Once again, it's time for another questions show.
I think this is turning into my favorite part about doing this channel, so thanks to everybody
who sent in your questions.
As always, if you're watching any episode and you've got an idea for a question, whether
it has anything to do with that episode or not, just go ahead and type in the question
into the YouTube comments and I will gather them up and answer them here.
Short questions are better.
Also, just want to again thank all the people who have come on Patreon on the last little
while, it's made a huge difference.
You've probably heard about the YouTube adpocalypse.
A lot of creators are being squeezed because of all of this ad funding.
So now is a really good time to directly support the creators that you love.
I support a pile of creators.
All the stuff I see on a regular basis, and you should probably do the same.
If there's someone that you like, figure out a way to support them directly so they can
just keep doing what they love, what you love and you don't have to worry the fickle advertising
industry.
All right, let's get on with the questions.
Zack the Ripper.
I still can't grasp a no-center Universe when it started from a one-point explosion.
I understand what you're saying I just can't put it together.
Understanding the topology and shape of the Universe is not one of those things that you
just say, oh, now I get it.
It takes some time and you're going to be uncomfortable for a while.
Now, we've done a whole episode on how you got from a singularity to potentially an infinite
Universe.
And that's a whole separate Universe that I did with Dr. Paul Matt Sutter.
But just this understanding that you can have a thing that is expanding that has no center.
And we can only work in analogies, right, because our brains are located in 3 dimensions
and we can't really understand this.
But the best example to use is - let's just make it as simple as possible.
Imagine a circle.
You've got a circle, and imagine a point on the circle, and you follow the circle around.
Go one way go the other way, and there is a set distance that it takes you to return
to your starting point.
Now if you make the circle bigger, now it takes you longer to get back to your starting
point.
But if you look at just the path that you take along the circle, there is no center.
Of course, you're looking at the circle and you say, the center is right at the middle
of the circle, but that is because you're looking at what is essentially a 1 dimensional
journey from a 2 dimensional point of view.
And so if you take a sphere and you've got an object, two objects on the surface of the
sphere, and you follow the path around that sphere to your starting point, it takes you
a set amount of distance.
And if you expand the sphere, that distance takes longer.
And yet, there is no place that is the middle of the surface, remember the surface of the
sphere.
And so, that's how you can have an expanding sphere, and everything's getting further apart,
but everything is seeing that equally.
Now of course, your 3 dimensional brain, you're imagining the middle of the sphere, and the
space, that's where the center is, but yet again, that's only because you have the ability
to see one more dimension.
And so when you imagine the Universe, with its three dimensions.
It behaves in the same way in that if it’s finite, you move in one direction far enough,
you return to your starting point and it acts like it is a sphere, but, y’know the surface
of a sphere but taken one more direction up.
And so, we always joke that a four dimensional creature can look at this and go “Oh I totally
get it.”
but because we’re three dimensional creatures, we have to keep trying to, sort of, use analogies
to try and wrap our brains around it.
Peter Houle: “Might it be necessary to “clean out” a Lagrange point for potential use?
I think I heard that Earth’s trojan asteroid is in one of them and the James Webb telescope
will be deployed at the Earth’s sun-point.
I’m worried that something is already chilling and would damage the telescope.”
There are a total of five Lagrange points.
There’s the L1 L2 L3 and they’re the ones that are, kind of, lined up in between the
two objects.
So if you’ve got - say the Earth and the moon - you’ve got the one, the L1 point
in between the Earth and the Moon, you’ve got the L2 point on the farside and you’ve
got the L3 which is on the far side of the Earth, right?
Those are your three, the first three Lagrange points; and they are unstable.
And what that means is if that you place an object in any one of those three Lagrange
points, like where the James Webb space telescope is gonna go, they will drift out just automatically.
They will just drift.
There is no way to keep them stable without using some kind of propulsion system.
So, there is nothing waiting in those Lagrange points, they are constantly, if you dropped
James Webb in the L2 Lagrange point without some way for it to maintain that position,
it’s just gonna move away.
Now, the L4 and the L5 points, the ones that are ahead or behind the, y’know, in orbit.
Those are stable.
And if you did try to place a spacecraft in one of those points, you would have to make
sure that there aren’t objects bumping around inside that Lagrange point, but, where James
Webb is, there’s nothing there, nothing can remain there without some kind of rocket.
It’s just that it doesn’t take very much energy.
It takes a tiny little amount of energy to maintain your position and as you drift out
of it, it takes more and more energy to back into that Lagrange point.
Re: Zero: “Question: How does gravity escape a black hole?”
Haha, that’s a great question, right?
You can imagine, a y’know, the black hole is so powerful that nothing, not even light
can escape its grasp, so how can gravity escape its grasp?
But, but, gravity is not this that’s reaching out and sucking things in like a vacuum cleaner,
right?
Gravity is the distortion of spacetime caused by mass.
So, the gravity from a black hole wouldn’t even exist if the black hole didn’t have
mass and it was distorting the spacetime around it.
And, and so, uh, you can kind of, you’ve seen that kind of classic picture of, of like,
something that looks like it’s, I don’t know, how to describe, like a funnel, right?
Where you’ve got this point of mass at the bottom and everything is kind of pushing in.
So, when objects are moving through space, going around a black hole for example, to
them, the space is straight and they’re moving forward.
But, actually they’re following a curved path around a black hole or down into a black
hole’s gravity wall.
So, so gravity is not a thing that a black hole can suck in, it’s just the - what you
get when you have a lot of mass.
StP77 Rising: “Your videos and knowledge have been instrumental in my upstanding of
Astronomy.
A hearty thank you to you.
Now, as a catholic apologist and amateur astronomer, I would love to hear you take on intelligent
design.
Keep it up, Fraser.
In my opinion, there is not any evidence for intelligent design.
The evidence is overwhelming for evolution.
If it evidence for intelligent design showed up, then, it would be something we would have
to take seriously.
But, so far, there has been no evidence presented for any kind of intelligent design and couldn’t
be also explained by evolution.
Now, there are deep questions about where, where did life, where did the first life come
from, where, uh y’know, how did some evolutionary steps, how did we go from single cellular
life to multi cellular life how did DNA, RNA.
These core questions to the theory of evolution and just to life itself, are still, they remain
unanswered.
But the only answer that we can really give is “I don’t know.”
I don’t know where they came from.
And anyone who tells you that they do know, they don’t know, and that’s, and until
we have a theory that really helps to explain it, we just have to go with I don’t know.
Sprsae: “I think humans are losing interest in space travel!
And that’s very very bad!”
Humans are not losing interest in space travel.
Right now we have Space X, which just re-used a rocket and is looking for ways to bring
down the cost.
They’re gonna build the biggest rocket that’s ever been built in the next couple of years
and they’re planning on sending hundreds of thousands of human beings, like a million
people before the end of the century.
They’ve got a competitor, the second richest man in the world, Jeff Bezos, building a rocket
company that is similar and it’s going to be producing rockets of the same capability.
At the same time, NASA is building the SLS which is a massive rocket capable of sending
humans back to the Moon and maybe even explorers to Mars.
Not to mention, what’s happening with the Chinese that have their own completely different
space exploration efforts.
They’ve got space stations and they’re planning to go to the Moon.
We have never had a time in human history where we are more capable and more enthusiastic
about exploring space; and to be there to stay.
There are companies working on mining asteroids, re-usable aircraft that may even be able to
fly to space.
There’s so many great ideas happening right now, I totally disagree with that.
MrWildbill47: “Fraser, you mentioned in a multiverse, each universe could have totally
different constants and laws of physics.
This has me wondering, could the speed of light in any multiverse be different than
the speed we know it to be?
Faster or slower?
In our universe, there are a bunch of constants.
There are these numbers that are, that sort of underlie the laws of physics as we understand
them.
The speed of light, the fine structure constant, the force of gravity, the binding force of
atoms.
And all of these numbers, they’re completely unrelated to each other and they seem completely
arbitrary.
So there’s no reason why the speed of light has to be the number that it is, it’s just
the number and you punch that into the calculations that you’re gonna make.
So the thinking is that in some other multiverse, all of those numbers would have different
constants.
And then that would have consequences.
So if the binding force of atoms was too strong, then matter couldn’t form properly, or gravity
wouldn’t work the way that it does and so the speed of light could totally be a different
number and that would have deep consequences and it could very well be that in the vast
majority of the universes out there, we can’t have life, we can’t have the things that
we see in our universe just because they’re all so different.
Lork Black: “Can a galaxy exist without a black hole in the center?”
Right now, astronomers think that there are supermassive black holes at the heart of pretty
much every single galaxy in the universe.
But, there are some without black holes, but it looks like some kind of event happened
to kick the black hole out.
And so what you can get, you can get these collisions between galaxies, especially when
there’s a big difference in the mass of the black holes at the heart of them.
So say you’ve got one that’s maybe got a black hole that’s five million times the
mass of the Sun, a tiny supermassive black hole.
And then one with, say, a billion times the mass of the Sun and they collide together,
the low mass one can actually get kicked right out of the galaxy.
And so you could end up with these two galaxies going past each other and now you’ve got
a galaxy where one has had its black hole stripped away.
But it wouldn’t, I mean the galaxy would be kind of torn up and messed up, but it wouldn’t
necessarily not be able to be a galaxy anymore.
These supermassive black holes, they don’t act like an anchor for the centre of the galaxy,
they’re really only a tiny percentage of the mass of the whole galaxy.
What really holds a galaxy together is the halo of dark matter that surrounds it.
James Craver: “Here’s another apocalypse level scenario for you.
If a planet is enveloped by its star, does that necessarily mean the end for that planet?
For example, if the surface temperature of the star is low enough, and the star contracts
again, could the planet survive?
I mean, obviously everything on the planet would be toast, but would the planet itself
be able to survive?
It really depends on how long the planet spends inside the atmosphere of the star.
But, like yes it’s awful, it would be terrible.
It would be inside a star, that can’t be good for your health.
But, when it’s inside the atmosphere of the star, this atmosphere causes friction,
right?
The planet is now ploughing through this material of the stellar atmosphere.
And that will cause the planet, that friction will cause the planet to slow down in its
orbit and start to lose orbital velocity, and it will start to spiral inwards deeper
and deeper into the star.
So, if it happens very quickly, then the planet would still be there.
But if it takes a long time, then the planet is going to spiral inwards and join the core
of the star and it’s never going to be revealed again.
Erick Horning: “I read somewhere that a photon produced in the core of the sun can
take up to ten thousand years to work its way out of the Sun and reach the Earth.
Is this true?
And if so, what makes it take so long to get out of the Sun?
It could even be a bigger number than that.
It might be fifty thousand or a hundred thousand years, maybe even a million years and what’s
happening you’ve got at the the core of the sun, you’ve got fusion and atoms of
hydrogen that are coming together and they’re forming helium and that process is exothermic,
it releases energy in the form of photons of gamma radiation.
So you’ve got gamma radiation, being released in the core of the star.
And then those photons are getting absorbed and reemitted over and over and over again
and it’s completely random.
And so, you imagine that you’ve got at the very centre of the star you’ve got this
photon going *Fraser makes sound effects* and what direction it moves in is a completely
random direction.
As it gets outside of the core, it moves to the radiative zone and where in the radiative
zone, that’s all that’s happening is these photons are radiating around.
They get radiated and absorbed.
And they’re moving at the speed of light, right!
They’re going *Fraser makes sound effects* but they take all this time because it’s
completely random.
They’ve got hundreds of thousands of kilometers of distance to randomly escape out into the
next level of the Sun where they can actually be pulled up by these pillars of plasma and
actually make it out into space.
It’s really just the Sun is so big, and the process of random, you could imagine,
a photon could go all the way out, almost to the end of the radiative zone and then
randomly make its way all the way back into the radiative zone and then across to the
other side of the star and do circles around it until it finally gets out.
So that time is average.
It could take much longer and it could happen much more quickly.
Philippe: “So, is the Sun big enough to dilate time, or do we really need something
as big and massive as a black hole?
I’m not even sure I understand what I just asked, this subject is so far out.”
All mass causes time dilation.
In other words, you being here on the surface of the Earth, you are getting time dilation
different from the astronauts that are on board the International Space Station.
And, if you were on the surface of the Sun, you would experience more time dilation.
Think about the movie Interstellar if you saw that, right?
They were close to the supermassive black hole and so, the rest of the universe experienced
more time than they did.
They thought they were down there for a couple of hours and they came back and it was decades
back on Earth.
And, it was the result of being close to a supermassive gravitational body.
Same thing happens here on Earth, it’s just that the difference is very low.
If you live on the top of the mountain, you experience time differently from the people
that live down at the bottom of the mountain.
But it is in nanoseconds for your entire life.
The cool thing is that that’s different from the time dilation that happens when you’re
moving quickly.
And so, when you think about the astronauts on board the International Space Station,
they are at a different level of gravity away from you on the surface of the Earth and at
the same time, they are moving much more quickly.
They are moving twenty-eight kilometers an hour around the Earth.
And so, their time dilation actually balances.
They’re experiencing one kind of time dilation from the gravity and a different kind of time
dilation from the motion.
And, in fact, and I don’t know the exact number but the place where those two things
actually balance out and the time dilation is cancelled out.
So, absolutely.
Nqina Dlamini: “Imagine if there are two kinds of life on Titan.
The surface/lake methane and propane based life and the subterranean one being water
and carbon.
Cool worlds out there.”
You can imagine there’s this vast ocean of water on Titan and deep inside, right?
There could be life, like, with Europa or Enceladus and at the same time you’ve got
that surface of Titan with these liquid hydrocarbons and there could be some exotic form of life
that uses liquid methane as a solvent instead of water and they could be two completely
different ecosystems or maybe they mix in some way.
It’s absolutely fascinating.
We have to send a spacecraft back to Titan.
Alex Gachupin: “When will space agencies switch to drone exploration instead of ground
based rovers?”
I guess when you’re saying drone like you’re talking about flying rovers?
Airplanes?
There are some plans to send some flying robots to other worlds.
There’s like only a couple in the solar system where that would really work.
Mars; it has very low gravity, it would be a hard place to send an airplane, but, it
is theoretically possible.
Venus; which…
sucks, but, it has a very thick atmosphere.
And so, you could theoretically have some kind of airplane there.
And Titan, which is the perfect place to send an airplane.
You couldn’t take solar power, but you could have some kind of nuclear thermal reactor,
and that could power an airplane that would be able to move in the thicker atmosphere
but lower gravity for a very long time.
I think Titan is the perfect place.
Let's send a airplane to Titan.
I’m on board.
Alright, well that’s it!
Another week, another question show.
Thanks everybody for sending in your questions.
As always, wherever you are, on the youtube channel and an idea for a question comes up,
go ahead and type it in there.
Also, you might have noticed I’ve been starting to do question shows specifically for teacher,
for classes, so if you are like a science teacher or you’re teaching some kids about
astronomy and you want a special question show just for you guys, let me know.
My email is in the description.
Alright, see you next week.
As we feel, uh, let me do this again.