Alan asked:

Is the speed of darkness faster than the speed of light?

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You might think darkness couldn't be any faster than light, since darkness can only arrive as quickly
as light departs.

A rather different question to yours, and one which you might need to ask an indulgent physicist
rather than a philosopher, is: Can the speed of a shadowbe faster than the speed of light? It strikes
me that the answer to this question might be different to the answer to the former question, and some
simple minded ideas about what light is would suggest that they are different questions: in the former
question one is asking about the speed of propagation of the particles or waves of light, and in the
second question one is asking about the speed of propagation of patternsin the particles or waves of
light.

With a layman's eye, it is at least temptingto think that the phenomena where the shadow of a car
cast by the street lamp appears to approach and overtake the car should also apply at higher speeds,
across vaster distances. Supposing a dark object passed between ourselves and the sun at a very
high speed, perhaps a speed approaching the speed of light, at what speed might it's shadow move
across the face of the earth? Faster than the speed of light? I do not know. It strikes me as the sort of
question one would ask if one wanted to test a physics student. Might we seem to get no shadow at
all? Might the speeding object seem elongated to us, casting a slow moving shadow? Might the
speeding object have peculiar effects on gravity, bending the light and the image of the sun? I do not
know. If you find out, tell me. It's the sort of question that Feynman used to address himself to.

Now, to get back to the kind of light Philosophers hope to deal in, there appears to be some further
evidence to complicate the picture. For it has been observed:

"A lie gets halfway around the world before truth can even get its boots on." — Winston Churchill

David Robjant

The Speed of darkness? Does darkness have a speed? What is darkness? It is simply the absence of
light. Now what happens when I stop seeing darkness and see light? At the beginning there are no
light waves incident on my retina, thus I see nothing (see darkness) and then, light waves, moving
with light velocity (3*10^8 m/s) reach my retina so I see light. Now, when light ceases falling on my
retina, I will see nothing, i.e. see darkness. After all, this is a physical question, not a philosophical
one.

Arthur Brown

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