In this thought-provoking episode of Space Nuts, hosts Andrew Dunkley and Professor Jonti Horner tackle intriguing questions from listeners that explore the wonders of the cosmos. From the fascinating similarities between the Sun and the Moon to the mysterious nature of Hoag's Object, this episode is filled with scientific insights and engaging discussions.
Episode Highlights:
- Sun and Moon Coincidences: Andrew and Jonti delve into the remarkable coincidences between the Sun and the Moon, including their similar apparent sizes and rotation rates. They discuss the implications of these coincidences for future lunar habitation and solar radiation protection.
- Speeding Through Space: Trevor’s question leads to an exploration of how fast comets and spacecraft can travel. The hosts discuss gravitational assists and the potential for achieving incredible speeds, as well as the limits imposed by the physics of motion and the expansion of the universe.
- Hoag's Object Unveiled: Austin's inquiry about Hoag's Object prompts a discussion about this unique ring galaxy. Andrew and Jonti analyze its stunning symmetry and the theories surrounding its formation, including the possibility of a high-speed collision between galaxies.
- Understanding Cosmic Event Horizons: Dan's question about cosmic event horizons sparks a deep dive into the boundaries of the observable universe. The hosts clarify the concepts of event horizons, including the limitations of what we can see due to the expansion of the universe.
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Stay curious, keep looking up, and join us next time for more stellar insights and cosmic wonders. Until then, clear skies and happy stargazing.
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00:00:00 --> 00:00:02 Andrew Dunkley: Hi there. Thanks for joining us on a Q and A
00:00:02 --> 00:00:04 edition of Space Nuts. My name is Andrew
00:00:04 --> 00:00:07 Dunkley. Thanks for your company. on today's
00:00:07 --> 00:00:10 episode, questions from the audience. Rusty
00:00:10 --> 00:00:12 is asking about the similarities between the
00:00:12 --> 00:00:14 sun and the moon. And there are several, and,
00:00:14 --> 00:00:16 most are, coincidental, as it turns out.
00:00:17 --> 00:00:19 Trevor wants to talk about speeding through
00:00:19 --> 00:00:22 space. Slap a couple of pay plates on and
00:00:22 --> 00:00:25 you're on your way. Austin, has asked,
00:00:25 --> 00:00:27 us about Hoag's object. This is really
00:00:27 --> 00:00:30 interesting. And Dan wants us to explain
00:00:30 --> 00:00:33 the cosmic event horizon. We'll do all of
00:00:33 --> 00:00:36 that shortly on this edition of
00:00:36 --> 00:00:39 space nuts. 15 seconds. Guidance is
00:00:39 --> 00:00:41 internal. 10, 9.
00:00:42 --> 00:00:43 Ignition sequence start.
00:00:44 --> 00:00:44 Jonti Horner: space nuts.
00:00:44 --> 00:00:47 Andrew Dunkley: 5, 4, 3, 2. 1, 2, 3, 4,
00:00:47 --> 00:00:49 5, 5, 4, 3, 2, 1.
00:00:49 --> 00:00:51 Jonti Horner: Space nuts.
00:00:51 --> 00:00:52 Andrew Dunkley: Astronauts report it.
00:00:52 --> 00:00:52 Jonti Horner: Neil's good.
00:00:53 --> 00:00:55 Andrew Dunkley: And to help us along with all of those
00:00:55 --> 00:00:58 questions is Jonti Horner, professor of
00:00:58 --> 00:01:00 astrophysics at the University of Southern Qu
00:01:00 --> 00:01:01 Queensland. Hi, Jonti.
00:01:02 --> 00:01:03 Jonti Horner: Good afternoon. How are you going?
00:01:03 --> 00:01:06 Andrew Dunkley: I'm well. Good to see you again. Nice T
00:01:06 --> 00:01:09 shirt, by the way. Is that a comet that's
00:01:09 --> 00:01:10 on a dinosaur? Yep.
00:01:11 --> 00:01:13 Jonti Horner: Fighting off the oncoming comment. These T
00:01:13 --> 00:01:15 shirts are great, actually. I use these for,
00:01:15 --> 00:01:16 when I'm doing outreach talks. And they're
00:01:16 --> 00:01:19 particularly good with kids. And I didn't
00:01:19 --> 00:01:21 realize when I got them, I just thought,
00:01:21 --> 00:01:23 these are fabulous. So these kind of printed
00:01:23 --> 00:01:26 T shirts with dinosaurs and rocks from space
00:01:26 --> 00:01:27 falling down and they're kind of funny and
00:01:27 --> 00:01:29 they're kind of cute. I didn't realize when I
00:01:29 --> 00:01:31 got them. I was giving all these talks and
00:01:31 --> 00:01:32 someone came up to me and said, oh, is that
00:01:32 --> 00:01:35 from Happy Little Dinosaurs? What's Happy
00:01:35 --> 00:01:37 Little Dinosaurs? Turns out that there is a
00:01:37 --> 00:01:40 card game. that's one of the many, many
00:01:40 --> 00:01:43 kind of board game card games that are out
00:01:43 --> 00:01:45 there. Fabulous. If I've got loads of games
00:01:45 --> 00:01:46 on the shelves behind me. Board gaming is
00:01:46 --> 00:01:49 great. game out there, which is basically
00:01:49 --> 00:01:51 about the end of the times for the dinosaurs.
00:01:51 --> 00:01:54 And they're not happy at all in actuality,
00:01:54 --> 00:01:55 but it's apparently really good fun and it's
00:01:55 --> 00:01:57 kid friendly. And apparently all these T
00:01:57 --> 00:01:59 shirts I've got are free advertising for
00:02:00 --> 00:02:00 game.
00:02:00 --> 00:02:01 Andrew Dunkley: Oh, there you go.
00:02:01 --> 00:02:04 Jonti Horner: Yeah, there you go. I'm a walking
00:02:04 --> 00:02:05 billboard and didn't even realize it.
00:02:05 --> 00:02:08 Andrew Dunkley: Yes, indeed. that's not a fat joke either.
00:02:08 --> 00:02:10 All right, let's answer, some questions. Now.
00:02:10 --> 00:02:13 I'm going to have to put an apology forward.
00:02:13 --> 00:02:15 Straight up. I've, been to my optometrist
00:02:15 --> 00:02:17 this week. I do have a Little bit of an eye
00:02:17 --> 00:02:20 issue, so everything's super blurry. And
00:02:20 --> 00:02:22 they're all text questions, as it turns out.
00:02:23 --> 00:02:25 But, we'll, we'll do our best. Rusty from
00:02:25 --> 00:02:27 Donnybrook is first up. I'm wondering just
00:02:27 --> 00:02:29 how many coincidences there are between the
00:02:29 --> 00:02:31 sun and the Moon. First, we have the almost
00:02:31 --> 00:02:34 exact apparent size coincidence, which has
00:02:34 --> 00:02:37 enabled us to, learn
00:02:37 --> 00:02:39 an amazing amount about the sun during solar
00:02:39 --> 00:02:41 eclipses. Yes, Fred and I have talked about
00:02:41 --> 00:02:43 that many times. Second, is the rotation
00:02:43 --> 00:02:46 rate, which is the same for the sun and the
00:02:46 --> 00:02:48 Moon at about the solar latitude where
00:02:49 --> 00:02:52 most sunspots are seen. What will
00:02:52 --> 00:02:54 this coincidence enable as we begin to
00:02:54 --> 00:02:57 inhabit the Moon permanently? Will we be able
00:02:57 --> 00:03:00 to avoid most solar radiation storms by
00:03:00 --> 00:03:02 moving to the night side when large groups of
00:03:02 --> 00:03:05 sunspots, are visible? After all, we
00:03:05 --> 00:03:07 don't want to be stuck dug in at, the
00:03:07 --> 00:03:10 poles forever. could we do this with
00:03:10 --> 00:03:12 spacecraft in large orbits around the Moon?
00:03:13 --> 00:03:15 Does the coincidence mean that large deposits
00:03:15 --> 00:03:18 of helium 3 may be found at certain lunar
00:03:18 --> 00:03:21 longitudes? are there any more Sun, Moon
00:03:21 --> 00:03:23 coincidence that, coincidences that you know
00:03:23 --> 00:03:26 of? Thanks for the show. moving on up, guys.
00:03:27 --> 00:03:29 you'll be number one soon. Well, we'll see
00:03:29 --> 00:03:31 about that. But we're happy where we are.
00:03:31 --> 00:03:33 Rusty, from Donnybrook. that was more than
00:03:33 --> 00:03:35 one question, basically, but, all centered
00:03:35 --> 00:03:36 around these, these
00:03:37 --> 00:03:40 coincidences that exist between the sun and
00:03:40 --> 00:03:40 the Moon.
00:03:41 --> 00:03:44 Jonti Horner: Absolutely. And the coincidences are really
00:03:44 --> 00:03:46 astonishing. And it's just our very good
00:03:46 --> 00:03:48 fortune to live at exactly the right time in
00:03:48 --> 00:03:50 the Earth's history where things line up like
00:03:50 --> 00:03:52 this. Because when the Moon formed air, the
00:03:52 --> 00:03:54 Earth was spinning much, much quicker, the
00:03:54 --> 00:03:56 Moon formed much closer to us. And at that
00:03:56 --> 00:03:58 point when the Moon moved in front of the
00:03:58 --> 00:04:00 sun, it would block the sun out totally by a
00:04:00 --> 00:04:03 long, long way. And, you'd have a fairly
00:04:03 --> 00:04:05 underwhelming eclipse of the sun, to be
00:04:05 --> 00:04:07 honest. And, as time has gone on, the Moon
00:04:07 --> 00:04:08 has moved further and further away from the
00:04:08 --> 00:04:10 Earth. The further it moves away, the slower
00:04:10 --> 00:04:12 the Earth, spins, the longer the Moon takes
00:04:12 --> 00:04:14 to orbit the, Earth and the slower it
00:04:14 --> 00:04:16 recedes. And we're now in this very
00:04:16 --> 00:04:19 privileged window where most
00:04:19 --> 00:04:22 of the time the Moon and the sun are
00:04:22 --> 00:04:25 so similar in size that if they line up
00:04:25 --> 00:04:28 perfectly, the sun will be blocked out by the
00:04:28 --> 00:04:29 disk of the Moon. And we can see the Sun's
00:04:29 --> 00:04:31 our atmosphere. And we get the wonders of a
00:04:31 --> 00:04:34 total solar eclipse. Now. Doesn't happen
00:04:34 --> 00:04:36 all the Time, because when the Moon is near
00:04:36 --> 00:04:38 apogee, when it's furthest from the Earth,
00:04:39 --> 00:04:41 it is small enough that you instead get the
00:04:41 --> 00:04:43 ring of fire type eclipse. You get an annular
00:04:43 --> 00:04:46 eclipse, where you get an annulus or a ring
00:04:47 --> 00:04:49 of the Sun's disk around the Moon. And
00:04:49 --> 00:04:52 that is presaging what is to come in millions
00:04:52 --> 00:04:54 of years into the future. So as time goes on
00:04:54 --> 00:04:57 and the Moon keeps edging away from us, and
00:04:57 --> 00:04:59 as the sun continues to get very, very, very
00:04:59 --> 00:05:01 slightly bigger as well, because these things
00:05:01 --> 00:05:04 also happen, what that means is that as time
00:05:04 --> 00:05:06 goes on, we will get fewer and fewer total
00:05:06 --> 00:05:08 eclipses and more and more annular eclipses.
00:05:08 --> 00:05:11 And eventually there will come a day in
00:05:11 --> 00:05:13 millions of years in the future where we no
00:05:13 --> 00:05:15 longer get total eclipses at all. And we will
00:05:15 --> 00:05:17 see the final ever total eclipse from the
00:05:17 --> 00:05:20 Earth, which will probably be sad, but
00:05:20 --> 00:05:22 it's so far away in the future that we don't
00:05:22 --> 00:05:24 really have to worry about it right now. So
00:05:24 --> 00:05:26 that's coincidence number one. And it's
00:05:26 --> 00:05:28 effectively that the Moon is about, I think
00:05:28 --> 00:05:31 it's 1 400th of the distance to the sudden
00:05:31 --> 00:05:34 1 400th of the size of the Sun. So,
00:05:34 --> 00:05:36 you know, similar triangles that we learned
00:05:36 --> 00:05:38 at school and thought we'd never use mean
00:05:38 --> 00:05:40 that they're about the same angle in the sky
00:05:40 --> 00:05:42 and they block each other out. That's all
00:05:42 --> 00:05:44 great. The second one, which
00:05:45 --> 00:05:47 Rusty, has pointed out, I'd actually never
00:05:47 --> 00:05:49 really given any thought to, to be honest.
00:05:49 --> 00:05:52 But it is true that the length of the
00:05:52 --> 00:05:55 lunar month, the length of the orbit of
00:05:55 --> 00:05:57 the Moon around the, Earth, is about the same
00:05:57 --> 00:06:00 as the period of rotation of the sun with an
00:06:00 --> 00:06:02 asterisk. And, the rotation period of the
00:06:02 --> 00:06:05 Moon when compared to the
00:06:05 --> 00:06:07 background stars is the same
00:06:08 --> 00:06:10 as its orbital period around the Earth
00:06:10 --> 00:06:11 compared to the background stars. It's
00:06:11 --> 00:06:14 tidally locked. It's trapped in this orbit.
00:06:14 --> 00:06:16 So it always keeps effectively one face
00:06:16 --> 00:06:18 towards the Earth, one face away from the
00:06:18 --> 00:06:19 Earth. And, that's a natural result of the
00:06:19 --> 00:06:21 tidal interaction between the two objects.
00:06:21 --> 00:06:23 And it's tied to these effects that are
00:06:23 --> 00:06:25 causing the Moon to gradually drift away.
00:06:27 --> 00:06:30 Now, the sun is a fluid object. It
00:06:30 --> 00:06:32 doesn't have the same rotation period at all,
00:06:32 --> 00:06:34 locations. It rotates quicker at the equator
00:06:34 --> 00:06:37 and slower at the poles. And that's thought
00:06:37 --> 00:06:38 to be part of the reason we get the sunspot
00:06:38 --> 00:06:41 cycles. What happens with that, is that the
00:06:41 --> 00:06:44 equator rotates around once every 24
00:06:44 --> 00:06:46 Earth days. The poles rotate about once every
00:06:46 --> 00:06:49 32, 34 Earth days and locations
00:06:49 --> 00:06:52 between have different rotation periods. So
00:06:52 --> 00:06:54 there is a latitude on the Sun's disk that
00:06:54 --> 00:06:57 rotates with a period of exactly one lunar
00:06:57 --> 00:06:59 month. And so what Rusty's talking about here
00:06:59 --> 00:07:02 is the idea that when sunspots are at that
00:07:02 --> 00:07:04 latitude, if you've got one dominant group of
00:07:04 --> 00:07:06 sunspots, then one side of the Moon will be
00:07:06 --> 00:07:08 getting hammered when those sunspots are
00:07:08 --> 00:07:10 creating activity. And the other side of the
00:07:10 --> 00:07:12 Moon will see the sun when the sunspots are
00:07:12 --> 00:07:13 on the other side and they won't see them.
00:07:14 --> 00:07:17 The reason that
00:07:17 --> 00:07:19 that doesn't mean you get one particular side
00:07:19 --> 00:07:21 of the moon getting all the solar radiation
00:07:21 --> 00:07:24 on the other side being protected, it is the
00:07:24 --> 00:07:26 fact that sunspots form at different
00:07:26 --> 00:07:29 latitudes on the sun and so go around at
00:07:29 --> 00:07:31 slightly different speeds. Early in a solar
00:07:31 --> 00:07:33 cycle, they're at higher latitude. Later in
00:07:33 --> 00:07:35 the solar cycle, they're at lower latitudes,
00:07:35 --> 00:07:38 so the rotation period changes a bit. Also,
00:07:38 --> 00:07:40 you get multiple groups of sunspots at a
00:07:40 --> 00:07:43 given time. And, the activity from a given
00:07:43 --> 00:07:45 sunspot group can hit the Earth and influence
00:07:45 --> 00:07:48 the Earth when it's at different locations on
00:07:48 --> 00:07:50 the sun, depending exactly what the magnetic
00:07:50 --> 00:07:52 field between the two is in the solar window
00:07:52 --> 00:07:54 doing. So. I've seen cases in the past where
00:07:54 --> 00:07:56 we've had a flare and they've been aurora.
00:07:56 --> 00:07:58 And you look at it, and the sunspot that had
00:07:58 --> 00:08:00 the flare wasn't dead center of the Sun's
00:08:00 --> 00:08:03 disk. Your intuitive thing is that when the
00:08:03 --> 00:08:05 sunspot is back in the middle of the Sun's
00:08:05 --> 00:08:07 disk, anything it ejects will come directly
00:08:07 --> 00:08:09 towards the Earth. But in actuality, we've
00:08:09 --> 00:08:11 had a lot of aurora when the sunspot is
00:08:11 --> 00:08:13 offset because things follow a curved path,
00:08:13 --> 00:08:16 all this kind of stuff. So in that sense,
00:08:17 --> 00:08:19 I don't think there is any particular
00:08:19 --> 00:08:21 longitude on the moon that would be favored
00:08:21 --> 00:08:23 over the others because, on longer
00:08:23 --> 00:08:25 timescales, everything would totally smooth
00:08:25 --> 00:08:28 out, totally average out. On a
00:08:28 --> 00:08:31 given sunspot group on a given event,
00:08:31 --> 00:08:33 you'll obviously have one half of the moon
00:08:33 --> 00:08:36 exposed and the other half protected by
00:08:36 --> 00:08:38 looking the other way. Effectively, I think
00:08:38 --> 00:08:40 in terms of people wandering around on the
00:08:40 --> 00:08:43 Moon and our, spacecraft on the Moon, it
00:08:43 --> 00:08:44 would be very inefficient to have to move
00:08:44 --> 00:08:46 halfway around the Moon to get into shelter.
00:08:46 --> 00:08:49 Yeah, I think it makes more sense to drill
00:08:49 --> 00:08:51 down and hide a few meters below the surface
00:08:52 --> 00:08:55 where the rocks shield you. Yeah. And so
00:08:55 --> 00:08:57 while I love the idea of us having the
00:08:57 --> 00:09:00 ability to duck around the corner, you'd
00:09:00 --> 00:09:01 actually have to move quite a long way. And
00:09:01 --> 00:09:04 that would be inefficient and time, time
00:09:04 --> 00:09:06 intensive and all the rest of it. When what
00:09:06 --> 00:09:07 you can do is just say, well, we're just
00:09:07 --> 00:09:09 going to nip indoors and watch movies for a
00:09:09 --> 00:09:11 couple of days. You know, we'll be under the
00:09:11 --> 00:09:13 shielding of all the rock and the rubble
00:09:13 --> 00:09:15 above us. That makes more sense.
00:09:16 --> 00:09:19 And, in terms of other
00:09:19 --> 00:09:22 coincidences, the one that I think of that
00:09:22 --> 00:09:24 isn't really a coincidence at all is if you
00:09:24 --> 00:09:27 look at the bulk composition of
00:09:27 --> 00:09:29 the solid material in the solar system
00:09:30 --> 00:09:32 is to first order, the same as the bulk
00:09:32 --> 00:09:35 composition of the sun minus the gases.
00:09:35 --> 00:09:37 And that's just because everything formed
00:09:37 --> 00:09:40 from the same stuff. What's interesting is
00:09:40 --> 00:09:43 that the Moon is depleted in the heavier
00:09:43 --> 00:09:45 elements and enriched in the lighter
00:09:45 --> 00:09:47 elements. Compared to that.
00:09:48 --> 00:09:50 And in the flip side, the Earth is actually a
00:09:50 --> 00:09:51 bit enriched in the heavier elements and
00:09:51 --> 00:09:54 depleted in the lighter elements. They formed
00:09:54 --> 00:09:56 at the same place in the solar system at the
00:09:56 --> 00:09:58 same time. So you'd expect them to form from
00:09:58 --> 00:10:00 the same stuff. And so the difference in
00:10:00 --> 00:10:02 their compositions actually telling us about
00:10:02 --> 00:10:04 the story of their formation and the fact
00:10:04 --> 00:10:07 that the Earth formed as a single object and
00:10:07 --> 00:10:09 then was smashed and torn asunder and formed
00:10:09 --> 00:10:11 the Earth and Moon. And the Moon was formed
00:10:11 --> 00:10:12 from the lightest stuff that had floated to
00:10:12 --> 00:10:14 the top, so primarily from the crust and the
00:10:14 --> 00:10:17 mantle. And therefore you get this different
00:10:17 --> 00:10:19 in composition where the overall
00:10:19 --> 00:10:21 bulk composition will be the same as the bulk
00:10:21 --> 00:10:23 composition of those materials in the, sun.
00:10:23 --> 00:10:25 But the differences are what tell us the
00:10:25 --> 00:10:27 story. So it's not really a coincidence, but
00:10:27 --> 00:10:29 it is an interesting link between a lot of
00:10:29 --> 00:10:31 them because we all formed at the same place
00:10:31 --> 00:10:34 at the same time from the same stuff. But the
00:10:34 --> 00:10:35 formation then shaped us.
00:10:36 --> 00:10:38 Andrew Dunkley: M Fascinating. There you go, Rusty. Hopefully
00:10:38 --> 00:10:41 that covered all your bases. Thanks for the
00:10:41 --> 00:10:41 question.
00:10:44 --> 00:10:47 0G and I feel fine. Space nuts.
00:10:47 --> 00:10:49 And our next question comes from Trevor in
00:10:49 --> 00:10:52 Port Macquarie. with Comet 3I
00:10:52 --> 00:10:55 Atlas heading through our solar system at a
00:10:55 --> 00:10:58 record speed of around 60 kilometers per
00:10:58 --> 00:11:00 second, it's got me thinking about how fast
00:11:00 --> 00:11:02 an object like a comet or indeed a
00:11:02 --> 00:11:05 spacecraft could reach. I'm assuming
00:11:05 --> 00:11:07 Comet 3i Atlas has acquired some of this
00:11:07 --> 00:11:10 speed with maybe a slingshot around
00:11:10 --> 00:11:12 another star or two in the past.
00:11:13 --> 00:11:15 And as it passes, the sun,
00:11:16 --> 00:11:18 it will probably pick up additional speed.
00:11:19 --> 00:11:22 Is there any limit to how fast a
00:11:22 --> 00:11:24 comet like this could reach if it continues
00:11:24 --> 00:11:26 to receive gravitational assistance from
00:11:26 --> 00:11:29 stars in the future? I know with a spacecraft
00:11:29 --> 00:11:31 we use gravitational assistance by going
00:11:31 --> 00:11:33 around, say, Venus and back to earth to pick
00:11:33 --> 00:11:36 up speed. But what would happen if
00:11:36 --> 00:11:39 we did, say, 50 times,
00:11:40 --> 00:11:43 before heading off into the direction we want
00:11:43 --> 00:11:46 to go? So 50 passes, he's saying, ah, could
00:11:46 --> 00:11:48 he reach speeds well in excess of, what deep
00:11:48 --> 00:11:51 space probes currently travel at? Or is
00:11:51 --> 00:11:54 there a level of diminishing return to this
00:11:54 --> 00:11:56 approach? Looking forward to your answer.
00:11:56 --> 00:11:56 Jonti Horner: Trevor.
00:11:57 --> 00:11:57 Andrew Dunkley: Love this question.
00:11:58 --> 00:12:01 Jonti Horner: Yes, this is really, really good fun. So,
00:12:01 --> 00:12:04 it's a bit of both, to be honest. The long
00:12:04 --> 00:12:06 and short of it is that if you could set up
00:12:06 --> 00:12:09 the perfect chain of
00:12:09 --> 00:12:11 slingshot assists with
00:12:12 --> 00:12:13 ever more massive objects moving at ever
00:12:13 --> 00:12:16 greater speeds around, there is no real limit
00:12:16 --> 00:12:18 up until the point you get very close to the
00:12:18 --> 00:12:19 speed of light, because you can't get faster
00:12:19 --> 00:12:22 than the speed of light. But the
00:12:22 --> 00:12:24 challenge inherent in that is that you're
00:12:24 --> 00:12:27 transferring a bit of the kinetic energy from
00:12:27 --> 00:12:28 one object to another. You're sealing
00:12:28 --> 00:12:31 momentum through a gravitational slingshot.
00:12:31 --> 00:12:33 So if you fly by Jupiter and Jupiter gives
00:12:33 --> 00:12:34 you a kick to speed you up, Jupiter actually
00:12:34 --> 00:12:37 slows down a little bit. Because Jupiter is
00:12:37 --> 00:12:39 much, much, much, much, much, much, much more
00:12:39 --> 00:12:41 massive than you are. The change in its speed
00:12:41 --> 00:12:44 is much, much, much smaller. Momentum is
00:12:44 --> 00:12:46 speed times mass, effectively. But
00:12:47 --> 00:12:49 you're taking a bit of that kinetic energy.
00:12:49 --> 00:12:51 And because of that, there's no real limit to
00:12:51 --> 00:12:53 how much you can boost. But any given
00:12:53 --> 00:12:56 encounter will only give you so much.
00:12:56 --> 00:12:59 The closer you get to the mass, the more of a
00:12:59 --> 00:13:01 kick you can get. If the orientation is
00:13:01 --> 00:13:04 right, the faster the mass is moving compared
00:13:04 --> 00:13:05 to you, the more of a kick you can get as
00:13:05 --> 00:13:08 well. So you can imagine setting up a
00:13:08 --> 00:13:10 situation where you have a few flybys and you
00:13:10 --> 00:13:11 gradually get more and more boosts. And
00:13:11 --> 00:13:14 that's how people have taken the cheapskate
00:13:14 --> 00:13:15 route to the outer solar system. You get
00:13:15 --> 00:13:17 these missions that have a flyby of the Earth
00:13:17 --> 00:13:19 and a flyby of Venus and a flyby of the Earth
00:13:19 --> 00:13:21 and a flyby of Venus and a flyby of the Earth
00:13:21 --> 00:13:23 and a flower flyby of Mars and so on. And
00:13:23 --> 00:13:25 they get gradual, little incremental kicks to
00:13:25 --> 00:13:28 get out to Jupiter. It's also
00:13:28 --> 00:13:31 how we saw the Voyager spacecraft get a kick
00:13:31 --> 00:13:33 from Jupiter to Saturn, then Voyager 2 got a
00:13:33 --> 00:13:35 kick from Saturn to Uranus, and Uranus kicked
00:13:35 --> 00:13:37 it onto Neptune, and you got to speed up
00:13:37 --> 00:13:39 every time. The problem becomes
00:13:40 --> 00:13:42 you eventually hit the escape velocity for
00:13:42 --> 00:13:43 the solar system, and Jupiter is really good
00:13:43 --> 00:13:45 at doing that. Once you're at the escape
00:13:45 --> 00:13:47 velocity, you're not coming back for a second
00:13:47 --> 00:13:48 pass by Jupiter. So what are you going to get
00:13:48 --> 00:13:51 your next slingshot by? Well, if everything's
00:13:51 --> 00:13:53 lined up just right, you can do like the
00:13:53 --> 00:13:55 Voyager spacecraft did and do the grand tour
00:13:55 --> 00:13:56 where you get one to the next to the next.
00:13:57 --> 00:13:58 Yeah, but that's got a bit of diminishing
00:13:58 --> 00:14:01 returns because they're only so massive. So
00:14:01 --> 00:14:03 you can only get so much out of a given kick.
00:14:03 --> 00:14:06 You could possibly in theory aim out of our
00:14:06 --> 00:14:09 solar system to fly past Alpha
00:14:09 --> 00:14:10 Centauri and get a kick from that, if you
00:14:10 --> 00:14:13 oriented right and try and aim your
00:14:13 --> 00:14:15 spacecraft to get a kick from Alpha Centauri
00:14:15 --> 00:14:17 to kick you onto, I don't know, Sirius and
00:14:17 --> 00:14:18 get a kick there and bounce around, and
00:14:18 --> 00:14:20 bounce around and gradually accumulate speed.
00:14:21 --> 00:14:22 But eventually you'd again reach the escape
00:14:22 --> 00:14:24 velocity of the galaxy and eventually you'd
00:14:24 --> 00:14:27 be on a one way trip out of our galaxy. So it
00:14:27 --> 00:14:29 would be very hard to set you up to get to a
00:14:29 --> 00:14:32 speed that is ludicrous speed, you know, a
00:14:32 --> 00:14:34 speed that is approaching the speed of light.
00:14:34 --> 00:14:36 You'd probably need to come incredibly close
00:14:36 --> 00:14:38 to a black hole to do that. And you need to
00:14:38 --> 00:14:41 engineer things such that you didn't get
00:14:41 --> 00:14:42 destroyed by the radiation and everything
00:14:42 --> 00:14:45 from the accretion disk around it and you had
00:14:45 --> 00:14:46 your angle right so that you gained enough
00:14:46 --> 00:14:49 momentum to get much quicker. So you could
00:14:49 --> 00:14:51 probably play games like that. It's certainly
00:14:51 --> 00:14:53 really useful in the solar system. It's very
00:14:53 --> 00:14:55 effective at getting things up to high speed
00:14:55 --> 00:14:58 without requiring huge amounts of fuel. You
00:14:58 --> 00:15:01 can supplement it by timing the burn of your
00:15:01 --> 00:15:03 rockets and using your limited propellant to
00:15:03 --> 00:15:06 get the maximum kick possible. And I've read
00:15:06 --> 00:15:08 about, special science fiction style
00:15:08 --> 00:15:11 maneuvers where you whiz around and
00:15:11 --> 00:15:13 you do your burn at the very closest approach
00:15:13 --> 00:15:15 to an object to get the maximum change in
00:15:15 --> 00:15:17 velocity and the maximum energy change for
00:15:17 --> 00:15:20 that given packet of fuel. I
00:15:20 --> 00:15:22 think it's called the Oberth manoeuvre or
00:15:22 --> 00:15:23 something like that. And it's really
00:15:23 --> 00:15:25 interesting because it, at, ah, first thought
00:15:25 --> 00:15:28 it defeats common sense.
00:15:28 --> 00:15:30 Do you think if you're speeding up by 1 meter
00:15:30 --> 00:15:33 per second, doing it anywhere in the orbit
00:15:33 --> 00:15:34 would have the same effect, but in fact
00:15:34 --> 00:15:36 speeding up by 1 meter per second when you're
00:15:36 --> 00:15:38 traveling really quickly creates a bigger
00:15:38 --> 00:15:41 change in your final speed once gravity and
00:15:41 --> 00:15:43 everything works out, than doing it when
00:15:43 --> 00:15:44 you're moving really slowly? There's all
00:15:44 --> 00:15:46 sorts of odd things like that going on. So
00:15:46 --> 00:15:48 there are games you can play with it and you
00:15:48 --> 00:15:51 could set up a theoretical path that could
00:15:51 --> 00:15:53 take you millions of years to complete, where
00:15:53 --> 00:15:56 you Chain path objects. You have a
00:15:56 --> 00:15:57 little bit of control in your spacecraft to
00:15:57 --> 00:16:00 refine your orbit, refine your path,
00:16:01 --> 00:16:03 so that you aim perfectly to the next target,
00:16:03 --> 00:16:05 and effectively get a slingshot from each.
00:16:06 --> 00:16:08 But the practical limits are that unless you
00:16:08 --> 00:16:11 could get very close to a black hole, you're
00:16:11 --> 00:16:13 going to be limited to some degree. And it
00:16:13 --> 00:16:15 becomes, like you said, diminishing returns.
00:16:16 --> 00:16:19 Not because the physics of it prevent you
00:16:19 --> 00:16:21 from getting any arbitrary speed you want,
00:16:21 --> 00:16:23 but because the faster you're moving, the
00:16:23 --> 00:16:25 less targets there are to hit and the longer
00:16:25 --> 00:16:27 you've got to wait to get there.
00:16:28 --> 00:16:30 Andrew Dunkley: Do you think the day will come, though, where
00:16:30 --> 00:16:32 we develop technology that stops us
00:16:32 --> 00:16:34 needing gravity assist,
00:16:35 --> 00:16:38 maybe ion engines or scramjets
00:16:38 --> 00:16:40 or whatever the things they're developing at
00:16:40 --> 00:16:40 the moment?
00:16:42 --> 00:16:45 Jonti Horner: We're always developing new things. And, as
00:16:45 --> 00:16:46 I've said before, you know, the one
00:16:46 --> 00:16:47 prediction you can make is that all
00:16:47 --> 00:16:49 predictions are wrong. Science fiction is
00:16:50 --> 00:16:52 amazing at coming up with things that have no
00:16:52 --> 00:16:55 grounding in current physics, but that
00:16:55 --> 00:16:57 suggest possible routes to do things that
00:16:57 --> 00:16:59 break the current laws of physics. And to
00:16:59 --> 00:17:01 some degree, everybody writes them off as
00:17:01 --> 00:17:04 purely fiction because they can't work in our
00:17:04 --> 00:17:06 current understanding of physics. But I
00:17:06 --> 00:17:07 remember that a long time ago, a lot of
00:17:07 --> 00:17:09 people were arguing that it was utterly
00:17:09 --> 00:17:11 impossible and physically impossible to have
00:17:11 --> 00:17:13 heavier than air travel. And our
00:17:13 --> 00:17:15 understanding of, physics and the cosmos is
00:17:15 --> 00:17:18 limited by the quality of observations that
00:17:18 --> 00:17:21 we have. And our theories are
00:17:21 --> 00:17:22 exceptionally good at explaining things to
00:17:22 --> 00:17:24 the level that our observations can currently
00:17:24 --> 00:17:27 be carried out and a bit more. But it's
00:17:27 --> 00:17:29 entirely feasible that as we get better at
00:17:29 --> 00:17:31 making observations, we reach the limits of
00:17:31 --> 00:17:34 where our current models, are accurate.
00:17:34 --> 00:17:36 And we need new and better physics, and new
00:17:36 --> 00:17:39 things will come out of that. We'll also get
00:17:39 --> 00:17:41 more efficient at, using the tools we know do
00:17:41 --> 00:17:43 work. And things like the ion engines which
00:17:43 --> 00:17:45 they have tested with spacecraft are
00:17:45 --> 00:17:48 interesting. Our common conventional kind of
00:17:48 --> 00:17:51 chemical rockets apply a very large amount of
00:17:51 --> 00:17:53 thrust for a very short period of time and
00:17:53 --> 00:17:55 burn fuel very intensively. And so you get a
00:17:55 --> 00:17:58 high acceleration for a short time. Ion
00:17:58 --> 00:18:00 engines are almost exactly the opposite in
00:18:00 --> 00:18:01 that they give you a very small acceleration,
00:18:01 --> 00:18:04 but that can be applied continuously for very
00:18:04 --> 00:18:06 long periods of time. And so they're much
00:18:06 --> 00:18:08 more efficient. And you can imagine stuff
00:18:08 --> 00:18:11 like that being scaled up. But the science
00:18:11 --> 00:18:12 fiction that
00:18:14 --> 00:18:16 leads to people moving at significant
00:18:16 --> 00:18:18 fractions of the speed of light nearly
00:18:18 --> 00:18:20 universally uses technologies that are beyond
00:18:20 --> 00:18:23 what our physics currently allows. And, it's
00:18:23 --> 00:18:25 where you get the blurring of hard sci Fi and
00:18:25 --> 00:18:28 soft sci fi of the degree to which you have
00:18:28 --> 00:18:30 things grounded in current science and things
00:18:30 --> 00:18:33 grounded in fantasy almost in
00:18:33 --> 00:18:35 science that is so advanced that it's magic
00:18:35 --> 00:18:36 to us because we can't explain how it works
00:18:36 --> 00:18:39 or know that it will. And so trying to say
00:18:39 --> 00:18:42 whether we'll ever get to a stage where
00:18:42 --> 00:18:44 our technology allows us to do these things
00:18:46 --> 00:18:48 quickly, to get to Mars in a week, to get to
00:18:48 --> 00:18:51 Pluto in a month or a week,
00:18:52 --> 00:18:54 you can imagine it is possible if you do the
00:18:54 --> 00:18:57 maths. If you accelerate at 1g, the
00:18:57 --> 00:18:59 acceleration due to gravity and you can
00:18:59 --> 00:19:01 maintain the acceleration for a while, you
00:19:01 --> 00:19:04 get to very high speeds very quickly. So if
00:19:04 --> 00:19:06 you accelerate at 10 meters per second per
00:19:06 --> 00:19:09 second, after 100 seconds you're going at
00:19:09 --> 00:19:11 1 kilometer a second, after 200 seconds,
00:19:11 --> 00:19:13 you're going at 2 kilometers a second. So you
00:19:13 --> 00:19:16 gain speed very, very, very quickly. But
00:19:16 --> 00:19:18 you've got to use fuel very efficiently to do
00:19:18 --> 00:19:21 that. And a sample of a lot of hard
00:19:21 --> 00:19:23 science fiction that's kind of near future
00:19:23 --> 00:19:25 sci fi relies on the idea
00:19:25 --> 00:19:28 of some form of drive system that allows
00:19:28 --> 00:19:30 you to maintain that level of acceleration
00:19:31 --> 00:19:33 for periods of hours or weeks or months.
00:19:34 --> 00:19:36 And if you could do that, the travel time to
00:19:36 --> 00:19:39 get to places like Saturn becomes
00:19:39 --> 00:19:41 manageable. On a holiday you could do what
00:19:41 --> 00:19:42 Fred's doing, but instead of going to
00:19:42 --> 00:19:45 Scandinavia, you could go and visit Titan.
00:19:45 --> 00:19:47 If you've got that level of technology and
00:19:47 --> 00:19:49 you do it in a certain degree of comfort
00:19:49 --> 00:19:50 because what you do is your Spacecraft's
00:19:50 --> 00:19:53 accelerating at 1G, so you feel an
00:19:53 --> 00:19:54 acceleration of 1G and it's like you're on
00:19:54 --> 00:19:57 Earth. You don't need artificial gravity. You
00:19:57 --> 00:19:59 just have that short period halfway through
00:19:59 --> 00:20:00 the flight where you're weightless while the
00:20:00 --> 00:20:02 spacecraft turns dark, turns around and
00:20:02 --> 00:20:03 starts accelerating at 1G in the other
00:20:03 --> 00:20:06 direction to slow you down for approach.
00:20:06 --> 00:20:08 And that's a step level mode of the more
00:20:08 --> 00:20:11 realistic sci fi. But it still
00:20:11 --> 00:20:13 requires technology that we don't yet have
00:20:13 --> 00:20:15 and we may never develop or we might. And you
00:20:15 --> 00:20:17 know, I'd love it if we did, but we'll just
00:20:17 --> 00:20:18 have to see.
00:20:18 --> 00:20:21 Andrew Dunkley: Time will tell. but you know, Flash Gordon
00:20:21 --> 00:20:23 was the first to put rockets,
00:20:24 --> 00:20:26 you know, that could reland themselves. And
00:20:26 --> 00:20:29 now, now we can do that. so yeah, there's
00:20:29 --> 00:20:31 all sorts of weird and wonderful stuff in sci
00:20:31 --> 00:20:34 fi that has become reality. Thanks,
00:20:35 --> 00:20:37 so much for the question, Trevor. This is
00:20:37 --> 00:20:39 Space Nuts with Andrew Dunkley and John de
00:20:39 --> 00:20:39 Ora.
00:20:42 --> 00:20:44 0G and I feel fine. Space
00:20:44 --> 00:20:47 Nuts. Our next Question comes from
00:20:47 --> 00:20:50 Austin. He said, I've, just been watching a
00:20:50 --> 00:20:52 long YouTube Music presentation on Hoag's
00:20:52 --> 00:20:55 object. A lonesome galaxy with
00:20:55 --> 00:20:57 lots of features that don't seem to fit with
00:20:57 --> 00:21:00 present knowledge. Do objects like that
00:21:00 --> 00:21:03 require a complete rethink of the standard
00:21:03 --> 00:21:05 model or are, there ready
00:21:05 --> 00:21:08 explanations of its features now?
00:21:08 --> 00:21:09 Hoag's object is
00:21:10 --> 00:21:13 astonishing, to say the very least. It's a
00:21:13 --> 00:21:15 very unusual ring galaxy.
00:21:16 --> 00:21:18 I know you've been doing some research on
00:21:18 --> 00:21:20 this, so we can sort this one out for Austin.
00:21:21 --> 00:21:23 Jonti Horner: I have. It's beautiful. The photos are
00:21:23 --> 00:21:25 amazing. I do encourage people to look at
00:21:25 --> 00:21:28 this. It is one of a
00:21:28 --> 00:21:30 number of galaxies that we've seen that have
00:21:30 --> 00:21:32 this kind of ring like structure. And the
00:21:32 --> 00:21:35 typical explanation is that you've had some
00:21:35 --> 00:21:37 kind of violent encounter between two
00:21:37 --> 00:21:40 galaxies where one has pushed through the
00:21:40 --> 00:21:43 other really quickly and set up a shockwave.
00:21:43 --> 00:21:45 And that shockwave has propagated outwards.
00:21:45 --> 00:21:47 And, the shockwave causes gas and dust pile
00:21:47 --> 00:21:49 up and drive the bursts of star formation.
00:21:50 --> 00:21:52 And as we know, the bulk of the
00:21:52 --> 00:21:55 most luminous stars in a galaxy are the
00:21:55 --> 00:21:57 hottest, brightest, shortest lived ones.
00:21:57 --> 00:21:58 Andrew Dunkley: Yes.
00:21:58 --> 00:22:00 Jonti Horner: And so it's natural that you'd get a ring
00:22:01 --> 00:22:03 where the shock wave has recently passed,
00:22:03 --> 00:22:05 where you've had a lot of massive stars
00:22:05 --> 00:22:07 formed that have not yet died. And you'd have
00:22:07 --> 00:22:09 a few reddish stars dotted through there,
00:22:09 --> 00:22:10 which are the stars that are about to die.
00:22:11 --> 00:22:12 And that the middle of the galaxy would look
00:22:12 --> 00:22:14 fairly yellowish and dull because there's no
00:22:14 --> 00:22:15 young stars there because all the gas and
00:22:15 --> 00:22:18 dust have been swept out. And, we do see a
00:22:18 --> 00:22:21 lot of these kind of galaxies, but I've never
00:22:21 --> 00:22:23 seen any of them that is as
00:22:23 --> 00:22:26 symmetrical and beautiful as Hoag's object.
00:22:26 --> 00:22:29 Hoag's object looks like if you
00:22:29 --> 00:22:31 got somebody to make a perfect fried egg
00:22:32 --> 00:22:34 and then they got two of those weird little
00:22:34 --> 00:22:36 poached egg rings and they put one around the
00:22:36 --> 00:22:39 yolk, and then they put a much wider one
00:22:39 --> 00:22:40 around near the outside of the white.
00:22:40 --> 00:22:43 Everything between those two rings was lifted
00:22:43 --> 00:22:44 out and thrown away. And then the rings were
00:22:44 --> 00:22:46 taken away and you were left with a yolk in
00:22:46 --> 00:22:48 the middle and then an empty gap and then a
00:22:48 --> 00:22:50 ring of white around the outside. Although in
00:22:50 --> 00:22:53 this case a ring of blue. It is beautifully
00:22:53 --> 00:22:55 symmetric. There's a little bit of a hint of
00:22:55 --> 00:22:56 rotation there. It almost looks like a
00:22:56 --> 00:22:58 turning salt to its blade when you look at
00:22:58 --> 00:22:58 it.
00:22:58 --> 00:22:59 Andrew Dunkley: It does.
00:22:59 --> 00:23:02 Jonti Horner: which is leftover of the original rotation
00:23:02 --> 00:23:03 of the galaxy itself.
00:23:04 --> 00:23:07 The level of symmetry and stuff is
00:23:07 --> 00:23:10 really Unusual. Now, what it
00:23:10 --> 00:23:12 suggests is that, and it should be said
00:23:12 --> 00:23:15 nobody's absolutely certain how this object
00:23:15 --> 00:23:17 formed, but there are ready explanations
00:23:18 --> 00:23:20 that people have put forward. One which seems
00:23:20 --> 00:23:23 to have been shot down is that this is an
00:23:23 --> 00:23:26 extreme example of what's described as a
00:23:26 --> 00:23:29 bar, instability. So you get these barbed
00:23:29 --> 00:23:30 spiral galaxies where you get a big, long,
00:23:30 --> 00:23:32 straight central bar and then beautiful
00:23:32 --> 00:23:34 curved spiral arms coming off the end of the
00:23:34 --> 00:23:37 bar. You can almost imagine the curved arms
00:23:37 --> 00:23:39 joining up and then the bar disappearing. For
00:23:39 --> 00:23:40 some reason, you'd be left with something
00:23:40 --> 00:23:43 that almost looks like this. That seems to
00:23:43 --> 00:23:45 be very disfavored for this object
00:23:46 --> 00:23:49 because of the shape of the central blob. The
00:23:49 --> 00:23:51 central blob is fairly circular rather than
00:23:51 --> 00:23:54 an elongated. And bad spirals tend to have an
00:23:54 --> 00:23:56 elongated central blob. So that seems to rule
00:23:56 --> 00:23:59 that out. Although there is still debate,
00:23:59 --> 00:24:02 the explanation that would make most sense
00:24:02 --> 00:24:04 is that, this was the result of a collision
00:24:04 --> 00:24:06 between two galaxies at high speed, where
00:24:06 --> 00:24:08 you've almost got one galaxy punching through
00:24:08 --> 00:24:11 very near to the center of Hurd's object at,
00:24:11 --> 00:24:14 high speed, triggering this shockwave and
00:24:14 --> 00:24:17 then running off and vanishing. Now, given
00:24:17 --> 00:24:19 the scale of that ring, the suggestion will
00:24:19 --> 00:24:21 be that the collision happened about 3
00:24:22 --> 00:24:24 billion years ago. Billion with a B, not
00:24:24 --> 00:24:26 million with an M. The problem with this is
00:24:26 --> 00:24:29 that nobody can see any object. That would be
00:24:29 --> 00:24:31 the bullet seems m. That would
00:24:31 --> 00:24:34 have disappeared. However, 3 billion
00:24:34 --> 00:24:36 years is a lot of time for things to happen.
00:24:36 --> 00:24:38 So I think the suggestion that most people
00:24:38 --> 00:24:40 have is that, the bullet,
00:24:41 --> 00:24:43 has been lost in 3 billion years. There's
00:24:43 --> 00:24:45 also the fact that this is so, perfectly
00:24:45 --> 00:24:48 symmetrical, so perfectly face on,
00:24:48 --> 00:24:50 that you could possibly wonder whether the
00:24:50 --> 00:24:52 bullet is actually hidden behind that central
00:24:52 --> 00:24:54 blob. In other words, the bullet has moved
00:24:54 --> 00:24:56 perfectly along our line of sight and we
00:24:56 --> 00:24:57 don't see it because the galaxy's in the way.
00:24:57 --> 00:25:00 Yeah, that would make sense to me. And that
00:25:00 --> 00:25:02 sounds like it's vanishingly unlikely. But to
00:25:02 --> 00:25:04 have this thing be so symmetrical means it
00:25:04 --> 00:25:07 must be almost perfectly face on, which means
00:25:07 --> 00:25:09 that the impact that created the shockwave
00:25:09 --> 00:25:11 must have been quite close to our line of
00:25:11 --> 00:25:13 sight. And so I can see some logical
00:25:14 --> 00:25:17 consistency there. But this
00:25:17 --> 00:25:19 is, and I know I say this all the time, but
00:25:19 --> 00:25:21 this is a really good example of that
00:25:21 --> 00:25:23 interplay between theory and observation,
00:25:23 --> 00:25:25 where whenever we see something new, we
00:25:25 --> 00:25:27 struggle to explain it. We get a better
00:25:27 --> 00:25:28 understanding of how the universe works and
00:25:28 --> 00:25:30 what all the models should say and what they
00:25:30 --> 00:25:32 should tell us, and that improves our
00:25:32 --> 00:25:34 understanding of other objects, and then we
00:25:34 --> 00:25:35 find something else that pushes the
00:25:35 --> 00:25:38 boundaries of that knowledge. It is clear
00:25:38 --> 00:25:40 that we do not have a defined, definitive
00:25:40 --> 00:25:43 answer for this yet. And that's true for many
00:25:43 --> 00:25:45 of these objects in space. I think the
00:25:45 --> 00:25:48 argument of it being formed through a
00:25:48 --> 00:25:50 collision is
00:25:51 --> 00:25:54 fairly compelling, even though, you know,
00:25:54 --> 00:25:56 there are a lot of reasons why a typical
00:25:56 --> 00:25:57 formation will be unlikely. I'm just looking
00:25:57 --> 00:26:00 here at, the summary of this on Wikipedia, to
00:26:00 --> 00:26:02 be honest, and that's got links to a few
00:26:02 --> 00:26:05 papers that have discussed this. now I'm
00:26:05 --> 00:26:06 sure some of the listeners are probably
00:26:06 --> 00:26:08 recalling in shock at me looking on
00:26:08 --> 00:26:09 Wikipedia.
00:26:09 --> 00:26:11 Andrew Dunkley: No, no, we actually do have it quite a lot
00:26:11 --> 00:26:14 because there's m. Some very valid stuff in
00:26:14 --> 00:26:16 there. You just got to work your way through
00:26:16 --> 00:26:17 the garbage.
00:26:17 --> 00:26:19 Jonti Horner: Stress this a lot to my students that, you've
00:26:19 --> 00:26:21 been brought up through high school that
00:26:21 --> 00:26:23 Wikipedia is unreliable because it's an
00:26:23 --> 00:26:25 alterable resource and people can change it.
00:26:25 --> 00:26:27 And I've known friends who are teachers who
00:26:27 --> 00:26:30 set their class some really obscure
00:26:30 --> 00:26:32 topic to research and then deliberately go in
00:26:32 --> 00:26:34 and edit the Wikipedia page to say something
00:26:34 --> 00:26:36 wrong and then change it back after their
00:26:36 --> 00:26:38 class have done the work to demonstrate.
00:26:38 --> 00:26:39 Andrew Dunkley: You're kidding.
00:26:39 --> 00:26:41 Jonti Horner: Cruel, but entertaining.
00:26:43 --> 00:26:45 what I stress to my undergrad students is
00:26:45 --> 00:26:47 that for astronomy, Wikipedia is a good first
00:26:48 --> 00:26:50 look quite often. And that's because
00:26:51 --> 00:26:53 we have people around the world who
00:26:53 --> 00:26:56 are into astronomy, have a lot of knowledge,
00:26:56 --> 00:26:58 and tend to be very obsessive. And I mean
00:26:58 --> 00:27:00 that in a really positive light and have
00:27:00 --> 00:27:03 their favorite objects. And if something is
00:27:03 --> 00:27:05 wrong, they're not backward in coming forward
00:27:05 --> 00:27:07 at fixing it. Added to which, a lot of the
00:27:07 --> 00:27:09 astronomical sites are not controversial, and
00:27:09 --> 00:27:11 they're not the kind of places that
00:27:11 --> 00:27:13 youngsters who want to be a bit rebellious
00:27:13 --> 00:27:16 will go to to put something funny in. They're
00:27:16 --> 00:27:17 not going to be your prime targets for
00:27:18 --> 00:27:21 malfeasance, let's say. And, so what that
00:27:21 --> 00:27:22 combined means is that a lot of Wikipedia
00:27:22 --> 00:27:25 articles out there are, a relatively good
00:27:25 --> 00:27:27 first stab for astronomy topics. Now, they're
00:27:27 --> 00:27:30 not often spot on. You know, I found things
00:27:30 --> 00:27:33 that have not included my own research
00:27:33 --> 00:27:35 when they've been talking about a subject.
00:27:35 --> 00:27:37 And that makes me sad. and sometimes
00:27:37 --> 00:27:38 therefore give a different opinion to what
00:27:38 --> 00:27:41 I'd have. And so it's always a case of use it
00:27:41 --> 00:27:43 with caution, go to the primary
00:27:43 --> 00:27:46 resources. But Wikipedia is really good
00:27:46 --> 00:27:48 at pointing you to some of the primary
00:27:48 --> 00:27:51 resources to get a good feel for it. And so I
00:27:51 --> 00:27:53 actually find using Wikipedia is often for
00:27:53 --> 00:27:56 astronomy things fairly Reliable and
00:27:56 --> 00:27:58 fairly accurate. Because when an error creeps
00:27:58 --> 00:27:59 in, it is fixed very, very quickly.
00:27:59 --> 00:28:02 Andrew Dunkley: Yes, that's absolutely true. I actually have
00:28:02 --> 00:28:04 found it very helpful in the past. when I was
00:28:04 --> 00:28:07 writing, the book about my grandfather in
00:28:07 --> 00:28:10 World War I, researching the minute by
00:28:10 --> 00:28:13 minute processes of the particular battles
00:28:13 --> 00:28:13 that he was in,
00:28:16 --> 00:28:18 I found a lot of good data on Wikipedia.
00:28:18 --> 00:28:21 So, yeah, don't write it off unless you're
00:28:21 --> 00:28:21 doing it.
00:28:21 --> 00:28:24 Jonti Horner: It wouldn't surprise me. Yeah, the kind of
00:28:24 --> 00:28:26 community that would look into that kind of
00:28:26 --> 00:28:27 thing probably has a lot in common with
00:28:27 --> 00:28:29 astronomy and that they'd be very detail
00:28:29 --> 00:28:32 oriented, are very precise and
00:28:32 --> 00:28:34 very knowledgeable about their particular
00:28:34 --> 00:28:36 topic. But again, I'd have thought that it's
00:28:36 --> 00:28:38 unlikely that someone who wanted, to do
00:28:38 --> 00:28:40 something funny would go to the report of a
00:28:40 --> 00:28:42 particular world, one battle and edit it.
00:28:42 --> 00:28:44 They'd probably go to Taylor Swift's
00:28:44 --> 00:28:46 Wikipedia page. I suspect the editors for
00:28:46 --> 00:28:48 Taylor Swift's Wikipedia page have been
00:28:48 --> 00:28:50 working very hard. I'm sure they are.
00:28:52 --> 00:28:52 Andrew Dunkley: Yeah.
00:28:53 --> 00:28:55 Jonti Horner: So, yeah, it does not surprise me, is a
00:28:55 --> 00:28:56 fabulous resource.
00:28:56 --> 00:28:58 Andrew Dunkley: Yes, indeed. yeah, I think most of the people
00:28:58 --> 00:29:00 who want to stir things up go to, Facebook,
00:29:00 --> 00:29:03 Instagram or TikTok. That's, that's generally
00:29:03 --> 00:29:05 where it all ends up. thank you, Austin.
00:29:05 --> 00:29:07 Great question. And I, would encourage people
00:29:07 --> 00:29:09 to have a look at Hoag's object online
00:29:09 --> 00:29:11 because it is quite a spectacular
00:29:12 --> 00:29:15 galaxy. Well worth a look. Our final
00:29:15 --> 00:29:17 question today, Jonti, comes from Dan in
00:29:17 --> 00:29:20 California. he said, a
00:29:20 --> 00:29:22 new term, I heard the other day was the
00:29:22 --> 00:29:25 cosmic event horizon. could
00:29:25 --> 00:29:28 you talk about this a bit? Thanks, Dan. Yes,
00:29:28 --> 00:29:31 we, we. This is another one that's a bit of a
00:29:31 --> 00:29:33 mystery. I mean, it's a thing,
00:29:35 --> 00:29:37 it's well known. It's. It's not something
00:29:37 --> 00:29:40 that someone's sort of suggested may exist.
00:29:40 --> 00:29:43 the question is, you know, where, where
00:29:43 --> 00:29:46 is the, the limit of
00:29:46 --> 00:29:49 this object? it's not really an object. It's
00:29:49 --> 00:29:50 a status, I suppose.
00:29:50 --> 00:29:53 Jonti Horner: Yes, yes, it's an interesting one.
00:29:53 --> 00:29:56 And more generally,
00:29:56 --> 00:29:57 an event horizon
00:29:59 --> 00:30:01 is a line that marks the
00:30:01 --> 00:30:03 boundary between things we can observe and
00:30:03 --> 00:30:06 things we cannot observe in the simplest
00:30:06 --> 00:30:08 possible terms. So the event horizon of a
00:30:08 --> 00:30:11 black hole. Anything outside the event
00:30:11 --> 00:30:13 horizon we can see happening. Anything
00:30:14 --> 00:30:16 interior to the event horizon we can't see
00:30:16 --> 00:30:19 because light can't escape. So the event
00:30:19 --> 00:30:21 horizon in that sense marks a boundary
00:30:21 --> 00:30:22 between what is observable and what is not.
00:30:23 --> 00:30:25 And that has led people to this concept of
00:30:25 --> 00:30:27 the cosmic event horizon or cosmological
00:30:27 --> 00:30:30 Event horizon. And when you look into it,
00:30:30 --> 00:30:32 there's actually two different definitions,
00:30:33 --> 00:30:35 two different types. One is
00:30:36 --> 00:30:38 effectively the maximum distance,
00:30:39 --> 00:30:41 at which a source can be and have
00:30:41 --> 00:30:43 emitted light in the past that we can see
00:30:43 --> 00:30:46 today. and that distance is
00:30:46 --> 00:30:49 smaller than the real extent of the universe.
00:30:49 --> 00:30:51 It's kind of set by the point of the
00:30:51 --> 00:30:53 cosmological microwave background, in
00:30:53 --> 00:30:55 actuality, because before that, the universe
00:30:55 --> 00:30:57 was foggy and the light couldn't escape.
00:30:57 --> 00:31:00 Now the universe is very roughly 14 billion
00:31:00 --> 00:31:02 years old. I know the numbers are more
00:31:02 --> 00:31:04 accurately than that, but we'll call it 14
00:31:04 --> 00:31:07 billion billion years. So you're. And
00:31:07 --> 00:31:09 certainly my naive expectation would be that
00:31:09 --> 00:31:12 the most distant thing we can see is 14
00:31:12 --> 00:31:14 billion light years away. And that
00:31:14 --> 00:31:17 is true for a given version of true.
00:31:18 --> 00:31:20 What it actually is, the case is that, the
00:31:20 --> 00:31:23 things we see that are 14 billion
00:31:23 --> 00:31:26 light years away, we're seeing,
00:31:26 --> 00:31:28 and I've got to word this very carefully,
00:31:29 --> 00:31:31 we're seeing where they were 14
00:31:32 --> 00:31:34 billion years ago, and the light
00:31:34 --> 00:31:37 has traveled from that point for 14 billion
00:31:37 --> 00:31:40 years to reach us today. So we see them
00:31:40 --> 00:31:43 14 billion years ago at the distance
00:31:43 --> 00:31:46 of 14 billion light years, but they are
00:31:46 --> 00:31:48 heavily redshifted. They're moving away from
00:31:48 --> 00:31:50 us. So the objects that emitted that light 14
00:31:50 --> 00:31:53 billion light years 14 billion years ago
00:31:54 --> 00:31:56 at, a distance of 14 billion light years,
00:31:56 --> 00:31:59 would now be 47 billion light years
00:31:59 --> 00:32:02 away. And light they emit now would never
00:32:02 --> 00:32:03 reach us because of the expansion of the
00:32:03 --> 00:32:04 universe.
00:32:04 --> 00:32:04 Andrew Dunkley: Yep.
00:32:05 --> 00:32:07 Jonti Horner: So what that means is that one sense of the
00:32:07 --> 00:32:10 cosmic event horizon is
00:32:10 --> 00:32:13 that we can see objects that can be as
00:32:13 --> 00:32:15 distant from us today as 47 billion
00:32:16 --> 00:32:18 light years in any direction. But
00:32:18 --> 00:32:21 we see them as they were 14 billion years
00:32:21 --> 00:32:24 in the past, when they were only 14 billion
00:32:24 --> 00:32:27 light years away from us, and they've moved
00:32:27 --> 00:32:30 away since. So that is the event horizon in
00:32:30 --> 00:32:32 terms of events that we can see today that
00:32:32 --> 00:32:35 happened in the past. The other
00:32:35 --> 00:32:38 version, which makes my head hurt slightly
00:32:38 --> 00:32:40 more, to be honest, is the concept in
00:32:40 --> 00:32:43 cosmology that there is an event
00:32:43 --> 00:32:46 horizon which is the
00:32:46 --> 00:32:48 most distant objects that if they
00:32:48 --> 00:32:51 emitted a photon of light today, could ever
00:32:51 --> 00:32:53 be seen from the Earth in the future.
00:32:54 --> 00:32:57 Now they're moving away as well. Now, this
00:32:57 --> 00:32:59 seems to be well defined, and there's maths
00:32:59 --> 00:33:01 around it, and people have discussed it, that
00:33:01 --> 00:33:03 because of the event horizon. Sorry, because
00:33:03 --> 00:33:06 of the expansion of the universe, you can't
00:33:06 --> 00:33:09 have an object that's arbitrarily far away
00:33:09 --> 00:33:11 emit a photon of light and expect that it
00:33:11 --> 00:33:13 would ever reach us, because the expansion of
00:33:13 --> 00:33:15 the universe is such that before that photon
00:33:15 --> 00:33:18 of light reaches us, we will be moving away
00:33:18 --> 00:33:20 from it at a speed faster than the speed of
00:33:20 --> 00:33:22 light. And so it can never catch us up. It's
00:33:22 --> 00:33:25 a bit like the hare and the tortoise. And,
00:33:25 --> 00:33:28 you know, at some point the hair is going so
00:33:28 --> 00:33:30 quickly that if you throw ping pong balls
00:33:30 --> 00:33:31 after it, they won't catch it up because it's
00:33:31 --> 00:33:33 going quicker than the speed of a ping pong
00:33:33 --> 00:33:35 ball. Yeah. Hugely mixed metaphor, but you
00:33:35 --> 00:33:38 can kind of see what I mean there. Now, this
00:33:38 --> 00:33:40 is fairly well defined as a concept. It's
00:33:40 --> 00:33:43 this idea that objects far
00:33:43 --> 00:33:45 away from us emit light towards us, but
00:33:45 --> 00:33:47 they're receding and they're receding from us
00:33:47 --> 00:33:49 at an ever increasing speed. And, we're
00:33:49 --> 00:33:51 receding from them at an ever increasing
00:33:51 --> 00:33:53 speed because the expansion of the universe
00:33:53 --> 00:33:55 doesn't matter where you are, it's all
00:33:55 --> 00:33:57 expanding. Yeah. And so there must be a
00:33:57 --> 00:34:00 horizon at some point, at some distance from
00:34:00 --> 00:34:02 us, where an object at that distance today
00:34:03 --> 00:34:05 would emit a photon of light and that light
00:34:05 --> 00:34:08 would never reach us because of the
00:34:08 --> 00:34:10 expansion. I cannot find
00:34:10 --> 00:34:13 a definitive number for that size
00:34:13 --> 00:34:15 anywhere. I've looked around.
00:34:16 --> 00:34:18 There's a lot of mathematical equations that
00:34:18 --> 00:34:20 people use to quantify it. But the reason
00:34:20 --> 00:34:21 that we don't have a definitive number for
00:34:21 --> 00:34:24 that is that there are many models that look
00:34:24 --> 00:34:26 at the expansion of the universe into the
00:34:26 --> 00:34:28 future that all have very slightly different
00:34:29 --> 00:34:31 expansion rates going into the future. And
00:34:31 --> 00:34:33 different expansion rates would move this
00:34:33 --> 00:34:35 event horizon to different distances.
00:34:36 --> 00:34:39 If the universe is expanding quicker, then
00:34:39 --> 00:34:41 that event horizon will get nearer to us
00:34:41 --> 00:34:43 because you'd have to be closer to us to
00:34:43 --> 00:34:45 overcome this barrier of the expansion. If
00:34:45 --> 00:34:47 the expansion is a bit slower in the future,
00:34:47 --> 00:34:50 the event horizon will be further away. If
00:34:50 --> 00:34:53 you go again, big up to the Wikipedia page.
00:34:53 --> 00:34:55 If you go to the Wikipedia page on Event
00:34:55 --> 00:34:57 Horizon and go down to the article
00:34:58 --> 00:35:00 heading Cosmic Event Horizon, there is a
00:35:00 --> 00:35:02 figure on the right that shows the reachable
00:35:02 --> 00:35:04 universe as a function of time and distance
00:35:05 --> 00:35:08 in the context of the expanding universe that
00:35:08 --> 00:35:11 has lots of different things on it. And it
00:35:11 --> 00:35:13 seems to suggest that if light were emitted
00:35:13 --> 00:35:16 from the Milky Way galaxy now, right now, if
00:35:16 --> 00:35:19 we shone a laser up into the sky, the most
00:35:19 --> 00:35:22 distant object from us that could
00:35:22 --> 00:35:24 ever reach is at 26
00:35:25 --> 00:35:28 billion light years from the edge of the
00:35:28 --> 00:35:31 Big Bang. that's not the same
00:35:31 --> 00:35:33 as saying 25 billion light years from us.
00:35:33 --> 00:35:35 This is where it all gets really, really,
00:35:36 --> 00:35:38 really confusing. They've got these light,
00:35:38 --> 00:35:41 light curves and things like this light ray
00:35:41 --> 00:35:43 emitted at 13 gig years from now
00:35:44 --> 00:35:46 would reach further out. So that figure
00:35:46 --> 00:35:49 suggests that, event
00:35:49 --> 00:35:51 horizon is something like 13 or 14 billion
00:35:51 --> 00:35:54 light years from us right now. If we
00:35:54 --> 00:35:56 emitted that light now, something further
00:35:56 --> 00:35:59 away from that than that could never see us.
00:35:59 --> 00:36:01 Yeah, but it's all up in the air. I can't,
00:36:01 --> 00:36:03 like I said, find an exact answer. And I
00:36:03 --> 00:36:05 think the reason I can't find an exact
00:36:05 --> 00:36:08 calculated distance is if you even
00:36:08 --> 00:36:10 vary the expansion rate of the universe by a
00:36:10 --> 00:36:13 very small amount, you change the location of
00:36:13 --> 00:36:15 that event horizon by a very large distance.
00:36:15 --> 00:36:17 So it's just hugely uncertain. So at the
00:36:17 --> 00:36:19 minute it remains a kind of theoretical
00:36:19 --> 00:36:21 conceit, a philosophical concept, but one
00:36:21 --> 00:36:24 that is important in us actualizing,
00:36:24 --> 00:36:27 in terms of. In us conceptualizing, I
00:36:27 --> 00:36:30 guess, the idea that no matter how far in
00:36:30 --> 00:36:32 the future or the past you go, there will
00:36:32 --> 00:36:34 never have been a time when the entire
00:36:34 --> 00:36:37 universe is visible from here. So it's a bit
00:36:37 --> 00:36:39 like walking around on the surface of the,
00:36:39 --> 00:36:40 Earth. No matter where you are on the, Earth,
00:36:40 --> 00:36:42 you cannot see the whole of our planet unless
00:36:42 --> 00:36:44 you look at photos. Because from your
00:36:44 --> 00:36:47 location, no matter how high above sea level
00:36:47 --> 00:36:49 you are, there is always some of the Earth
00:36:49 --> 00:36:52 heat you cannot see even when you're in
00:36:52 --> 00:36:54 space. It's absolutely.
00:36:54 --> 00:36:56 Andrew Dunkley: There's always another side to it. That's.
00:36:56 --> 00:36:59 Jonti Horner: So when we get. It makes people's head hurt
00:36:59 --> 00:37:02 hugely, the idea that the universe can be
00:37:02 --> 00:37:04 infinite and finite at the same time, that we
00:37:04 --> 00:37:06 only see a small fraction of the universe
00:37:06 --> 00:37:09 that's out there. But to me, it does
00:37:09 --> 00:37:10 make sense when you think about it in the
00:37:10 --> 00:37:12 context of the Earth. I look out of my window
00:37:12 --> 00:37:13 here and I can see the beautiful bunny
00:37:13 --> 00:37:16 mountains in the distance. They're about 60
00:37:16 --> 00:37:17 kilometers away, something like that.
00:37:18 --> 00:37:20 That's a long way away. I can see a large
00:37:20 --> 00:37:22 part of the Earth's surface, but that's a
00:37:22 --> 00:37:24 trivially small amount of the Earth. I'm
00:37:24 --> 00:37:26 aware at this instant of a pool of, Earth
00:37:26 --> 00:37:29 around me. And in all honesty, the rest of
00:37:29 --> 00:37:30 the Earth could have disappeared and I
00:37:30 --> 00:37:32 wouldn't know now. I mean, obviously we're
00:37:32 --> 00:37:34 still on our connection, so that hasn't
00:37:34 --> 00:37:37 happened. But we can visualize in
00:37:37 --> 00:37:39 that sense that the whole of something can be
00:37:39 --> 00:37:41 bigger than the fraction that we see. The
00:37:41 --> 00:37:43 whole of the Earth is bigger than the
00:37:43 --> 00:37:44 fraction of the Earth that you can see from
00:37:44 --> 00:37:47 any one location. The universe is a bit like
00:37:47 --> 00:37:48 that. And this is another way of discussing
00:37:48 --> 00:37:51 that, where it's discussing the maximum
00:37:51 --> 00:37:52 extent that you could see in the past, the
00:37:52 --> 00:37:54 maximum extent that you could see in the
00:37:54 --> 00:37:56 future. Yeah, so hopefully that makes a
00:37:56 --> 00:37:59 bit of sense, and gives you some direction.
00:37:59 --> 00:38:01 If you want to read more about it, I guess.
00:38:01 --> 00:38:03 Andrew Dunkley: Yes, yes, it's, it's when you do
00:38:04 --> 00:38:06 research on it, it yeah, you come up with all
00:38:06 --> 00:38:09 sorts of theories about the universe. Is it
00:38:09 --> 00:38:12 infinite, is it finite? But you know, beyond
00:38:12 --> 00:38:14 our capability to see because of its
00:38:14 --> 00:38:17 expanding rate and you know, the position of
00:38:17 --> 00:38:19 objects emitting light that could not reach
00:38:19 --> 00:38:22 us because of this, that, it just goes on.
00:38:22 --> 00:38:22 Jonti Horner: And on and on.
00:38:22 --> 00:38:25 Andrew Dunkley: It's, it is really interesting and it, it
00:38:25 --> 00:38:28 does get your, your mind swimming. but the
00:38:28 --> 00:38:31 bottom line is that the objects
00:38:31 --> 00:38:33 behind, beyond the cosmic event horizon,
00:38:34 --> 00:38:36 they just, there's just not enough time for
00:38:36 --> 00:38:39 that light to ever reach Earth. that's the
00:38:39 --> 00:38:42 bottom line, isn't it? So hopefully that
00:38:42 --> 00:38:43 explains it for you. Dan, thanks for the
00:38:43 --> 00:38:46 question. It's been great. A couple of real
00:38:46 --> 00:38:49 thought provoking questions today. Much
00:38:49 --> 00:38:51 appreciated. And if you do have a question
00:38:51 --> 00:38:53 for us, please send it through via our
00:38:53 --> 00:38:56 website. we've got a new batch of audio
00:38:56 --> 00:38:58 questions, two thirds of which come from one
00:38:58 --> 00:39:00 person. But that's okay.
00:39:01 --> 00:39:03 we'll get through those, but we, we do need
00:39:03 --> 00:39:05 more. if you've ever considered sending a
00:39:05 --> 00:39:07 question, just never got around to it, jump
00:39:07 --> 00:39:09 on our website, Space Nuts SpaceNutspodcast
00:39:09 --> 00:39:11 uh.com spacenuts IO
00:39:12 --> 00:39:14 and click on the AMA link at the top and send
00:39:14 --> 00:39:17 us text or audio questions. That away
00:39:17 --> 00:39:19 and we look forward to hearing from you.
00:39:19 --> 00:39:21 Don't forget to tell us who you are and where
00:39:21 --> 00:39:24 you are from. And thanks to all our
00:39:24 --> 00:39:26 patrons too. I don't thank you enough. these
00:39:26 --> 00:39:29 are the people who enjoy the program and
00:39:29 --> 00:39:31 pitch in with a couple of dollars here or
00:39:31 --> 00:39:34 there to keep us afloat. you are amazing
00:39:34 --> 00:39:36 people. We never asked for that. But we
00:39:36 --> 00:39:38 certainly appreciate your support and if
00:39:38 --> 00:39:40 you'd like to become a patron, you can find
00:39:40 --> 00:39:43 out more on our website. Not mandatory,
00:39:43 --> 00:39:45 but certainly appreciate it. Jonti,
00:39:45 --> 00:39:47 you're appreciated too. Thank you very much.
00:39:48 --> 00:39:49 Jonti Horner: That's absolute pleasure. Thank you for
00:39:49 --> 00:39:51 having me. And yeah, the more questions the
00:39:51 --> 00:39:51 better.
00:39:51 --> 00:39:54 Andrew Dunkley: Yes, they're good fun. It's a great segment.
00:39:54 --> 00:39:55 I'm glad it's developed into that. It used to
00:39:55 --> 00:39:57 just be something that we tacked onto the end
00:39:57 --> 00:39:59 of one episode, but we've made it its own
00:39:59 --> 00:40:01 show. It's become bigger than Ben Hur,
00:40:01 --> 00:40:04 really. and I'm wearing a wristwatch in the
00:40:04 --> 00:40:06 scene as well. Some people will understand
00:40:06 --> 00:40:08 that. and, yeah, thanks, Jonti. We'll catch
00:40:08 --> 00:40:10 you soon. Jonti Horner, professor of
00:40:10 --> 00:40:12 Astrophysics at the University of Southern
00:40:12 --> 00:40:14 Queensland. Also, thanks to Huw in the
00:40:14 --> 00:40:16 studio, who couldn't be with us, he's taken a
00:40:16 --> 00:40:18 holiday beyond the cosmic event horizon.
00:40:19 --> 00:40:21 So, we can't see his light, but I'm sure
00:40:21 --> 00:40:23 it'll return and he can tell us how he got
00:40:23 --> 00:40:25 there when he gets back in about 47 billion
00:40:25 --> 00:40:28 years. And from me, Andrew Dunkley, thanks
00:40:28 --> 00:40:29 for your company. Catch you on the next
00:40:29 --> 00:40:31 episode of Space Nuts. Bye. Bye.
00:40:32 --> 00:40:35 Jonti Horner: You'll be listening to the Space Nuts
00:40:35 --> 00:40:37 podcast, available
00:40:37 --> 00:40:40 at Apple Podcasts, Spotify,
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00:40:44 --> 00:40:46 demand@bytes.com M.
00:40:46 --> 00:40:48 Andrew Dunkley: This has been another quality podcast
00:40:48 --> 00:40:50 production from bytes.com.