system
Given the following post, respond as if you're commenting on Reddit:
human
How can we see photons from distant Galaxies?

OK, I know "why" but to me it doesn't make much sense or perhaps I am not thinking properly.

Photons travel in a basically (putting gravity aside for a minute) straight line. Yes?  If so then every photon we can see would have to have an origination point. That point would have to be exactly lined up with our telescope, our eyes etc.. if not that particular photon could not be registered?  Yes? (Like if a flash light was pointed away from us)

If I think of a big ball (a star) and I draw a straight line from each conceivable point on that ball outward (where the photon originated and started travelling), *eventually* the trajectory of every line would move farther and farther away from each other (think of a V")

I can see what we are able to see our Sun, as the distance is not great enough to angle all the trajectories completely away, but something hundreds of light years away?

How do those photons get to us? Is it that there is just an almost infinite resource flying out at every trajectory?
gpt
Everything you've described is correct. It's not an "infinite" resource of photons, but for a star like the sun it's roughly 10^45 per second.

Galaxies emit a **lot** of photons, so many of them arrive at the Earth even though we make up a tiny fraction of the total solid angle. When we start looking at far enough sources, or in parts of the spectrum that are dimmer, we start to see photons arriving one at a time instead of as a continuum.