What makes them do this?

[Mart]

I've frequently seen what appear to be rays of light passing through gaps in clouds. These always diverge fron the sun's position. But since the sun is so far away it's effectively a point source so what makes the rays not parallel?

[CanadaAotS]

sun's light radiates in all directions. It's not really a point source...

[Xyph]

Wouldn't the rays spread out more the further away the sun was? It's still pretty far from a point, anyway...

 

Although it could also be partially an illusion because the gaps in the clouds are far away and look smaller.

[Skye]

http://en.wikipedia.org/wiki/Crepuscular_rays

[NeonBlack]

Diffraction

[swansont]

Diffraction

 

 

No, not diffraction. Skye's link covered it.