[thedoc (OP)]

david gardner  asked the Naked Scientists:
   Does light still  exist after the source is extinguished
As in the old saying that light from a star that died fifty thousand years ago and the light is just reaching us, does the light still travel after the source is gone?
Dave

 
What do you think?

[evan_au]

Yes, light that was emitted when a star was shining can still propagate through space for thousands or millions of years after the star that emitted it has exploded and/or turned into a black hole. The light keeps traveling until it hits something and is absorbed.

You can imagine a star emitting light in the form of photons, like little bullets travelling through space. They will continue traveling until they run into something, even if the gun that fired them has been melted down into a puddle.