What, besides light and spaceships in Star Trek, can travel at the speed of light?

Question

btaylor · Answer

@ParthKohli @KingGeorge is there anything?

ghazi · Answer

it's electric current in wire that approximately travels at the speed of light

kinggeorge · Answer

First, any particle that has no mass. The particles with no mass are photons and gluons (and possibly gravitons, although these are not confirmed to exist).

 Also, gravity travels at the speed of light.

btaylor · Answer

so, would it be possible to use photons and gluons to propel a vehicle at the speed of light (at least in theory)?

ghazi · Answer

how could you use these particle to propel vehicle ....these are mass less and if vehicle travels at the speed of light it's mass would be infinite...so theoretically it seems possible up to a certain extent but beyond that it's not possible

kinggeorge · Answer

@BTaylor No, because the vehicle has mass. If it has any sort of mass, then it can't travel at the speed of light. Period. End of story.

@ghazi It is possible to propel vehicles using only light. It has a very slow acceleration, but in theory one could go quite fast eventually.

btaylor · Answer

thanks...I guess that ruins that invention idea... :(

ghazi · Answer

@KingGeorge  here vehicle has got mass so how could you propel it using light?

btaylor · Answer

@KingGeorge how does gravity travel at the speed of light? gravity is a force...

kinggeorge · Answer

I can't explain it very well, so I'll let wikipedia do the explaining. http://en.wikipedia.org/wiki/Solar_sail Long story short, you need a big, reflective mirror made out of lightweight materials, and lots of patience.

dominusscholae · Answer

Actually you CAN PROPEL something using light. Light actually exerts pressure since it has momentum, even though a photon is massless. The thing is, anything with mass cannot go at the speed of light due to theory of relativity. But if one were to travel the stars, one could use photons to propel themselves using a "solar sail" that soaks up light.

dominusscholae · Answer

^oops sorry. Didn't see the post above me.

unklerhaukus · Answer

how does gravity travel at the speed of light?  Gravitons

anonymous · Answer

Gravity has wave/particle duality. Gravity waves travel at the speed of light. There are many ongoing searches to discover gravity waves.

ghazi · Answer

has gravity wave been detected yet?

dominusscholae · Answer

^It has been implied via model simulation I believe.

anonymous · Answer

If your ship entered a black hole, the acceleration of gravity could permit you to approach the speed of light, but even then, matter can only approach the limit C, it can never achieve the speed of light as matter.

btaylor · Answer

@ghazi If electric current flows at the speed of light, and current is the flow of electrons, don't electrons have mass? Or is it that the current goes against the flow of electrons? What particles make up current?

dominusscholae · Answer

Electric current doesn't fly at the speed of light for number of reasons. One is relativity, second is random collisions between the conductive material and the electrons.

kinggeorge · Answer

^^ What he said. Electric current in a wire does not actually travel at the speed of light. It may be close, but it's not quite that fast.

ghazi · Answer

see it's electric field in a wire that drifts electron from a higher potential to a lower potential (electric current) approximately at the speed of light (as soon as potential difference is applied)

dominusscholae · Answer

^If that was in a vacuum possibly. In normal conductive materials, though, it's far less.