How far does the laser from a laser pointer go?

Question

If there were people on the moon for example, could they see my laser pointer if I somehow managed to aim it on the surface close to where they were standing?

And light is just made up of photons, so could one actually count the # of photons in a beam of light? I mean theoretically, are photons quantifiable?

Answer 1

People on the Moon would probably not be able to see your pointer. The beam from even the best lasers diverge somewhat so by the time light from a pointer reaches the distance of the Moon the intensity would be too low to be detected by eye. I'm sure there are some instruments that would be able to detect the light however.

I suppose you could count the # of photons in a beam of light. Some astronomical instruments detect only a very few photons from far away objects.  Since the energy of a photon is h x f where h is Plank's constant and f is the frequency and since lasers are nearly monochromatic--one frequency--we could measure the intensity of the laser and divide by the energy of each photon and 'calculate' the # of photons.

Answer 2

It depends on the power of the laser, but its possible.. Not sure what the light of a laser is measured in.. I think wavelength.. Anywho, the more wavelength the further it goes.. a wavelength of 532 nm can go as far as 9000ft in the dark.