Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / #418: From Cosmic Drag to Holographic Hype: Unraveling the Mysteries of Space Travel

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#418: From Cosmic Drag to Holographic Hype: Unraveling the Mysteries of Space Travel · Space Nuts: Astronomy Insights & Cosmic Discoveries

0:00
Hi there, thanks for joining us on the Q and A edition of Space
0:04
Nuts. My name is Andrew Dunkley, your host on this episode where you're
0:08
going to be answering questions about light. It's an interesting question about how far
0:14
away light has to travel before it's undetectable. And he even gives you a
0:20
measurement of how strong that light is, so we'll talk about that. Are
0:24
we living in a holographic universe? I think we've had that question in several
0:30
forms over several years, so we will tackle that one again. And how
0:37
fast is fast enough to create drag when traveling through space? And relative relative
0:45
trouble with this word relativistic speed. That's all coming up on this edition of
0:51
Space Nuts Q and A fifteen second channel ten nine ignition Space Nuts or three
1:02
two space and I record it real good and he's back again for more.
1:11
Don't ask me why, Professor fred what's an astronomer at large? Cello fred
1:15
Illo, Andrew, It's good to be back, whatever the reason is.
1:21
Yes, indeed, everything good, Yeah, all good. Well, it's
1:26
all firing on two cylinders as usual, so that's yes, trouble as we're
1:32
driving a V eight anyways, shall we get on with it and go straight
1:40
to our first question. This one comes from Allan. Hi. This is
1:47
Alan Scahill from Medicine Canada. My question is if an led light one candle
1:55
power in strength were to be turned on in space, what would be the
2:00
greatest distance a space tele telescope would be able to detect it? Thank you
2:06
and love your podcast. Thank you, Allen. Medicine Hat. Do you
2:09
say medicine hat in Canada? If that's an interesting name, I wonder why
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it's called that. He might have to tell us. We might want to
2:20
know what he's got a British accent as well. That happens, I could
2:24
ask the same about you. That's a really good point. I never thought
2:30
of that. Yes, medicine Hat. It's a city in southeast Alberta.
2:35
It's located along the South Saskatchewan River. It's a problem in one hundred and
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sixty nine kilometers east of Lethbridge, two hundred and ninety five kilometers southeast of
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Calgary. The city and the adjacent town of Redcliffe to the northwest are within
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Cypress County. There is don't know why it's called medicine Hat, though it's
2:53
a great name. It might have something to do with a nearby mountain,
2:58
I suspect. Yeah, yeah, it's the nearest we got to it during
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our expedition last month was to Calgary. We flew out of Calgary when we
3:07
left Calgary a lovely place. The bits I saw of it looked very nice.
3:12
Yes, that's right, but it was only the airport. Really we
3:15
were. We were traveling down from Lake Louise that day, and Lake Louise
3:20
is stunning. So I can answer for that. I think you've been I
3:23
was wrong. It's got nothing to do with a mountain. Apparently, it's
3:28
derived from the Blackfoot Indian words samus, meaning the headdress of the medicine man.
3:34
There you go, There you go. If I'm looking at the right
3:38
place, I just did get quickly. I stand to be corrected. Alan
3:40
so police. If I'm wrong, let me know. Led light? Yeah,
3:46
one one candlepower? How far out before we can't see it? Or
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something to that. I've no idea. Look, it's it's it's all about.
4:00
This is the interesting thing about light. It's yes, we regard it
4:06
as a stream of photons, but it's also a wave motion and light is
4:13
something that basically has infinite travel possibility, and so that one the photons that
4:21
that one candle power is emitting, or the the light waves that the LEDs
4:29
emitting essentially gone forever. But what limits your ability to detect them is the
4:36
equipment that you've got to do that. And you know if you've got and
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that's the key thing about telescopes. The bigger your telescope, the bigger the
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light gathering area of your telescope, the faint of the objects you can see,
4:51
and therefore the further away you be able to see your one candle power
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LED. I like, take it on notice, Andrew, and see if
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I can do a calculation for that, because I do this sort of thing,
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or I used to when I was thinking about star magnitudes and things like
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that. So one kind of power LED and how far away could for example,
5:14
the Hubble space telescope. See I did have a quick look myself,
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and I I just found this on the physicsforums dot com website and it says,
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and you said this earlier, there is no known limit to how far
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light can travel. Yes, that's right, but we're talking about the detectability
5:31
of it indeed, and it depends on the instrument. And I think Allen
5:36
mentioned the hubble, Yeah, or just a space telescope. Anyway, it
5:41
doesn't matter that. We'll try and do some calculations on that. Okay,
5:45
Well that was easy, No, it wasn't. Well it was easy in
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the sense that you know. The answer is that light goes on forever.
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Basically, it's just whether you can detect it or not. That's the tricky
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bit, that's the hard part. Yeah, for sure. Okay, Alan,
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we'll get back to you shortly. Now let's move on to our next
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question. This is a text question that came in from Charles. What do
6:10
you think of the theory that we live in a holographic universe? Now we
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better qualify that by explaining what a holographic universe actually is or is supposed to
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be. Let's just say that. So, let's quote Leonard Suskind, who
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was one of the great proponents of the holographic universe. The quote is the
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three dimensional world of ordinary experience, the universe, filled with galaxies, stars,
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planets, houses, boulders, and people, is a hologram, an
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image of reality coded on a distant two dimensional surface. There you go.
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What's when does that date from that quote? It's probably about twenty five years
6:54
ago, because that's how long this thinking has been going on about the holography.
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Actually that goes back only to two thousand and eight, and it's from
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his book The Black Hole War, My battle with Stephen Hawking to make the
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world safe for quantum mechanics. I love the title. I've read that.
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So what you've got is the idea and it comes from so think about what
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a hologram is. It is a way of encoding lights. It's actually we
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would call it an interferogram in the world of physics. You've got a film,
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in fact, a two dimensional surface which is transparent, that has a
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pattern on it, which when you illuminate it with what we call coherent light,
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that's light from a laser where all the waves are in step, all
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the light waves are in step with each other, then it will basically that
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light will be diffracted. It will break up to form a three dimensional image.
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One of the best holograms I know of is at Macquarie University in the
8:03
physics department. I haven't honor appointment there, so I go there quite a
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lot. And what they've got is it's actually it's a conference room, just
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a small conference room with the table and chairs in it. But one wall
8:16
of it is lined with windows, and on the other side of the windows
8:18
is a corridor where you can walk, and that window. The windows have
8:24
a hologround on them, and so when you look through the hologround through the
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window at what is in fact just a room full of chairs, what you
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see is a succession of images of a bar as the night wears on,
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and the bottles are full to start with, and everybody's everything's neat and tidy.
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By the time you get to the other end of it, there's empty
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bottles all over the place. It really not in good shape. So that
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is what we normally think of as a hologram. It's something that gives us
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a three dimensional representation of a two dimensional from a two dimensional So so this
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idea that the unit the universe is like that I've always had trouble with because
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you know, a direct analog with that with a hologram is that you illuminate
9:13
it with something and the illumination forms that three dimensional image. And so where
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does the illumination come from in the you know, the holographic universe. So
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I think you've really got to look at the details of this, and well,
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if I if I can read from the Wikipedia entry on holographic principle,
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which is what it's all about. The holographic principle is a property of string
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theories and a supposed property of quantum gravity that states that the description of a
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volume of space can be thought of as encoded on a lower dimensional boundary to
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the region, such as a lightli like boundary like a gravitational horizon. There
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you go. So that's that's that's what you're supposed to imagine with a holographic
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universe. So it's, as I said, it goes back twenty five years,
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probably more than that. I've never been that keen on it because it
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seems highly contrived to me, but it does have a theoretical basis for people
10:18
to think it might be the case. I'd like to see more evidence that
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there is, you know, there is a holographic event horizon, if I
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can put it that way, because I think that's the idea that the you
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know, if we're a black hole, the event horizon is actually where the
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hologram lies. And there's a whole lot of gobbledygood on the Wikipedia page that
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if Charles wants to plow through he might be even more illuminated on it than
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I. I find the theory very confusing. It doesn't sort of gleane with
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traditional thinking, And no, it's not intuitive. I find it hard argue
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against traditional thinking. Yes, I understand that. I think by traditional thinking,
11:07
I think you might mean something that makes sense. Yes, the way
11:13
we generally understand things the moment. Yeah, traditional thinking. That's my perception
11:18
of it. And who you are really doesn't it. It's a thinking Yeah,
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well that's it. I mean, we should be open to all possibilities,
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because the mystery of our existence at all is one we can't answer.
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We don't know why it happened. We don't know what caused it to happen.
11:35
We don't know how things developed to create what has been created. The
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more we look, the more questions that are raised, the more we know,
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we get confused about things that shouldn't have been able to happen, that
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happened, And it just goes on and on and on. So you can't
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write off anything, I suppose No, and I wouldn't write off the holographic
11:58
principle either. I think it's a really interesting idea. I don't fully understand
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it as you've probably realized by now, I don't understand it that much,
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and that's so we So yeah, So the answer to Charles's question is,
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yeah, I think it's it's interesting. As I said, I've never been
12:16
a big fan. That's because I perhaps I'm a traditional thinker, as you
12:20
would put it. I'd like to think about the universe as being made of
12:24
atoms and things that really owe their existence not to a hologram, but to
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to being where we are, to being within a universe that was created in
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a big bang and has all these other particles generated from that. That makes
12:39
more sense to me. Now, the next question that's going to come up
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is, hang on a minute, what if the hologram is made of dark
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matter? Ah? Yes, I think you've put your finger on something.
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Then you reckon probably just stirred the pot even more and made it murky.
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But you know, the holographic universe theory is fantastic in science fiction, really
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is. Yes. Yeah, I am actually watching a TV series at the
13:05
moment which I'm thoroughly enjoying. It's called Dark Matter, and it centers around
13:11
multiple universe theory. And I was going to take a little bit of a
13:18
break, but we might as well throw straight into this. This is about
13:20
a bloke who gets abducted and when he wakes up, he's in a different
13:24
universe and he's trying to figure out what the hell happened because it's the world,
13:30
but not as he knows it. Same people, different situations, different
13:33
relationships, different career path situations. It's all out of whack and he thinks
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he's going mad. There's only been three episodes so far, but g it's
13:45
good. It is really good. But the reason I bring it up and
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thanks for your question, Charles, but this question popped into mind and I'm
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giving it to you without notice from Rennie, who is a regular contributor.
13:56
Could it be possible that our universe is in a universe cluster as our Milky
14:01
Way is in a galaxy cluster. If all universes are expanding, would they
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eventually overlap each other at some point? I think the sort of standard multiverse
14:13
idea is exactly that, that you've got multiple universes which may be clustered together
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or not necessarily. One way of looking at this is the M theory universe
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and M nobody's ever a short M stands for mystery membrane is probably where it
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comes from, because the idea is that we are all on a living in
14:41
a three dimensional membrane which is right next to other three dimensional membranes that contain
14:48
other universes, and when membranes collide, you get a big bang. Yeah,
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that theory. I remember checking it out once in quite some detail.
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And you know, we think of these membranes as being well membranes with a
15:05
universe somehow imprinted on it. But it turned out in the theory it's actually
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when I think about it, it's called the act pyotic theory of the origin
15:16
of the universe, and it turns out that these membranes are only separated by
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something like zero point five of a millimeters. When nic collide, you get
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a big bang, and you're thinking, oh, that's a bit close.
15:30
You know, something went wrong. I'm not sure where m theory is at
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the moment in terms of its acceptance by the cosmological community, but I think
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the answer terraneous question is yes, that's possible. And if they keep expanding,
15:46
which ours is, would they eventually overlap at some point? I'm sure
15:52
overlap would be I mean, what if two universes that are expanding ump into
15:56
each other. I think bump would be an understate. Yeah, but they
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might be expanding in a higher dimensional space, which might preclude that. Well,
16:06
there's a thought too. And here's another thought. If you've got two
16:11
universes expanding towards it, towards each other, and let's just say ours is
16:15
one of them, Ours is expanding at an accelerating rate. What if the
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one that's near us is expanding at an accelerating rate, but their acceleration is
16:23
faster than ours. Now, it doesn't stand a reason that we're all going
16:27
to hit at exactly the same speed. No, I think. I think
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you've got to ensure that your other universe is in a different bit of the
16:37
higher dimensional space than you are, and then it can expand as much as
16:41
it likes. And it doesn't doesn't it ours unless it's a membrane. And
16:45
that if it's a membrane and it collides with us, you've got a big
16:48
bang. Yeah, it's just like watching child's balloons burst or rum or bubbles
16:55
bubbles, they go boom. Yes, they could be mini universe versus that
17:00
live for a fleeting moment and the people go, oh, look at don
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it's all. It's really interesting to talk about that. It's fascinating theory,
17:08
and this dark matter series sort of leans on that particular multiverse theory very very
17:17
well, and they travel around in a box just like Doctor whod Yeah.
17:23
Thanks Rennie. This is Space Nuts with Andrew Dunkley and Professor Fred Watson.
17:30
Okay, we've tacked all space nuts. One more question, Fred, and
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this one comes from Craig. Professors. I'm Craig Miller calling from sunny Umbula
17:44
in New South Wales. I have a confession. I have a solitary habit
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n't usually mentioned in public. I write science fiction, so that's this question
17:53
is a little what if the vacuum of space is, as we know,
18:00
not exactly empty. The density is low, but gas and dust fill the
18:03
vac human space. So I'm wondering how fast you would have to be traveling
18:10
before that gas and dust began to produce drag. Surely, if you went
18:15
fast enough, you'd have to consider aerodynamic principles for the profile of your spaceship.
18:22
As a secondary question, wouldn't a ship traveling at relativistic speed smash into
18:26
that aforementioned gas and dust like a mobile particle collider. If there were lots
18:33
of spaceships traveling at light speed, you'd see the trails all over the sky.
18:41
Maybe. Anyway, thanks for answering my question. Keep up with the
18:47
great work. I love your show. Thanks very much, Chow, thank
18:51
you very much. Craig, lovely to hear from you. You'll have to
18:53
send us some book titles. I'd like to take a look at those,
18:56
if you don't mind. I'd love to see what your what your angle is
19:00
and science fiction and steal your ideas. Now I'm kidding now my thoughts on
19:07
his first question. You know, how much speed to create the drag in
19:11
the vacuum of space would be dependent on the concentration of particles, would it
19:15
not? Because some parts of space only have one speck of stuff per gazillion
19:21
miles. Now I'm exaggerating slightly. Well, you're not exaggerating that much.
19:27
Maybe the gazillion is a bit some Yes, you're at the level of a
19:33
handful of particles per cubic meter. And it's a really interesting question actually,
19:40
that Craig, that he poses because even at those low densities, so we've
19:48
got a sort of a bit of an example of this around the Earth.
19:52
When you get to heights of one hundred, two hundred and three hundred kilometers,
19:56
there's still enough of the atmosphere that you're going to get drag on your
20:00
spacecraft if it's in orbit, and that's what brings them down. So here's
20:06
the International Space Station four hundred kilometers high that has to have its orbits boosted
20:14
periodically every few months, I think, in order to counteract the effects of
20:18
drag. And there's not that many atoms of atmosphere up at that height.
20:26
It's certainly well over one per cubic meter. But yes, so the the
20:32
atmosphere drag on a spacecraft is a real thing, and I think to extrapolate
20:37
that as Craig is doing, is actually a valid thing to do. Should
20:44
you think in aerodynamic terms, if you were designing very, very high speed
20:49
spacecraft, And I think the answer is probably in the second part of Craig's
20:56
question, because yes, those relativistic velocities where you are approaching the speed of
21:03
light, then your spacecraft is more like a particle accelerator. It's more like
21:10
what's going on at the Large Hadron Collider where you might well see you know,
21:17
atomic scale impacts that would have showers of other particles coming off them.
21:26
So you know, your occupants of your spacecraft might be being irradiated by highly
21:32
ionizing radiation from the particle impacts that you're traveling through, which would be not
21:40
very nice. If you've got dangerous rays coming out of the walls of your
21:42
spacecraft, no matter how aerodynamic it is, you're not going to be very
21:47
happy about it. So I don't know that specific answers to the questions,
21:52
but it's really it's a really interesting one. You know, I can't tell
21:56
you what velocity you really need to think about designing. And you're absolutely right
22:02
as well, Andrew in that different bits of space have got different densities.
22:06
If you're looking at the star formation region, a nebula, as we would
22:11
see it as the pressure there is unbelievably low. It's lower than the hardest
22:17
vacuum you can make on the Earth, but there are still enough particles there
22:22
that you're essentially forming an EBuLa. You're seeing the glow of it, Whereas
22:29
in regions between the galaxies the density of particles is very low, indeed,
22:34
but it's still there. They're still there. The particles subatomic particles are still
22:38
there. So yeah, if you were capable of traveling at the light speed
22:45
and you wanted to travel any significant distance, you'd have to really be able
22:51
to calculate your navigation with so many parameters in play. It's not just about
22:56
I want to go from there to there, because there won't be there you
23:00
get there, it'll be there somewhere, and you've got to allow for what's
23:03
in between to make the trip without sort of hitting something, you know,
23:08
like a giant star or whatever. It's it's it's uh. I think interstellar
23:17
navigation would be a very tricky little thing, tricky chop. Well, we've
23:25
got spacecraft that are doing that, you know, basically with with the Voyagers
23:32
and the Pioneers there in effectively interstellar space. They're still they're still feeling,
23:38
all of them, but some of them are feeling the magnetic field of the
23:41
Sun rather than the magnetic field of the galaxy. I think Voyager one feels
23:45
the magnetic field of the galaxy. So yeah, you're out there in in
23:49
very deep space. I wonder whether you know we certainly. I'm just trying
23:59
to think of this the other way around. Particles what they do. When
24:04
I was building instruments for ground based astronomy. Back in the eighties, nineties,
24:11
early two thousands, we were often beset by the effect of cosmic rays,
24:17
which are seatomic particles coming in at a very high speed on our detectors.
24:19
You'd get you get an image that was supposed to be the spectrum of
24:23
an object, but it have all these It looks as if somebody had thrown
24:27
a whole lot of just white bits of sand all over the image, and
24:30
they were the impacts of cosmic rays which were being recorded by the detector.
24:36
Wow. So that sort of thing must happen when you've got a spacecraft,
24:41
you know that's doing science or imaging or whatever. You must have this cosmic
24:45
ray flocks anyway. But if you've got a significant velocity in a particular direction
24:51
that might affect the cosmic ray flocks, you might see more than more than
24:55
you expected or less than you expected. Yeah, it's a really interesting thought.
25:00
Thank you for bending our minds in that direction, Craig. Indeed,
25:03
yes, and I mean it when I say send it. Send me some
25:07
intro about your sci fi books. I'd love just see what you write about
25:11
and if you do have questions for us, of course, please send them
25:15
through our website, spacenuts podcast dot com or spacenuts dot io. You can
25:19
click on the AMA link at the top and send us text and audio questions,
25:23
or the little purple button on the right hand side to send audio questions
25:29
only. But as we always say, please remember to tell us who you
25:33
are and where you're from. You might be from medicine hat in Canada,
25:37
who knows. And thanks to everyone who contributed, Alan, Charles, Rennie
25:41
and Craig. Looking forward to some new questions in coming weeks. And that
25:48
wraps it up for another episode. Fred, thank you very much, Oh
25:52
thank you. Thanks for having me and thanks for everybody's questions. Is very
25:56
stimulating, it is, isn't It gets a brain going sometimes he does.
26:00
Yeah, people dooms a lot. Yeah. Thanks Fred. We'll see you
26:07
soon and see your light to cheers for the bye. Fred Watson, astronomer
26:11
at large and here in the studio. Who does what? Who does in
26:14
the studio? When he's not in the studio, I don't know what he
26:18
does? And from me Andrew Duncley, thanks for your company. See on
26:21
the next episode of space Nuts coming to you real soon. Oh Bynuts to
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