Our subject for today is Warp Drives, the
entire general concept not just the version discussed by Miguel Alcubierre. Truth be told, unless you’ve really dug
into the heavy math end of it discussion of the Alcubierre Drive normally are just discussing
Warp Drives in general. Now, as is getting to be a habit in this series,
we also have a general subject of physics we’ll be talking about as well only in this
case it’s going to be four of of them, and it means we’ll be spending more time on
them then the warp drive, but they are key to understanding it. To talk about warp drives we need to talk
a bit about general relativity, which we’re going to need for the next episode on wormholes
too. We also need to talk about mass, specifically
negative mass but also in general the way mass actually has multiple traits that might
not be entirely connected, like how it interacts with gravity and inertia. We also need to take a look at the notion
of why Warp Drives, in spite of getting you from Point A to Point B far faster than light
normally would, don’t actually violate the rules, and in that respect we need to also
explain how distant galaxies can travel away from us faster than the speed of light without
doing so themselves. And lastly we need to talk about the Unruh
Effect, which is very like Hawking Radiation but for event horizons caused by objects accelerating
very fast. Now if you’ve already got a good familiarity
with the Alcubierre Drive from reading pop-sci articles about it you’ve probably heard
this term and negative mass as well, but those generally don’t go into much detail, and
that detail is what this channel is all about. But the basic concept of a warp drive is actually
very straight forward and you probably are already familiar with it. By various proposed means, typically by using
negative mass or energy as part of the process, a ship creates a bubble around itself where
in front of it space has gotten all crunched together and shrunk down, and behind it space
has gotten expanded. It warps space-time in front and behind it
and this shoves the bubble of normal space-time between them forward and at speeds not constrained
by the speed of light. Nothing can move through space-time faster
than light, except space-time itself which is exempt from this, and it carries the ship
along. This is very handy since it not only allows
you to go faster than light but to jump up or down from those effective speeds without
turning your crew into messy pancakes. You don’t need inertial dampeners in a warp
bubble because there’s no change in inertia to dampen. And physics tells us that if certain things
turn out to be true it is actually possible we might be able to build one of these things
one day and while they do have a maximum speed limit the last calculations on this I’ve
seen for that maximum let you jump between galaxies on timescales so short you’d need
an atomic clock to measure them. The faster you want to go, the harder, but
fundamentally the Warp Drive let’s you travel the galaxy quickly and could even eventually
be refined to let you get across the whole Universe even, in very short times. It will probably turn out to be impossible
but we can’t rule it out yet. That’s all you really need to know about
the Warp Drive and if that satisfies, hey, great, thanks for watching, from this point
on we’ll be digging into the guts of how it works. Now this concept is rightly associated to
Miguel Alcubierre since he took the concept and changed it from a seemingly impossible
concept into… well an almost certainly impossible concept, and his 1994 paper on it, which is
linked in the video description, reignited a lot of interest in the concept both from
the public and scientists too. But the concept does predate him, in myriad
forms, of either contracting space in front of you using mass or somehow actually creating
or deleting space behind or in front of you. Of Warping space-time in order to get around
the speed of light. Unfortunately most of these ideas were either
flat out impossible or relied on using something we’re not even sure exists or actually pretty
sure does not, and that remains the case today, but a lot of folks with genuine credentials
to be looking at this subject have made a lot of new improvements on it but they also
found a lot of new problems too, now that it was getting a serious look. The two key ones are getting your hands on
negative mass and getting burned to a crisp inside the bubble, but before we discuss either
of those let’s do a quick overrun of General Relativity, and I mean quick. General Relativity was a follow up on Special
Relativity done by Einstein to deal with the concept of acceleration, what’s going on
when you’re actually speeding up or slowing down. Now back in episode 1 we did a three minute
review of Special Relativity and I pointed out there that it was based on 2 core assumptions. The first being that speed of light was constant
in all inertial frames and the second being that physical laws basically work the same
anywhere and at any speed. The problem is that an inertial frame of reference
is just a complex way of saying that something is moving at a constant speed, which to them
seems like zero speed, you can’t tell when you’re moving at constant speed and the
only reason you think you can is because if you’re zipping down a highway you notice
all the interactions of wheels on pavement or car slamming through air that are moving
at different speeds relative to you. So I can say my speed is zero and everything
else is moving relative to me, to my inertial frame, and all the math and physics works
just fine. Unless you’re accelerating, changing your
speed, changing your inertial reference frame. Then you get problems. Problems patched up by General Relativity. What Einstein realized was that acceleration
and gravity are fundamentally the same thing, or at least can not be told apart. Now unfortunately the classic example of this,
a guy standing in an elevator or box being accelerated, actually does let you tell the
difference between the two, but let’s look at the example anyway. If I’m sitting in an elevator that doesn’t
let me see outside that’s inside a vacuum tube I have no way of knowing if I’m moving
or not, but I can definitely tell which way is up or down and I can tell if the box is
accelerating. But I actually couldn’t tell if that up
and down feeling was from gravity or from acceleration. This isn’t quite true since gravity generated
by roughly spherical objects noticeably weakens as you get further from the source, so if
I have very sensitive equipment I can measure the force of gravity at my feet and at my
head and find a slight difference. This difference is a lot more than slight
around very dense and massive objects like black holes and that difference is what rips
you to pieces, it’s also what rips virtual particle pairs apart to generate Hawking Radiation
as we discussed in the video on that, though today we’ll see another version of that
with the Unruh Effect. But they key thing is you can’t tell the
difference between gravity and acceleration except in terms of traits specific to how
its being generated, I would know I was accelerating for instance if I could feel a giant rocket
motor thrumming underneath me too, or if I cut a hole in the wall and looked outside,
that’s all incidental. Now if I take a little laser, hang it on the
wall, and level it with the floor so it should be hitting the exact same height on the other
side of the elevator, something strange happens if I’m feeling gravity or acceleration. The beam will hit just a little bit lower,
and much lower the more acceleration or gravity I’m under. That’s not surprising with acceleration,
the box has moved since the photons came out of the laser and even though normally that
motion wouldn’t matter since the laser had that same motion, by accelerating you’ve
actually got the box moving faster when those photons hit the other wall then when they
left the laser. The path of the laser will seem to be bent,
though of course we know that it isn’t and it’s just because the elevator moved relative
to when those photons came out. Except we see this exact same effect from
gravity, and the box didn’t move at all. It’s identical, whether the force acting
on you and the box and the laser is from gravity or acceleration by a rocket, the bending of
that light beam will be the same for the same force. More force, more bending. So gravity and acceleration seem to be the
same thing and that is General Relativity. That’s the basic premise of general relativity
anyway, the result of it is that space and time can be warped by gravity, which means
they can be warped by mass, and since mass is a type of energy, E=mc squared, it can
also be warped by energy. That’s one trait of mass but there’s actually
three more of some interest to us today. Mass is also the thing that resist changes
of inertia. But is also the thing which controls how much
an object is effected by gravity or effects other things with its own gravity, and that’s
actually a bit weird. I mean we’ve got four fundamental forces,
gravity, electromagnetism, and the strong and weak nuclear forces, but while an object’s
electric charge controls how strong the electrostatic force it pushes or pulls on things with is,
it’s still its mass that controls how the objects inertia is effected. Also weird, as you probably know, is that
these three other forces have a positive and negative value, but mass and gravity only
seem to have a positive and attractive aspect. So it’s not surprising we’d kick around
the notion of a negative mass, or a repulsive gravity, anti-gravity. But negative in what respect? I just listed three traits it has, how it
resists changes of inertia and how it emits or responds to gravity. Negative in all three? Or just one or two? Could it be possible for instance to make
something’s inertial mass negative only? Or even just much lower, so that a shove sends
it flying away far faster than we’d expect. Or for negative inertial mass, sends it flying
toward us when we push it, instead of the other way around. On the same note could we make an object respond
more weakly to gravity, so we could lift very massive objects with ease or build massive
building more easily, or even make this negative so we can shove a ship off a planet’s gravitational
field instead of being pulled by it. Or for active gravity, the aspect which pulls
on stuff, could we make this repulsive instead to shove everything away from that object,
or increase it to generate artificial gravity? Pretty interesting stuff, and lowering inertial
mass is sadly underused in science fiction since it not only solves the energy problem
for making things go fast but also the unintended consequence that spaceships that can go fast
have access to enough energy to smash worlds. Generally speaking sci-fi stories don’t
want the Millenium Falcon to be able to blow up planets. If you can just lower something’s inertial
mass to a tiny fraction of normal, a regular old rocket engine would speed you up to relativistic
speeds and when you turned the effect off it would just stop like a brick, dropping
to its natural speed from that rocket acceleration, or even lower if you could go the other way
too and increase inertial mass. And the passive and active gravitational aspects
of mass give you similar tricks. One for active gravitational mass is letting
you ramp that up, not just for handy artificial gravity on ships or space stations but to
warp space like a massive bodies do. And the reverse effect would let you expand
space. So negative mass regardless of its specific
properties in terms of these traits would be very useful stuff regardless of its FTL
options. But that’s the one that interests us for
the warp drive, because if you warp space enough, in front and behind you, expanding
behind and contracting in front, you will start moving a long, do it enough and you
will move faster than light. Now this in and of itself isn’t a problem. Nothing can move through spacetime faster
than the speed of light except spacetime itself, and it can carry stuff along. Like Galaxies. The effect of an expanding Universe, usually
attributed to Dark Energy these days, is that stuff is moving ever farther apart and actually
accelerating away from each other, and if you go far enough away you can’t see each
other anymore because you are moving away faster than light can catch up. That’s not a problem for Relativity, the
notion that tiny pockets of new space are constantly popping into existence everywhere,
probably in little Planck Volume units that are as small compared to an atom as an atom
is to a solar system, is certainly a strange thing. You probably have tons of these little new
bits of space popping up in you all the time, but it doesn’t matter because local forces
easily keep everything glued together, but over intergalactic distances the forced binding
everything together, which is basically just gravity at that point, already the weakest
and freakishly weakest force in the Universe, just can’t keep everything bound together
with all the huge amounts of new space popping out of nowhere. Over long enough distances this can result
in truly immense apparent speeds between galaxies, and light can’t cover the gap because new
space is popping up between these places that it has to travel through too and at such a
fast rate it will never reach us. So effectively every galaxy is an FTL spaceship
from the perspective of some other galaxies, actually most of them, though of course they
can’t see us or us them, and this has some effects, specifically the Unruh Effect, in
terms of Event Horizons, which we’ll get to momentarily. Warp Drives fundamentally operate on this
same principle, there’s some variations in styles but generally they work by either
crunching up and expanding space time, or by outright deleting chunks of it and adding
them in behind. This gets around the FTL problem the same
way the cosmic expansion we just discussed does too, and its why Dark Energy gets a lot
of looks, since that’s the force currently assumed to drive it. Of course we really don’t know how much
energy it takes to make a new piece of space since theory and evidence on vacuum energy
slightly mismatch, uh, well slight is probable an understatement. The difference is like 100 orders of magnitude,
which is sort of like the difference between a grain of sand and a galaxy, except bigger,
and this has been dubbed the Vacuum Catastrophe as well as the worst Theoretical Prediction
in the history of Physics. Still, at a strictly theoretical level it
ought to be possible to artificially create or delete chunks of space, the former happens
constantly after all, and we can certainly contract space, gravity does that all the
time, I mean you’re doing it just sitting there. And if negative mass or energy exists we can
expand it too, and while we don’t have a shred of evidence indicating negative mass
does exist we do have a bit better indications that negative energy does. So the ability to contract and expand space,
and thus do a warp bubble, does seem like it might really be on the table. If so, you ought to be able to do a warp drive,
and while Alcubierre and other earlier versions of this tended to require an amount of negative
mass on par with large planets or even more, newer calculations have indicated we might
be able to do it with even just a thousand or so pounds of it. But on this channel we’ve never flinched
away from building truly huge objects, often ones much larger than a planet, so even those
higher-end values shouldn’t be considered prohibitive. So if we’ve got our warp bubble all is well,
and there’s good reason to think it might be possible. Except for two problems. As I said Alcubierre’s 1994 paper inspired
a lot of other deeper looks into the idea, and just as that paper is linked below in
the video description, so is one by Finazi from 2009. He noted one problem, having to deal with
the bubble destabilizing when he looked at the Renormalized Stress Energy Tensor, but
we can’t really discuss anything involving the word Tensor on this channel without devoting
many hours to going through complex math. He also pointed out another problem that will
exist for warp drives, and that’s the problem that once you hit FTL speeds you will end
up with a white hole in front of you, a topic we’ll discuss another time and has plenty
of its own problems, and a black hole behind you, and both will just follow along with
you. Now that’s a topic we did discuss a lot
before, in the video on Micro Black Holes, Virtual Particles, and Hawking Radiation. And here we get a similar sort of effect. Black hole event horizons are caused by gravity,
but as has been mentioned gravity and acceleration act a lot alike so it’s probably no surprise
that acceleration can also cause an event horizon. And an event horizon is just any place that
you can’t see events on the other side of. For a black hole that’s where nothing occurring
on the other side can get light out to show you what’s going on. This same thing can occur with accelerating
objects. Normally no matter how fast you’re going
light will catch up to you, but if you’re constantly accelerating it’s a bit of a
different story, and more to the point, if you are traveling faster than the speed of
light when you look out the back of your ship you won’t see stars flying past, you’ll
see nothing, black empty space because the light they’re emitting can’t catch up
to you anymore. Even before you get to the speed of light
those particles will red-shift down into near invisibility as you get faster and faster. They do the reverse in front of you, blue-shifting
so much they also become invisible as they blue-shift to Ultraviolet, then X-ray, the
gamma, which is a bit of problem itself. But behind you there’s an event horizon,
you can’t see or hear anything behind your ship. Okay, so what? That’s inconvenient but not really a problem
right? Well, no, this is where we get to the Unruh
Effect comes in. The concept is that a vacuum depends on the
observer, like so many other things do. Now this requires a quick caveat, in physics
a vacuum isn’t quite the same as empty space, something that doesn’t really exist anyway,
but rather is a place where everything is in its lowest possible energy states, you
can think of that as meaning very cold. If you’re accelerating and you look at it,
it won’t seem quite as cold, for one-gee of acceleration, the same as normal Earth
gravity, this isn’t much warmer, about a billion of a trillionth of a degree. But if you’re accelerating fast enough it
can be a lot hotter, and hot things give off blackbody radiation, and again a vacuum in
physics isn’t empty, in fact it’s full of lot of stuff like virtual particles. Now acceleration and gravity are basically
the same thing so it shouldn’t surprise you that this effect looks basically identical
to the Hawking Radiation we looked at before, and in fact it’s often just called Hawking-Unruh
Radiation and you can use the Unruh effect to look at the event horizon of a black hole
and get the same results. Well the slip-side applies too, and that event
Horizon trailing your ship doesn’t just look like a black hole, it basically really
is one complete with Hawking Radiation. And a whole lot of it too once you hit FTL
speeds. Finazi calculated an effective temperature
for this event horizon pretty close to Planck Temperature, and while those of you familiar
with Planck Distance and Planck Time are used to thinking of Planck Units as ridiculously
small, Planck Temperature is the exact opposite and usually considered the opposite of Absolute
Zero, or Absolute Cold, as being Absolute Hot, the hottest something can be before physical
laws simply breakdown. So this black hole trailing our ship is burning
at temperatures that make the core of the largest hottest stars look winter in Antartica. So you’d be burnt to a crisp. I’d like to spend more time on Unruh Radiation,
but its not something everyone agrees actually exists and it’s also hard to give a proper
visualization for where the energy being emitted is coming from. I suppose, for those of you who saw the Hawking
Radiation video and remember my explanation in terms of Virtual Particles, it would be
probably be decently accurate to think of it in those terms. There we said that right over the surface
of an event horizon, same as everywhere else in the Universe, virtual particles are constantly
popping up in pairs and usually annihilating with each other almost instantly, but every
so often one ends up on the other side of an event horizon before this can happen and
the other sails off as a now real particle with real radiation. On small black holes in particular this is
very powerful because right over that event horizon the change in gravitational force
from even a tiny extra distance can be monstrous, and rip the virtual particle pair apart as
the one slightly closer gets yanked away. Here you could think of it in similar terms,
since gravity and acceleration are, again, pretty much the same thing. If that event horizon rolling behind you is
separating virtual particle pairs before they can reunite and mutually annihilate then the
ones on your side of that horizon are acting just like the escaping Hawking Radiation of
Black Hole. Either way, while the Unruh effect is debated,
and we’ve never actually seen Hawking Radiation either, the same physical models that are
letting the warp drive work strongly indicate the interior of that warp bubble is getting
blasted with huge amounts of Hawking Radiation or its equivalent. Now if we can get around that or its wrong,
if we can keep the fields stable, and if negative mass exists, there’s still two more problems
with the concept. First is that you’re probably collecting
an awful lot of energy at the front of the ship, and some feel that when the ship decelerates
that energy is going to slam forward and hit your destination with planet destroying forces… I don’t consider that a problem really,
don’t aim your ship exactly at your final destination, and as we’ve discussed in the
past even a regular old sub-light ship traveling at relativistic speeds can just jettison some
of its garbage before slowing down and expect tit to whack into the planet ahead like a
bunch of nuclear bombs. Plus it makes a handy weapon, and an FTL one,
so while it’s a concern it has nothing to do with the functionality of the concept and
just about every technology brings in new concerns for destructive use. The second and last one for today is only
applicable to certain versions of the warp drive but brings up an interesting point in
terms of the Fermi Paradox, which we spend a lot of time discussing on this channel. There’s a concern where you need to pre-place
matter along the path to get this warp effect to work at all, sort of like a railroad track. Now that’s fine in and of itself, it’s
great for the Fermi Paradox since as I discussed in the Dyson dilemma and Compendium the Fermi
Paradox is a whole lot worse when you bring FTL into things but if you have to make the
first trip at slower than light speed to allow you to get there and back in the future at
FTL speeds it isn’t really a problem for the Fermi Paradox. Aliens can’t just pop across intergalactic
distances without building the track first. But it does limit the utility of the Warp
Drive since it means you have to get to new destinations the first time the hard way,
and we’ll see this again when discussing wormholes in the case where you have to make
the opening and the exit next to each other and then tow them to their final destinations
at sub-light speeds. But that’s still makes it very useful. The problem is that in some analyses of this,
the only way to properly pre-place these masses actually requires you have a working FTL drive
to begin with, and if that turns out to be true you have a Catch-22, you can’t make
a FTL highway without already having a FTL highway there. Of course the idea of using regular old mass,
or preferably dark matter if you can find a way to manipulate it, in big long conduits
that would contract space around them and let you send things along them seemingly faster
as a sort of pseudo-FTL highway or Telegraph, is nothing new either and something we’ll
look at more in the future too, and they also have the issue that you have to go there the
long way the first time, but without any Catch-22. So if we can come up with negative mass, if
we don’t need whole planets worth of it, if it turns out we can keep the field stable
and either there is no Hawking-Unruh Radiation burning you, and if you can build one without
need to pre-position mass or at least without needing a FTL ship to preposition it, then
we finally do have a working faster than light ship. And the good news is NASA is doing some basic
proof of concept of the idea, articles you’ve seen on this tend to over-hype that a lot
and view it way too optimistically but it is being done and promises some interesting
new data regardless. So that’s the Warp Drive, so far our best
candidate for FTL. Next time we’ll look at another, more familiar
FTL system when we look at wormholes, which we’ll see also need negative mass to work
and will bring us back to look at the time travel problems we saw last time. That video will be a little while as we take
an initial look at Transhumanism technologies and concepts next week and then a trip back
to the Fermi Paradox to look at the Simulation Hypothesis, the notion that we might be living
inside a giant computer simulation. After that we have a number of subjects in
the queue that might come before or after the wormhole video but it will probably be
at least three to six weeks before we get there. If you want alerts when those videos come
out, make sure to subscribe to the channel, and if you enjoyed the video, hit the like
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and feel free to try out some of these other video playlists. Thanks for watching, and have a great day!
