Kind: captions
Language: en
[laughter] Happy 500,000. Thank you guys
so much for subscribing to my channel
and for joining me on this scientific
adventure. You know, if you got 500,000
people together and we all held hands in
a line, it would stretch from Sydney to
Melbourne or from San Francisco to San
Diego or from London to Inesse. Oi, what
are you forming a line here for? You're
gonna scared off Nessie,
right? So, I suppose I should get down
to answering your questions. Go ahead,
hit me with your best shot.
I understand that the sky is blue due to
scattering. Short wavelengths get
scattered way more and blue light
dominates because it's so short. If
that's the case, why isn't the sky
violet? Okay, here's the thing. The sky
isn't really blue. It's bluish white.
So the sky is illuminated by the sun and
the sun emits all colors but not
equally. [music]
The sun doesn't emit that much red nor
does it emit that much violet. Most of
the light it emits is kind of in the
greeny part of the spectrum. Now as you
point out due to rally scattering more
of the shorter wavelengths are scattered
and that is why the sky looks blue
because it's basically the sun's white
spectrum shifted [music] a little bit
towards the blue. This is the spectrum
of the blue sky. And as you can see,
it's quite broad. And in fact, there is
a fair amount of violet light in there.
But there's not as much violet light as
there is blue [music] light because the
sunlight that we started with had much
more blue than it had violet. If I have
a laptop on the International Space
Station with a hard disc drive in it,
will the torque from it spinning cause
the laptop to spin as well? Well, by the
law of conservation of angular momentum,
yes, the laptop should spin. I did a
quick back of the envelope calculation
and I found that if you spun up your
hard disk from [music] rest up to 5400
RPM, then it would cause the laptop to
spin in the opposite [music] direction
at a rate that would cause it to do
about one revolution every 17 seconds.
[music]
What would happen if you poured liquid
oxygen on a fire?
Kaboom. Say you were able to pass the
event horizon of a black hole and come
back. What would coming back look like
for the person? And for an observer,
well, to an outside observer, it would
look as though you never came back at
all. And to the person, it would look as
though you didn't come back either.
Because once you're past the event
horizon, that's it. Your entire future
lies within the black hole. And it will
only be a matter of seconds before you
are in the singularity, the very core of
this black hole, and you are no longer.
Now, if you could bring a rocket pack
with you and try to fight it, if you
tried to accelerate away from the black
hole, you would find that you actually
live for less time. You might see more
space, but your time [music] uh would
pass more slowly and so you would end up
in the singularity sooner. So, I guess
the lesson is don't fight it. If you
want to live longer, just relax and go
with it. You've met a lot of interesting
people on your adventures, but is there
someone specific that you would love to
meet? I would love to meet Bill Nye,
Neil deGrasse Tyson, Richard Dawkins,
and President Obama as a a non-scientist
inclusion. I really like his book. So,
if you haven't read the Audacity of
Hope, that's a good [music]
recommendation. If all the galaxies are
constantly accelerating away from each
other, will they ever reach the speed of
light or stop accelerating altogether?
So yeah, all the galaxies do seem to be
accelerating away from each other faster
and faster, [music] which makes this
kind of a unique time in the history of
the Earth because right now we can still
see that there are hundreds of billions
of [music] galaxies. But sometime in the
future, due to the expansion of the
universe, those galaxies will be so far
away and yes, they will be receding at
faster than light [music] speed. And
then you might say, well, nothing can go
faster than light. And it's kind of true
in that these galaxies won't be moving
through space at a speed faster than
light. But the space in between us and
them will be expanding at a rate [music]
which means that they will be moving
relative to us faster than light. If
that makes any sense. So their [music]
light that they're emitting will never
be able to reach us because it'll never
be able to make progress through this
expanding [music] space. It's kind of
interesting to think about what will
happen as that time approaches. [music]
Well, the light that is coming from
those distant galaxies travels across
this expanding [music] space and so it
becomes redshifted cosmologically
and eventually the wavelength of this
light will be so big that its wavelength
is the size of the whole universe and
that is impossible to detect. [music] So
at some point probably about 2 trillion
years in the future we will only see our
local cluster of galaxies. [music] Now,
the reason they haven't gone out to
infinity or very very far away is
because they're gravitationally bounded
to us. So, even though space is
expanding on a large scale, the
gravitational force is enough to hold
all of us together. So, we will be in it
for the long haul. But this still means
that there's going to be strange
cosmology. [music] If we're still around
trillions of years from now, if we tried
to look out, we would see a very
different universe, a universe which is
much emptier than the one we see [music]
today. So, we live at a unique point in
um spaceime. We should appreciate that.
Is there such a thing as randomness in
the universe? And if so, isn't that
contradictory to science? Yes, I think
there is randomness in the universe. And
no, I do not think this contradicts
science. [music]
Though perhaps you're thinking along the
lines of Albert Einstein when he said,
"God does not play dice." He wasn't
happy when in quantum mechanics it
seemed as though some events have
probabilistic outcomes. I mean, he
thought that there were some hidden
variables there and we just didn't know
what was determining the outcome. So we
thought it was probabilistic. But all
experiments seem to show up to this
point anyway that there are some things
which are randomly determined. They are
probabilistic in their nature. For
example, you can get quantum random
number generators. And even the FBI and
CIA can't seem to find any pattern in
those numbers. So they really truly do
seem to be random. So yes, it seems from
all the experimental evidence that
randomness is a fundamental part of our
universe, albeit mostly on the quantum
scale.
What shape is the universe and could
light from our sun go around the
universe and come back and hit the other
side of earth?
The shape of the universe seems to be
flat which means there is no large scale
curvature of spaceime and the supposed
reason for this is inflation. this idea
that very very very shortly after the
big bang the whole universe just started
accelerating at an incredibly fast rate.
So even if it was kind of wiggly or
warped or curved around on itself before
inflation after inflation [music] it
basically would have been flattened out
just like blowing up a balloon that side
is going to become you [music] know more
or less flat. So within the limits of
our our observational capabilities to
these days we [music] think that the
universe is flat. So, if you go out in
one direction, you probably shouldn't
return uh the way [music] you came. So,
no, the universe does not appear to be
closed, and you'd probably never see the
light [music] coming up behind you. Hey,
man. I have one fantastic topic for you
to make a video about, but [music] I
need your response. You want to do it?
Otherwise, I contact Vsauce.
Hey, Michael, you want this one or shall
I take it?
No, no, no. Go ahead, Derek. Take it.
So we are really reaching the atomic
size but not in some exotic laboratory
device in every device you have in your
computer and your mobile phone.
How many transistors are on the chip
now? About a billion depending what you