# Dark v Light

1. Jan 18, 2008

### samsam

Let " d" equal the speed of dark
d = SQRT( e/m ) + 1

I am at a loss can anyone help me !

2. Jan 18, 2008

### samsam

Please someone help !! its for a challenge Samssin

3. Jan 18, 2008

### blochwave

There's really no such thing as the "speed of dark", light is actually something, and the speed of light is the speed of that something. Dark is the lack of light.

The speed of light can be given as c=1/sqrt(e*u) where e and u are the permitivity and permeability of a vacuum(I forget which is which)and that's the only thing that looks similar to your equation

4. Jan 18, 2008

### Shooting Star

We are more than at a loss, we are zonked or something to that effect.

(Let the speed of darkness be 'd'.)

Suppose a region was lit by a light source. Then you switch off the light. The envelope of darkness then would proceed at the speed of light, from the has-been light source. We may call this the speed of darkness, for which slightly contradicting but well meaning formulas had been given by you two.

Hence, c=d.

:tongue2:

5. Jan 20, 2008

### samsam

Hi me again, totally lost can anyone help ?

what's that experiment when they slowed down light?

6. Jan 20, 2008

### belliott4488

samsam, can you tell us where all this is coming from? Who is asking you about the "speed of dark"?

As for light being slowed down, light will always travel through any medium at a speed somewhat less than its speed in vacuum. That's not a specific experiment, it's just an outcome of the way light propagates through media.

Perhaps you're referring to the recent experiments where light was effectively brought to a stand-still and stored for a short while before being released again? That's due to something called Quantum Entanglement, and cannot be explained by simple expressions from Classical Electrodynamics, such as what you seemed to be offering in your original post (although I'm still not sure what that was ... )