Will the ‘light’ we now ‘see’ in the universe all fade to nothing?

Answer

The light that is emitted into the universe does indeed die out when it is absorbed by something, and not reflected. But that light then releases its energy to the body that absorbs it, and can therefore be re-emitted as radiation. It never completely goes out, because energy is never lost. The law of conservation of energy is an essential basic law of physics, and as such has always been affirmed.

If the light doesn’t meet anything on its way, it just keeps going. How far along the way that happens, therefore, depends on how much matter it encounters or not along the way, and also on the wavelength of the light (long-wavelength radiation travels further). When we see nebulae, in visible light, in the thousands of years that their light travels, typically a few tens of percent of the way has already been absorbed by the interstellar dust and gas. But the afterglow of the big bang, which has been underway for more than 13 billion years, we still ‘see’ (in quotes, because it’s about radio waves) coming towards us for more than 90%.

Those 13 billion years are small relative to infinity anyway, and in an infinitely long universe no radiation can hope to survive forever. But the energy it gives off when it disappears causes new processes elsewhere, which in turn radiate energy.