Why is it that when you squint and look at a light source, it looks as though there are rays coming out of it?

Question

Suppose you're looking at a light.

If you s***w up your eyes to just before you close them and look at the light, you see... Sort of light 'beams' or 'rays' coming out of the light. (I don't know if that makes sense). There are often two of them, one going up and one going down. You do sometimes get horizontal ones, and little ones go off in different directions around the light. And if you rotate your head while doing this, the 'beams'/'rays' rotate, too.

#1 - What are these 'beams'/'rays' and why do they occur?

#2 - Is there any reason why they rotate as you move your head around?

Oh, and just in case you're wondering, yes, I really do have too much spare time on my hands. Either that, or I don't really have a life.

It's a combination of both, really.

Answer 1

I would attribute this to the diffraction of light through your eyelashes, there may be other answers, but I have little knowledge of the anatomy of the eye.

I do think that the eyelashes being nearly closed during squinting could diffract the light such that it appeared in forms of rays

I dont understand about the rotation you are talking about, I dont think they rotate, but your head is doing the moving, so relative to you, it appears as if the rays are moving.