# Will I be able to see a monochromatic ray of light in space?

1. Feb 11, 2016

### Fiona Rozario

If I had a red laser light, will i be able to see this red beam in space?

2. Feb 11, 2016

### CrackerMcGinger

I'm not sure you would be able to see the beam coming from the laser light, but you should be able to see it when it hits a solid object.

3. Feb 11, 2016

### Fiona Rozario

But if light doesn't need a medium to travel, I should be able to see the monochromatic beam, right?

4. Feb 11, 2016

### CrackerMcGinger

Light doesn't need a medium to travel, but since space is empty, what is there to allow the beams light to reach your eyes unless it hits something? This is my logic; on Earth the beam hits the particles in the atmosphere, but since space is empty, it should only be visible once it hits something.

5. Feb 11, 2016

### Fiona Rozario

Do you mean to say that light (poly or monochromatic) needs to be scattered by something so that it may be seen?

6. Feb 11, 2016

### CrackerMcGinger

No, I'm saying the reason we see light is because the reflected parts reach our eyes, you would still see the laser, but not the beam like you would on earth because their is nothing to direct the light to your eyes until it hits something. It may be possible that a camera that uses different methods of capturing images than our eyes do can see the beam, but the naked eye can't see it because the light doesn't reach us. Now the only thing I know that could allow the beam to be seen(however slightly) without an object scattering the light is gravity, but I'm still learning if that's true.

7. Feb 11, 2016

### Staff: Mentor

If the light doesn't reach your eyes, it won't reach the camera.

It all depends, as does the question in the OP, in the relative orientation of the person and the direction of propagation of the light. Light travels in a straight line unless there is some object to make it change trajectory, through reflection, scattering, bending because of refractive index (e.g., optical fiber), or something similar. If the light is not aimed at your eyes, you wont see it unless part of it gets deviated towards you.

8. Feb 11, 2016

### A.T.

It needs to reach your eyes to be seen.

9. Feb 11, 2016

### nasu

This is not something specific to space.
If you have a red laser pointer you can easily "see" that you son'd see the beam from the side unless there is fog, smoke dust or such in the air.
Pure air scatters very little in this range.

10. Feb 12, 2016

### Fiona Rozario

Thank you, everyone...