The Inverse Square Law states that the further you are from a light source (or light reflector in this case) you will see exponentially less of the light it produces or reflects.

A big, bright, light source like our Sun will be visible for a long, long way, but it the further the viewer is, the dimmer it'll be. As distance tends towards infinity, so light received will tend to 0.

So yeah, mathematically, light being detectable into infinity doesn't work. You can have vast distances depending on the amount of light involved (vastly smaller for the reflections from a human than for a light creating star), but you can't have eternity.


>>That was a pretty boring response. Do better. ;)
>
>You'd make a good physics teacher for young teenagers... I can
>totally see your wide-eyed enthusiasm getting young people
>hyped to the point where they want to go further with the
>subject.
>
>Your assumption is obviously only correct for photons that
>aren't absorbed by walls (i.e. anything you did inside a
>building isn't 'recorded'), clouds (anything you did on a
>cloudy day...), the Earth's atmosphere which bounces a fair
>bit back down, any other object between you and the observer
>which could absorb the photons or add so many more that your
>image is inseparable from the rest of the light from the Sun
>or another star along the way and, of course, Red Shift, which
>would mean that after a couple of billion light years your
>light wouldn't be visible light anymore, just infra-red and
>microwaves.
>
>Totally mind blowing until you actually consult your mind.