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
There is a law of physics called inertia, which means that objects in motion stay in motion and objects at rest stay at rest. The particles of light, photons, are unique in that they are born going super fast (the speed of light). Most objects have mass, meaning friction can be applied against their movement. Because photons are massless but the law of inertia still applies, photons will continue going the speed of light under almost any conditions.
The question marks are redshifts, as others have explained here, and black holes.
As far as our perception of it, think of a flashlight. If you shine it at something 6 inches away, the light is very concentrated and it’s very bright. If you shine it at a wall 20 feet away, it’s less bright because the photons are spreading out evenly towards the wall and less photons hit any one point. In the case of a star, such a small amount of the emitted light happens to hit earth. 99.9% of it misses us.
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