Harriet Young, of Rangi Ruru School, asks :-
If nothing can travel faster than the speed of light, and supposedly strange things happen if anything exceeds the speed of light, how can light travel faster than the speed of light if, for example, you throw a torch that was switched on?
Geoffrey Stedman, a physicist at the University of Canterbury, responded.
Whenever we make a measurement of the speed of light in a vacuum we always get the same result, ie about three hundred million metres per second or c for short, no matter what speed the torch is travelling at. Relativity determines that no ordinary massive object can be accelerated to travel faster than light travels in a vacuum.
Like all things in relativity it takes several lectures to explain all things like this properly and it is very easy to make up difficult paradoxes.
Actually it's not just above c that "funny things appear to happen". Even at speeds slower than c things like time dilation can become very important, usually when light or electromagnetic waves are involved. For example, in position location using global positioning satellites (GPS), ship navigation, magnetism etc.
When it comes to switch the power on we cannot beat the electrons to the filament because the signal to move goes along the wire at approximately the speed of light. The exact details depend on the shape of the wire, its resistance and capacitance, and the material surrounding it, eg plastic insulation.
As for the waved torch, we have to be careful to distinguish different types of signal speeds. Some can be greater than c. For example, consider the light from a rotating torch or light-house. If we are far enough away and rotate the beam fast enough the far end of the beam can be moving around at a speed faster than c.
For all that in fact, the torch beam, the wire to a light-bulb, and the power pylon wires from Benmore all carry mass at speed c, because mass and energy are related according to E = mc2.