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AngleWyrm_2 said:
The Doppler effect applies to both sound (pitch changes) and light (red shift). It does not change the speed, only the frequency. The speed of sound changes with the rigidness of the medium through which it travels, and the speed of light changes with the refraction index of the medium through which it travels.
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I'm not talking about Doppler shift (which is different than red shift, by the way). Sound travels at roughly 340m/s at sea level. If I'm moving at 100m/s away from the sound source, as far as I'm concerned the sound is moving at 240m/s. This is not the case with light, however. Light (or information, if you prefer) travels at 3x10^8m/s. If I'm moving away from the light source at 1x10^8m/s, then as far as I'm concerned, the light is
still moving at 3x10^8m/s.
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These two examples are not orthinagonal. In the sound example, the traveller is accepted as travelling at the speed of sound, but in the light example the traveller is accepted as travelling less than the speed of light. It could be just as valid to switch the roles, and say running towards the target at light speed means you never see the gun go off, but running at some speed arbitrarily close to the speed of sound you still hear the gun go off.
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Again the difference is that's possible to travel faster than sound, while it is
impossible to travel faster than light (information).
EDIT: Let me add that it would take infinite energy to accelerate a massive object (like a spaceship/person/electron) to light speed (3x10^8m/s).