November 15, 2018 • 34 mins
Why can't we travel faster than light? Can we ever reach the stars?
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Speaker 1 (00:07):
Have you ever wanted to travel to a distant star
or to a planet orbiting another sun all the time? However,
I've heard that it's impossible. Yeah. The problem is that
the universe is just so big and it comes with
it's built in speed limit makes it pretty tough. So
that means that we'll never build a spaceship that will
get us to another star within the span of a
(00:29):
human left time. That's almost true. It's almost a hard
and fast rule. It turns out there's one or two
exceptions to that, immortality being frozen like an ice cube. Hello,
(00:57):
a lot more hand And I'm Daniel and this is
our podcast Daniel and Jorge explain the universe, where we're
going to take the whole universe, break it into little
bits that are bite size, and feed them to you
one at a time. Today on the program, we are
going to ask the question, will we ever be able
to travel faster than the speed of light? Zoom? That's
(01:20):
the sound it would make if we traveled faster than
the speed of light. Right there. We're going full throttle
on this episode. Pedal to the metal, that's right, Pedal
to the podcast, that's right. And I love this question
because not only do people like traveling fast, but it
gives us a sense for like, will we ever be
able to I feel like the subtext to the question
is will we ever travel to other stars and get
(01:41):
to other places in the universe? Because the universe is
so darn big that it's hard to get places. Right.
So if we could travel fast in the speed of light,
we can actually see some cool stuff. Like what's the
nearest star to us? Oh, man, I should ask Siri,
but I think it's about four light years away. Okay,
So even if we're able to go at this peed
of light, you still have to sit in a spaceship
(02:02):
for four years to get there. Let's if you could
travel at the speed of light. Yeah, but there's also
the question of accelerating to the speed of light, Like
if you could, if you had a spaceship which could
get up to the speed of light, it would take
a long time to get going that fast because, oh,
just to get to the speed of light, yeah, you
can't tolerate a huge amount of acceleration, you know, like
fighter pilots can take like eight or nine g s, right,
(02:25):
the eight or nine times the acceleration you feel on Earth.
But squishy people like me, and you get into a jet,
we can't tolerate, tolerate more than a couple of geese.
You know, it'd be like being on the craziest roller
coaster ride for like a year, years just to get
to the speed of light, just to get to the
speed of light. Yeah, and if you accelerate faster, you
would just get smushed against the sea. Yeah, exactly. You'd
(02:45):
arrived as a puddle of Google. And don't forget you
have to decelerate also because you don't want to arrive
someplace going the speed of light. To you'll be traveling
as a puddle of goo, and you would arrive as
a splatter of Google on the front. When that's right.
But hey, if you're public good, it doesn't really matter
when you arrive, does it. You're not feeling it or
(03:06):
if you arrive or if you arrive. Yeah, that's why
in a lot of these awesome science fiction books I've
been reading, you spend half the trip accelerating and then
you turn the ship turns around and spends the second
half the ship decelerating, slowing down because you know, if
you arrive at your destination going a gazillion miles an hour.
You just blow right through their solar system. You can't
even stop or you know, get a smoothie or anything. Okay,
(03:28):
So the question is is their hope of us ever
getting to other stars or planets out during the universe?
Can we ever go faster than the speed of light?
That's right, So we went around and we asked people
on the street. Here's what they had to say. I
do believe that one day we'll be able to travel
faster than to speak the light. Essentially, yes, I don't
(03:49):
think so because it's you know, Einstein series, something based
on nothing, coin Fester p Night someone say no, honestly,
with like the way technology is going, I do think
eventually we'll reach the point. Yeah optimistic. Okay, So the
first thing I find interesting about the responses is that
everyone has an opinion, you know, like it's like no evidence,
(04:12):
no theoretical background. They're like I think so, or they're
like no, I don't think So's everybody feels like technological
progress is inevitable, Like you can say whatever bar you
want and eventually we'll get there. Science will figure it out.
I love that optimism and enthusiasm that like, yeah, scientists
can do anything. Yeah, Well, think about all the crazy
(04:34):
things we have been doing, right, Yeah, absolutely, you know,
like um downloading pictures of cats from the internet. Yeah,
and then you're able to like change your genome using
your cell phone or something like that. You want to
be a ginger, there's an app for that. You want
to be dial it on your phone? That would oh man,
swipe right for redhead taller. Well, I think we're spinning
(04:57):
off ideas for science fiction novels here, But I love
that optimism. And you know, frankly, I was surprised because
these days a lot of people aren't really believing in science,
and like people aren't accepting global warming, and people aren't
accepting this and that the other. But everybody seems to
believe that technological advancements will just be continue to be
delivered on pace. And you know, people, you want technological deliverance,
(05:17):
if you want technological marvels, you've got a fun science.
So if you want a fancy new iPhone or to
travel fast in the speed of light, you better call
your congress person and tell them to fund basic science.
All right, and Brant, it's such so permeated in science
fiction and movies and things right, Like, without faster than
light travel, most science fiction stories that involve other planets
(05:40):
would be super boring. Right, that's right exactly because it
tells us something about the scale of the universe, right, Like,
the universe is really big. No, the speed of light
is super fast. Like, let's remind people it's three times
tend to be eight meters per second or a hundred
and eighty six thousand miles per second. It's like blindingly fast, right,
It's not like any kind of speed we're used to.
(06:03):
It's like, in one second, a ray of light can
go around the Earth six times? Is that about it?
Six or seven times? Yeah, in a single second. It's
incredible to like one, that's it. We went around the
world six times. That's right. It brought us postcards and
and uh and drink it exactly, and so it's incredibly fast.
But the amazing thing is that even though the speed
of light is so fast, the universe is ridiculously big.
(06:26):
So even going at the speed of light, it takes
you forever to get anywhere, right, thousands of years to
get somewhere, even if you're traveling as a light beam. Well,
so let's just ask the question. Daniel can we go
faster than the speed of light? No, boat, We're done.
That's right, We're done. It's a hard no, you're saying
(06:47):
it's a hard cannot go faster than the speed of light.
It's a hard note with a couple of asterisks and loopholes,
which maybe we'll get too later. Okay, Well, let's talk
about first, like what kind of speed limit is it? Right, Like,
if you go faster than this beeed of light, does
the intergalactic police like pull you over and say and
give you the intergalactic ticket? No, it's actually they're snipers,
(07:07):
so they don't even bother the ticket, just take you
out right thereak you out. They don't mess around the
laws of physics we're talking about here, dude. Okay, so
it's embedded in the laws of physics. Yeah, And the
right way to say it is that you can't travel
through space faster than light can travel through space. So
that sounds like a loophole for later. Yeah, there's some
lawyerly caveats I'm setting up for later. Some intergalactic law
(07:31):
firms salivating, They're like, I found a loophole. That's right.
I'm I'm on retainer for some Andromeda lawyers exactly. So
what does happen? Like if I'm in a spaceship and
I would say I live forever and I have infinite energy,
and I just hit the accelerator on my spaceship and
I just wait pedal to the metal for as long
as it takes. What's going to happen? So in a scenario,
(07:53):
you're an infinitely rich alien with who lives forever, and
this is how you're gonna spend your time. Wow, Well,
first of all, you don't know that I'm an not
an infinitely rig It's true. Okay, So you're an infinitely
rich alien and you're doing a podcast with I think
even more perplexing. I've lived forever, so you know I
give my kicks this way. Alright. So you're getting down
(08:13):
to item number three thousand four in two on your
bucket list and this is it? So what? Yeah, like,
do you hit us like you hit a wall? Do
you know what I mean? Like? At some point I
can't go faster that do I crash? Does my engine
burn out? At some point? What happens if I try
to go faster than the speed line? Yeah? Well, people
have intuition about this kind of stuff because they're used
to balls and airplanes and cars and stuff, and they
(08:34):
think that if you put in twice as much energy,
you should go twice as fast. And that is true
if you're on the surface of the Earth or you're
going pretty slowly, meaning like if you burn a certain
amount of fuel you should get you should accelerate a
certain amount, you should go faster a little bit, that's right,
And if you burn the same amount of fuel again,
you should go twice as fast. Yeah, there's a linear relationship.
Doesn't matter what your speed is. If you add energy,
(08:56):
add speed. That's the people's intuition, But that's not true.
That's not the way the universe actually works. So what
happens in your scenario is you keep pouring on energy,
but your speed, the increase in your speed, starts to
slow down. So at first you speed up a lot
when you when you're burning rocket fuel, but then you
just can't get faster very quickly, and you start to
approach the speed of light slower and slower and slower,
(09:19):
so that every pile of energy or bottle of fuel
you burn gives you a smaller increase in your speed.
So somebody watching you do this like from the outside
of your spaceship, they're gonna see you take off really fast,
and but at some point you're not. They're not going
to see you go faster and faster. They're just gonna
see you peek in velocity. Yeah, your legions of screaming
(09:41):
fans are just gonna watch. It's gonna get kind of
boring because you're gonna get faster and faster and approach
to the speed of light, but never actually get there. Right,
But what's happening to me inside the spaceship though? Do
I think I'm going faster than the speed of light?
Or no? No, you don't. You are aware of your speed,
and you are aware of the fact that you're not
going fast in the speed of light, and you're are
you frustrated? And you're screaming at your agent to get
(10:02):
your bettership or whatever whatever infinitely rich horhe alien Jorge does,
and but you just never get there. So, but it
doesn't time slow down for me too. I've heard the
time slows down for me so that I think I'm
going faster, but I'm actually times slowing down for me.
This isn't that how it works? Am I just infinitely wrong? Here. Well,
(10:23):
you on the spaceship, time always moves for you at
one second per second, but um, other people looking at
you will think the time is slowing down for you.
So people watching you will will see if they're like
watching a clock that's in your ship, they'll see it's
slowing down. And that's one of the really bizarre things
about relativity is that not only does it tell us
that there's a speed limit, which is hard to understand,
(10:45):
but it also tells us that time is not the
same for everybody. Time is a local thing. Like how
I feel time depends on where I am and how
fast I'm going, So it's kind of an incremental uh
slowing down of you. Like I was thinking, like that's
really cool because we think of the speed limit as
like a hard stop, but it really kind of affects
(11:05):
us all the way to the speed of light. Right,
that's right, Like even now, if I burn hot twice
the amount of fuel, I'm not going to go twice
as fast with my car. I'm actually gonna go a
little bit less than twice as fast, right, Yeah, But
it's a really tiny effect until you get anywhere close
to the speed of light. You can get up to
like half the speed of light without really noticing the
(11:26):
limits of relativity. It's not because and and then it
starts to get very very strong the closer you get
to the speed of light. So unless you have a
really sleepy car, you won't notice. Yeah, but I think
people are used to thinking of it as like this
thing that happens in spaceships or like physics experiments, but
really it's happening all around. Is like if I move
my arm back and forth here and in my studio, Um,
I'm being affected by relativity, like it's slowing me down somehow.
(11:49):
That's right. Yeah, And the fact that you're looking at
your arm means you're using light to see it. And uh,
and so relativity is everywhere. It's it's deeply woven into
the very fabric of our understanding of physics. Now, it's
amazing that we went so long without understanding this really
basic concept that space and time are different from what
we thought they were. So I guess the question then,
(12:13):
is why should there be a speed limit? Like why
does relativity have this weird limit baked into it? Yeah,
it's a really bizarre feature, and it comes from the
observation that light always travels at the speed of light.
No matter what you're doing or how fast you're going
relative to the thing that's shooting out the light. Light
(12:34):
is always traveling at the speed of light. That's like
saying Jorge is always traveling at the speed of Joge,
that's right, orhe is always at maximal humor right? Or
are always the same funny? Um? Well, I mean it's
kind of a weird statement. It's like saying I'm always
going as fast as I'm going, that's right. So think
about it like this. You're you know, if you have
a ball you can throw at ten miles an hour. Cool. Now,
(12:57):
what if you're sitting in a car that's moving at
ten miles an hour, then you throw the ball. Somebody
on the ground is going to see the balls going.
It's twenty miles an hour. Right, that's cool. It's like
the velocities add. Yeah, velocities add. They're supposed to add.
You feel like they should add. It makes sense. It's
it's an intuitive thing for us. Right. What if the
person in the car, instead of having a ball, has
a flashlight. Well, they shine their flashlight. How fast is
(13:20):
the light going from their flashlight at the speed of light, duh, right,
speed of light. Okay, But if they're in the car
and they're moving at ten miles an hour and I'm
on the ground, how fast do I measure the speed
of light? Well, your intuition would say speed of light
plus ten miles an hour, right, because they add and
that's where it breaks. You measure those photons is leaving
(13:41):
your flashlight the speed of light, and I'm outside the
car on the ground, I still measure those photons as
moving at the same speed. So like if I put
a rocket on a flashlight and the flashlight is going
super fast, Let's say the flashlights going at the speed
of light or close to the speed of light, and
then it shoots the Pope boton or a beam of light.
(14:02):
The light coming out of the flashlight is not going
to go faster than the speed of light either. That's right.
Two people always measure light traveling at the same speed,
no matter how fast they're going relative to each other,
which is really weird. That's the core nugget of the
counterintuitive bits of relativity, and everything follows from that. So
you can ask why does light always travel at the
(14:22):
speed of light? And let's get to that in a minute.
But first, let's connected back to what we were saying earlier.
So if light always travels at the speed of light,
that's the thing that makes it impossible to go faster
than light. Okay, because it's this observation that light can
go faster than the speed of light or never does
that then limits our ability to go faster than the
speed of light. Is that what you're saying. Yeah, because
(14:43):
velocity and time are connected in relativity. If you're moving
really fast past the Earth, you see time on the
Earth passing more slowly. If you were moving the speed
of light, you would see Tom and Earth as frozen.
If you were moving faster than the speed of light,
you would see Tom and Earth moving backwards, which is
totally impossible and breaks causality. I mean, trains would arrive
(15:05):
at the station before they left. It would be crazy.
I have so many questions for you, But before we
dive in, let's take a short break so we can
(15:27):
go fast in the speed of light. Because light can't
go faster than the speed of light. And if we
were to go fast in the speed of light, things
just like don't don't make any time would be reversed
and crazy stuff like that, and to understand that in
great detail you have to have a few moving bits
in some sort of thought experiments. We actually go into
that in some fun detail in our book We have
(15:47):
no idea. There's a whole chapter outlining that and and
dotting all the logic lines from the statement that lights
always traveling at the same speed to nothing can go
faster than the speed of light. So that's pretty solid. Yeah,
And so that all comes from this one observation that
light travels at the same speed no matter what. And
people discovered that about a hundred years ago, and that
(16:09):
blew people's minds. It didn't make any sense at all.
I mean, people did this experiment, it's called the Michaelson
Morley experiment, and they shot beams of light in two
different directions and then measured how fast they went and
came back. And the idea as well, the Earth is moving,
and so if the Earth is moving through space, it
has some speed, right, and so we should be able
to measure that speed by seeing how fast light is
(16:30):
moving in one direction versus another direction. But no matter
when they did it or how they did it, they
always got the answer that light is traveling at the
same speed, which shocked everybody was like, it's the kind
of result I always fantasize about, you know, the kind
of physics experiment where you get the result and people say, no,
that doesn't make any sense. You must have done something wrong.
(16:50):
But instead it requires unraveling like the whole foundation of physics. Well,
I think it's weird for people because you can't imagine
light going faster than light that you can imagine a
little photon, little wave moving faster and faster and faster,
Like why should this little photon be limited in speed?
Like why can't it just keep going faster? Yeah? Why
(17:11):
should there be a maximum speed limit at all? Right? Yeah,
even for light? Right, Yeah, it's totally but saying like
that's not how then, like the universe doesn't like things
to go faster than that, Like I know it was
an idea of them either at some point in physics history,
like maybe we're swimming in some kind of goo that
just doesn't let things travel very fast through it, right, Well,
(17:32):
the idea of ether was trying to explain what light
is wiggling through, right, I mean, light is a wave,
and most waves like sound waves or pressure waves are
waves through something like sound waves are pressure waves in air, right,
So people were wondering what is light moving through because
if lights a wave, it has to be the wiggling
of something. And that's why they invented the ether. They thought, well,
(17:54):
light must be wiggles in this invisible thing we've never
seen before, called the ether. And it was not a
terrible It just turned out to be wrong, you know,
and so um, that's what that was the origin of
this experiment. People thought, let's measure the velocity of the
Earth through the ether, and then we'll be able to
tell how fast light is going relative to the ether.
(18:15):
But it turns out it wasn't. Light is not wiggling
through ether. Light is an electromagnetic radiation that moves through
vacuum on its own. It's a really bizarre thing. It
doesn't have to wiggle something else, right, but it's it
is limited in like speed, like there's only so fast
and this stuff we call space around this there's only
there's a kind of a maximum propagation speed. Yeah, so
(18:38):
light is this really bizarre thing that can only move
at a certain maximum speed and nothing can move faster
than that. And no matter how how fast you're going,
you always measure light moving at the same speed, And
that always boggled my mind because it makes me feel
like two people can observe the same things and get
different answers and both be right. You know, Like if
you shoot a flashlight and I'm traveling at half the
(19:00):
speed of light to try to catch up with it,
It's strange to me that you'll measure those photons going
at the speed of light, and I'll also measure those
photons are going at the speed of light. It feels
like our observations disagree, but we're both correct, you know,
we can have different views of the same events and
both be right. That's the craziest thing about relativity. I
(19:23):
feel like a really great um way to kind of
visualize how things break down that you once told me
about was this idea that like, if there's a ray
of light going through the universe, and like you, you
were able to catch up to it, Like you could
go as fast as that beam of light, and you
were standing next to it, going at the speed of light,
(19:44):
it wouldn't make any sense for you to see a
beam of light just standing there, you know what I mean.
Like if I'm going down the highway and I catch
up to a truck and I match it speed to me,
the truck will seem like it's just standing there. But
for a ray of light like that just doesn't make
any sense to see a light ray just standing there
(20:05):
like that's where things would sort of break down, right, Yeah,
because not only did I no, No, that's totally right.
Not only can you never go the speed of light
because you have mass, and things that have mass can
approach to the speed of light and never get there,
But things that are mass less always go the speed
of light. So not only photons, but also gravitons and
and other things that have no mass always go the
(20:26):
speed of light. And the reason is that exactly what
you said, that if they weren't going the speed of light,
then you could eventually catch up to them and be
next to them. But what is a photon, right, It
has no mass, there's no stuff to it, there's nothing there.
It's just it's velocity. So if you catch up to
it and it's not moving relative to you, then it
doesn't really exist. So it actually makes more sense for
(20:50):
light to always be zooming along at the speed of
light relative to everybody who's measuring it at the maximum
speed at the maximum speed. Yeah, and I think something
you said earlier is interesting. Why should there be a
maximum speed? Right? And um, I think that's really cool,
But it tells you something about our universe. Right. We
we need there to be a maximum speed so that
(21:11):
there's causality, so the things make sense, that things don't
happen out of order, so that cause happens before effect. Right,
if you go faster than the speed of light, then
cause and effect breaks. Well, let's let's break it down.
Like I think, maybe it breaks down to the question
what would happen if we had no speed limit in
the universe? Like, what if things could go faster than
the speed of light? What would happen? Well, you'd have
(21:32):
to have a totally different universe because the way our
universe is set up, that's pretty much baked in at
the at the ground level, and so the universe would
be totally different if there was no maximum speed. I
think one thing that's fun to think about is what
if the maximum speed was different? Right, what if it
was like twice as much or ten times as much
or a tenth as much. Because one deep question we
(21:53):
have is why is the speed of light this speed?
And not some other speed, Right, that's a thing idea,
the idea that that's just how our universe is put together,
Like that's just baked into the rules. And maybe there's
another universe where the speed of light is different or
there's no speed of light. Is that kind of what
you're saying, Like, it's possible maybe to construct the universe
(22:14):
without a speed limit. I'm not sure if it's possible
to construct the universe with no speed limit, but it's
definitely possible to construct the universe with a different speed limit,
one that's much higher or one that's much lower. I mean,
as far as we know. You know, if you're like
at the control panel of the universe, this is just
a parameter that you can set, and if you change
the speed of light to something else, physics still works.
(22:35):
So we don't know why the speed limit is what
it is, um it. We can't construct the universes that
don't have speed limits, where things travel instantaneously um across
time and space. Those things don't work because they break causality.
Things can arrive before they leave and stuff like that.
But we can make universes where the speed of light
is different, and that's fun to think about because it
(22:55):
changes your relationship, like we were talking about earlier, with
far away things. You know, the fact that stars are
really far away really tells you about how far the
way they are relative to the speed of light. Yeah,
let's talk about that, but first let's take a quick break.
(23:22):
How would breaking the speed of light break the fundamental
like logic of the universe. It's it would break the
universe because it would break causality. And by that I
mean that things could happen out of order. Relativity tells
us that things happen differently depending on your velocity, right,
and so, and time works differently depending on your velocity.
As you go faster, you can see the order of events,
(23:45):
the time of events change, and if you go fast
in the speed of light, some things flip so that
the effect happens before the cause. Like the equations just
no longer make any sense. It just no longer makes sense,
like it it just breaks. And it comes from this
this fact that how you see time changes based on
how fast you're going, which again is totally connected to
(24:06):
the fact that everybody sees the speed of light always
moving at the same speed no matter what. Wow. But
the basic idea is just that it's just baked into
the equations that nothing can go faster than the speed
of light. That's right, Like it's just big. If you
try to go faster, it will just break the equations
by which the universe is put together. And we have
tested it a zillion ways from here to Sunday, and
(24:29):
relativity is very solid. This part of relativity, it's called
special relativity, that describes how light moves and time is affected,
is totally well tested and we really believe it, and
and it's the underpinnings of everything we've built. So if
it's wrong, then we're going to throw everything away. Now
I'm not saying that doesn't mean it's wrong, right, It
could be wrong. And it could be that we discover
that it's replaced by a different theory and and everything
(24:51):
is wrong. That would be frankly kind of awesome. I
love these revolutions in physics. But so far it seems
to be pretty solid. Like maybe like your kids or
some kid out there right now, future physicists might figure
it out that it's a that real special realtibilities is wrong. Yeah,
And in fact, there was a result a few years
ago where people thought they had figured that out there
was this result from the opera experiment at CERN that
(25:13):
sent new trinos zooming through Italy, and they thought they
measured some new trinos going faster than the speed of light,
and they put out this big paper and then it
turned out to be wrong and turned out to be
an operatic track. That's right. Um, it was actually quite embarrassing.
One of the cables they were using to measure the
timing had come loose and there was a little bit
(25:33):
of jiggle and and that was the source of the
whole mistake and they had to pull it back and
the spokespeople resigned, and it was embarrassing. So if you're
gonna try to disprove all of modern physics, check your cables.
Make sure they're right. That's right. If you're going up
against Einstein, doubill check the box that's right. If you're
gonna shoot for the king, you better kill him, so
(25:54):
I guess. And the last question is like, does that
mean that we can never reach these like far away
planets in a decent amount of time without turning into
puddles of ooze? Like does that mean, like you know,
like you and me will never get to step on
another solar system and things like that, or uh, you know,
if we can't go fast through the speed of light,
does that mean that interstellar travel is impossible? Right, So
(26:17):
it's time to return to those caveats we talked about.
Traveling through space faster than the speed of light is
impossible and as far as we can tell, will never
be possible. It's not like there's some technological breakthrough or
waiting for. It's like just difficult or expensive or something
or complicated. Right, it seems totally impossible to move through
space fasten the speed of light. Now, I say through
(26:39):
space because that's the caveat we've recently learned the last
couple of decades that space is not this fixed thing
that you move through. It's not like this empty backdrop.
It's squishy, it's dynamical. It can do things, and we
can squeeze it and expand it and ripple in it.
So instead, so the caveat is, instead of trying to
move through space faster than the speed of light, change
(27:00):
the space we're moving through. So you want to go
from here to Alpha Centauri, can we squeeze that space
to make the distance shorter? Right? Then breaking the rules
of physics to go through it. So it's kind of
like we're we're not Space is not an empty and
empty noess right, It's like maybe we are in some
kind of like a sponge or some kind of liquid
as if you know, just in as an analogy, and
(27:22):
you can't move through this sponge faster than the speed
of light, but you could maybe like bend the sponge
or squish the sponge to get from one side of
the sponge to the other side. You could do tricks
like that. Is that what? That's exactly what I mean,
And that is theoretically totally possible, though experimentally very very difficult.
It's not like we've achieved this or we're like on
(27:42):
the on the edge of being able to do this
or whatever. But you know, the first step in a
project like this is go from impossible to possible, and
then the rest is engineering to go from possible to practical. Right, So, um,
I leave that for the engineers. The physicist job is
to go from impossible to possible. Next week will be
it will be a feature on your test LA Autopilot
(28:04):
to Alpha Centauri. Anyways. Um, yeah, so you might be wondering, well,
how is it possible? Well, you know that space can
bend right, I mean where the Earth goes around the
Sun because Sun has bent space, so the Earth moves
around it because the space is bent right, And gravitational
waves shows that, like colliding black holes can make ripples
(28:24):
in space. So how did you actually get from here
to there? You'd have to squeeze the space, which takes
a huge amount of energy. So just like a gravitational
wave cannot propagate, you can maybe like create a giant
wave that somehow compresses space from here to Alpha Centauri
so that it's just really close. Yeah, or some sort
of standing wave that's always compressing the space right in
(28:46):
front of you so that you can move through it rapidly. Yeah,
like you're surfing a gravitational wave exactly. Surfing a gravitational
wave exactly. But remember the gravitational wave caused by like
colliding black holes squeezes space by one part in ten
to the twenty. So you need an even bigger source
of gravitational energy than colliding black holes. So that's a
(29:08):
tall order. Well, in the movies like Star Wars and
Star Trek, whenever they go into warp speed, you see
kind of they always show it as this kind of
like distortion of space, right, like the stars stretch out
or like the spaceships stretches out before it disappears. But
maybe there's something I mean, they got something right about that, right,
Like maybe that's why we're thinking. They were thinking, like
(29:29):
you're actually like stretching space or you're like compressing space,
and that's how you're moving faster than like, Yeah, I'm
pretty sure the guys who wrote Star Trek did these
calculations before they wrote those episodes, and it's been motivated
by actual physics. Yeah. Yeah, everyone in Hollywood has a PhD. Right,
that's right. That's why they never called me to ask
for physics help, right, they just understand it themselves. And
(29:52):
that's why there are no physics mistakes in any Hollywood movies.
I think you've totally figured it out. So that's one loophole,
is that you can squeeze space so that you and
travel faster through And are there are the other loopholes
or is that the main like possibility for getting top Yeah,
So if you're out there about to write a check
for our warp drive company, hold on a moment, because
there are other options, right, And another option is wormholes right.
(30:16):
This is the idea that space might not be simply connected.
It might not be that every piece of space is
connected to the piece of space next to it. The
connection could be a little bit more complicated. It could
be that, like some piece of space is connected to
a piece of space that's far far away. Right, That's
what a wormhole is, this connection between pieces of space
that are far away, and that requires space. Maybe it's
(30:38):
not this like just homogeneous thing. It could have like
little loops in it. It could be like tangled up. Yeah, exactly.
It requires you to think about space in a really
different way. It's not just this emptiness you move through.
It's more like nodes on a subway station, right, and
you can they can be connected in any way. You
can travel from one to the other. And so why right, yeah,
why not? Exactly? In fact, we think that space probably
(31:00):
is that way. That the tiny quantum level space might
even be quantized um and discreet, and and that you
can move around like you move around a subway map um.
And it could be that on the macroscopic level these
things exist too. And general relativity, the theory that tells
us about how space time's bent and all that stuff
does allow for wormholes, it's totally possible. Now, there's a
(31:22):
huge number of caveats there, like, we've never seen a wormhole. Um,
so we're not sure. So they're theoretical only they're theoretical. Okay, yeah,
but you know what black holes used to be theoretical.
It used to be like, well, here's a funny property
of general relativity, but nobody's ever seen one. Gravitational ways
worth theoretical to write, and we just exactly exactly. So
(31:42):
maybe you know, wormholes are last year's black holes, right,
wormholes are the new forty and the trending wormhole. Yeah,
hashtag put Kanye in a wormhole? Um, And so we
think they might exist, but we've never seen one. We
(32:02):
have no idea how to make one, We have no
idea how to keep them open, and man, maybe most importantly,
we don't know what we like to go through them.
Probably if you went through it, it would stretch and
squish you and you'd be that pile of goo anyway.
But you can maybe send like a signal or a
probe or maybe something answer. Are you gonna say, hamster,
don't send the hamster. I'm gonna call the SPC on
(32:25):
you not my hamster. My answer, yes, you probably could
send information through the work, so you can talk to
the aliens interesting you know, or whoever is on the
other side of the word, or the future you or whatever. Yeah. So,
even though you can't travel through space fasten the speed
of light and that's pretty solid, there are some ways
you might be able to traverse huge distances without waiting
(32:48):
at zillion years. So there is some hope. You're saying,
theoretically it's possible, and so maybe, like our people on
the street that we talked to, maybe there's some future
engineer or physicist to figure out how to make it happen.
That's right, And if you do, please send us a
note because we want to be involved. Yeah, we want
to be able to spend my infinite riches out there.
(33:09):
That's right. And I think probably that's what the folks
we interviewed, that's probably what they were expressing. They probably
weren't thinking, well and starting special world too, so it's
just impossible. So no, they were thinking, well, humans figure
it out, and whenever we're faced with the problems, somebody
comes up with a solution. There's so many smart people
out there with their brains cooking on this. That me
other that somebody will figure out a way to get
(33:30):
there faster than lightspeed travel, even if you're not actually
going faster than lights to feed through space. So that's
why I like to think that people were thinking that
they were this optimistic view of science solving every problem
that we have, and maybe the person who figures it
out is like out there right now, you know, could
be some kid or some person out there whom it
(33:51):
could be somebody listening to this podcast getting inspired right now.
Scribble those ideas down, don't forget them. Include us in
the patent please, or we will sue you. I have
some good lawyers from Office Centar. We will see you
at the speed of light. Well, thank you very much.
Hope you enjoyed that. We'll see you guys next time
(34:11):
as we explain the whole universe. If you still have
a question after listening to all these explanations, please drop
us a line. We'd love to hear from you. You
can find us at Facebook, Twitter, and Instagram at Daniel
(34:31):
and Jorge that's one word, or email us at Feedback
at Daniel and Jorge dot com.
Have you ever wanted to travel to a distant star
or to a planet orbiting another sun all the time? However,
I've heard that it's impossible. Yeah. The problem is that
the universe is just so big and it comes with
it's built in speed limit makes it pretty tough. So
that means that we'll never build a spaceship that will
get us to another star within the span of a
(00:29):
human left time. That's almost true. It's almost a hard
and fast rule. It turns out there's one or two
exceptions to that, immortality being frozen like an ice cube. Hello,
(00:57):
a lot more hand And I'm Daniel and this is
our podcast Daniel and Jorge explain the universe, where we're
going to take the whole universe, break it into little
bits that are bite size, and feed them to you
one at a time. Today on the program, we are
going to ask the question, will we ever be able
to travel faster than the speed of light? Zoom? That's
(01:20):
the sound it would make if we traveled faster than
the speed of light. Right there. We're going full throttle
on this episode. Pedal to the metal, that's right, Pedal
to the podcast, that's right. And I love this question
because not only do people like traveling fast, but it
gives us a sense for like, will we ever be
able to I feel like the subtext to the question
is will we ever travel to other stars and get
(01:41):
to other places in the universe? Because the universe is
so darn big that it's hard to get places. Right.
So if we could travel fast in the speed of light,
we can actually see some cool stuff. Like what's the
nearest star to us? Oh, man, I should ask Siri,
but I think it's about four light years away. Okay,
So even if we're able to go at this peed
of light, you still have to sit in a spaceship
(02:02):
for four years to get there. Let's if you could
travel at the speed of light. Yeah, but there's also
the question of accelerating to the speed of light, Like
if you could, if you had a spaceship which could
get up to the speed of light, it would take
a long time to get going that fast because, oh,
just to get to the speed of light, yeah, you
can't tolerate a huge amount of acceleration, you know, like
fighter pilots can take like eight or nine g s, right,
(02:25):
the eight or nine times the acceleration you feel on Earth.
But squishy people like me, and you get into a jet,
we can't tolerate, tolerate more than a couple of geese.
You know, it'd be like being on the craziest roller
coaster ride for like a year, years just to get
to the speed of light, just to get to the
speed of light. Yeah, and if you accelerate faster, you
would just get smushed against the sea. Yeah, exactly. You'd
(02:45):
arrived as a puddle of Google. And don't forget you
have to decelerate also because you don't want to arrive
someplace going the speed of light. To you'll be traveling
as a puddle of goo, and you would arrive as
a splatter of Google on the front. When that's right.
But hey, if you're public good, it doesn't really matter
when you arrive, does it. You're not feeling it or
(03:06):
if you arrive or if you arrive. Yeah, that's why
in a lot of these awesome science fiction books I've
been reading, you spend half the trip accelerating and then
you turn the ship turns around and spends the second
half the ship decelerating, slowing down because you know, if
you arrive at your destination going a gazillion miles an hour.
You just blow right through their solar system. You can't
even stop or you know, get a smoothie or anything. Okay,
(03:28):
So the question is is their hope of us ever
getting to other stars or planets out during the universe?
Can we ever go faster than the speed of light?
That's right, So we went around and we asked people
on the street. Here's what they had to say. I
do believe that one day we'll be able to travel
faster than to speak the light. Essentially, yes, I don't
(03:49):
think so because it's you know, Einstein series, something based
on nothing, coin Fester p Night someone say no, honestly,
with like the way technology is going, I do think
eventually we'll reach the point. Yeah optimistic. Okay, So the
first thing I find interesting about the responses is that
everyone has an opinion, you know, like it's like no evidence,
(04:12):
no theoretical background. They're like I think so, or they're
like no, I don't think So's everybody feels like technological
progress is inevitable, Like you can say whatever bar you
want and eventually we'll get there. Science will figure it out.
I love that optimism and enthusiasm that like, yeah, scientists
can do anything. Yeah, Well, think about all the crazy
(04:34):
things we have been doing, right, Yeah, absolutely, you know,
like um downloading pictures of cats from the internet. Yeah,
and then you're able to like change your genome using
your cell phone or something like that. You want to
be a ginger, there's an app for that. You want
to be dial it on your phone? That would oh man,
swipe right for redhead taller. Well, I think we're spinning
(04:57):
off ideas for science fiction novels here, But I love
that optimism. And you know, frankly, I was surprised because
these days a lot of people aren't really believing in science,
and like people aren't accepting global warming, and people aren't
accepting this and that the other. But everybody seems to
believe that technological advancements will just be continue to be
delivered on pace. And you know, people, you want technological deliverance,
(05:17):
if you want technological marvels, you've got a fun science.
So if you want a fancy new iPhone or to
travel fast in the speed of light, you better call
your congress person and tell them to fund basic science.
All right, and Brant, it's such so permeated in science
fiction and movies and things right, Like, without faster than
light travel, most science fiction stories that involve other planets
(05:40):
would be super boring. Right, that's right exactly because it
tells us something about the scale of the universe, right, Like,
the universe is really big. No, the speed of light
is super fast. Like, let's remind people it's three times
tend to be eight meters per second or a hundred
and eighty six thousand miles per second. It's like blindingly fast, right,
It's not like any kind of speed we're used to.
(06:03):
It's like, in one second, a ray of light can
go around the Earth six times? Is that about it?
Six or seven times? Yeah, in a single second. It's
incredible to like one, that's it. We went around the
world six times. That's right. It brought us postcards and
and uh and drink it exactly, and so it's incredibly fast.
But the amazing thing is that even though the speed
of light is so fast, the universe is ridiculously big.
(06:26):
So even going at the speed of light, it takes
you forever to get anywhere, right, thousands of years to
get somewhere, even if you're traveling as a light beam. Well,
so let's just ask the question. Daniel can we go
faster than the speed of light? No, boat, We're done.
That's right, We're done. It's a hard no, you're saying
(06:47):
it's a hard cannot go faster than the speed of light.
It's a hard note with a couple of asterisks and loopholes,
which maybe we'll get too later. Okay, Well, let's talk
about first, like what kind of speed limit is it? Right, Like,
if you go faster than this beeed of light, does
the intergalactic police like pull you over and say and
give you the intergalactic ticket? No, it's actually they're snipers,
(07:07):
so they don't even bother the ticket, just take you
out right thereak you out. They don't mess around the
laws of physics we're talking about here, dude. Okay, so
it's embedded in the laws of physics. Yeah, And the
right way to say it is that you can't travel
through space faster than light can travel through space. So
that sounds like a loophole for later. Yeah, there's some
lawyerly caveats I'm setting up for later. Some intergalactic law
(07:31):
firms salivating, They're like, I found a loophole. That's right.
I'm I'm on retainer for some Andromeda lawyers exactly. So
what does happen? Like if I'm in a spaceship and
I would say I live forever and I have infinite energy,
and I just hit the accelerator on my spaceship and
I just wait pedal to the metal for as long
as it takes. What's going to happen? So in a scenario,
(07:53):
you're an infinitely rich alien with who lives forever, and
this is how you're gonna spend your time. Wow, Well,
first of all, you don't know that I'm an not
an infinitely rig It's true. Okay, So you're an infinitely
rich alien and you're doing a podcast with I think
even more perplexing. I've lived forever, so you know I
give my kicks this way. Alright. So you're getting down
(08:13):
to item number three thousand four in two on your
bucket list and this is it? So what? Yeah, like,
do you hit us like you hit a wall? Do
you know what I mean? Like? At some point I
can't go faster that do I crash? Does my engine
burn out? At some point? What happens if I try
to go faster than the speed line? Yeah? Well, people
have intuition about this kind of stuff because they're used
to balls and airplanes and cars and stuff, and they
(08:34):
think that if you put in twice as much energy,
you should go twice as fast. And that is true
if you're on the surface of the Earth or you're
going pretty slowly, meaning like if you burn a certain
amount of fuel you should get you should accelerate a
certain amount, you should go faster a little bit, that's right,
And if you burn the same amount of fuel again,
you should go twice as fast. Yeah, there's a linear relationship.
Doesn't matter what your speed is. If you add energy,
(08:56):
add speed. That's the people's intuition, But that's not true.
That's not the way the universe actually works. So what
happens in your scenario is you keep pouring on energy,
but your speed, the increase in your speed, starts to
slow down. So at first you speed up a lot
when you when you're burning rocket fuel, but then you
just can't get faster very quickly, and you start to
approach the speed of light slower and slower and slower,
(09:19):
so that every pile of energy or bottle of fuel
you burn gives you a smaller increase in your speed.
So somebody watching you do this like from the outside
of your spaceship, they're gonna see you take off really fast,
and but at some point you're not. They're not going
to see you go faster and faster. They're just gonna
see you peek in velocity. Yeah, your legions of screaming
(09:41):
fans are just gonna watch. It's gonna get kind of
boring because you're gonna get faster and faster and approach
to the speed of light, but never actually get there. Right,
But what's happening to me inside the spaceship though? Do
I think I'm going faster than the speed of light?
Or no? No, you don't. You are aware of your speed,
and you are aware of the fact that you're not
going fast in the speed of light, and you're are
you frustrated? And you're screaming at your agent to get
(10:02):
your bettership or whatever whatever infinitely rich horhe alien Jorge does,
and but you just never get there. So, but it
doesn't time slow down for me too. I've heard the
time slows down for me so that I think I'm
going faster, but I'm actually times slowing down for me.
This isn't that how it works? Am I just infinitely wrong? Here. Well,
(10:23):
you on the spaceship, time always moves for you at
one second per second, but um, other people looking at
you will think the time is slowing down for you.
So people watching you will will see if they're like
watching a clock that's in your ship, they'll see it's
slowing down. And that's one of the really bizarre things
about relativity is that not only does it tell us
that there's a speed limit, which is hard to understand,
(10:45):
but it also tells us that time is not the
same for everybody. Time is a local thing. Like how
I feel time depends on where I am and how
fast I'm going, So it's kind of an incremental uh
slowing down of you. Like I was thinking, like that's
really cool because we think of the speed limit as
like a hard stop, but it really kind of affects
(11:05):
us all the way to the speed of light. Right,
that's right, Like even now, if I burn hot twice
the amount of fuel, I'm not going to go twice
as fast with my car. I'm actually gonna go a
little bit less than twice as fast, right, Yeah, But
it's a really tiny effect until you get anywhere close
to the speed of light. You can get up to
like half the speed of light without really noticing the
(11:26):
limits of relativity. It's not because and and then it
starts to get very very strong the closer you get
to the speed of light. So unless you have a
really sleepy car, you won't notice. Yeah, but I think
people are used to thinking of it as like this
thing that happens in spaceships or like physics experiments, but
really it's happening all around. Is like if I move
my arm back and forth here and in my studio, Um,
I'm being affected by relativity, like it's slowing me down somehow.
(11:49):
That's right. Yeah, And the fact that you're looking at
your arm means you're using light to see it. And uh,
and so relativity is everywhere. It's it's deeply woven into
the very fabric of our understanding of physics. Now, it's
amazing that we went so long without understanding this really
basic concept that space and time are different from what
we thought they were. So I guess the question then,
(12:13):
is why should there be a speed limit? Like why
does relativity have this weird limit baked into it? Yeah,
it's a really bizarre feature, and it comes from the
observation that light always travels at the speed of light.
No matter what you're doing or how fast you're going
relative to the thing that's shooting out the light. Light
(12:34):
is always traveling at the speed of light. That's like
saying Jorge is always traveling at the speed of Joge,
that's right, orhe is always at maximal humor right? Or
are always the same funny? Um? Well, I mean it's
kind of a weird statement. It's like saying I'm always
going as fast as I'm going, that's right. So think
about it like this. You're you know, if you have
a ball you can throw at ten miles an hour. Cool. Now,
(12:57):
what if you're sitting in a car that's moving at
ten miles an hour, then you throw the ball. Somebody
on the ground is going to see the balls going.
It's twenty miles an hour. Right, that's cool. It's like
the velocities add. Yeah, velocities add. They're supposed to add.
You feel like they should add. It makes sense. It's
it's an intuitive thing for us. Right. What if the
person in the car, instead of having a ball, has
a flashlight. Well, they shine their flashlight. How fast is
(13:20):
the light going from their flashlight at the speed of light, duh, right,
speed of light. Okay, But if they're in the car
and they're moving at ten miles an hour and I'm
on the ground, how fast do I measure the speed
of light? Well, your intuition would say speed of light
plus ten miles an hour, right, because they add and
that's where it breaks. You measure those photons is leaving
(13:41):
your flashlight the speed of light, and I'm outside the
car on the ground, I still measure those photons as
moving at the same speed. So like if I put
a rocket on a flashlight and the flashlight is going
super fast, Let's say the flashlights going at the speed
of light or close to the speed of light, and
then it shoots the Pope boton or a beam of light.
(14:02):
The light coming out of the flashlight is not going
to go faster than the speed of light either. That's right.
Two people always measure light traveling at the same speed,
no matter how fast they're going relative to each other,
which is really weird. That's the core nugget of the
counterintuitive bits of relativity, and everything follows from that. So
you can ask why does light always travel at the
(14:22):
speed of light? And let's get to that in a minute.
But first, let's connected back to what we were saying earlier.
So if light always travels at the speed of light,
that's the thing that makes it impossible to go faster
than light. Okay, because it's this observation that light can
go faster than the speed of light or never does
that then limits our ability to go faster than the
speed of light. Is that what you're saying. Yeah, because
(14:43):
velocity and time are connected in relativity. If you're moving
really fast past the Earth, you see time on the
Earth passing more slowly. If you were moving the speed
of light, you would see Tom and Earth as frozen.
If you were moving faster than the speed of light,
you would see Tom and Earth moving backwards, which is
totally impossible and breaks causality. I mean, trains would arrive
(15:05):
at the station before they left. It would be crazy.
I have so many questions for you, But before we
dive in, let's take a short break so we can
(15:27):
go fast in the speed of light. Because light can't
go faster than the speed of light. And if we
were to go fast in the speed of light, things
just like don't don't make any time would be reversed
and crazy stuff like that, and to understand that in
great detail you have to have a few moving bits
in some sort of thought experiments. We actually go into
that in some fun detail in our book We have
(15:47):
no idea. There's a whole chapter outlining that and and
dotting all the logic lines from the statement that lights
always traveling at the same speed to nothing can go
faster than the speed of light. So that's pretty solid. Yeah,
And so that all comes from this one observation that
light travels at the same speed no matter what. And
people discovered that about a hundred years ago, and that
(16:09):
blew people's minds. It didn't make any sense at all.
I mean, people did this experiment, it's called the Michaelson
Morley experiment, and they shot beams of light in two
different directions and then measured how fast they went and
came back. And the idea as well, the Earth is moving,
and so if the Earth is moving through space, it
has some speed, right, and so we should be able
to measure that speed by seeing how fast light is
(16:30):
moving in one direction versus another direction. But no matter
when they did it or how they did it, they
always got the answer that light is traveling at the
same speed, which shocked everybody was like, it's the kind
of result I always fantasize about, you know, the kind
of physics experiment where you get the result and people say, no,
that doesn't make any sense. You must have done something wrong.
(16:50):
But instead it requires unraveling like the whole foundation of physics. Well,
I think it's weird for people because you can't imagine
light going faster than light that you can imagine a
little photon, little wave moving faster and faster and faster,
Like why should this little photon be limited in speed?
Like why can't it just keep going faster? Yeah? Why
(17:11):
should there be a maximum speed limit at all? Right? Yeah,
even for light? Right, Yeah, it's totally but saying like
that's not how then, like the universe doesn't like things
to go faster than that, Like I know it was
an idea of them either at some point in physics history,
like maybe we're swimming in some kind of goo that
just doesn't let things travel very fast through it, right, Well,
(17:32):
the idea of ether was trying to explain what light
is wiggling through, right, I mean, light is a wave,
and most waves like sound waves or pressure waves are
waves through something like sound waves are pressure waves in air, right,
So people were wondering what is light moving through because
if lights a wave, it has to be the wiggling
of something. And that's why they invented the ether. They thought, well,
(17:54):
light must be wiggles in this invisible thing we've never
seen before, called the ether. And it was not a
terrible It just turned out to be wrong, you know,
and so um, that's what that was the origin of
this experiment. People thought, let's measure the velocity of the
Earth through the ether, and then we'll be able to
tell how fast light is going relative to the ether.
(18:15):
But it turns out it wasn't. Light is not wiggling
through ether. Light is an electromagnetic radiation that moves through
vacuum on its own. It's a really bizarre thing. It
doesn't have to wiggle something else, right, but it's it
is limited in like speed, like there's only so fast
and this stuff we call space around this there's only
there's a kind of a maximum propagation speed. Yeah, so
(18:38):
light is this really bizarre thing that can only move
at a certain maximum speed and nothing can move faster
than that. And no matter how how fast you're going,
you always measure light moving at the same speed, And
that always boggled my mind because it makes me feel
like two people can observe the same things and get
different answers and both be right. You know, Like if
you shoot a flashlight and I'm traveling at half the
(19:00):
speed of light to try to catch up with it,
It's strange to me that you'll measure those photons going
at the speed of light, and I'll also measure those
photons are going at the speed of light. It feels
like our observations disagree, but we're both correct, you know,
we can have different views of the same events and
both be right. That's the craziest thing about relativity. I
(19:23):
feel like a really great um way to kind of
visualize how things break down that you once told me
about was this idea that like, if there's a ray
of light going through the universe, and like you, you
were able to catch up to it, Like you could
go as fast as that beam of light, and you
were standing next to it, going at the speed of light,
(19:44):
it wouldn't make any sense for you to see a
beam of light just standing there, you know what I mean.
Like if I'm going down the highway and I catch
up to a truck and I match it speed to me,
the truck will seem like it's just standing there. But
for a ray of light like that just doesn't make
any sense to see a light ray just standing there
(20:05):
like that's where things would sort of break down, right, Yeah,
because not only did I no, No, that's totally right.
Not only can you never go the speed of light
because you have mass, and things that have mass can
approach to the speed of light and never get there,
But things that are mass less always go the speed
of light. So not only photons, but also gravitons and
and other things that have no mass always go the
(20:26):
speed of light. And the reason is that exactly what
you said, that if they weren't going the speed of light,
then you could eventually catch up to them and be
next to them. But what is a photon, right, It
has no mass, there's no stuff to it, there's nothing there.
It's just it's velocity. So if you catch up to
it and it's not moving relative to you, then it
doesn't really exist. So it actually makes more sense for
(20:50):
light to always be zooming along at the speed of
light relative to everybody who's measuring it at the maximum
speed at the maximum speed. Yeah, and I think something
you said earlier is interesting. Why should there be a
maximum speed? Right? And um, I think that's really cool,
But it tells you something about our universe. Right. We
we need there to be a maximum speed so that
(21:11):
there's causality, so the things make sense, that things don't
happen out of order, so that cause happens before effect. Right,
if you go faster than the speed of light, then
cause and effect breaks. Well, let's let's break it down.
Like I think, maybe it breaks down to the question
what would happen if we had no speed limit in
the universe? Like, what if things could go faster than
the speed of light? What would happen? Well, you'd have
(21:32):
to have a totally different universe because the way our
universe is set up, that's pretty much baked in at
the at the ground level, and so the universe would
be totally different if there was no maximum speed. I
think one thing that's fun to think about is what
if the maximum speed was different? Right, what if it
was like twice as much or ten times as much
or a tenth as much. Because one deep question we
(21:53):
have is why is the speed of light this speed?
And not some other speed, Right, that's a thing idea,
the idea that that's just how our universe is put together,
Like that's just baked into the rules. And maybe there's
another universe where the speed of light is different or
there's no speed of light. Is that kind of what
you're saying, Like, it's possible maybe to construct the universe
(22:14):
without a speed limit. I'm not sure if it's possible
to construct the universe with no speed limit, but it's
definitely possible to construct the universe with a different speed limit,
one that's much higher or one that's much lower. I mean,
as far as we know. You know, if you're like
at the control panel of the universe, this is just
a parameter that you can set, and if you change
the speed of light to something else, physics still works.
(22:35):
So we don't know why the speed limit is what
it is, um it. We can't construct the universes that
don't have speed limits, where things travel instantaneously um across
time and space. Those things don't work because they break causality.
Things can arrive before they leave and stuff like that.
But we can make universes where the speed of light
is different, and that's fun to think about because it
(22:55):
changes your relationship, like we were talking about earlier, with
far away things. You know, the fact that stars are
really far away really tells you about how far the
way they are relative to the speed of light. Yeah,
let's talk about that, but first let's take a quick break.
(23:22):
How would breaking the speed of light break the fundamental
like logic of the universe. It's it would break the
universe because it would break causality. And by that I
mean that things could happen out of order. Relativity tells
us that things happen differently depending on your velocity, right,
and so, and time works differently depending on your velocity.
As you go faster, you can see the order of events,
(23:45):
the time of events change, and if you go fast
in the speed of light, some things flip so that
the effect happens before the cause. Like the equations just
no longer make any sense. It just no longer makes sense,
like it it just breaks. And it comes from this
this fact that how you see time changes based on
how fast you're going, which again is totally connected to
(24:06):
the fact that everybody sees the speed of light always
moving at the same speed no matter what. Wow. But
the basic idea is just that it's just baked into
the equations that nothing can go faster than the speed
of light. That's right, Like it's just big. If you
try to go faster, it will just break the equations
by which the universe is put together. And we have
tested it a zillion ways from here to Sunday, and
(24:29):
relativity is very solid. This part of relativity, it's called
special relativity, that describes how light moves and time is affected,
is totally well tested and we really believe it, and
and it's the underpinnings of everything we've built. So if
it's wrong, then we're going to throw everything away. Now
I'm not saying that doesn't mean it's wrong, right, It
could be wrong. And it could be that we discover
that it's replaced by a different theory and and everything
(24:51):
is wrong. That would be frankly kind of awesome. I
love these revolutions in physics. But so far it seems
to be pretty solid. Like maybe like your kids or
some kid out there right now, future physicists might figure
it out that it's a that real special realtibilities is wrong. Yeah,
And in fact, there was a result a few years
ago where people thought they had figured that out there
was this result from the opera experiment at CERN that
(25:13):
sent new trinos zooming through Italy, and they thought they
measured some new trinos going faster than the speed of light,
and they put out this big paper and then it
turned out to be wrong and turned out to be
an operatic track. That's right. Um, it was actually quite embarrassing.
One of the cables they were using to measure the
timing had come loose and there was a little bit
(25:33):
of jiggle and and that was the source of the
whole mistake and they had to pull it back and
the spokespeople resigned, and it was embarrassing. So if you're
gonna try to disprove all of modern physics, check your cables.
Make sure they're right. That's right. If you're going up
against Einstein, doubill check the box that's right. If you're
gonna shoot for the king, you better kill him, so
(25:54):
I guess. And the last question is like, does that
mean that we can never reach these like far away
planets in a decent amount of time without turning into
puddles of ooze? Like does that mean, like you know,
like you and me will never get to step on
another solar system and things like that, or uh, you know,
if we can't go fast through the speed of light,
does that mean that interstellar travel is impossible? Right, So
(26:17):
it's time to return to those caveats we talked about.
Traveling through space faster than the speed of light is
impossible and as far as we can tell, will never
be possible. It's not like there's some technological breakthrough or
waiting for. It's like just difficult or expensive or something
or complicated. Right, it seems totally impossible to move through
space fasten the speed of light. Now, I say through
(26:39):
space because that's the caveat we've recently learned the last
couple of decades that space is not this fixed thing
that you move through. It's not like this empty backdrop.
It's squishy, it's dynamical. It can do things, and we
can squeeze it and expand it and ripple in it.
So instead, so the caveat is, instead of trying to
move through space faster than the speed of light, change
(27:00):
the space we're moving through. So you want to go
from here to Alpha Centauri, can we squeeze that space
to make the distance shorter? Right? Then breaking the rules
of physics to go through it. So it's kind of
like we're we're not Space is not an empty and
empty noess right, It's like maybe we are in some
kind of like a sponge or some kind of liquid
as if you know, just in as an analogy, and
(27:22):
you can't move through this sponge faster than the speed
of light, but you could maybe like bend the sponge
or squish the sponge to get from one side of
the sponge to the other side. You could do tricks
like that. Is that what? That's exactly what I mean,
And that is theoretically totally possible, though experimentally very very difficult.
It's not like we've achieved this or we're like on
(27:42):
the on the edge of being able to do this
or whatever. But you know, the first step in a
project like this is go from impossible to possible, and
then the rest is engineering to go from possible to practical. Right, So, um,
I leave that for the engineers. The physicist job is
to go from impossible to possible. Next week will be
it will be a feature on your test LA Autopilot
(28:04):
to Alpha Centauri. Anyways. Um, yeah, so you might be wondering, well,
how is it possible? Well, you know that space can
bend right, I mean where the Earth goes around the
Sun because Sun has bent space, so the Earth moves
around it because the space is bent right, And gravitational
waves shows that, like colliding black holes can make ripples
(28:24):
in space. So how did you actually get from here
to there? You'd have to squeeze the space, which takes
a huge amount of energy. So just like a gravitational
wave cannot propagate, you can maybe like create a giant
wave that somehow compresses space from here to Alpha Centauri
so that it's just really close. Yeah, or some sort
of standing wave that's always compressing the space right in
(28:46):
front of you so that you can move through it rapidly. Yeah,
like you're surfing a gravitational wave exactly. Surfing a gravitational
wave exactly. But remember the gravitational wave caused by like
colliding black holes squeezes space by one part in ten
to the twenty. So you need an even bigger source
of gravitational energy than colliding black holes. So that's a
(29:08):
tall order. Well, in the movies like Star Wars and
Star Trek, whenever they go into warp speed, you see
kind of they always show it as this kind of
like distortion of space, right, like the stars stretch out
or like the spaceships stretches out before it disappears. But
maybe there's something I mean, they got something right about that, right,
Like maybe that's why we're thinking. They were thinking, like
(29:29):
you're actually like stretching space or you're like compressing space,
and that's how you're moving faster than like, Yeah, I'm
pretty sure the guys who wrote Star Trek did these
calculations before they wrote those episodes, and it's been motivated
by actual physics. Yeah. Yeah, everyone in Hollywood has a PhD. Right,
that's right. That's why they never called me to ask
for physics help, right, they just understand it themselves. And
(29:52):
that's why there are no physics mistakes in any Hollywood movies.
I think you've totally figured it out. So that's one loophole,
is that you can squeeze space so that you and
travel faster through And are there are the other loopholes
or is that the main like possibility for getting top Yeah,
So if you're out there about to write a check
for our warp drive company, hold on a moment, because
there are other options, right, And another option is wormholes right.
(30:16):
This is the idea that space might not be simply connected.
It might not be that every piece of space is
connected to the piece of space next to it. The
connection could be a little bit more complicated. It could
be that, like some piece of space is connected to
a piece of space that's far far away. Right, That's
what a wormhole is, this connection between pieces of space
that are far away, and that requires space. Maybe it's
(30:38):
not this like just homogeneous thing. It could have like
little loops in it. It could be like tangled up. Yeah, exactly.
It requires you to think about space in a really
different way. It's not just this emptiness you move through.
It's more like nodes on a subway station, right, and
you can they can be connected in any way. You
can travel from one to the other. And so why right, yeah,
why not? Exactly? In fact, we think that space probably
(31:00):
is that way. That the tiny quantum level space might
even be quantized um and discreet, and and that you
can move around like you move around a subway map um.
And it could be that on the macroscopic level these
things exist too. And general relativity, the theory that tells
us about how space time's bent and all that stuff
does allow for wormholes, it's totally possible. Now, there's a
(31:22):
huge number of caveats there, like, we've never seen a wormhole. Um,
so we're not sure. So they're theoretical only they're theoretical. Okay, yeah,
but you know what black holes used to be theoretical.
It used to be like, well, here's a funny property
of general relativity, but nobody's ever seen one. Gravitational ways
worth theoretical to write, and we just exactly exactly. So
(31:42):
maybe you know, wormholes are last year's black holes, right,
wormholes are the new forty and the trending wormhole. Yeah,
hashtag put Kanye in a wormhole? Um, And so we
think they might exist, but we've never seen one. We
(32:02):
have no idea how to make one, We have no
idea how to keep them open, and man, maybe most importantly,
we don't know what we like to go through them.
Probably if you went through it, it would stretch and
squish you and you'd be that pile of goo anyway.
But you can maybe send like a signal or a
probe or maybe something answer. Are you gonna say, hamster,
don't send the hamster. I'm gonna call the SPC on
(32:25):
you not my hamster. My answer, yes, you probably could
send information through the work, so you can talk to
the aliens interesting you know, or whoever is on the
other side of the word, or the future you or whatever. Yeah. So,
even though you can't travel through space fasten the speed
of light and that's pretty solid, there are some ways
you might be able to traverse huge distances without waiting
(32:48):
at zillion years. So there is some hope. You're saying,
theoretically it's possible, and so maybe, like our people on
the street that we talked to, maybe there's some future
engineer or physicist to figure out how to make it happen.
That's right, And if you do, please send us a
note because we want to be involved. Yeah, we want
to be able to spend my infinite riches out there.
(33:09):
That's right. And I think probably that's what the folks
we interviewed, that's probably what they were expressing. They probably
weren't thinking, well and starting special world too, so it's
just impossible. So no, they were thinking, well, humans figure
it out, and whenever we're faced with the problems, somebody
comes up with a solution. There's so many smart people
out there with their brains cooking on this. That me
other that somebody will figure out a way to get
(33:30):
there faster than lightspeed travel, even if you're not actually
going faster than lights to feed through space. So that's
why I like to think that people were thinking that
they were this optimistic view of science solving every problem
that we have, and maybe the person who figures it
out is like out there right now, you know, could
be some kid or some person out there whom it
(33:51):
could be somebody listening to this podcast getting inspired right now.
Scribble those ideas down, don't forget them. Include us in
the patent please, or we will sue you. I have
some good lawyers from Office Centar. We will see you
at the speed of light. Well, thank you very much.
Hope you enjoyed that. We'll see you guys next time
(34:11):
as we explain the whole universe. If you still have
a question after listening to all these explanations, please drop
us a line. We'd love to hear from you. You
can find us at Facebook, Twitter, and Instagram at Daniel
(34:31):
and Jorge that's one word, or email us at Feedback
at Daniel and Jorge dot com.
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
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