is there a limit to how far light can travel?

Question

Looking at stars yesterday set me to thinking if there was such a thing as a maximum distance that light can travel…?

Clearly stars are less bright than our sun and this must be a function of their distance from us (and also their initial brightness). But these distances are absolutely, mind-bendingly huge: we can see stars thats are hundreds of millions of light years away. And they are still visible not only after huge distances but also massive amount of time.

So is light not subject to “decay” or some form of “resistance” to travel that would mean there is a limit to how far (length) or how long (time) it could travel before it becomes completely unseen?

I realise I am using analogies that would be more relevant to sound or waves in a liquid so it may just be my incomprehension of the “light” phenomena and how it works that means ive missed the point… 😀

In: Physics

Answer 1

Imagine a small blob of paint.

Now use that same amount of paint to paint a ring.

Now again, but paint a larger ring.

Now a larger ring

Now larger again.

Each time using the same amount of paint.

You have to spread out the paint more and more to finish each ring, so the larger rings are more faded.

—————–

Now imagine a star.

It’s constantly pumping out light, but let’s focus on the light it creates this instant in time.

Now imagine that light is traveling out in all directions. The light all moves the same speed, so at any moment the light that was created in that instant forms a shell around the star.

As time marches on the light gets further from the star. The shell formed by the light grows lager and larger, so the light is more and more spread out.

When you look at a star, you see less light if the star is further away, because the light from that star is more spread out by the time it reaches you.