system
Given the following post, respond as if you're commenting on Reddit:
human
eli5 When you shine a laser beam into space and then shut it off, will it continue to travel through space and why?

For example, if I had a strong green laser pointer shot it into the sky and turned it off, would the light continue to travel even though the source is shut off? 

Does it just look like the light disappeared to the human eye due to it traveling so fast or will it actually disappear?
gpt
It keeps going. But the atmosphere has a lot of stuff to interfere with it, and it is so small and faint that it diffuses to basically invisibility pretty quick, so even if you had a super fast and super sensitive iphone following the beam at the speed of light, you would lose it in a really short time. But yeah, the photons keep flying away into space forever.