The Speed of Light and The Sonic Boom.

Excuse my stupidity because I feel the answer to this will be easy.

Me and my friend were pondering this over a bottle of wine the other day:

If light goes soooo much faster than sound, why do we not hear a sonic boom everytime we turn on a light. And if light is going so quick, why do we not feel an impact?

The title should read “Speed”, not “Speef”
Me am smart.
I e-mailed faithful manny, hopefully he will fix it soon.

[note: Gotcha covered. -manhattan]

[Edited by manhattan on 03-01-2001 at 09:02 AM]

There is no boom because the light doesn’t have to move the air out of its way as it travels.

You don’t feel an impact because the light has no mass.

Interestingly, though, there is an analogous phenomenon when a body travels faster than light in a given medium. (Note: Relativity only forbids FTL travel in a vacuum, not in a medium). The body gives off a strange blue light called “Cerenkov radiation” - do a search on Google for it.

If you were sensitive enough you actually would feel an impact. Light has no mass but it does have momentum.

A photon’s momentum equals Plancks constant times the frequency divided by the speed of light (p=hv/c)or plancks constant divided by wavelength (h/lambda).

You could theoretically power a spaceship via sails that capture momentum from sunlight. In fact I think that some time this year NASA is going to run an experiment using solar sail technology.