Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / Cosmic Questions: Time, Mass, and the Spectacle of Auroras

Transcript

Cosmic Questions: Time, Mass, and the Spectacle of Auroras · Space Nuts: Astronomy Insights & Cosmic Discoveries

• 0:00
  Andrew Dunkley: Hi there. Thanks for joining us again. This
• 0:02
  is Space Nuts, a Q and A edition. My name is
• 0:04
  Andrew Dunkley. Hope you're well. Stick
• 0:07
  around. We have got questions from, uh,
• 0:10
  our audience. One about time in
• 0:13
  anti gravity and the speed of time.
• 0:17
  Uh, that's always fun to talk about.
• 0:20
  Uh, we've got another question about
• 0:22
  supernova remnants, uh, the colors
• 0:25
  of aurora and uh,
• 0:28
  a light speed boost idea. This is a. Could
• 0:31
  I. Would I. Should I type of with my
• 0:34
  spaceship do something that might give me a
• 0:37
  light speed boost? We'll see if it works on
• 0:39
  this edition of space nuts. 15
• 0:42
  seconds. Guidance is internal.
• 0:44
  Professor Fred Watson: 10, 9. Ignition
• 0:47
  sequence start. Uh, space nuts.
• 0:49
  Andrew Dunkley: 5, 4, 3.
• 0:50
  Professor Fred Watson: 2. 1, 2, 3, 4, 5, 5, 4,
• 0:53
  3, 2, 1.
• 0:54
  Andrew Dunkley: Space nuts. Astronauts report it feels
• 0:57
  good. And he's back, uh, once
• 0:59
  again to try and solve all your little
• 1:02
  riddles. Here's Professor Fred Watson,
• 1:04
  astronomer at large. Hello, Fred.
• 1:06
  Professor Fred Watson: Hello there, Andrew. It's very good to be
• 1:09
  talking with you. It is. I'm sorry I've
• 1:11
  turned into an Irishman.
• 1:13
  Andrew Dunkley: Because I wonder what was happening there.
• 1:14
  Professor Fred Watson: Yeah, I said my trip to Ireland, which is
• 1:17
  great.
• 1:18
  Andrew Dunkley: There's nothing wrong with the Irish. When we
• 1:19
  were there in would have been July.
• 1:23
  Professor Fred Watson: Yeah, July.
• 1:24
  Andrew Dunkley: Uh, they really bunged it on for us at
• 1:27
  um, a place called Cove. It used to be
• 1:30
  called, um, I think
• 1:32
  Victoria. Was that what it was called?
• 1:35
  Um, no, no. Uh, anyway, it's where
• 1:38
  the, uh, Titanic, uh, made its last
• 1:41
  stop before heading out to the Atlantic and
• 1:44
  picked up its last groups of passengers. And
• 1:46
  some very sad stories as well. Uh,
• 1:49
  yeah, the pier where everybody got on board,
• 1:52
  um, the boats to go out to the Titanic
• 1:55
  because it couldn't actually anchor it at
• 1:57
  port. Have had to anchor outside the harbor
• 2:00
  at, um, uh, Cove.
• 2:02
  Um, um,
• 2:05
  it's still there, parts of it.
• 2:08
  So you can still see the remnants of that
• 2:10
  old. Um. And the White Star Line
• 2:13
  office is still there as well, which is now a
• 2:16
  museum where you can learn about the Titanic
• 2:18
  through the Titanic experience. I highly
• 2:20
  recommend that in the town of COVID which is
• 2:23
  nearby. County Cork. County
• 2:26
  Cork it is, yeah. Ah, lovely place.
• 2:29
  And they had Australian and New Zealand flags
• 2:31
  everywhere and music playing and they know
• 2:34
  how to party, those people. Yeah, terrific.
• 2:37
  Uh, shall we, um, do some questions, Fred?
• 2:40
  Professor Fred Watson: No, no, I think we should just have a cup of
• 2:43
  tea.
• 2:43
  Andrew Dunkley: Yeah, we probably have less trouble.
• 2:47
  Uh, let's firstly get a question from
• 2:50
  Andy.
• 2:51
  Speaker C: Hi guys, it's Andy here from the uk,
• 2:54
  first time questioner. Two questions,
• 2:57
  both time related. Um,
• 3:00
  the first question,
• 3:03
  um, as mass and
• 3:06
  gravity are so closely related
• 3:09
  and the higher a mass is, the
• 3:12
  slower time will flow.
• 3:15
  What would happen to the flow of time in an
• 3:18
  anti gravity field? So that's the
• 3:21
  first question. Um, the
• 3:24
  second question. If a
• 3:27
  planet had life that was
• 3:30
  intelligent and um, was evolving
• 3:33
  and had the potential to become
• 3:36
  space faring, but the planet was
• 3:40
  high gravity, is the playoff between
• 3:43
  gravity and the speed of time
• 3:46
  enough that that will make a significant
• 3:49
  difference to the evolution of the planet
• 3:52
  on galactic scales? Hope that one makes
• 3:54
  sense. Great program, no doubt. I'll be back
• 3:57
  again.
• 3:58
  Andrew Dunkley: Wow, Andy, where. Gee whiz, you've been
• 4:00
  pondering that for a while. There's some
• 4:02
  great questions there. Um, we'll tackle the
• 4:04
  first one first. Unless you want to do the
• 4:06
  first one second and the second one, I don't
• 4:07
  know. Uh, time, the effect of,
• 4:10
  um, uh, the effect on time,
• 4:13
  um, if it passes through an anti gravity
• 4:16
  field or just the effect on time in an anti
• 4:19
  gravity field.
• 4:21
  Professor Fred Watson: Yes. So, um,
• 4:23
  Andy's right actually. Uh, so
• 4:26
  what you've got is this phenomenon called
• 4:28
  time dilation. Appears that clocks slow
• 4:31
  down when you're in a gravitational field.
• 4:35
  Um, they only appear to be slowed down
• 4:38
  to outside observers. To you as the person
• 4:40
  in the gravity field, it makes no difference.
• 4:43
  The clock's just ticking at the same speed as
• 4:45
  it always did. But to an outside observer,
• 4:47
  your clocks are ticking more slowly. Uh, if
• 4:50
  there was such a thing as an anti gravity
• 4:51
  field, and we have no knowledge of
• 4:54
  anything like that at the moment, although
• 4:56
  people have worked very hard to try and
• 4:59
  demonstrate anti gravity, uh, as you can
• 5:01
  imagine, it would be a very useful thing to
• 5:03
  be able to harness, um,
• 5:06
  um, if you could have anti gravity. In other
• 5:09
  words, something that uh,
• 5:12
  actually repelled rather than attracted. Yes,
• 5:14
  the, the, um, or, or at
• 5:17
  least no, Let me put it another way. It's not
• 5:19
  repel repulsion, it's reducing the
• 5:21
  effect of gravity. I think anti gravity
• 5:24
  might, might reduce the effect of gravity.
• 5:27
  Uh, and it could, if you reduce it beyond
• 5:29
  zero, it could produce a repulsion. But
• 5:32
  that is not, that doesn't really matter for
• 5:35
  this argument because what happens is,
• 5:37
  um. Yes, relativity says that time would
• 5:40
  actually speed up. Uh, time, as I
• 5:43
  said to the person in the anti gravity field
• 5:45
  would keep on ticking away as normal. But to
• 5:48
  the outside observer, uh, the time would
• 5:50
  appear to be passing more quickly.
• 5:51
  Andrew Dunkley: Isn't it the same effect if you are falling
• 5:54
  into a black hole, what you're seeing is
• 5:56
  happening in real time because you're living
• 5:59
  your life like you do anywhere. But to
• 6:02
  the observer you would be,
• 6:06
  you know, a completely different Bucket of
• 6:08
  fish.
• 6:09
  Professor Fred Watson: That's right. Time slows down. Uh, everything
• 6:12
  appears more slowly. And when you cross the
• 6:14
  event horizon, you're sort of frozen on it.
• 6:17
  Yeah. Which means that event horizons are
• 6:19
  always splattered with things that have
• 6:22
  fallen into the. Maybe. Yeah.
• 6:25
  Hard to imagine.
• 6:26
  Andrew Dunkley: It's like the front of a car.
• 6:29
  In summer.
• 6:30
  Professor Fred Watson: White hopped. Yes. Um,
• 6:32
  yep.
• 6:33
  Andrew Dunkley: I think this was portrayed quite well in the
• 6:36
  movie Interstellar, where they had to go down
• 6:38
  onto a planet that was under the effect of a,
• 6:40
  A black hole. And every hour on the planet's
• 6:43
  surface equated to seven years back on the
• 6:46
  spaceship. Um, they, they did
• 6:49
  portray that quite well.
• 6:52
  That effect.
• 6:53
  Professor Fred Watson: Yeah.
• 6:54
  Andrew Dunkley: Okay, so there's no such thing really as an
• 6:56
  anti gravity field, but, um,
• 6:59
  he'd be right. The effect would be.
• 7:01
  Professor Fred Watson: That's right.
• 7:02
  But the second part of Andy's question.
• 7:04
  Andrew Dunkley: Yes. Um, high levels of gravity and
• 7:07
  its effect on the speed of time.
• 7:10
  Professor Fred Watson: Well, what he's saying is, if you had a
• 7:13
  planet or if you had a
• 7:15
  civilization working in a very high
• 7:18
  gravitational field, uh, would that mean
• 7:21
  that they would evolve more quickly and
• 7:23
  things would develop more quickly? Um, and
• 7:26
  I suppose the answer is yes, but only to an
• 7:27
  outside observer. To the people
• 7:30
  doing it, it would be just the same.
• 7:33
  Um, so, yes, maybe if our planet had
• 7:36
  a hugely different gravitational field
• 7:39
  from what it does have. Uh, seen from the
• 7:42
  outside, we might look as though we're
• 7:43
  evolving more quickly and developing
• 7:46
  technology more quickly, but to
• 7:49
  us, it would be just the same as if we had,
• 7:51
  you know, a lower gravitational field.
• 7:55
  Andrew Dunkley: This would complicate the search for
• 7:56
  intelligent life, wouldn't it? Uh, I mean,
• 7:59
  you might find a planet, um, and go,
• 8:02
  hey, something's going on there. Um,
• 8:05
  but it's in, it's in a, you know, high
• 8:07
  gravity environment. And, um,
• 8:10
  maybe it was happening
• 8:13
  some time ago, but it's all over. Red Rover.
• 8:15
  I mean, I don't know, it's. It's a head
• 8:18
  scratcher.
• 8:20
  Professor Fred Watson: Or.
• 8:21
  Andrew Dunkley: Here's one. If you do find a civilization
• 8:24
  living in a, in a, on a planet and, uh, you
• 8:26
  land to say hello, and then you take off
• 8:29
  again and find out that everyone at home's
• 8:31
  dead because you've been gone 500 years, but
• 8:33
  you were only gone a week.
• 8:34
  Professor Fred Watson: Yeah. Well, there's that, too. That's right.
• 8:38
  Yeah. That's, um, special relativity. That's,
• 8:41
  uh, the.
• 8:41
  Andrew Dunkley: That's the one.
• 8:42
  Professor Fred Watson: The relativistic difference in time. Well,
• 8:44
  because you're traveling at speeds near the
• 8:46
  speed of light. Yeah.
• 8:47
  Andrew Dunkley: I mean, it happens. Happens. On Earth,
• 8:50
  they've done those tests with, um, highly
• 8:52
  sensitive clocks and tested them at
• 8:55
  different altitudes and they've come back
• 8:58
  and went, well, look, there's a thousandth of
• 9:00
  a second difference in their performance. So
• 9:03
  we've moved through time. I read a story the
• 9:06
  other day, Fred, which I wish I'd kept it,
• 9:09
  um, about a cosmonaut, I think it was, who'd
• 9:12
  spent so much time in space that they
• 9:15
  estimated that, um,
• 9:18
  he was actually slightly ahead of time
• 9:21
  than everybody else. And I can't
• 9:23
  remember the details, but, uh, it was really
• 9:26
  fascinating.
• 9:27
  Professor Fred Watson: Um.
• 9:29
  Andrew Dunkley: They'Ve released a paper about it. I'll see
• 9:31
  if I can find it interesting. I might do
• 9:34
  that while you answer this next question.
• 9:36
  Thank you, Andy. I love that idea though. Um,
• 9:39
  keep them coming.
• 9:43
  Three, two, one.
• 9:45
  Speaker C: Space nuts.
• 9:48
  Andrew Dunkley: Uh, this question comes from Mark. Hi, Andrew
• 9:50
  and Fred and team. My name is Mark Turner
• 9:53
  and I live in the south of England. I'm sorry
• 9:55
  about that. About five, about five minutes
• 9:58
  from Patrick Moore's house as a point of
• 10:01
  interest. Wow. Um, I've been
• 10:04
  listening now for just over three years and
• 10:06
  always look forward to Thursday lunchtime
• 10:08
  when I sit down and listen to you guys.
• 10:10
  Sorry, we were talking about toilet stuff
• 10:12
  earlier. I hope that didn't mess you up. Uh,
• 10:14
  my question is, it's generally accepted
• 10:17
  that all of the heavy elements were produced
• 10:19
  in an even larger star than ours that
• 10:22
  went supernova. Which leads me, uh, to this.
• 10:26
  Can we still see the remains of the star
• 10:29
  that made us in the night sky,
• 10:31
  or do we know, uh, at what point in the
• 10:34
  night sky the star would have been by turning
• 10:37
  back the cosmic time clock? Keep up the great
• 10:40
  work, Mark.
• 10:43
  What do you reckon about that one?
• 10:44
  Professor Fred Watson: Um, so the answer is no.
• 10:47
  Um, because.
• 10:50
  So, yes, um, uh,
• 10:54
  what we call the interstellar medium, the gas
• 10:56
  between the stars, is enriched
• 10:58
  in its chemical, um,
• 11:01
  abundance. The amount of heavier elements
• 11:03
  that are in it enriched over time because
• 11:06
  of supernova explosions.
• 11:09
  Stars that have detonated and
• 11:12
  gone through this high temperature process
• 11:14
  where you get heavier elements created. And
• 11:17
  some of the heavy elements we now know are
• 11:20
  created in neutron star collisions,
• 11:22
  um, but that doesn't matter which
• 11:25
  it is. Um, the bottom line is that
• 11:28
  it's the general interstellar
• 11:31
  medium that is enriched. So you've got an
• 11:33
  explosion that takes place and over
• 11:36
  millions of years, the debris from
• 11:39
  that explosion just gets absorbed into
• 11:42
  the clouds of gas and dust that are then
• 11:44
  going to form, uh, later generations of
• 11:47
  stars. So there's really no way
• 11:50
  that the remnants of the star that gave
• 11:53
  us. Uh,
• 11:56
  the heavier elements, um, there's
• 11:59
  no way that we can pinpoint
• 12:01
  that it may be that some of the
• 12:04
  supernova remnants that we see, and we see
• 12:07
  many around the sky, that some of those
• 12:10
  were responsible for some of the
• 12:13
  stuff.
• 12:17
  They were probably responsible for enriching
• 12:19
  the interstellar medium closer to them than
• 12:22
  we are. That's kind of the point, I guess, I
• 12:25
  want to make. The debris that gave us
• 12:28
  our enriched interstellar medium
• 12:30
  is probably long dissipated. And we could
• 12:33
  not identify, uh, it with any of
• 12:36
  the known supernova remnants because
• 12:39
  they're still enriching their local
• 12:41
  environment, if I can put it that way,
• 12:43
  because they're still intact structures.
• 12:45
  They're expanding and dissipating, but we see
• 12:48
  them as intact structures. And so the
• 12:51
  debris that made us 4.6
• 12:53
  billion years ago is, uh,
• 12:56
  basically is nowhere near. You know,
• 12:59
  it's nothing to do with them.
• 13:02
  Um, and partly because those explosions took
• 13:04
  place more recently than the 4.6 billion
• 13:06
  years ago origin of our own solar system.
• 13:10
  So, uh, the.
• 13:13
  Basically, uh, yes, the answer is,
• 13:16
  well, no, we can't identify those
• 13:19
  remains. Uh, and turning back the cosmic time
• 13:22
  clock, we can do that, but we can't do it in
• 13:25
  the sort of detail. I mean, we can do it in a
• 13:28
  physical modeling sense. We're not looking at
• 13:30
  anything unless we're looking at things at
• 13:32
  great distances where we are looking back in
• 13:34
  time. Uh, but for the
• 13:37
  physics that we use to model the universe,
• 13:40
  um, we can't, um, wind back the clock
• 13:43
  in enough detail to see where
• 13:45
  these objects exploded. Uh, they may be,
• 13:48
  you know, many, many thousands, tens of
• 13:51
  thousands of light years away, uh, from where
• 13:53
  we are now. Uh, all they did was enrich the
• 13:56
  medium around them. And that's where we found
• 13:58
  our own, uh, solar system being formed.
• 14:01
  So we can't. We can't look back in time in
• 14:03
  that regard. Okay, thank you,
• 14:06
  Mark. Uh, by the way, I, uh, was a pretty
• 14:08
  regular visitor to Patrick Moore while, uh,
• 14:11
  he was still alive. So I know that house.
• 14:13
  Well, at Selsey, it was called Farthings, uh,
• 14:15
  is a lovely house, actually. Uh, and, um,
• 14:18
  when I used to visit him, he was always very
• 14:21
  welcoming, uh, and, um, always glad to show
• 14:23
  me around.
• 14:25
  Andrew Dunkley: Wonderful. Wow. Lucky you. Yeah.
• 14:27
  Professor Fred Watson: Yeah.
• 14:28
  Andrew Dunkley: Now, um, just to sort of draw on
• 14:31
  Mark's question, um, so he's
• 14:33
  right about a supernova creating the heavy
• 14:36
  elements.
• 14:37
  Professor Fred Watson: Yes.
• 14:37
  Andrew Dunkley: So how do they end up being a
• 14:40
  part of our planet? Is that because the
• 14:42
  supernovas created the.
• 14:45
  The spawning ground or being, you know,
• 14:48
  run through it? What. How does that work?
• 14:51
  Professor Fred Watson: Yeah, I mean, it's what I was saying.
• 14:53
  Basically, the, the. You Know, you get a
• 14:55
  supernova explosion which um,
• 14:57
  sends shockwaves out, uh, it sends
• 15:00
  enriched gas out and that gas
• 15:03
  gradually diffuses into the
• 15:06
  background, uh, what we call the
• 15:09
  interstellar medium. This, the, the gas
• 15:11
  between the stars. It's very, very rarefied,
• 15:14
  but that's where that stuff. And as
• 15:17
  you then get concentrations of that gas
• 15:20
  into clouds of hydrogen, mostly hydrogen, but
• 15:23
  other M elements as well, because it's been
• 15:25
  enriched, then that is what would form the
• 15:28
  next solar system. Uh, and so that, you
• 15:31
  know, that gradual process of
• 15:34
  uh, stars forming, exploding,
• 15:36
  enriching the uh, interstellar medium,
• 15:39
  then interstellar medium creates other star
• 15:42
  systems which do the same thing. It's why
• 15:45
  as the universe ages, you're going to get an
• 15:48
  enrichment of the number of heavy,
• 15:50
  of, you know, quantities of heavier elements
• 15:53
  that there are within the universe. And
• 15:54
  that's actually one way that we can measure
• 15:57
  the ages of stars, by how much of this stuff
• 16:00
  they've got in them. Because when they were
• 16:02
  formed, the universe would have been at a
• 16:03
  certain point of enrichment. Uh, and you
• 16:06
  know, that point is fossilized,
• 16:09
  if I can put it that way, in the star itself
• 16:12
  by the chemical composition that it
• 16:14
  demonstrates.
• 16:16
  Andrew Dunkley: Okay, very good. Um, it's a law
• 16:18
  of diminishing returns though, isn't it?
• 16:20
  Eventually all of this is going to stop
• 16:22
  happening.
• 16:23
  Professor Fred Watson: Yes, that's right. Eventually the universe
• 16:25
  will die because of that. Because there won't
• 16:27
  be any more. There won't be any gas
• 16:29
  in which to create supernova explosions,
• 16:32
  which is the raw material of stars, hydrogen
• 16:34
  gas that will all be used up eventually and
• 16:37
  we'll have what used to be called the heat
• 16:39
  death of the universe. Unless it starts
• 16:41
  collapsing on itself again.
• 16:43
  Andrew Dunkley: Well, yeah, I mean there's all these
• 16:46
  terrible perilous things that are going to
• 16:48
  happen, but um. It'S
• 16:51
  not going to happen next week, the week after
• 16:52
  maybe, because we're on holidays, if we're
• 16:55
  lucky.
• 16:55
  Professor Fred Watson: The week after. Yeah, that's right.
• 16:58
  Andrew Dunkley: Yeah. Thank, uh, you Mark. Great question.
• 17:00
  Uh, now that thing I was trying to look up, I
• 17:02
  can't find the exact story, but um,
• 17:05
  I found something that kind of explains the
• 17:08
  concept. Apparently, um, for a six month
• 17:10
  mission on the International Space Station.
• 17:12
  And as astronaut ages,
• 17:14
  0.005 seconds less than they
• 17:17
  would on Earth. So this, this particular
• 17:21
  um, ah, cosmonaut that I'm talking about
• 17:23
  apparently has spent so much time in space
• 17:26
  that he's actually, I think it's
• 17:29
  0.22, um,
• 17:32
  minutes younger than he.
• 17:35
  Had he drawn into space.
• 17:38
  Professor Fred Watson: It's only seconds rather than minutes. Yeah.
• 17:40
  Andrew Dunkley: Oh, 0.22 seconds. Yes, exactly.
• 17:43
  Yeah. Um, so I, I, yeah, I read
• 17:46
  it last week. I meant to send it to you and I
• 17:48
  completely forgot. So, uh, but that's the,
• 17:50
  that's the, the, the guts of the story.
• 17:53
  This uh, is Space Nuts. Andrew Dunkley with
• 17:56
  Professor Fred Watson.
• 17:58
  Professor Fred Watson: Space Nets.
• 18:00
  Andrew Dunkley: Uh, we have a, uh, question from one of
• 18:03
  our regular contributors. This is Casey.
• 18:05
  Speaker C: Hi guys. This is Casey from Colorado. Um,
• 18:08
  I just saw red northern lights and it
• 18:11
  was, it was really incredible.
• 18:13
  Professor Fred Watson: I, um, was hoping that you could.
• 18:15
  Speaker C: Please explain why auroras come in different
• 18:17
  colors. I hope you're both well and thanks
• 18:20
  for the podcast.
• 18:21
  Andrew Dunkley: Uh, thank you, Casey. Casey sent in a few,
• 18:24
  um, questions in recent times and we're more
• 18:26
  than happy to answer. She comes up with some
• 18:28
  interesting ideas. Uh, I just thought this
• 18:30
  was a good question to answer. Uh, I know
• 18:32
  we've talked about it before, but there's
• 18:35
  been some great auroral activity of late.
• 18:38
  And even in parts of
• 18:41
  Australia where you just don't see them, they
• 18:42
  have been absolutely stunning. Even as
• 18:45
  recently as a week or two ago, we had some
• 18:47
  fabulous photographs coming out of, um,
• 18:50
  many, many parts of southeastern Australia
• 18:53
  and. Prompted a
• 18:56
  thought in my mind that the one, the aurora
• 18:59
  we see here generally are pink.
• 19:02
  But when you see photos up in the northern
• 19:05
  hemisphere, when you're practically
• 19:07
  underneath them, they're green. Uh, and
• 19:10
  I'm sure the colors can vary
• 19:13
  into many areas. Fred,
• 19:16
  uh, I mean you've taken tours on these, um,
• 19:18
  to see these things you've seen that like
• 19:21
  this is boring for you.
• 19:22
  Professor Fred Watson: But, uh, it's never boring.
• 19:25
  Actually. I didn't imagine it wouldn't be
• 19:27
  just always spectacular. But you're
• 19:29
  absolutely right. So when we're up in uh,
• 19:32
  uh, Alta, which is far northern
• 19:34
  Norway, or um, Kirino, which is
• 19:37
  far northern Sweden, or Abisko, which is also
• 19:39
  far northern Sweden. And looking at the
• 19:41
  aurora, you're basically standing
• 19:44
  underneath it. And so you see the aurora
• 19:47
  as it really is. Uh, and
• 19:50
  you've got lots of colors in it. Um,
• 19:53
  but the pink and red
• 19:56
  aurorae are typically, uh, seen
• 19:59
  when you're a long way from the action.
• 20:02
  Uh, and the green, the bottom line is the
• 20:05
  green.
• 20:05
  Andrew Dunkley: Is we talking rate shift? No,
• 20:08
  no, but we're talking atmospheric.
• 20:12
  Uh.
• 20:12
  Professor Fred Watson: We'Re talking emission line spectroscopy.
• 20:16
  Andrew Dunkley: I never would have thought about.
• 20:18
  Professor Fred Watson: Yeah, so, um, the pink
• 20:20
  and red aurorae, uh, you'd see them
• 20:23
  if you're in the northern hemisphere. You'd
• 20:25
  see them on the northern horizon in the
• 20:27
  southern hemisphere here in Tasmania, you see
• 20:29
  them very often down in the south Usually the
• 20:32
  green part is below the horizon.
• 20:35
  It's too far over the Earth's curvature to
• 20:37
  see. And that's why you only see the red. And
• 20:40
  that's a clue to what's happening here. So,
• 20:43
  um, what you've got is the
• 20:45
  atmosphere, uh, being excited
• 20:48
  by radiation from the sun.
• 20:51
  Um, these subatomic particles charge
• 20:55
  out from the sun. If you've got a solar flare
• 20:57
  or something like that. They going at
• 20:59
  typically a million kilometers an hour. Uh,
• 21:01
  so they take a couple of days to get here.
• 21:04
  And then they're sort of funneled down the
• 21:06
  Earth's, uh, magnetic field lines. Um, and
• 21:09
  they're most concentrated near the magnetic
• 21:11
  poles. Which is why it's around the magnetic
• 21:13
  poles that you see most aurora. This is a
• 21:16
  sort of simplified version of the story. But,
• 21:18
  um, what happens is these electrons,
• 21:21
  they're accelerated. They're quite high
• 21:23
  energy. They hit atoms
• 21:26
  of oxygen and nitrogen in
• 21:28
  the Earth's atmosphere and they make them
• 21:30
  glow. And the important
• 21:33
  thing here is that those
• 21:36
  atoms of oxygen and nitrogen, actually
• 21:38
  they're molecules as well. Uh, O2,
• 21:41
  which is a pair of oxygen atoms, or N2, which
• 21:44
  is a pair of nitrogen atoms. Um, they behave
• 21:47
  differently at different pressures. And of
• 21:49
  course, as you go up through the atmosphere,
• 21:51
  the pressure gets steadily lower. So the most
• 21:54
  common one is the green light. And
• 21:57
  that's, uh, when you've got
• 21:59
  oxygen burn. Being excited to emit
• 22:02
  this green color. It's what we call a
• 22:04
  spectrum line. It's a particular wavelength,
• 22:06
  which means it's a particular color. Uh, but
• 22:09
  it's green. Uh, and that, uh,
• 22:11
  works for pressures that you see
• 22:14
  between about 100 and 200
• 22:16
  kilometers above the Earth's atmosphere.
• 22:20
  Above 200 kilometers, the
• 22:22
  pressure is lower, uh, and
• 22:25
  the green line doesn't form, or the green
• 22:27
  light is not formed. Uh, it's actually
• 22:30
  quenched. And there is a different atomic
• 22:33
  process that gives rise to red light.
• 22:37
  Uh, 630 nanometers, if I remember rightly,
• 22:40
  is the wavelength. So you get this red light,
• 22:42
  which is still oxygen, but it's oxygen at
• 22:45
  a lower pressure than what comes out
• 22:48
  from the green. So between 1 and 200
• 22:50
  kilometers, you're going to see green aurora.
• 22:52
  Above that, you're going to see red aurorae.
• 22:54
  And that's why we only see the red ones. If
• 22:57
  you're looking from Australia, because the
• 22:58
  green is way below the horizon. Um,
• 23:01
  if you've got a really, um, powerful
• 23:05
  stream of subatomic particles, then
• 23:08
  they will penetrate below 100km.
• 23:11
  And that then excites not
• 23:14
  the oxygen, but the Nitrogen. You get um,
• 23:16
  what's called molecular excitation. Nitrogen
• 23:19
  molecules start emitting light and they
• 23:21
  emit in several different colors. Light,
• 23:24
  um, deep blue, um, there is
• 23:28
  different red, there's sort of greens, uh,
• 23:30
  and all those mixed together to give you
• 23:32
  something like a purple. Often in a bright
• 23:35
  aurora you've got the green auroral curtains
• 23:38
  and below that there might be a purple layer
• 23:40
  as well. And sometimes the colors are so
• 23:42
  mixed that it turns white that you actually
• 23:45
  get a white bottom edge to an aurora. Then
• 23:47
  you know, you've got really high energy
• 23:50
  electrons and then you saw all.
• 23:52
  Andrew Dunkley: You see in one of those.
• 23:53
  Professor Fred Watson: Yes, I have. Uh, yeah, actually the very
• 23:56
  first time we went up there, I've got
• 23:57
  photographs taken from a place called
• 23:59
  Lingenfjord in northern Norway. A very dark
• 24:02
  site. It was a wonderful place to see the
• 24:04
  aurora from. And yeah, there were definitely
• 24:06
  white, white, white bottoms on my auroral
• 24:09
  curve. Um, so
• 24:12
  uh, but what I was going to say
• 24:14
  was that's the basic story. But in
• 24:17
  reality you get these things all mixing and
• 24:20
  so sometimes you do get pinks and you get,
• 24:21
  you can actually get some quite odd colors.
• 24:25
  Actually I took some photographs at the
• 24:27
  beginning of this year in uh, far, again far
• 24:30
  northern Norway, uh, and later in Greenland
• 24:32
  where the coloring was almost like a brown
• 24:35
  color rather than the reddish that you expect
• 24:38
  uh, from high altitude aurora. So it's the
• 24:41
  way the colors mix that give you the
• 24:43
  different effects. Plus you've got to add to
• 24:45
  that the color response of your camera as
• 24:47
  well, which can sometimes tell you
• 24:50
  um, you know, give you falsehoods. Because
• 24:53
  the, the camera itself is, is basically
• 24:56
  tuned to take photographs of everyday
• 24:58
  objects. It's not really tuned to take
• 25:00
  photographs of things that are emitting only
• 25:02
  on one wavelength, uh, which the aurora does.
• 25:05
  Andrew Dunkley: Yes, yes, I know. Um, although while we were
• 25:08
  uh, up there, um, northern,
• 25:11
  northern parts of Europe, Norway, um,
• 25:13
  Greenland, Iceland, people, um,
• 25:16
  did try to um, take photos of
• 25:18
  aurora and a couple of them were successful.
• 25:21
  I was not. Yeah, I'll say
• 25:23
  one.
• 25:24
  Professor Fred Watson: But it was summer. Yes, summer's the, that's
• 25:27
  the problem because there's still so much
• 25:28
  twilight there. Um, I used to
• 25:31
  cut around a digital, proper digital
• 25:34
  camera with me and a tripod to do all these
• 25:36
  long exposure photographs. But to be honest,
• 25:38
  now with a smartphone they are so sensitive
• 25:41
  you can hand hold them and get really
• 25:44
  fantastic auroral photographs.
• 25:47
  Um, which blew me away the first time I did
• 25:49
  it, which was the beginning of this year.
• 25:52
  Uh, I tried it a little bit on the previous
• 25:55
  trip that we had up to northern parts which
• 25:57
  was in Canada, actually. Uh, but this time at
• 26:00
  the beginning of this year, in Norway,
• 26:01
  Sweden, Iceland, uh, and Greenland. I just
• 26:04
  held the smartphone up and, well, I've
• 26:06
  got more photographs than I know what to do
• 26:08
  with, and they're all dramatically good. Uh,
• 26:11
  the smartphone is such amazing technology.
• 26:14
  Andrew Dunkley: It's changed the world. Has in many ways, uh,
• 26:17
  particularly when it comes to photography.
• 26:18
  Um, it was the old, um, the old
• 26:21
  Canon Snappies and all those that we used to
• 26:23
  have with film in them. You got one shot at
• 26:26
  it and you didn't find out if it was any good
• 26:27
  for a couple of weeks.
• 26:28
  Professor Fred Watson: Yeah, the odds are that it, it wouldn't be
• 26:31
  because this sensitivity of film is so much
• 26:33
  lower than the, you know, than the sensors
• 26:35
  that we now use for images. That's the bottom
• 26:38
  line. Yep. Yeah.
• 26:38
  Andrew Dunkley: The gears are good now. Makes. Makes
• 26:40
  everybody a professional. Well, not quite,
• 26:43
  but you know what I'm saying.
• 26:43
  Professor Fred Watson: Talk to a professional photographer. And they
• 26:45
  won't actually agree with that?
• 26:46
  Andrew Dunkley: No, they would. They work out.
• 26:49
  Uh, thank you, Casey. Great question and
• 26:51
  good, uh, to hear from you again. Okay, we
• 26:54
  checked all four systems, and being with a
• 26:56
  girl, space nuts, our final question today.
• 26:59
  Uh, hi, guys, love the show,
• 27:02
  etc. Etc. He doesn't bandy around
• 27:04
  much. He's straight to the point. Uh, an idea
• 27:07
  just occurred to me. Uh, mass increases
• 27:10
  the faster you go, becoming infinite
• 27:13
  at the speed of light. So if it were possible
• 27:16
  to accelerate particles up to a
• 27:18
  relativistic. I hate that word.
• 27:20
  Relativistic speeds in some compact
• 27:23
  device and then throw them out of the back of
• 27:26
  a spacecraft, would the acceleration increase
• 27:29
  because you're throwing more mass out
• 27:32
  the back? Yeah, I did that the other day.
• 27:35
  It's not pleasant. Uh, kind of
• 27:38
  an ion engine on. On
• 27:40
  steroids. Uh, I'm envisioning some kind
• 27:43
  of small particle accelerator powered by a
• 27:46
  nuclear power source, preferably fission.
• 27:49
  Any thoughts? Absolutely. Welcome.
• 27:51
  Speaker C: Many.
• 27:51
  Andrew Dunkley: Uh, thanks, and keep up the great work. Lee
• 27:53
  in Sweden, not to be confused with Swede in
• 27:56
  Leighton.
• 27:59
  Professor Fred Watson: Oh, okay.
• 28:00
  Speaker C: Really? Yeah.
• 28:01
  Andrew Dunkley: That's somebody else. Um,
• 28:05
  no, Lee in Sweden. So, um,
• 28:08
  okay, so he's got a particle accelerator on
• 28:10
  his spaceship, and he's accelerating
• 28:13
  the particles up to relativistic
• 28:16
  speeds and then he's shooting them
• 28:19
  out the back of the spacecraft. Bigger mass,
• 28:22
  whatever. Can it accelerate the spacecraft?
• 28:26
  Professor Fred Watson: Um, yeah.
• 28:27
  All right, I'm going to read, uh, what I've
• 28:29
  just brought up on the screen in front of me.
• 28:33
  Um, relativistic mass ejection in
• 28:36
  ion motors is not a current technology, but a
• 28:38
  theoretical concept. For future propulsion,
• 28:40
  where ions would be accelerated to speeds
• 28:43
  approaching the speed of light. The
• 28:45
  relativistic aspect refers to the effect of
• 28:47
  special relativity, where an object's mass
• 28:50
  appears to increase as it approaches the
• 28:52
  speed of light, making it harder to
• 28:54
  accelerate it further. This would require
• 28:56
  extremely high energy inputs and would
• 28:59
  involve complex physics. Unlike current ion
• 29:02
  thrusters that use less energetic but still
• 29:04
  very high ion, uh, ejection velocities
• 29:08
  that came from A.I. so how's that?
• 29:10
  Andrew Dunkley: Yeah, well, I mean,
• 29:13
  A.I. can be very useful.
• 29:15
  Professor Fred Watson: Yeah, that's kind of what I steer.
• 29:17
  Andrew Dunkley: You up the wrong path. It kept getting done.
• 29:19
  Professor Fred Watson: Yeah.
• 29:20
  Andrew Dunkley: Like, I had to make some pretty significant
• 29:22
  inquiries last, uh, last
• 29:25
  year, early this year, whatever, uh, about a
• 29:27
  housing situation, and it just got it
• 29:30
  so wrong constantly. Yeah,
• 29:33
  um. But. Yeah, um.
• 29:37
  Professor Fred Watson: So what I've just read out is putting nicely
• 29:39
  into words what I was going to say, but
• 29:43
  it's putting it rather more nicely than I
• 29:45
  would have put it. So there you go. Yeah.
• 29:47
  Andrew Dunkley: All right. So the. The
• 29:50
  concept of, um, creating
• 29:53
  engines that can do these
• 29:56
  kinds of things is real in science,
• 29:58
  but only to a certain degree.
• 30:00
  Professor Fred Watson: Yeah, My only worry about it would be, um,
• 30:03
  and I guess this is what, you know, the
• 30:06
  complex physics bit was.
• 30:08
  Um, you've got different reference frames.
• 30:11
  You've got the reference frame of the. Of the
• 30:13
  spacecraft, You've got the reference frame of
• 30:16
  the flow of, uh, charged
• 30:18
  particles coming out the back of it, and
• 30:20
  you've got a stationary reference frame, and
• 30:23
  the mass looks different to all of those. Uh,
• 30:26
  so, uh, that will be my only
• 30:29
  worry about that. And it's the thing that I
• 30:31
  would like to go a bit further into it rather
• 30:32
  than rely on A.I. uh, but
• 30:36
  the basic principle, I think, is quite right.
• 30:39
  Uh, but I have a
• 30:42
  caveat about just watch out for your
• 30:44
  reference frame, if I can put it that way.
• 30:46
  Andrew Dunkley: Yeah. Um, I've been toying
• 30:49
  with AI just to, uh, sort of get some
• 30:51
  concepts in my head about. You know, I
• 30:54
  mentioned. I don't know if it was this
• 30:56
  podcast or the previous one where we, uh,
• 30:58
  where I'm writing a new book, but, um.
• 31:02
  I. There's some concepts I wanted to
• 31:04
  include, but my brain wouldn't go there.
• 31:07
  So, um, I did use AI to try and
• 31:10
  learn what I needed to learn to make
• 31:13
  the. The thing work the way I wanted to in
• 31:16
  the story. Uh, it's very clever when you want
• 31:18
  to do things like that.
• 31:20
  Professor Fred Watson: Did it help?
• 31:21
  Andrew Dunkley: Yeah, very much.
• 31:22
  Professor Fred Watson: That's interesting.
• 31:22
  Andrew Dunkley: Yeah. Um, in fact, it
• 31:26
  sometimes gave me way too many concepts. I
• 31:28
  only wanted one, but it gave me 10. And I'm
• 31:31
  thinking, oh, hang on, that's all good
• 31:34
  stuff. I can't use it all, so I had to pick.
• 31:37
  But um.
• 31:40
  I found it very useful. But um, if you use
• 31:43
  it the right way, it's a great tool. Uh,
• 31:45
  but if, um, for general
• 31:48
  information, sometimes it can just hit the.
• 31:52
  You're throwing a dart and hitting that metal
• 31:55
  thing around the edge.
• 31:56
  Professor Fred Watson: All right, okay.
• 31:57
  Andrew Dunkley: Because it's throwing information back at you
• 31:59
  that's too generic, I suppose.
• 32:02
  Professor Fred Watson: Yeah.
• 32:03
  Andrew Dunkley: Sometimes I uh, think when it comes to AI,
• 32:07
  you've got to know how to use it to get the
• 32:09
  best out of it.
• 32:11
  Professor Fred Watson: Otherwise maybe that's right. Yes. Mhm.
• 32:13
  Otherwise it's dangerous.
• 32:14
  Andrew Dunkley: Yeah. Absolutely
• 32:17
  true. Yeah. I have found it very handy
• 32:20
  for like I, I've had a few photos over
• 32:23
  the years that I've wanted to keep, but
• 32:24
  they've, they've not been really good photos
• 32:27
  and it's been really good at cleaning them
• 32:29
  up. Taking, taking out some of the um,
• 32:32
  this one particular photo that I really love.
• 32:35
  But it's, it's grainy.
• 32:37
  Professor Fred Watson: Yeah.
• 32:37
  Andrew Dunkley: So you just upload the photo and say, can
• 32:40
  you um. I can't remember the terminology I
• 32:43
  used, but can um, you do this? And it
• 32:46
  takes like a minute or two to
• 32:49
  re. Calibrate the photo and then it gives
• 32:52
  you its result. And uh, I
• 32:55
  had a couple of big hits with that. That uh.
• 32:58
  Professor Fred Watson: Well.
• 32:58
  Andrew Dunkley: But I've had a couple that didn't.
• 33:00
  Professor Fred Watson: Yeah.
• 33:01
  Andrew Dunkley: Um, because the um, it had to
• 33:03
  try and fill in spaces because of
• 33:06
  the graininess of the photo and what it
• 33:09
  filled them in with actually changed the
• 33:11
  subject too much and I didn't like it, if
• 33:13
  that makes any sense at all. But
• 33:16
  um, yeah, I do find it useful. But m.
• 33:20
  It's not a perfect science and you've got to
• 33:22
  keep that in mind.
• 33:24
  Lee, thanks for your question. Uh, did we
• 33:25
  finish with Lee?
• 33:26
  Professor Fred Watson: I'm pretty sure we did.
• 33:27
  Andrew Dunkley: Yeah. Yeah. Good on you, Lee. Hope all is
• 33:29
  well in Sweden and I'm sure you get to see
• 33:32
  lots of aurorae. To you, lucky duck.
• 33:34
  Um, that's it, Fred. We are
• 33:37
  finished. Thank you.
• 33:40
  Professor Fred Watson: Uh, you're welcome.
• 33:43
  Yeah, uh, I, um, I've enjoyed um,
• 33:46
  going, getting my mind bent around some of
• 33:48
  those issues myself. So thank you Space
• 33:51
  Nuts listeners. You keep me on my toes.
• 33:54
  Andrew Dunkley: Yes, they do, don't they? If you would like
• 33:56
  to send us a question, you uh, can do that
• 33:59
  through our website, spacenutspodcast.com
• 34:02
  or spacenuts IO
• 34:05
  and you click on the AMA link at the top
• 34:08
  of the home page. And, uh, just fill in
• 34:11
  the blanks. Uh, you can send us your text
• 34:12
  questions that way. Or you can send us an
• 34:15
  audio question if you've got a device with a
• 34:18
  microphone. And just remember, uh, to tell us
• 34:20
  who you are and where you're from. Most
• 34:21
  people do these days. Or you can send us
• 34:24
  questions via YouTube Music. We've been
• 34:25
  getting a few of those and sometimes they
• 34:27
  just turn up on social media. Uh, it doesn't
• 34:30
  matter. We'll, um, we'll get to them.
• 34:31
  Although on social media, the audience
• 34:34
  tends to deal with them for us. Um,
• 34:37
  not many of them filter through, but, uh,
• 34:39
  yeah, keep, uh, those questions coming. Um,
• 34:42
  and, uh, yeah, that'll all be good, Fred.
• 34:45
  We'll see you next week. I think it'll be our
• 34:47
  last couple of programs before the Christmas
• 34:49
  break.
• 34:49
  Professor Fred Watson: May well be. That's right.
• 34:51
  Andrew Dunkley: All right, we'll catch you then. Thanks,
• 34:53
  Fred.
• 34:53
  Professor Fred Watson: Sounds great.
• 34:54
  Andrew Dunkley: And thanks to Huw in the studio, who went
• 34:56
  supernova on us because he's got a lot of
• 34:58
  heavy elements and he's gone to see a
• 35:00
  dietitian. And from me, Andrew Dunkley,
• 35:02
  thanks for your company. We'll see you on the
• 35:04
  next episode of Space Nuts.
• 35:05
  Speaker C: Bye. Bye.
• 35:07
  Andrew Dunkley: Uh, you'll be listening to the Space Nuts
• 35:09
  podcast. Available at
• 35:12
  Apple Podcasts, Spotify,
• 35:15
  iHeartRadio or your favorite podcast
• 35:17
  player. You can also stream on
• 35:19
  demand@bytes.com. this has been another
• 35:22
  quality podcast production from
• 35:24
  bytes.com.