If you shoot laser beam, how far can it travel (if there are no obstacles)?

Question: If you shoot laser beam, how far can it travel (if there are no obstacles)?
- Keywords:
  distance,
  laser,
  properties
Asked by Lottie to Chris, Josh, Rebecca, Rob, Susan on 18 Jun 2015. This question was also asked by 643hafc45.
- Chris Armstrong answered on 18 Jun 2015:
  
  Well with no obstacles at all (i.e perfect vacuum) it would travel forever completely non dispersively meaning the initial beam profile and the end beam profile would be the same.
  
  If you tried this in air the particles making up the air would scatter and disrupt the beam, meaning it wouldn’t make it nearly as far.

Question: If you shoot laser beam, how far can it travel (if there are no obstacles)?