[thedoc (OP)]

Ronald Maxwell asked the Naked Scientists:































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































   I have read that light travelling through a Bose-Einstein condensate may be slowed down to about 38mph.  This is a big drop from 186000 miles per second. How does it happen?































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































What do you think?

[evan_au]

This effect of slowing down light works over a relatively narrow part of the spectrum.
See: https://en.wikipedia.org/wiki/Slow_light

[yor_on]

Depends on definitions.
I use 'c', doing so 'light' has no reference frame in where you can be 'at rest' with it.
So no, you can't 'slow light'.

[AndroidNeox]

Light is slowed when it passes through matter. The optical density gives the degree of slowing.

Also, light takes longer to traverse a gravity well than to go between the same points with no intervening gravity well. This "Shapiro Delay" is due to the path length increase due to spacetime dilation. Locally, light will move at c but viewed from outside the gravity well, it would appear to slow down.

[Georgia]

I heard it described nicely one - light slows down when going through some substances, but it's like a person walking through a busy room. The person walks at exactly the same speed, but goes from person to person, meaning it takes him longer to get through the room than if there was no-one there. Similarly, light doesn't get slower, but takes longer to get through some things.

[jerrygg38]

I heard it described nicely one - light slows down when going through some substances, but it's like a person walking through a busy room. The person walks at exactly the same speed, but goes from person to person, meaning it takes him longer to get through the room than if there was no-one there. Similarly, light doesn't get slower, but takes longer to get through some things.

  It seems to me that there are two parts to the speed of the light wave. There is the period of time where the wave jumps from point to point, this I call the jump speed. there is also a tiny delay time from one jump to the next.  the jump speed will be very slightly higher than the measured speed of light C. This is the ideal light speed in pure vacuum in a near zero gravitational field. Once we add things in space this will cause a greater delay time. Thus the speed of light C that we measure upon this earth has a tiny delay time. In a black hole the delay time will increase greatly.
   It seems to me that the speed of light in a black hole will reach zero as the light will stop jumping.

[yor_on]

Or, there is a probability

[AndroidNeox]

  It seems to me that there are two parts to the speed of the light wave. There is the period of time where the wave jumps from point to point, this I call the jump speed. there is also a tiny delay time from one jump to the next.

What? "Jump speed"?