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Will This Go Faster Than Light?

Will This Go Faster Than Light?

The speed of light is meant to be the ultimate
speed limit in the universe. According to Einstein’s special theory of relativity,
nothing should move through space faster than light. But that doesn’t stop people from
trying. Every day I get a lot of messages proposing ways to go faster than the speed
of light. There is the classic method where you shine
a laser at the moon. If you can flick that beam across the moon’s surface in less than
a hundredth of a second, which is not hard to do, then that laser spot will actually
move across the surface of the moon faster than the speed of light. Imagine what that
would look like if you were standing on the moon. If you were quick enough to perceive
it, you would see this laser spot move faster than the light coming out of your own laser.
How is that even possible? Well, in truth, nothing here is really travelling
faster than the speed of light. The individual particles of light, the photons coming out
of my laser are still traveling to the moon at the speed of light. It is just that they
are landing side by side in such quick succession that they form a spot which moves faster than
the speed of light. But really it is an illusion, nothing is actually going faster than the
speed of light. So you couldn’t transmit any information this way.
Dan asked: What if instead of a laser we used a long rigid stick instead? Now surely if
you flick your wrist, the tip of this stick must move across the surface of the moon,
faster than the speed of light. Well, unfortunately this won’t work either.
As we learned in the slinky drop experiment, the fastest a force can propagate through
an object is the speed of sound, that is because each atom needs to bump into the one next
to it to transmit that force. And this is a lossy process. So you would be lucky if
you any of the energy you have put in at the start actually made it to the tip. You would
be lucky if the tip moved at all. Now this is a really sophisticated idea. Gerard
writes: A very special space age engine would need to be designed that is capable of doing
10,000 plus rpm in outer space with very high torque. Consult Elon Musk for this. As the
engine is spinning it slowly deploys two very long tethers made from carbon nanotubes on
opposing sides. Eventually each carbon nanotube tether reaches an amazing length of 285 kilometers.
At this point, the end of the tether will be traveling at the speed of light. Can you
point out some reasons as to why it would not work?
Yes, Gerard, yes, I can. First, any object going in a circle requires
a force pulling it in towards the middle of that circle. That is called centripetal force.
And you can feel it when you whirl a ball above your head. Now that force is dependent
on the speed of the object squared. So if that gets to be too great the tether breaks.
Now if you had a single gram rotating at 99 percent of the speed of light, the amount
of force required to pull it towards the center would be 300 meganewtons. That is the weight
of 6000 fully African elephants. But, you are right, carbon nanotubes are tremendously
strong. If you had a fiber just eight centimeters wide, you could support all of that force. But now he problem is if you have less than
a centimeter of that fiber, it adds another gram to the tip of you tether. And so now
you need a thicker fiber in order to support that additional force. And that would happen
all the way to the base, so the fiber would need to get thicker and thicker and thicker
all the way back to the motor. And if you do the calculation you find that basically
30 meters from the tip the fiber already has to be as wide as the observable universe in
order to support all of that force. It is nuts.
But it gets worse. As an object moves faster its inertia actually increases. That means
it requires more force to accelerate it. In fact, that one gram mass going 99 percent
the speed of light would require seven times the amount of force we calculated before.
And so the tether would have to be even thicker. But things get even more problematic if you
think about speeding up the tip of the tether that extra one percent to the speed of light.
I mean, since the inertia keeps getting greater and greater, it requires more and more force
to accelerate it. And, in fact, to speed it up that extra little bit to go the speed of
light would require an infinite amount of energy.
Ok, well putting the infinite energy aside, let’s say we could create an incredible
motor and we could find a material much stronger and lighter than carbon nanotube. Is it at
least in principle possible that the tip could go faster than light? No. There is one final
problem which is insurmountable which is that a tether, like anything, is held together
by the electromagnetic interaction. That is, the attractions between all the tiny little
charges that makeup the material. Now the problem is, electromagnetism is a force carried
by photons. I mean, the way that something knows that another thing is there to attract
it, is by the exchange of photons, these force carrying particles. And the problem is the
photons themselves move at the speed of light. So even if you could create this incredible
apparatus with ridiculously strong materials and spin it up with infinite energy, it still
wouldn’t go the speed of light, because the force carrying particles that hold the
whole thing together only go the speed of light. The speed of light really is the ultimate
speed limit in the universe. Hey, did you see that I made a video about
the problem with Facebook over on my second channel? It really seems to have struck a
cord, so you should check it out if you haven’t already.
Now I want to thank Audible for supporting this episode of Veritasium. They are a leading
provider or audio books with over 150,000 titles in all areas of literature from fiction
to non fiction and periodicals. Now this week I wanted to recommend the book by Bill Bryson
called A Brief History of Nearly Everything. When this book first came out I really wanted
to dislike it, because I felt like it was just piggy backing on Stephen Hawking’s
Brief History of Time, but what Bill Bryson has done is something truly different and
extraordinary. I really think it is a great summary and a great sort of investigation
of what happens in science. It is a brilliant thing to listen to. Also, if you go to,
you can download this book for free, or another of your choosing. Now they actually have this
book in an abridged form read by Bill Bryson himself. It is really interesting to hear
the author’s voice. To me he sounds a little bit like C. G. P. Gray, but with a hint of
a British accent. So you should really check that out. Just go to All right. Thanks for watching and thanks
to Audible for supporting me. But there are some things which are going
faster than the speed of light, relative to us. There are some distant galaxies which
are receding at a velocity than the light, so we will never be able to see the light
that they emit. But this doesn’t violate Einstein’s theory
of relativity, because they are not moving through space faster than light, it is just
that the space between us and them is expanding so quickly that their effective velocity is
greater than the speed of light.

Reader Comments

  1. What of we increase speed relatively….like in a circular track , a train is moving with max speed, inside that something else is moving with max speed and again in that something os moving with its max speed so from a static reference one can notice that the actual final thing is moving with a very high velocity……
    I know this has to be in vacuum so there is no air resistance…..
    Mind well…..this could be absurd…as I am in class 11….and just have started loving and knowing physics…..😅😂

  2. But what if there was a way to expand and shrink space around you. to form a bubble of displaced space and some how move that bubble and the things in the bubble. I don't know how though.

  3. oops – Tachyons?

  4. Isn’t a black hole faster than the speed of light because light cannot escape from a black hole. So a black hole is the fastest object in the universe because if this

  5. 1400 years from now: "lol this idiots thaught that light was the ultimate speed limit" *wooshes away at the speed of 6.23 galaxies per universal standart time unit

  6. I've got the blueprints to move faster than the speed of light right here in my lap bro I got to go and get my patent tomorrow I'm bypassing the patents office I'm getting it notarized and mailing it to myself overnight delivery from one post office to the other secured my patent I'll give you a little peek at it though

  7. What is we used warp drive
    They bend the space time in front and expand it in the back therefore making the space the one that make the ship moves

  8. I was surprised that you did not mention the preservation of momentum. The spinning thingymigic with extending nanotube arms is just a fancy equivalent of the old "spinning ice skater slowing down by spreading her arms" example.

    Adding energy as the arms are extending to keep the angular speed constant is not a solution either. Since you need to keep adding energy anyway, you can start from a random point, for example zero. So we are back at the beginning, swinging a long stick and hoping the end moves faster than light.

  9. So our innate ability to create and destroy worlds within that wondrous enigma known as our imagination must also obey this law? I am glad Gene Roddenberry was not restricted by such oppressive, short-sighted concepts. ie isn't the speed of thought > speed of light? Have fun hashing that out while I return to bingeing Star Trek episodes. =)

  10. Well I was wondering because what about the conservation of momentum. I guess this gets back to the idea of would headlights work if you were moving at the speed of light? If you were moving at half the speed of light and proceeded to extend something ahead of you at half the speed of light while maintaining enough acceleration to counteract the "recoil" would this be possible?

  11. Great explanation and beautiful silver nose hair or whatever that thing is in your right nostril. Sorry, Derek.

  12. I'm surprised to hear someone say centripetal force. We were told repeatedly in Uni that it is NOT a force but centripetal acceleration.

  13. What happens if you get a long pole that gets put in a mechanic that makes a semi circle with the stick in 0.001 of a second across the moon surface then the end has to move at the speed of light

  14. Correction: The speed of light is a limit for signal speed in observable universe. If there is something travelling faster than light, we will not… observe it.

  15. Nothing can go faster than light because to see something you need light and its speed is definite so even if you move something faster than the speed of light it would be seen as moving as same as the speed of light

  16. Sorry got really distracted by the little white thing hanging out of your nose at 3:10, grey hair? dunno. Good video

  17. I think it's possible to move faster than speed of light but you cant get informations sooner than speed of light provides

  18. What if we had blue light travel on a beam of red light? We need a particle that jumps from red light photon to red light photon.

  19. Imagine that you are in a space station traveling at 5000m/s towards the moon. Then you take your laser torch and you shined it forwards. Wouldn't the speed of that laser beam be "Speed of light" + 5000m/s?

  20. There are lasers that move particles in a particle accelerator. Maybe we could use a laser to move a ship?

  21. If you shot a flashlight out of a gun it would be going speed of light plus bullet miles per hour. Checkmate.

  22. 00:05 Not really. Einstein found his theory building upon that axiom (or fact not sure). Thus, that limit was known before his theory.

  23. Lol the more I learn about science the more nihilistic I feel, it’s very bitter sweet for me.

  24. I guess the simplest answer would be, anything that travels faster than light will have infinite mass and wouldn't exit, may be turn into a sucker like black holes. And sir just as always best video 😉

  25. What would happen if you were traveling 90mph less than the speed of light and a professional pitcher threw a 100mph pitch. Obviously relativistically it would look the same to the thrower, but how would it look to an outside viewer. What would happen in theory.

  26. So there is a theory that once something is moving it does not stop in space there For if there is still something like and engine / force pushing it won't it just keep going faster and faster

  27. Ok hear me out light can’t escape black holes so in theory if you fall in a black hole you go the speed of light plus the exerted force of the black hole?

  28. What would it look like if you switched on a light bulb, traveling nearly at the speed of light? Would it be asymmetrically shaped? 💡

    Greetings from Germany 🇩🇪

  29. In case of ridiculously strong material we face time dialation and spacetime curvature (by theory not busted so far) thus the interaction fotons explanation is littlebit too much off the truth. The speed difference between 2 fast moving particles is not high at all but the space axes compared to center of rotation are off.

  30. What if:
    1. Two spinning super black holes beside each other, spinning like gears, and a beam of light passes through the center of the edges of both in the direction of spin, wouldn't that Push the beam of light faster, even just a tiny fraction above c ?
    Similar to how a potato gun would work except light is the potato and the Push force is generated by 2 spinning super black holes.

    2, Two or more super blackholes collide and collapse upon each other and a beam of light is traveling towards the center of the collapse. Wouldn't that pull th beam of light even a bit faster than c ?

    3. A beam of light is travelling away from a big bang, and as the big bang expands, wouldn't that push the beam of light away faster than c, since the expanding universe is pushing it away?

  31. Ok so even though it's said that the speed of light is the fastest something can go which is not true it's just the fastest something can go and we just barely being able to see it or even notice it's a thing happening if something went faster and went away from us we would never see said object

  32. And another dummy refers to speed of light as a limit…. its not a limit its variable at wich body mass become infinite, not all thingss have mass, some move already faster then light…

  33. Fastest force can move trought the object at the speed of sound ? WtF??? You make few good videos, now somebody pays you to say nonsense or what ?

  34. I heard that the universe is expanding faster than the speed of light. And dark energy is the cause of the expansion of the universe. So can't we use dark energy to go faster than the speed of light. If thats the case. Then noice…..

  35. But now fr, what if I'm in space and I have a tube that is 2 light seconds long, and at the other side is a button, if i push the tube won't it push the button in 1 second? Even tho it's 2 light seconds away

  36. I think, it is enough right now just to go speed of light or near to it. So we can explore our neighbor stars.

  37. Hi, thanks for the awesome channel! Little question : Isn't Cherenkov radiations and Tachyons particles proof of faster than light particles ?

  38. The sad part of the story is…even if you have achieved the ultimate speed limit it would still take millions of years to reach neighbouring galaxies with that speed. 😢😢

  39. Nothing solid can go faster than light. That's why you have to cheat, but the cheat is not yet discovered, only theorized ( warp engines, folding of spaces, artificial wormholes, etc. )

  40. If you want to move an electron faster than light, just removed the quantum fields from space… electron vibrations in QF will cease… no wave will propogate… than it would be only particles moving instantaneously through empty space…

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