(This is most likely not true, because I was just dreaming. lol.)
So the astronomers and physicists out there tell us of a mysterious class of matter that they call dark matter that makes the universe expand faster and faster. The reason it’s called dark matter is that while we don’t know what it is and can’t explain how it got there, we can feel its effects. Even more mysteriously, the older the universe gets, the more dark matter there is. Matter doesn’t come out of nowhere, so where does dark matter come from?
Let’s imagine, for a moment, that we’re among a super-advanced civilization of a super-advanced species in the far, far future. We already have all the technological gadgets that people from the past could only dream about; we’ve got things like plasma phasers, teleporters, hyperdrive, and time machines.
Well, as you can imagine, the more advanced a civilization gets, the more waste products it produces. At some point, it becomes impossible to process these wastes, and they start accumulating. Well, this scientist at a waste-processing plant soon comes up with an ingenious idea: the people who lived in the past did not have as much waste to deal with, so we should let them handle some of our waste; in fact, the more primitive the civilization is, the less trash it produces, so we should use a time machine to send our trash way back, preferably right to the beginning of the universe. Scientists had entertained this idea from time to time in the past ever since the first time machine was invented, but nobody had been daring enough to risk destroying their past. However, the situation with the waste accumulation has grown to such a degree that it is necessary to offload some of our responsibilities to our past.
Such a smart scientist, eh? Let’s thank him/her for our endless supply of dark matter.