# Einsteins light beam Lets go for a ride again

1. Feb 14, 2010

### tiger51

Einsteins light beam....Lets go for a ride...again

I am not directly in the physics field, but I use physics at work and have always been enamored by it. If I did not post this question in the right place forgive me.

So here is my ponder if you will. I read Walter Isaacson's book when it came out a few years ago, and kept thinking and imaging riding that beam of light that Einstein rode many times in his head. Than I thought about the power of light. If you have a flat plane (imagine our world is indeed flat) and turned on a light and you start backing up while always looking at the light. Soon the light to you the observer has faded with the distance. Does this mean the beam of light has stopped? if riding at the tip of the beam does that mean that you would stop to? Then increase that size to the sun and start backing about from the sun at some point the light can not go any further I imagine, so where is the absolute light? I think about this because we use light to calculate time in light years. right?

2. Feb 14, 2010

### Naty1

Re: Einsteins light beam....Lets go for a ride...again

no, it just means the beam is spreading out with distance and hence becoming attenuated...weaker...the beam dims as the surface area of a square increases from the source....

like a hose you spray...the water flow weakens with distance from the nozzle..but don't take that analogy to far....

3. Feb 14, 2010

### Naty1

Re: Einsteins light beam....Lets go for a ride...again

Not really true, gravity and electromagnetic waves (light) extend to infinity but of course approach zero strength at infinite distance. On the other hand, if you get far enough away from a light source, the universe may be expanding fast enough that the light will never reach your location....yet tomorrow there will be some cosmic background radiation visible to us that was not visible yeterday....

4. Feb 15, 2010

### Mentz114

Re: Einsteins light beam....Lets go for a ride...again

No, a light-year is the distance travelled by light in one year.