# Why was the speed of light even considered to be infinite?

russ_watters
Mentor
Well, on second thought, maybe it takes too specific configuration to get infinitely bright everywhere.
What it takes is for light to go through stars so that the brightness adds instead of stars blocking light from other stars (or, for the temperature to increase without bound due to all of the extra radiation bouncing around). The standard setups of Olbers' paradox result in a universe where every line of sight ends on the surface of a star and therefore the brightness is that of the surface of a star.
But still, it makes sense that at the very least, it would be much brighter if speed of light is infinite, which was essentially my main point in the OP. I mean, infinite light speed implies we would be getting light from far away stars that we wouldn't have otherwise on a regular basis. This high brightness should be the case in a finite universe or an infinite eternal universe when there is no speed limit.
Yes, it can make for a brighter universe depending on the assumptions made about the large scale dynamics of the universe (infinite or finite, expanding or not, etc.).

jbriggs444
Homework Helper
But still, it makes sense that at the very least, it would be much brighter if speed of light is infinite, which was essentially my main point in the OP.
Are you assuming an infinite homogeneous universe with a finite age?

An infinite homogenous distribution of stars everywhere is more unlikely.

And therefore there is no reason to favour it over a finit speed of light.

Moreover, even if on average the the stars are homogenous, just by having an infinite amount of them, there is a finite probability of some configuration at some distance where nearly and infinite amount of light just hits us at once due to their infinite speed.

There is no configuration where the amount of light goes infinite. It seems you are missing something (e.g. the reversed quare law for the intensity).

russ_watters
Mentor
There is no configuration where the amount of light goes infinite. It seems you are missing something (e.g. the reversed quare law for the intensity).
Having spent more time than I care to admit trying to educate someone on this once, I can say that where this can come from is the assumption (on purpose or without realizing it) that stars are points.

jbriggs444
Homework Helper
Having spent more time than I care to admit trying to educate someone on this once, I can say that where this can come from is the assumption (on purpose or without realizing it) that stars are points.
Eek. If stars are pointlike then there will not be a star in every exact direction one can look. Instead it will merely be the case that the stars will be dense in the sky. With probability one, no one star will occlude any other star and the luminous intensity will be infinite. [for an infinite, static, homogeneous, eternal universe]

russ_watters
sophiecentaur
Gold Member
2020 Award
How many cars arrive in Providence per day? As many as there are specific degrees in a circle. So infinite.
I think you are going off in the wrong direction with this argument. You are choosing a 'degree' as a fundamental step in angle size, which doesn't make sense but the question is considering a single track road (one dimension) - a much simpler statement of the problem.
Stars don't follow the 'trees in a forest' model, where you will see 'wood' wherever you look in an infinite forest (whatever the size and spacing of trees). That implies that either the universe is not infinite or that it is infinite and there is 'something going on with' the light from very distant stars. (Or both of course)

One car per day leaves Boston for Providence at 30 mph. How many cars per day arrive in Providence?
One car per day leaves Boston for Providence at 45 mph. How many cars per day arrive in Providence?
One car per day leaves Boston for Providence at 60 mph. How many cars per day arrive in Providence?

I think it depends on how many cars leave other locations for Providence each day, how many breakdowns occur, etc.

sophiecentaur