I know where all the dark matter and dark energy went.
If it’s true that time travel is possible, then, it’s also true that, all matter and energy from any particular instance in time, have all gone into the past. The past and the present interact, and the present feels the effect of the matter and energy that have “passed on”.
The most current instance of the “past energy and matter”, can be called the “most recent instance of the past universe”, and that instance will be the most felt in measurements. The instance before, will also have an effect on measurements, but not as great as the most recent. The third instance before the current instance of the universe, will also have an effect on the current universe... and so on... up to the very first instance of the universe. All of those instances comprise the “universes”. All of those universes (or instances of the universe), all interact, and they do exist, and it’s why it might be possible to travel to the past. We won’t be able to travel into the future, since, no instances of the universe have “passed” into future times. We can’t interact with what hasn’t already occurred.
Are you saying that dark matter is where the things that went into the past were?
So, the past exists presently. If we were to go there would time stop in the present? And could we come back to the same time in the present that we left, or would we come back to a point in time that was as far along in time as the amount of time we were gone?