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black holes and the big crunch. I

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knew we'd get a question about the big crunch

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because we talked about it so recently. And

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the speed of re entry is a question from

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Andy. We'll deal with all of that on this

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episode of space nuts.

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Voice Over Guy: 15 seconds. Guidance is internal.

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10, 9. Uh, ignition

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sequence start. Uh, space nuts. 5, 4, 3,

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2. 1, 2, 3, 4, 5, 5, 4,

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3, 2, 1. Space nut astronauts

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report it feels good.

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Andrew Dunkley: And with us once again is Professor Fred

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Watson, astronomer at large. Hello, Fred.

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Professor Fred Watson: Hi, Andrew. Good to talk again. Uh, it

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seems like only a few minutes ago that we

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were talking. It does, doesn't it?

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Andrew Dunkley: Yes, that's called relativity, I think.

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Professor Fred Watson: Time dilation. Yeah.

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Andrew Dunkley: Um, I'll tell you something funny. We had our

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granddaughters around last night. They were

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supposed to stay the night, but they both

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chickened out so dad had to come and pick

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them up at 9 o'.

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Speaker C: Clock.

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Andrew Dunkley: But um, um, they were, um,

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having a bit of fun and um, they liked doing

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craft. And one of them built a telescope with

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a piece of paper and was looking through it.

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And Judy said, what have you made? And it was

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the four year old she said, I made

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a looking through thing.

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That's what a telescope. It's a looking

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through thing.

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Professor Fred Watson: Um, which is nearly what they were

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originally called before the telescope was

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intended of a time

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device. Device for seeing afar. Uh,

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yeah, it's.

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Andrew Dunkley: Well, m. Looking through things.

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Professor Fred Watson: Looking through thing. Yeah.

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Andrew Dunkley: Very cute.

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Professor Fred Watson: I love that. Yeah. Um,

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yeah, you know, you know, you don't know what

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you might have, you know, released in that

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child's brain. She might become the

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next great astronomer. Uh, uh, using a

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looking through thing to make discoveries

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about the universe.

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Andrew Dunkley: Yeah. Yeah. Well, that's why we called it

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Vera. No, her name's. Her name's

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Felicity.

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Professor Fred Watson: That's a good name as well. I like it.

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Andrew Dunkley: It is nice. Shall we get to

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our first question?

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Professor Fred Watson: Oh, all right.

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Andrew Dunkley: All right. Uh, if black holes are, uh, the

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center of most galaxies, uh, and have

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been eating up matter almost from the

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Beginning of the universe. Can this be a

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possible explanation of dark matter? The

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black holes have eaten it.

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Now this, uh, comes from Ross Simon. I

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uh, had to smile when I read his name because

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Ross Simon used to be a famous newsreader on

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the Australian Broadcasting Corporation's TV

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news service. I remember Ross. He was, he was

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brilliant. Might be the same one. You

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never know.

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Professor Fred Watson: I was gonna say it's not the same Ross, is

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it? I hope so.

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Andrew Dunkley: It would be lovely. But, uh, it's not.

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Professor Fred Watson: Yeah. So, um, whether or not you are the

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famous Ross Simon. Ross, lovely to hear

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from you. Uh, and um, I mean

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it's, it's, it is tempting,

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uh, to lump black holes and dark

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matter together. Indeed. Um, that was

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looked at as being one of the first

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explanations of dark matter. Uh,

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that we've got space full of black holes

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that we don't see because they're black

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holes, um, and that they might account

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for the dark matter. This was the so called

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macho theory. Massive compact halo

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objects, uh, which was

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popular in the 80s,

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um, because it was only in the late

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70s that people started taking the idea of

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dark matter seriously when we realized

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that um, something like

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80% of the matter in the

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universe is invisible to us.

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Uh, now that's perhaps

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slightly different from what Ross is asking

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about because he's talking about material

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being sucked into black holes. Uh, and

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um, that is certainly

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something that happens. But that's not matter

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that's missing. That's just gone. Uh,

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the bottom line is that the universe as we

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see it today has this mystery in

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that we know that there is stuff there that

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has a gravitational effect. It holds galaxies

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together, it holds galaxy clusters together,

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causes uh, gravitational lensing

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all over the place. Um, but

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we have no way of detecting what it is other

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than through its gravity. So it's, it's. Some

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people used to call it missing matter. It's

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not missing. It's definitely there. Uh, this

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dark matter is around and it's probably in

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the rooms that you and I are sitting in, uh,

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at the moment. Uh, because it, it tends to be

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where normal matter is and we can.

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Andrew Dunkley: Judy and I were actually talking about a dark

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matter the other day, but you know, I won't

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elaborate.

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Professor Fred Watson: Uh, well, what you do in your spare time,

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Andrew, is entirely up m to you,

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especially with your wife. Um,

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um, so, yeah, so, so, but, um, but the,

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the, the black hole thing did come

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in because of this theory back in the 80s

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that Machos massive compact halo objects,

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objects that um, kind of dead

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stars or orphan planets or more Especially

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black holes might be, uh, the

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source of dark matter. The source of this GR

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we see present in large, on large scales

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like galaxy clusters and galaxies. What ruled

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that out was, uh, work carried out at a

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number of observatories, including here, uh,

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in Australia, uh, in fact, in a survey

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which was called macho, uh, looking for

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these things. Uh, and it was, um,

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that if you, if you had a universe full of

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black holes that you can't see, you would

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still be able to detect them by what's called

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gravitational microlensing. Because

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occasionally one of these black holes would

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pass in front of a distant star. Uh, and

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because black holes distort the space around

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them that behaves like a lens. And

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you magnify the light of the distant star.

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So you get a microlensing event has a

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very characteristic shape. It's a star

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getting brighter, uh, to a

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sharp cusp and then fading away again quite

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symmetrically. Uh, and we do

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see them. They're caused by normal stars and

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their planets. But in the numbers that you

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would have to have for black holes to

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be dark matter, they are not

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there. There weren't enough. The numbers were

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far too low. And that's when the emphasis

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shifted to WIMPs, the weakly interacting

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massive particles, which is just one class

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of, uh, subatomic particles that we think

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dark matter might be. So that's where the

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theory stands at the moment. So black holes,

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uh, you know, and I think Ross is

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talking about supermassive black holes at the

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centers of galaxies. Yes, They've been

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swallowing stuff up for 13.8 billion years,

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as far as we can tell. Um, but they don't

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explain why today in

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universe, um, something like 4/5 of the

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matter in the universe is invisible to us.

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Andrew Dunkley: Yeah, um, well, there's so many things we

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don't understand. And as yet, uh,

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which was brought up in a question recently,

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we have not been able to capture

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or identify, uh,

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a dark matter particle. So, um,

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until we can find some absolute proof

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and study it, we're probably going

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to just keep working with theory, I would

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imagine.

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Professor Fred Watson: Yeah, there are, um,

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techniques that can be brought to bear. Um,

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one of the theories about

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dark matter is that if

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that while dark matter particles don't

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interact with normal matter particles, they

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may interact with each other. In other words,

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if you bring two dark matter particles

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together, it's thought they might annihilate

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and produce a signal in gamma radiation.

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So you get this flash of gamma rays which

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might have a characteristic spectrum. And

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people are looking for that

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phenomenon in the centers of

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galaxies because that's where you would

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expect the dark matter to be at its densest.

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So it's where you would expect the dark

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matter particles to interact with each other.

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Um, so far the results have been a bit mixed

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on that. But it's one possible way that we

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might eventually discover, uh, what

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dark matter is.

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Andrew Dunkley: Maybe dark matter is like a, uh, negative

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photograph. Remember in the days of manual,

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um, photography, you'd take the film and

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it would be negative, and then you turn it

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into the photograph. Maybe dark matter

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is the negative of the universe.

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Professor Fred Watson: Well, yeah, I mean,

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there might well be, uh, a way that

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there is a sort of dark. What can I

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call it? A dark particle physics.

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A whole, uh, sweep of

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subatomic particles which

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fall under what we lump together as dark

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matter. But it's not just a single particle,

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it's many different ones. Just like the

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particles of normal matter. The 16 normal,

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uh, matter. Sorry, 16 subatomic

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particles. They include forces as well as

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matter when you count the 16. But you know

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what I mean, You've got this suite of

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different particles that make up normal

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matter. Maybe there's a suite of different

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particles that in some ways are a negative,

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uh, um, that make up dark matter.

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So I think that's not a bad one.

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Andrew Dunkley: We've been assuming it's just the one thing.

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It could be all sorts of things.

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Professor Fred Watson: There could be atoms and molecules made out

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of dark matter because

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they interact with each. I don't know. Look,

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I'm not a particle physicist, but, um, the

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possibilities seem, not exactly endless

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because particle physics has certain rules

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that you've got to follow. Uh, but I'm

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still pretty optimistic that we're going to

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get to the bottom of dark matter, uh,

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hopefully while I'm still al. Because I want

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to know.

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Andrew Dunkley: Yeah, we all do. We all do. Uh, thanks for

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the question, Ross. Uh, really good

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discussion point.

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We get a lot of questions about dark matter

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and black holes. Uh, while we're on the

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subject of black holes, there was, uh, an

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article released on the BBC, uh,

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early this year. Uh, I know it's still early

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this year, but.

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Professor Fred Watson: Right.

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Andrew Dunkley: You know, I'm talking the 3rd of January,

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where scientists captured the first ever

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visual proof of two supermassive black holes

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in a death spiral. So we're really starting

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to be able to find out more and more,

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uh, through our increased technology and the

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capacity to observe and create images

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of these things. So, uh, that was pretty

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exciting story. I read that one the other

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day. I thought I'd, um, give it a mention.

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But, um. Yeah, they,

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uh, of Course, uh, the popular

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press, uh, created their own photo which

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has absolutely got nothing to do with it.

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But, uh, yeah, it sells the story,

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doesn't it? Um, but uh, they've got the image

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of these two black holes, um,

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basically getting ready to devour each other.

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I think the big one will win.

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Professor Fred Watson: Yes, probably. Well, you.

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Andrew Dunkley: Thanks, Ross.

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Professor Fred Watson: Yeah, probably.

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Andrew Dunkley: Yeah, thanks, Ross. Good to hear from you.

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Professor Fred Watson: Okay, we checked all four systems and.

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Speaker C: Being with a go space nats, our.

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Andrew Dunkley: Uh, next question comes from Sandy.

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Speaker C: G', day, Fred and Andrew. It's Sandy here

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from Melbourne again. Thanks for a cracking,

290
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ah, show as usual. Um, my question today

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is about navigation in the solar system for

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the various spacecraft that we've sent into

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deep space. Being a sci fi

294
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nerd, my mind naturally goes to fancy

295
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graphics of star charts and orbit parts on a

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giant screen. However, wanted to

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ask how mission planners at various space

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agencies plot orbits. Do they take

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into account objects like asteroids for any

300
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close calls or is the space so vast

301
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it's not really necessary? Thanks heaps,

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00:12:29.590 --> 00:12:30.870
Sandy. Cheers.

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Andrew Dunkley: Thank you, Sandy. Good, uh, to hear from you.

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I don't think we've heard from Sandy in a

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little while, but, um. Yeah, um,

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he does a lot of great

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astrophotography and he's got a pretty

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amazing setup that he's shown me in the past

309
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about, uh, how he does it. Computers all

310
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plugged into telescopes and yeah, all this

311
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great software. It's a bit out of my league.

312
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Um, I might get there one day. Uh,

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navigation in space, plotting orbits, all

314
00:12:59.880 --> 00:13:02.040
that kind of jazz. Um, I

315
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must confess I struggle to get my head around

316
00:13:05.240 --> 00:13:07.840
it. Uh, it's not like driving a car. You've

317
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got to do, um, you know, when it comes to

318
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space, you've got, um, much less

319
00:13:12.760 --> 00:13:15.440
resistance, much, uh, more, much

320
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more reaction to minute, um,

321
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thrust and micro thrust and all

322
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sorts of other things. But you've got to be

323
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looking in all directions, not just, you

324
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know, on the plane of the planet. When

325
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you're driving a car type of thing. I don't

326
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know what I'm trying to say, but, um. Yeah.

327
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How does it all work, Fred?

328
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Professor Fred Watson: Uh, it's. It's sort of

329
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the equivalent of plotting things on a

330
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screen, but not quite the same. Um,

331
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but yeah, you know, the,

332
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uh, idea that, um. Excuse me

333
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a minute. Um, I'm sorry, I've got this cough.

334
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Sandy's, uh, idea that we

335
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need to take into account. I'm all right. I'm

336
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all right. Yeah,

337
00:14:01.310 --> 00:14:03.230
we need to take into account the positions of

338
00:14:03.230 --> 00:14:04.790
asteroids and things of that sort. That's

339
00:14:04.790 --> 00:14:07.230
exactly right. Um, so when you,

340
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um, chart, uh, the

341
00:14:10.190 --> 00:14:13.190
pathway through space, which

342
00:14:13.190 --> 00:14:15.670
is all done numerically, you know, it

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00:14:15.670 --> 00:14:18.460
doesn't. We can make displays of them, and

344
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I think people do as well. But the

345
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reality is that the real hard core is locked

346
00:14:24.460 --> 00:14:26.980
up in the numbers and the equations. Um, what

347
00:14:26.980 --> 00:14:29.660
you have to do is to, uh, at any

348
00:14:29.660 --> 00:14:32.580
instant along the orbit, uh, of the

349
00:14:32.580 --> 00:14:34.700
spacecraft. Because it is always an orbit.

350
00:14:35.260 --> 00:14:37.660
Usually, uh, for something, you know, going

351
00:14:37.660 --> 00:14:39.220
between the planets, it will be in orbit

352
00:14:39.220 --> 00:14:41.860
around the sun. Uh, that's the way

353
00:14:41.860 --> 00:14:44.580
orbital mechanics work. As, uh, soon as you

354
00:14:44.580 --> 00:14:47.380
switch on your thrusters, then you change

355
00:14:47.380 --> 00:14:50.160
that orbit. Uh, but when all the

356
00:14:50.160 --> 00:14:52.320
thrusters are off and your main engines are

357
00:14:52.320 --> 00:14:54.800
off, you are following a trajectory which is

358
00:14:54.800 --> 00:14:56.530
essentially an orbit. Um,

359
00:14:57.800 --> 00:15:00.000
not always a closed one. It could be an open

360
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orbit, uh, which is what's happening to the

361
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five spacecraft that are leaving the solar

362
00:15:04.159 --> 00:15:06.920
system. Uh, but that

363
00:15:06.920 --> 00:15:09.920
orbit, uh, the future position

364
00:15:09.920 --> 00:15:12.560
of your spacecraft is dictated by the

365
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gravitational influence. Not just of the sun

366
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and the Earth and probably the Moon, but all

367
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the planets. All of them exert a

368
00:15:20.280 --> 00:15:22.910
gravitational pull. Uh, and, um,

369
00:15:23.370 --> 00:15:25.720
um, that goes down to the asteroids as well.

370
00:15:26.040 --> 00:15:27.960
If you're passing through the asteroid belt,

371
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you need to know where they all are, all the

372
00:15:30.720 --> 00:15:32.560
ones which are known. And there's more than a

373
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million known asteroids now.

374
00:15:35.320 --> 00:15:38.240
You would have them kind of built into your

375
00:15:38.240 --> 00:15:40.520
software that's looking, uh, at

376
00:15:41.000 --> 00:15:42.880
the direction that your spacecraft is going

377
00:15:42.880 --> 00:15:44.800
in. If there was any risk of a collision, it

378
00:15:44.800 --> 00:15:47.600
would flag that. And, um, it would also

379
00:15:47.600 --> 00:15:50.040
take into account the gravitational influence

380
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of any close encounters of asteroids. So

381
00:15:52.980 --> 00:15:55.710
it's a very precise science, um,

382
00:15:56.180 --> 00:15:58.820
as you know, because we know

383
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when, for example, the New Horizons, uh,

384
00:16:01.940 --> 00:16:04.420
flyby of Pluto a decade ago,

385
00:16:04.920 --> 00:16:07.780
uh, in 2015, um, the precision

386
00:16:07.780 --> 00:16:09.460
with which that was executed was

387
00:16:09.460 --> 00:16:11.780
unbelievable. And it's because of orbital

388
00:16:11.780 --> 00:16:13.780
mechanics and how well we understand these

389
00:16:13.780 --> 00:16:16.780
gravitational influences, uh, that let you do

390
00:16:16.780 --> 00:16:19.780
that. Um, so, uh, yes, space navigation,

391
00:16:19.780 --> 00:16:22.410
in some ways it's easier, uh, than navigating

392
00:16:23.040 --> 00:16:25.960
on, uh, than driving a car. Because

393
00:16:25.960 --> 00:16:28.240
with driving a car, you've always got the

394
00:16:28.800 --> 00:16:31.520
unpredictability of the other road users.

395
00:16:31.520 --> 00:16:33.840
The great thing about orbital mechanics is,

396
00:16:34.000 --> 00:16:36.000
you know, what the other planets, the other

397
00:16:36.000 --> 00:16:37.720
asteroids and all the rest of it are going to

398
00:16:37.720 --> 00:16:40.080
do. And just one other

399
00:16:40.480 --> 00:16:42.560
adjunct to this, if I may. Um,

400
00:16:43.410 --> 00:16:46.040
uh, some years ago, there was, um, several

401
00:16:46.040 --> 00:16:48.480
papers which talked about the interplanetary

402
00:16:48.480 --> 00:16:51.120
superhighway. Uh, and these are

403
00:16:51.360 --> 00:16:53.800
effectively low energy trajectories between

404
00:16:53.800 --> 00:16:56.260
the planets. And it's based on exactly what

405
00:16:56.260 --> 00:16:59.190
I've just been Saying you can map where, um,

406
00:16:59.190 --> 00:17:02.060
the gravitational pull of all the objects

407
00:17:02.060 --> 00:17:04.300
will take you. And it turned out that

408
00:17:05.260 --> 00:17:07.940
if you can put um, a spacecraft at one of

409
00:17:07.940 --> 00:17:10.619
your Lagrange points, these gravitationally

410
00:17:10.619 --> 00:17:13.260
stable points, then leading from that

411
00:17:13.500 --> 00:17:15.860
are these various low energy pathways that

412
00:17:15.860 --> 00:17:17.740
take you to the Lagrange points of other

413
00:17:17.740 --> 00:17:20.340
planets. Uh, and that's the interplanetary

414
00:17:20.340 --> 00:17:22.900
superhighway. It might take you decades to

415
00:17:22.900 --> 00:17:25.820
get, uh, um, from

416
00:17:26.360 --> 00:17:28.920
the Earth Lagrange points to something like

417
00:17:28.920 --> 00:17:31.640
Mars or Jupiter's Lagrange points. It's a

418
00:17:31.640 --> 00:17:34.200
very slow process, but it does exist.

419
00:17:35.960 --> 00:17:38.040
Almost like an imaginary highway which is

420
00:17:38.040 --> 00:17:39.920
changing all the time as the planets go

421
00:17:39.920 --> 00:17:41.920
around in their orbits. Uh, just an

422
00:17:41.920 --> 00:17:44.280
interesting aspect of the navigation in

423
00:17:44.280 --> 00:17:44.600
space.

424
00:17:45.000 --> 00:17:47.160
Andrew Dunkley: Yeah, I would imagine that a lot of

425
00:17:47.720 --> 00:17:50.440
this, uh, would be pre

426
00:17:50.440 --> 00:17:53.080
programmed into the uh, computers of

427
00:17:53.240 --> 00:17:56.130
these vessels. Um, they do

428
00:17:56.210 --> 00:17:58.970
everything ahead of time because these things

429
00:17:58.970 --> 00:18:01.890
are on autopilot, the long haul spacecraft

430
00:18:01.890 --> 00:18:03.650
that are going out to do these missions.

431
00:18:04.430 --> 00:18:07.370
Uh, so it would. And I've been

432
00:18:07.370 --> 00:18:10.090
in the cockpit of a commercial uh,

433
00:18:10.090 --> 00:18:13.050
airliner, um, long before you can't

434
00:18:13.050 --> 00:18:15.090
do that anymore. Long before we had any

435
00:18:15.090 --> 00:18:17.850
issues like that. And

436
00:18:17.850 --> 00:18:20.850
watching the process, the plane flies itself

437
00:18:21.590 --> 00:18:24.590
and the pilots sit back and tell dad jokes to

438
00:18:24.590 --> 00:18:27.590
the tower. Um, that's what happened.

439
00:18:28.070 --> 00:18:30.950
But I would imagine it's the same in space.

440
00:18:30.950 --> 00:18:33.310
All these things are pre programmed, pre

441
00:18:33.310 --> 00:18:35.430
calculated, uh, and then

442
00:18:35.670 --> 00:18:38.310
contingencies built in just in case something

443
00:18:38.310 --> 00:18:40.390
gets in the way that you didn't anticipate.

444
00:18:40.950 --> 00:18:43.390
Um, they modify the

445
00:18:43.390 --> 00:18:46.030
spacecraft to sense a problem and go around

446
00:18:46.030 --> 00:18:47.920
it, I would imagine.

447
00:18:49.760 --> 00:18:52.000
Professor Fred Watson: Yeah. In fact

448
00:18:52.560 --> 00:18:55.480
the likelihood of something, it's so

449
00:18:55.480 --> 00:18:57.520
predictable. And our uh, knowledge

450
00:18:58.400 --> 00:19:00.880
of the sort of

451
00:19:01.360 --> 00:19:03.480
congestion in space, if I can put it that

452
00:19:03.480 --> 00:19:06.130
way, is so deep that um,

453
00:19:06.560 --> 00:19:08.880
it's unlikely that something's going to come

454
00:19:08.880 --> 00:19:10.920
along to surprise you. You suddenly see

455
00:19:10.920 --> 00:19:13.090
something ahead that you've got to avoid, uh,

456
00:19:13.090 --> 00:19:15.040
because that avoidance might actually be very

457
00:19:15.040 --> 00:19:17.960
difficult. Um, you can do things. So

458
00:19:17.960 --> 00:19:20.860
apparently, perhaps the best example

459
00:19:20.860 --> 00:19:22.860
I can give you again, it goes back to New

460
00:19:22.860 --> 00:19:25.500
Horizons and that is that once the

461
00:19:25.500 --> 00:19:27.980
Jupiter encounter, sorry, the Pluto encounter

462
00:19:27.980 --> 00:19:30.060
had happened, uh, back in July

463
00:19:30.220 --> 00:19:32.910
2015, um,

464
00:19:33.260 --> 00:19:35.980
they looked for other potential targets

465
00:19:36.540 --> 00:19:39.460
and eventually found the object

466
00:19:39.460 --> 00:19:41.860
Arrokoth that was discovered as part of

467
00:19:41.860 --> 00:19:44.380
surveys looking for future targets. And they

468
00:19:44.380 --> 00:19:46.900
worked out at what point they had to

469
00:19:47.220 --> 00:19:50.100
apply a thrust to the spacecraft to change

470
00:19:50.100 --> 00:19:52.500
its trajectory so that it would intersect

471
00:19:52.820 --> 00:19:55.140
with Arrokoth. And it all happened,

472
00:19:55.620 --> 00:19:58.570
you know, perfectly smoothly. Um,

473
00:19:58.570 --> 00:20:00.859
I think it was a couple of years later when

474
00:20:00.859 --> 00:20:03.820
the Arrokoth, uh, flyby took place. I Can't

475
00:20:03.820 --> 00:20:05.860
remember when it was. Maybe even a bit later

476
00:20:05.860 --> 00:20:08.260
than that. Maybe five years later.

477
00:20:09.700 --> 00:20:12.700
But yeah, that all happened. That was the

478
00:20:12.700 --> 00:20:14.870
nearest thing to, oh, there's something

479
00:20:14.870 --> 00:20:17.230
ahead, we need to change course to either

480
00:20:17.230 --> 00:20:19.790
interact with it or avoid it. Um, and it was

481
00:20:19.790 --> 00:20:21.110
a very leisurely process.

482
00:20:22.150 --> 00:20:24.990
Andrew Dunkley: And you're right about, uh, navigation on the

483
00:20:24.990 --> 00:20:27.830
planet on roads being much more dangerous.

484
00:20:27.830 --> 00:20:29.390
We were walking along the street the other

485
00:20:29.390 --> 00:20:31.510
day and somebody turned right off the main

486
00:20:31.510 --> 00:20:34.070
road into our, uh, part of town and,

487
00:20:34.910 --> 00:20:37.190
uh, went to the right hand side of the

488
00:20:37.190 --> 00:20:38.750
traffic island instead of the left.

489
00:20:38.750 --> 00:20:40.070
Professor Fred Watson: Right where we were walking.

490
00:20:42.390 --> 00:20:42.430
Yeah.

491
00:20:42.430 --> 00:20:44.550
Andrew Dunkley: Ah, I don't think she noticed, to be honest.

492
00:20:44.550 --> 00:20:46.190
Honest, she just went up the wrong.

493
00:20:46.190 --> 00:20:48.030
Professor Fred Watson: Side of the road. Hm.

494
00:20:48.310 --> 00:20:51.230
Andrew Dunkley: Anyway, it happens, but we, we always keep an

495
00:20:51.230 --> 00:20:53.270
eye out for that kind of thing. Um, there you

496
00:20:53.270 --> 00:20:54.870
go, Sandy. Thanks for the question. The

497
00:20:54.870 --> 00:20:57.190
answer is easy peasy, really.

498
00:20:58.150 --> 00:21:00.550
Professor Fred Watson: With modern computers, it's a lot harder if

499
00:21:00.550 --> 00:21:02.630
you're doing it by hand. Yeah.

500
00:21:03.430 --> 00:21:05.390
Andrew Dunkley: All right. This is a Q and A edition of Space

501
00:21:05.390 --> 00:21:07.630
Nuts with Andrew Dunkley and Professor Fred

502
00:21:07.630 --> 00:21:08.230
Watson.

503
00:21:11.560 --> 00:21:14.200
Space Nuts. Okay. Uh, our next question

504
00:21:14.520 --> 00:21:17.240
comes from John in 27

505
00:21:17.240 --> 00:21:19.440
parts. Hey, guys. Love the show. Every time I

506
00:21:19.440 --> 00:21:22.320
listen to a new episode, my mind goes crazy

507
00:21:22.320 --> 00:21:23.880
thinking about new possibilities and

508
00:21:23.880 --> 00:21:25.800
questions. I have two questions about

509
00:21:26.520 --> 00:21:29.080
time dilation. Uh, in general

510
00:21:29.080 --> 00:21:31.240
relativity, uh, if general

511
00:21:31.480 --> 00:21:34.040
relativity causes time to be observed at

512
00:21:34.040 --> 00:21:36.690
different rates, would that mean

513
00:21:36.690 --> 00:21:39.090
someone orbiting very close to one of the

514
00:21:39.170 --> 00:21:41.330
first black holes in existence would

515
00:21:41.330 --> 00:21:44.290
experience a universe that has existed for a

516
00:21:44.290 --> 00:21:46.050
much shorter period of time?

517
00:21:47.260 --> 00:21:49.570
Uh, as a follow up to this, if the

518
00:21:50.050 --> 00:21:52.730
new theory about the Big Crunch turns out to

519
00:21:52.730 --> 00:21:55.650
be true, would the finite

520
00:21:55.730 --> 00:21:58.370
time of the universe form the Big Bang

521
00:21:58.770 --> 00:22:01.770
to, uh, uh, from the Big Bang to the Big

522
00:22:01.770 --> 00:22:04.690
Crunch be considerably shorter if again,

523
00:22:04.850 --> 00:22:07.170
you were orbiting close to a black hole,

524
00:22:07.750 --> 00:22:09.670
uh, we see the universe as being

525
00:22:09.670 --> 00:22:12.590
13.79 billion years old.

526
00:22:12.590 --> 00:22:15.310
And uh, new estimates put the big crunch

527
00:22:15.390 --> 00:22:18.150
at 20 billion years into the

528
00:22:18.150 --> 00:22:20.670
future. My brain hurts thinking that these

529
00:22:20.750 --> 00:22:22.710
timescales could be considerably different

530
00:22:22.710 --> 00:22:25.210
due to time dilation. All the best, John. Uh,

531
00:22:25.550 --> 00:22:27.230
from Suffolk in the uk.

532
00:22:29.310 --> 00:22:30.350
There's a lot in there.

533
00:22:31.370 --> 00:22:33.650
Professor Fred Watson: Um, yeah. And so, so

534
00:22:34.610 --> 00:22:37.330
it's quite complicated because time

535
00:22:37.330 --> 00:22:39.970
dilation depends, uh, on your

536
00:22:39.970 --> 00:22:42.890
vantage point. So yeah, if you're in

537
00:22:42.890 --> 00:22:45.690
orbit around a black hole, uh, you're in an

538
00:22:45.690 --> 00:22:47.250
intense gravitational field.

539
00:22:47.970 --> 00:22:50.570
Andrew Dunkley: You're also stuffed. But we'll just deal with

540
00:22:50.570 --> 00:22:51.330
that another time.

541
00:22:52.780 --> 00:22:53.970
Professor Fred Watson: Um, yeah,

542
00:22:55.810 --> 00:22:58.770
you experience time just at the normal rate.

543
00:22:59.720 --> 00:23:00.080
Uh,

544
00:23:02.930 --> 00:23:05.770
what, um, an outside observer looking at you

545
00:23:05.770 --> 00:23:08.170
would see would be your time going very

546
00:23:08.170 --> 00:23:11.170
slowly. The time would be Dilated. So,

547
00:23:11.680 --> 00:23:14.650
um, I suppose what we're talking about

548
00:23:14.650 --> 00:23:16.690
here is that in terms of

549
00:23:17.650 --> 00:23:19.690
what you might call the frame of rest of the

550
00:23:19.690 --> 00:23:22.490
universe itself, uh,

551
00:23:22.530 --> 00:23:25.090
that's what we

552
00:23:25.650 --> 00:23:27.730
see when we look at the universe in general.

553
00:23:27.730 --> 00:23:30.410
And that's what gives us the 13 point, 13.79

554
00:23:30.410 --> 00:23:33.090
or 13.8 billion year age of the

555
00:23:33.090 --> 00:23:36.090
universe. Um, your perception of that,

556
00:23:36.330 --> 00:23:38.650
so that time effectively wouldn't change,

557
00:23:39.330 --> 00:23:41.170
uh, but your perception of it if you were in

558
00:23:41.170 --> 00:23:43.330
orbit around the black hole would. It would

559
00:23:43.330 --> 00:23:45.369
probably appear to look as though it was

560
00:23:45.369 --> 00:23:47.770
going very quickly. Uh, but that's because

561
00:23:48.090 --> 00:23:50.970
your time's slower. And uh,

562
00:23:51.050 --> 00:23:53.550
likewise, um, uh,

563
00:23:54.170 --> 00:23:56.730
with the density of the universe being

564
00:23:56.730 --> 00:23:59.330
higher, uh, at earlier

565
00:23:59.330 --> 00:24:02.010
stages, yes, we do know time dilation takes

566
00:24:02.010 --> 00:24:04.770
place. You can actually see that, uh,

567
00:24:04.770 --> 00:24:07.630
because, um, when scientists, uh,

568
00:24:08.370 --> 00:24:10.930
look at, uh, the light curves of

569
00:24:10.930 --> 00:24:13.410
supernovae, exploding stars, they have a

570
00:24:13.410 --> 00:24:15.650
light curve. Their light increases and then

571
00:24:15.650 --> 00:24:18.650
decreases, uh, in a more gradual

572
00:24:18.650 --> 00:24:21.380
way with a very characteristic shape. Uh,

573
00:24:21.380 --> 00:24:24.050
those light curves, uh, are dilated, they're

574
00:24:24.050 --> 00:24:26.530
stretched when we look at ones in the early

575
00:24:26.610 --> 00:24:29.090
universe. So the phenomenon does happen,

576
00:24:29.570 --> 00:24:32.550
but, but, um, it doesn't happen at a

577
00:24:32.550 --> 00:24:35.310
level that's going to significantly shorten

578
00:24:35.310 --> 00:24:37.950
our, um, perception. You know, the

579
00:24:37.950 --> 00:24:40.870
universe's perception of its own history. If

580
00:24:40.870 --> 00:24:42.910
I put it that way. I think I'm talking a

581
00:24:42.910 --> 00:24:44.750
little bit in riddles here, but I hope John

582
00:24:45.230 --> 00:24:47.950
follows me, that it really is all about your,

583
00:24:48.550 --> 00:24:50.630
um, frame of rest, as we call it, your

584
00:24:50.630 --> 00:24:53.310
vantage point, uh, on the universe. Because

585
00:24:53.310 --> 00:24:55.230
that's what time dilation is all about. It's

586
00:24:55.230 --> 00:24:57.750
about people seeing time going differently,

587
00:24:57.750 --> 00:25:00.230
depending on their viewpoint. Our viewpoint

588
00:25:00.230 --> 00:25:03.210
here, uh, from Earth is probably

589
00:25:03.530 --> 00:25:06.410
that of the universe as a whole, effectively,

590
00:25:06.990 --> 00:25:09.170
uh, because we are not in an intense

591
00:25:09.170 --> 00:25:12.050
gravitational field. The gravitational

592
00:25:12.050 --> 00:25:14.290
field of the sun is the strongest thing we

593
00:25:14.290 --> 00:25:17.170
feel that keeps the Earth in orbit. But it's

594
00:25:17.170 --> 00:25:18.890
nothing like what you would find around a

595
00:25:18.890 --> 00:25:21.250
black hole. And so we've got probably a

596
00:25:21.250 --> 00:25:24.170
fairly unbiased view of the

597
00:25:24.410 --> 00:25:25.930
universe and its history.

598
00:25:26.490 --> 00:25:28.090
Andrew Dunkley: Now, uh, are we in a gravity well?

599
00:25:30.030 --> 00:25:32.030
Professor Fred Watson: Yeah, we are. I mean, the, the Earth itself

600
00:25:32.030 --> 00:25:34.550
creates a gravity well and that's what keeps

601
00:25:34.550 --> 00:25:36.670
us stuck to the Earth. Because the

602
00:25:36.990 --> 00:25:39.790
gravitational potential at your head

603
00:25:39.790 --> 00:25:41.830
is a little bit different from what it is at

604
00:25:41.830 --> 00:25:43.990
your feet. And that's what's pulling you

605
00:25:43.990 --> 00:25:46.790
down. The change in shape of space. There you

606
00:25:46.790 --> 00:25:47.070
go.

607
00:25:47.710 --> 00:25:48.270
Andrew Dunkley: All right.

608
00:25:48.430 --> 00:25:49.950
Professor Fred Watson: I'm not spaghettifying you.

609
00:25:50.430 --> 00:25:52.730
Andrew Dunkley: No, no. So, um,

610
00:25:53.390 --> 00:25:54.990
did we unpack everything there?

611
00:25:58.010 --> 00:25:59.770
Professor Fred Watson: Yeah, I think so. I think we. I think we've

612
00:25:59.770 --> 00:26:02.330
covered most of it. Okay, look,

613
00:26:02.570 --> 00:26:05.450
I know. Sorry. Go ahead.

614
00:26:05.770 --> 00:26:07.290
Andrew Dunkley: No, I was going to say that, uh, he also

615
00:26:07.290 --> 00:26:08.890
asked if the Big Crunch would happen

616
00:26:10.250 --> 00:26:12.250
faster than the expansion.

617
00:26:12.810 --> 00:26:15.130
Professor Fred Watson: So. Yes. So that I kind of, you know, lumped

618
00:26:15.130 --> 00:26:17.650
that into the. The fact that the times that

619
00:26:17.650 --> 00:26:20.290
we observe from, uh, our location in the

620
00:26:20.290 --> 00:26:22.330
universe, probably. Yes. 20 billion years

621
00:26:22.330 --> 00:26:24.130
down the track seems about right from the Big

622
00:26:24.130 --> 00:26:26.490
Crunch. If the recent desi results.

623
00:26:27.000 --> 00:26:29.180
Yeah, it's what happens. Um, um.

624
00:26:30.330 --> 00:26:32.840
Uh, I was going to say that,

625
00:26:33.080 --> 00:26:35.760
like you, John, uh, these things make my

626
00:26:35.760 --> 00:26:38.200
brain hurt. So don't think it's

627
00:26:38.680 --> 00:26:41.600
peculiar to, uh, um, a

628
00:26:41.600 --> 00:26:44.600
few people. Uh, I think most physicists,

629
00:26:45.000 --> 00:26:47.560
you know, they get their. They really have to

630
00:26:47.560 --> 00:26:49.720
get their heads around the things, like

631
00:26:51.240 --> 00:26:52.960
seeing things from different vantage points.

632
00:26:52.960 --> 00:26:55.160
It's not entire. Uh, it's not intuitive at

633
00:26:55.160 --> 00:26:55.290
all.

634
00:26:56.320 --> 00:26:59.120
Andrew Dunkley: No, no. All right, John, thank you. And I

635
00:26:59.120 --> 00:27:01.190
hope all is well in Suffolk. That's, uh,

636
00:27:01.190 --> 00:27:04.080
that's basically like one of.

637
00:27:04.080 --> 00:27:05.920
One of the easternmost points of England,

638
00:27:05.920 --> 00:27:06.400
isn't it?

639
00:27:06.480 --> 00:27:08.810
Professor Fred Watson: I used to live in Suffolk. Oh, there you are.

640
00:27:08.810 --> 00:27:11.720
Uh, yeah, not. Not far from Cambridge, which

641
00:27:11.720 --> 00:27:14.280
is in Cambridgeshire, but Suffolk. I was over

642
00:27:14.280 --> 00:27:16.240
the border in Suffolk. Uh, you're right,

643
00:27:16.240 --> 00:27:18.480
Suffolk. Uh, Norfolk and Suffolk are the two

644
00:27:18.480 --> 00:27:20.560
counties in East Anglia. That sort of

645
00:27:21.120 --> 00:27:23.370
semicircular bit that sticks out not very,

646
00:27:23.440 --> 00:27:25.520
very much north of the Thames Estuary.

647
00:27:25.920 --> 00:27:26.960
Andrew Dunkley: There you go. All right.

648
00:27:26.960 --> 00:27:27.440
Professor Fred Watson: Very pretty.

649
00:27:27.440 --> 00:27:27.920
Andrew Dunkley: Thanks, John.

650
00:27:28.400 --> 00:27:28.840
Professor Fred Watson: Yeah.

651
00:27:28.840 --> 00:27:29.280
Andrew Dunkley: Yes.

652
00:27:30.080 --> 00:27:32.080
Good to hear from you. Our final question

653
00:27:32.080 --> 00:27:34.720
today comes from Andy.

654
00:27:35.680 --> 00:27:38.320
Speaker D: Hi, guys, this is Andy from London. I'm a new

655
00:27:38.320 --> 00:27:40.680
listener to your podcast and quite new to

656
00:27:40.680 --> 00:27:43.440
science, so forgive me if this is a stupid

657
00:27:43.440 --> 00:27:46.320
question, but I was just wondering, um, when

658
00:27:46.800 --> 00:27:49.520
craft re enter atmosphere and they have to

659
00:27:49.520 --> 00:27:51.000
come in at a certain angle to stop from

660
00:27:51.000 --> 00:27:53.130
burning up, um,

661
00:27:54.170 --> 00:27:57.050
why do they not just come through slowly to.

662
00:27:57.690 --> 00:27:59.770
To get away with the friction effect

663
00:28:00.410 --> 00:28:03.290
which causes, uh, the heat. Thanks.

664
00:28:04.570 --> 00:28:07.170
Andrew Dunkley: Thank you, Andy. Um, and thanks for finding

665
00:28:07.170 --> 00:28:09.220
space Nuts and being a new listener. Uh,

666
00:28:09.290 --> 00:28:11.970
you've only got 590 odd

667
00:28:11.970 --> 00:28:14.570
episodes to catch up now, so. Yeah,

668
00:28:14.890 --> 00:28:17.650
have fun with that. We've certainly had fun

669
00:28:17.650 --> 00:28:20.480
with it. Um, I think we've had this question

670
00:28:20.560 --> 00:28:23.230
before, maybe asked a different way. Um,

671
00:28:27.440 --> 00:28:29.920
And when it comes to a spacecraft, we're

672
00:28:29.920 --> 00:28:31.520
orbiting the planet, which is essentially,

673
00:28:31.520 --> 00:28:33.520
it's just constantly falling. You're just

674
00:28:33.520 --> 00:28:36.320
maintaining a velocity that stops you falling

675
00:28:36.320 --> 00:28:39.160
in. Um, you do have to

676
00:28:39.160 --> 00:28:42.040
slow down to re enter so that that

677
00:28:42.040 --> 00:28:42.960
arc is,

678
00:28:45.370 --> 00:28:47.130
you know, reduced or increased, can't

679
00:28:47.130 --> 00:28:49.610
remember which. Uh, and then you fall through

680
00:28:49.610 --> 00:28:52.610
the atmosphere. Um, you can't stop

681
00:28:52.610 --> 00:28:54.570
and just sort of ease your way back in

682
00:28:55.370 --> 00:28:58.090
as against a space elevator, which would be

683
00:28:58.090 --> 00:29:00.970
able to do that if we ever build

684
00:29:00.970 --> 00:29:03.570
one. Uh, but that's a different set. But a

685
00:29:03.570 --> 00:29:06.170
space elevator is essentially not orbiting.

686
00:29:06.170 --> 00:29:09.170
It is stationary to a point on

687
00:29:09.170 --> 00:29:10.950
the planet, which means it goes up and down.

688
00:29:11.900 --> 00:29:12.940
Is that making sense?

689
00:29:13.660 --> 00:29:15.500
Professor Fred Watson: Yeah, um, yes, it is.

690
00:29:16.540 --> 00:29:17.260
Andrew Dunkley: That's good.

691
00:29:17.260 --> 00:29:19.460
Professor Fred Watson: That's the first time ever everything you've

692
00:29:19.460 --> 00:29:21.920
said is correct. Um, space elevators are, uh,

693
00:29:22.540 --> 00:29:25.340
hypothesized. Buzz, uh, Aldrin told me

694
00:29:25.660 --> 00:29:27.700
that night I had dinner with him, it's never

695
00:29:27.700 --> 00:29:29.860
going to happen. And he was quite right

696
00:29:29.860 --> 00:29:32.180
because, um, the space elevator has to sit on

697
00:29:32.180 --> 00:29:34.780
the equator. Uh, uh, every spacecraft in the

698
00:29:34.780 --> 00:29:36.780
sky crosses the equator. So you're always

699
00:29:36.780 --> 00:29:39.740
going to get things banging into, uh, will

700
00:29:39.740 --> 00:29:42.300
be very difficult to build one, uh, you know,

701
00:29:42.300 --> 00:29:44.580
apart from the structural thing, uh, so

702
00:29:44.740 --> 00:29:46.820
neglecting the space elevator for a minute,

703
00:29:46.820 --> 00:29:48.940
what you said is absolutely right. In order

704
00:29:48.940 --> 00:29:51.620
to stay in orbit, you have to achieve

705
00:29:51.700 --> 00:29:54.460
basically a horizontal velocity of about

706
00:29:54.460 --> 00:29:56.930
8 kilometers per second. Uh,

707
00:29:57.140 --> 00:29:59.860
and that's, uh, otherwise you just fall back

708
00:29:59.860 --> 00:30:02.580
to Earth. So that's what all

709
00:30:02.580 --> 00:30:05.510
the, you know, the, the huge amount of

710
00:30:05.510 --> 00:30:07.830
fuel that is carried by a rocket being

711
00:30:07.830 --> 00:30:10.190
launched. That's what it's all about. It's

712
00:30:10.190 --> 00:30:12.670
about getting up to a height of 2 or

713
00:30:12.670 --> 00:30:15.630
300 km and getting that

714
00:30:15.630 --> 00:30:17.790
orbital velocity, getting that horizontal

715
00:30:17.790 --> 00:30:20.790
velocity of 8 kilometers per second. So,

716
00:30:21.010 --> 00:30:22.390
um, what you could do,

717
00:30:24.110 --> 00:30:27.030
uh, is, and, you know, going, this

718
00:30:27.030 --> 00:30:29.430
is hopefully helping Andy,

719
00:30:29.790 --> 00:30:31.800
uh, if you, you had

720
00:30:32.200 --> 00:30:35.080
unlimited amounts of fuel, you could

721
00:30:35.320 --> 00:30:38.120
turn the rocket round, uh, from its orbital

722
00:30:38.120 --> 00:30:40.550
position and fire, uh,

723
00:30:40.920 --> 00:30:43.880
your rockets to act as a braking system

724
00:30:43.880 --> 00:30:45.960
to slow the thing down. And then you could

725
00:30:45.960 --> 00:30:48.440
gently tiptoe down through the atmosphere,

726
00:30:48.760 --> 00:30:50.800
constantly firing your rockets. It's actually

727
00:30:50.800 --> 00:30:53.320
what, um, Musk does with

728
00:30:53.880 --> 00:30:56.200
his, uh, Falcon rockets.

729
00:30:57.080 --> 00:30:59.360
He's got enough fuel left that he can bring

730
00:30:59.360 --> 00:31:02.280
the empty spacecraft back down intact,

731
00:31:02.500 --> 00:31:05.220
uh, and use it again, uh, without

732
00:31:05.300 --> 00:31:07.590
needing a heat shield. Um,

733
00:31:08.340 --> 00:31:10.940
so you could do that. Uh, and he's

734
00:31:10.940 --> 00:31:13.860
demonstrated that we can. Uh, but it

735
00:31:13.860 --> 00:31:16.820
turns out that, uh, it's much more

736
00:31:16.820 --> 00:31:19.700
effective to use this process called

737
00:31:19.700 --> 00:31:22.620
aerobraking, where you actually use the

738
00:31:22.620 --> 00:31:25.100
atmosphere itself to slow the

739
00:31:25.100 --> 00:31:27.500
spacecraft down, uh, because you don't need

740
00:31:27.500 --> 00:31:29.220
any fuel for that. You just need something

741
00:31:29.220 --> 00:31:31.620
that's going to stop it burning up. Uh, so

742
00:31:31.620 --> 00:31:34.420
getting from this 8km per second down

743
00:31:34.720 --> 00:31:37.320
to a few, you know, a meter or two per

744
00:31:37.320 --> 00:31:39.920
second, uh, for a splashdown or a touchdown,

745
00:31:40.690 --> 00:31:43.600
uh, is the tricky bit. And you've got to,

746
00:31:44.030 --> 00:31:46.560
uh, you know, you've got to use whatever

747
00:31:46.720 --> 00:31:49.240
means are at your disposal. And the easiest

748
00:31:49.240 --> 00:31:51.360
one is aerobraking using the atmosphere

749
00:31:51.360 --> 00:31:53.800
itself to slow you down. I should point out

750
00:31:53.800 --> 00:31:56.360
that, um, I think the first stage Falcon

751
00:31:56.360 --> 00:31:59.130
rockets, they're not at orbital velocity. Uh,

752
00:31:59.130 --> 00:32:00.760
when they turn around and come back, they

753
00:32:00.760 --> 00:32:03.480
haven't got up to that 8km per second because

754
00:32:03.480 --> 00:32:05.960
there's a second stage that lets them do that

755
00:32:05.960 --> 00:32:08.820
and they still burn up basically coming back

756
00:32:08.820 --> 00:32:11.100
into the atmosphere. The second stages.

757
00:32:11.890 --> 00:32:14.380
Um, but yeah, good question. Not a stupid

758
00:32:14.380 --> 00:32:15.140
question at all.

759
00:32:15.140 --> 00:32:17.580
Andrew Dunkley: No, no. And, and you know,

760
00:32:19.020 --> 00:32:21.860
it's rocket science. I mean we

761
00:32:21.860 --> 00:32:24.100
often say when something's not difficult,

762
00:32:24.100 --> 00:32:25.860
it's not rocket science. This is rocket

763
00:32:25.860 --> 00:32:28.820
science. Um, orbital speeds

764
00:32:28.820 --> 00:32:31.180
are, ah, significant. They're to stay

765
00:32:31.820 --> 00:32:34.060
out there, they've got to, um, do

766
00:32:34.060 --> 00:32:35.520
17,000 miles an hour.

767
00:32:35.670 --> 00:32:37.790
Professor Fred Watson: Hour, uh, which is eight kilometers per

768
00:32:37.790 --> 00:32:38.470
second. Yeah.

769
00:32:38.470 --> 00:32:41.350
Andrew Dunkley: Mark 25. Um, to slow

770
00:32:41.350 --> 00:32:43.990
down so that you can return to Earth safely,

771
00:32:43.990 --> 00:32:46.430
you've got to go from that speed to

772
00:32:46.430 --> 00:32:49.270
subsonic speed. Uh, and

773
00:32:49.830 --> 00:32:52.310
using fuel to do that would be exhaustive.

774
00:32:52.310 --> 00:32:54.630
Professor Fred Watson: Yeah, that's right. That's exactly right. You

775
00:32:54.630 --> 00:32:57.590
know, basically you're looking at the

776
00:32:57.590 --> 00:33:00.470
same amount of hardware

777
00:33:00.630 --> 00:33:03.260
in terms of a rocket and its fuel to

778
00:33:03.420 --> 00:33:05.420
get you up there. You'd need the same amount

779
00:33:05.420 --> 00:33:07.820
to bring you back just to do a gentle

780
00:33:07.820 --> 00:33:10.580
touchdown on the Earth. M.

781
00:33:10.860 --> 00:33:13.660
Um, notwithstanding the first stage

782
00:33:13.660 --> 00:33:15.660
recovery that we're starting to see with.

783
00:33:15.660 --> 00:33:17.380
Well, not starting. They've been doing it for

784
00:33:17.380 --> 00:33:20.060
10 years with the Falcon 9 rockets.

785
00:33:20.900 --> 00:33:23.340
Andrew Dunkley: M. Yeah, I'm sure the technology will improve

786
00:33:23.340 --> 00:33:25.340
and we'll find better ways, but at the

787
00:33:25.340 --> 00:33:27.500
moment, using the atmosphere as a free

788
00:33:27.500 --> 00:33:30.480
braking system. Yeah, yeah, works really

789
00:33:30.480 --> 00:33:33.080
well. Except when it doesn't. But that's only

790
00:33:33.080 --> 00:33:35.640
happened a couple of times. Yeah, um,

791
00:33:35.760 --> 00:33:38.480
yeah, thank you Andy. Great question though.

792
00:33:38.760 --> 00:33:40.600
Uh, really appreciate it. And don't forget,

793
00:33:40.600 --> 00:33:42.600
if you've got questions for us, you can send

794
00:33:42.600 --> 00:33:44.360
them through via our website,

795
00:33:44.360 --> 00:33:47.200
spacenutspodcast.com spacenuts

796
00:33:47.200 --> 00:33:49.720
IO you click on the little AMA link at the

797
00:33:49.720 --> 00:33:52.600
top. Uh, which means ask me anything. I

798
00:33:52.600 --> 00:33:55.080
finally figured that out. Ask me anything

799
00:33:55.080 --> 00:33:58.060
ama. Uh, and you just fill in the blanks. Uh,

800
00:33:58.060 --> 00:33:59.960
whether it's a text question or you can hit

801
00:33:59.960 --> 00:34:02.800
the start recording button and record a

802
00:34:02.800 --> 00:34:05.760
question for us. Um, any device with

803
00:34:05.760 --> 00:34:08.560
a microphone will do spacenutspodcast.com or

804
00:34:08.560 --> 00:34:11.560
spacenuts IO uh, while you're there

805
00:34:11.560 --> 00:34:13.280
you might want to hit the supporter button

806
00:34:13.280 --> 00:34:16.120
and um, look at, uh, ways of supporting

807
00:34:16.120 --> 00:34:18.600
us, uh, financially. It is not

808
00:34:18.680 --> 00:34:21.080
essential. We do not demand that of you,

809
00:34:21.080 --> 00:34:23.680
never will. But uh, we do have a lot of

810
00:34:23.680 --> 00:34:26.200
people who volunteer to do that. In fact, it

811
00:34:26.200 --> 00:34:28.540
was the listener's idea in first place to set

812
00:34:28.540 --> 00:34:30.300
that up for us. We didn't even think about it

813
00:34:30.300 --> 00:34:32.220
until someone said, how do I contribute to

814
00:34:32.220 --> 00:34:34.820
the program? And it all took off from there.

815
00:34:35.349 --> 00:34:38.300
Um, and we do appreciate our supporters very,

816
00:34:38.300 --> 00:34:40.980
very much. Um, thank you so much for

817
00:34:41.060 --> 00:34:43.140
thinking enough of us to put a couple of

818
00:34:43.140 --> 00:34:45.980
bucks behind. Um, our words. We

819
00:34:45.980 --> 00:34:47.060
appreciate it greatly.

820
00:34:47.889 --> 00:34:49.500
Uh, I think we're all done. Fred. Thank you

821
00:34:49.500 --> 00:34:49.940
so much.

822
00:34:51.469 --> 00:34:53.500
Professor Fred Watson: Uh, a pleasure, Andrew. Great to hear from

823
00:34:53.500 --> 00:34:55.780
the listeners, as always. Great questions,

824
00:34:56.069 --> 00:34:58.800
uh, get my mind, mind thinking again.

825
00:34:59.650 --> 00:35:02.250
Uh, so thank, uh, you everybody and thanks,

826
00:35:02.250 --> 00:35:04.920
uh, to you, Andrew too, for keeping on the

827
00:35:04.920 --> 00:35:05.440
rails.

828
00:35:06.250 --> 00:35:09.120
Andrew Dunkley: Uh, I do my best and sometimes I don't,

829
00:35:09.280 --> 00:35:11.520
but yes, thank you, Fred. We'll see you next

830
00:35:11.520 --> 00:35:14.210
time. Professor Fred Watson, astronomer, uh,

831
00:35:14.210 --> 00:35:16.400
at large. And thanks to Huw in the studio who

832
00:35:16.480 --> 00:35:17.960
definitely does keep it all together.

833
00:35:17.960 --> 00:35:19.360
Although he couldn't be with us today

834
00:35:19.360 --> 00:35:21.800
because, um, he re entered his garage at

835
00:35:21.800 --> 00:35:24.640
excess velocity, couldn't get down to some

836
00:35:25.120 --> 00:35:27.560
sonic speed. And, uh, well, he'll be in

837
00:35:27.560 --> 00:35:29.790
traction for, for a couple of weeks. Uh, from

838
00:35:29.790 --> 00:35:31.190
me, Andrew Dunkley. Thanks for your company.

839
00:35:31.270 --> 00:35:33.550
You'll see on the next episode of Space Nuts.

840
00:35:33.550 --> 00:35:34.070
Bye Bye.

841
00:35:35.270 --> 00:35:37.470
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