system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When you cross two beams of light, e.g. from flashlights, why are they not interfering with each other at all?
gpt
***TL;DR:*** *Because light isn't really a physical beam so much as a group of little packets of energy that don't interact with each other.*

Imagine you and a friend are standing on a 10 foot wide diagram of a clock, with you at 6 and them at 3, both facing the middle. You both grab a handful of fine but very heavy sand. At a count of three, you both fling and spray your sand toward the centre... and the two clouds of sand pretty much pass through each other. There might be a collision or two that knocks a few grains of sand out of their path, but almost all of the sand would go through cleanly and end up at the other side of the clock.

Light is *a little* like that sand, except the photons (really, little packets of energy) are INCREDIBLY small and moving INCREDIBLY fast. So the odds that two particles are going to impact each other are almost impossibly slim. So the light in general goes through rather than be impacted by a collision.

But where the sand analogy fails is that light 'particles' don't really "collide" or interact anyway, not unless they're under very special circumstances. You can have one photon "touching" another and it doesn't really do anything to either. So off they go, not changing direction or anything, until they eventually blind a deer or annoy a light-sleeping neighbor.

{**edit** to include a second analogy for two photons intersecting}

Toss two pebbles into a calm pond at the same time, about two feet apart, and watch the ripples. You'll see they intersect and touch, but afterward just keep on going. Those two waves don't really CHANGE each other - their direction and speed remains exactly as it was *before* they hit as it does afterward. Same with photons - they'd just pass right through each other and keep going, unchanged from previous.