One of my old interesting thought ideas was that of a “dark saber,” the logical opposite of a “light saber” as depicted in the Star Wars movies. Rather than having a sword-like contraction that emits light, you have a sword-light contraction that absorbs light like a black hole. What happens when you turn off a light saber? Easy, it just stops emitting light. But what happens when you turn off a dark saber? Well, all that light had to go somewhere, so where will it go when the device is no longer powered? Well, naturally, it would all escape, so then when you turn of the device, you have an explosion of light.
This is interesting when you think about it on a more philosophical level. Our understanding of the Universe as a whole is bounded at the present. When have warm bodies of stars generating light and heat, but ultimately that heat radiates out into space. The Universe is also constantly expanding, so in the far future, the fate of the Universe is that it will become a cold, dark, black place, completely incapable of supporting any like as we know of it here on Earth.
A recollapsing Universe that ends with “the big crunch” would be nice and warm, but sadly it looks not to be a reality.
Our understanding of light is that it only escapes us and spreads out away from us. Once it’s used, that’s the end of it as we know it, for we do not know how to get that light back to Earth once it radiates out into space.
But, there’s a flip-side. On the other side of the Universe, there is an equivalent of what we can see as the “cosmic microwave background” on our side of the Universe. What is that? It’s an image of the early structure of the Universe, what the Universe looked like in a much earlier stage of its life. Somewhere else in the Universe, you can look up into the sky, and you’ll see a radio frequency patterned image that records the whole history of human society on Earth. You just need the right equipment to be able to decode that encoded data in order to get a glimpse into the full details of what life on Earth was like in its earlier history.