When light travels through intergalactic space (vacuum?) does it get weaker?

Question

If so, what makes it weaker?

Answer 1

Yes, as it spreads out, it gets weaker. Each tiny star is a mighty sun in its own right. We see them as tiny dim stars because they are so far away.

Each photon carries the same energy, but there are far fewer photons for any given area, like the area of your pupil into your eye.

Geomotry of space makes it weaker. It simply has to cover more area as it travels out in all directions.

There is an "Inverse square" rule to describe how it gets weaker.

twice as far is 1/4 the strength.
three times as far is 1/9 the strength.

hundreds of light years would make the sun look like a tiny dim star.

Answer 2

The most important effect to make it aparently weaker is that it spreads out - the farther from the source, the greater the total surface illuminated at that distance. (As a simple analogy single lightbulb will illuminate the inside of a shoe box real well, but not the walls of an airplane hangar.)
This effect is dependant on the square of the distance to the light source; it's also the only diminishing effect you'll normally have in intergalactic space, which is normally very close to a perfect vacuum.

Answer 3

Actually, it DOES get weaker, due to the expansion of space. As space expands, it stretches the wavelength of the photon, so that the photon gradually goes from "bluer" to "redder". Redder photons have less energy, so the photon is "weaker."

Because space is not expanding very fast in any one area, a photon needs to travel for many thousands of years before this effect becomes noticible. This is called the "cosmic redshift" and is noticed in light that originated in distant galaxies millions or billions of years ago.

A common misconception is that the cosmic redshift is the same as the "doppler" redshift. Although the two effects are similar, they produce slightly different quantitative results.

Answer 4

It does not weaken. However, light is made up of photons, tiny particles of light energy. These disperse as the light traverses farther distances, making it appear to become dimmer as you get farther away from it. This happens everywhere, though, not just in space.

Answer 5

Like ripples in a pond after a rock is thrown in, the total energy has not diminished, however, the *amount* of energy over a single point is less because the wave itself is dispersing as it travels.

Answer 6

I think it does not become weaker it does not require any medium for its propagation.

Answer 7

ligth never weakens it travels at the same speed no matter the atmosphere