No mass, no mas.

However, there's no place that a perfect vacuum exists.

#10 | POSTED BY TRUEBLUE

While that may be true the universe is still mostly empty space. We are all mostly empty space.

Turns out Nothing Matters. A lot. Without Nothing there would be no place for MATTER to exist in.

Also light does lose energy. Because the universe is expanding spacetime is expanding. And light is just electromagnetic energy (sometimes acts like a wave sometimes a particle depending on your frame of reference and how you look at it) so it shifts to red as space time stretches. But the white light you see made across without encountering anything that would scatter it or cause it to lose energy. You, of course, just don't see the light that did not make it. Though there are other forms of electromagnetic energy you still can "see" thru the particles of dust like radio waves and microwaves etc.