system
Given the following post, respond as if you're commenting on Reddit:
human
Are there naturally occurring straight lines?

My friend asked "If light travels in straight lines then does the sun define angles"... "Light is the only thing I can think of that creates a naturally occurring straight line". I don't believe he is completely correct in saying this as I can think of things such as crystals or certain rock formations like slate, or even a taut strand of spider web which produce straight edges/lines. Is this incorrect or are there instances of naturally occurring straight lines besides a beam of light that "define angles"?
gpt
At the molecular level, are these rock formation or spider web strands truly straight? 

Additionally, even photons must obey gravity; we can detect massive gravitational sources by watching light bend around them, so do photons following the curvature of space still count as travelling a straight line?