Light Speed: Is Life Truly "Indefinable"?

[Bluesand2]

If light from long dead stars is only just reaching us, does this mean that if I shine a Lazer pointer into space, the light beam will continue long after I have turned of the power .. If this is true would a light beam continue to travel indefinably ?

 

[phyzguy]

If light from long dead stars is only just reaching us, does this mean that if I shine a Lazer pointer into space, the light beam will continue long after I have turned of the power .. If this is true would a light beam continue to travel indefinably ?

Yes, the light pulse from your laser pointer will continue to travel out into space indefinitely, unless it hits something ( a star, a planet, gets absorbed by dust, etc.)

 

[Amir Livne]

Actually, the light will dim slightly as it goes. This happens for 2 major reasons.

For one, the outer space isn't completely empty. It is actually a very thin gas, but it still blocks some of the light. The second reason is that a laser is not perfectly collimated, instead the light spreads (usually a few cm/km for laser pointers), and if someone looks at it from very far away it will be very dim.

 

[James Leighe]

also the photons that make up the laser beam will become redshifted with the expansion of space itself, causing them to become dimmer over a long period of time

 

[Paradox?]

that brings me to a question, is the speed of light, or indeed anything, affected by the expansion of the universe?

 

[James Leighe]

galaxies are getting further apart
it's not really fast enough to be thought of as a force however

but if the universe were to be expanding incredibly fast gravity wouldn't be able to hold the galaxies together for example