Why can't we see a beam coming from a laser gun?

Question

In science fiction films they use a laser beam coming from a laser gun as a special effect. Why would we not see a beam coming from the laser gun?

Answer 1

Unless the laser was fired in a completely sterile environment, you WOULD see the beam, as it struck dust particles in the air and they in turn were illuminated by the laser. In space, generally, there is no dust or matter from which the laser would reflect so you wouldn't see the beam.

Answer 2

You might see the beam from a laser gun if the laser consisted of visible light AND there was sufficient material in the air to scatter the beam.

Some lasers are built to operate in the energy spectrum outside of the visible light range (like infrared) so they cannot be seen by the unassisted (i.e. naked) human eye.

Even if the laser is in the visible spectrum, any light must either be pointed into your eye or reflected off of some object (like dust in the air) and into your eye in order to see it. You can test this by shining an ordinary flashlight into the night sky...you won't know the light is on unless some dust floats in front of the beam.

Answer 3

The only time we can see ANYTHING -- be it a lightbulb, a pencil, or the moon -- is when some light beams coming from the object are aimed directly at our eyes.

In the case of a laser beam, the light beams are NOT generally aimed at our eyes. (If they were--that is, if somebody were pointing the laser directly at your face--you would definitely see a bright light.)

If you fire a laser in an environment where the air is smoky or steamy, some of the photons coming from the laser will bounce off the particles of smoke or water vapor, and will reflect toward your eyes. In that case, you can "see" the beam.

Answer 4

laser light is focused into a very small point.
for it to be visible as a beam, or more accurately a burst of energy, we would have to have more knowledge and greater technology to change how laser light can be generated.
What you are talking about is science fiction,
you cant draw conclusions from fiction, it is only there to interest us and help scientist and layman alike to imagine what could be.