It stands to reason: if it didn't, the entire sky would be covered with stars shining blindingly day and night.
But what causes a light wave (or an electromagnetic wave) to fade if there are no celestial bodies in its way? Or, alternatively, why doesn't it fade sooner? Some stars are visible to the naked eye that are hundreds of light years away. Others, closer, can only be detected with the aid of a telescope. Why?
Answer
As the individual photons move away from a point they spread out so the same size telescope or eyeball picks up less of them as you move farther away.
There are more than two phenomena at work here (sorry HDE), in addition to just spreading out based on their initial direction individual photons can be 1. diffracted by moving into more dense space 2. reflected (by any object with a greater diameter than it's wavelength) or 3. absorbed... Especially after picking on him I must encourage everyone to upvote HDE for having a cool picture though!
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