If a LASER is fired from earth into space;will the pulse beam keep going or break down and "evaporate"?

Answer 1

i read the other answers - they are accurate but dont REALLY answer your question.

you want to know if the beam eventually "evaporates" or ends .

i will answer with two scenarios :

1. in a perfect theoretical vacuum ( not reality ) , the beam will continue forever and disperse variably ( depending on the source focus ) . It will NEVER evaporate.

2. in reality, the purest vacuum is that of intergalactic space, which is theorized to still have a density of one atom per cubic centimeter ( thats pretty good ). HOWEVER, these sparsely scattered atoms will stll interact with some the light particles ( photons ) and absorb them and release them in different directions. this action will lead to eventual degradation of the light beam over long distances to thereby evaporate this beam.

to answer your question, in reality, YES, the light beam will eventually dissappear ( depending on the "thin-ness" of the vacuum ).

hope it sheds some light ...

:)

Answer 2

The beam will continue indefinitely, having nothing to absorb it. It will, however, become more spread out over time (as all light sources do) - how quickly it does this will depend on how well the beam was focused to begin with -- the better the focus, the more slowly it will spread. In principle, a perfectly focused beam would not spread out at all, however it is physically impossible to create a perfectly focused laser beam (at the very least, the uncertainty principle would require some variance in the momentum of the photons, since they are all constrained to a known position when they pass through the aperture of the laser).

Answer 3

The EM waves of the laser will interact with free electrons in the atmosphere causing them to oscillate and collide with neutral atoms which will dissipate the energy in the beam. If the beam is intense enough these collisions will produce more electrons and you will get a cascade effect which will stop the beam by absorbing all of its energy. (ground to space weapons will not work) If the beam is not intense you will still get some absorption and scattering in the atmosphere.

Answer 4

The lasers emit what is called Gaussian Beam due to the fact how electromagntic field behaves in a laser cavity. due to small laser diameter, there will be diffraction of the EM wave passing the laser openning (aperture). This diffraction causes the EM waves to "leak" to the sides of the beam and eventually the beam will spread. The only way to have a perfectly collinear beam is to use infinite size aperture. The total angle of divergence is roughly = wavelenght/pi/w0. where w0 is aperture radius

Focusing can't compensate for diffraction

Answer 5

No matter where you fire it, the beam will become wider (our lasers aren't perfect).

If you fire it from the equator, it'll get absorbed or reflected by dust particles, atoms, and possibly other objects within the plane of our solar system.

If you fire it from one of the poles, some of it could keep going quite a ways -- might go indefinitely, might hit dust and stuff.

Answer 6

The beam will degrade progressively with distance.