according to special relativity nothing travel faster than speed of light...what is the fate of special relativity if we really build a space ship that travels greater than or equal to the speed of light?
a) What theory would you use to design the ship?
b) Consider the Alcubierre "warp drive".
@ George Dishman.
My dear George Dishman, what theory we are using to design motor bike, ship, aeroplane, etc...?
I asked a question on reaching the speed of light not on how you prepared space ship to reach that speed
There is nothing in Special relativity to forbid faster than light propagation. It only shows that an inertial system at the speed of light is singular and above the speed of light it is described in complex numbers to which there is no interpretation.
Any theoretical signal faster than light can be transformed from one inertial system to another quite easily, however the interpretation of transformed faster than light equation of motion can be quite bizarre depending on one's understanding of relative simultaneity.
@ Andrew Wutke ...
my dear Andrew Wutke what about energy mass equivalence?
Dear @ s h s hussainsha
I am not claiming particle can travel faster than light. I am also not convinced that tachyons are plausible entities, but Lorentz Transformations validly handle equations of motion with arbitrary velocity. Every faster than light signal in one frame appears to travel backwards or forwards in time in others, which does not suprise me because this is only showing the conventional nature of Einstein's synchronisation and it is nothing stranger than crossing the boundary between two time zones on Earth in one or the opposite directions.
I have a firm belief however, that some forms of instantaneous or arbitrary fast communication are theoretically possible. One of the candidates may be synchroneous states in entangled pairs of particles but I cannot judge this right now.
+++ to what Thierry said.
Special relativity derives a geometry for empty space that conforms to the principle of relativity (for imaginary observers watching imaginary objects), and then assumes that precisely the same geometry holds in exactly the same way once we start to populate the region with actual matter.
The trouble is, in real life, it doesn't. Real matter interacts with light and distorts the light-grid. The presence of stationary matter distorts lightspeeds (otherwise reading glasses wouldn't work, and human eyeballs wouldn't focus), and if that matter also moves, we get dragging effects analogous to gravitomagnetic effects (predicted by Fresnel, and confirmed experimentally by Fizeau).
Einstein's two classical theories of relativity either ignore these effects ("particulate matter effects lie outside SR's remit"), or retrofit them by hand, as "common-sense" additions that do not however, mesh well with the theories' core assumptions.
General relativity does provide us with tools for modelling the effects of moving bodies with associated curvatures ("gravitomagnetic effects"), but the effect of applying those arguments to particulate matter is that we find ourselves invalidating special relativity's logic, and becuase the 1916 general theory assumed that SR was correct description of inertial physics, also invalidating Einstein's general theory.
So if we try to apply the principle of relativity consistently to particulate matter, we end up trashing both major C20th theories of relativity and starting over.
This means that there are currently no reliable theoretical tools to answer your question of whether we can ever build a craft able to travel faster than background lightspeed. SR geometry is invalidated as soon as you start talking about hypothetical warpdrives, and GR logic is currently an inconsistent mess because of the desire to incorporate special relativity as a limiting case (which kinda violates the principle of equivalence, making the overall theory logically inconsistent).
Oh, a fun thought-experiment:
- Allow yourself to slowly drift into the field of influence of a black hole, be captured by the gravitational field, and end up hurtling into the horizon. By the time you reach the horizon, you should arguably be travelling at the background speed of light (but still slower than the velocity of light in your immediate vicinity, that's falling in with you).
- Now, instead of drifting into the hole, fire up your rocket engines and power-dive into the hole. Your velocity as you pass through the horizon should now be greater than before, in other words, you are now meeting your doom at a velocity faster than the distant background speed of light. But you're still not moving faster than the velocity of light around you, that is moving in the same direction you're moving.
So it seems to be perfectly legal to travel at more than background lightspeed, as long as you're not moving faster than local light-velocity (for light aimed in the same direction you're moving in).
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