How does light travel through space for millions of years/?

Why doesn't it lose it's strength over such long distances?

It does lose strength(disperses)
think of a star like a candle,it sends light out in straight in all directions.the closer you are the brighter the light.
Now remember that most stars are millions of times bigger than our sun(which is millions of times bigger than our earth)
so even though the stars light loses strength it's still quite bright when it reaches us.

There is a consensus among physicists that accepting the general theory of relativity, Einstein's prevailing physics theory, entails accepting the speed of light in a vacuum as a constant. Therefore, any experiment proposing that the speed of light in a vacuum changes over time is viewed in the physics community with great suspicion. It is widely known, however, that the speed of light is variable when the light is not moving through a vacuum. The ratio of the speed of light through a given medium and through a vacuum is called the medium's refractive index or optical density. Some media have such a high refractive index that they can slow light to the speed of a person walking, or even bring it to a temporary standstill.For example, the speed of light through air is very close to the speed of light in a vacuum. Depending on how dense the transparent media is, it can slow light to a greater or lesser degree. Water and glass can slow light to 3/4 and 2/3 of c, respectively. Different wavelengths of light also travel at different speeds through different media. For example, blue light travels a different speed than red light when passing through a prism, causing the two to separate in a process called dispersion.In reality, the speed of light never actually slows down. It is just delayed as the photons are absorbed and re-emitted by atoms in the intervening space. When a light beam exits a transparent medium into a vacuum, it continues traveling at the same rate as when it originally entered, without any added energy. This shows that slowdown is merely illusory.

It is awesome, isn't it. This just gives an idea how powerful those celestial objects are. Traveling through the space, if there is obscured by the interstellar clouds, there is really nothing to weaken the light. Its intensity, however, would decrease inversely proportional to the spare of the distance. For us to see the objects that far, yes, they have to be immensely bright.

Well, it *does* lose brightness (flux) over those distances. The stars are all distant Suns--- does it seem to you that they are as bright as the Sun, or has their light lost brightness? Most galaxies, collections of hundreds of billions of stars, are so far that a telescope is required to see them. So yes, their brightness does fade with distance.

Because there is very little matter there to absorb and scatter photons. And as you know, in physics EVERYTHING needs a cause. No matter... no cause for the photon to be absorbed or change its momentum.

A photon does not know about time, by the way. Emission and absorption happen at exactly the same moment in the coordinates system of the photon. Photons are therefor the ideal implementation of yard sticks. All they "know and care about" is distance.

Ask that cartoon character whats his name
the one with the light bulb
What watts do you use
wait let me check got to go in too that shed
cause now you made me Curious
IS YOUR NAME GEORGE !!
i love my GEORGE'S !!!