Anything that happens, happens.
Anything that, in happening, causes something else to happen, causes something else to happen.
Anything that, in happening, causes itself to happen again, happens again.
It doesn't necessarily do it in chronological order, though.
The history of the Galaxy has got a little muddled, for a number of reasons: partly because those who are trying to keep track of it have got a little muddled, but also because some very muddling things have been happening anyway.
One of the problems has to do with the speed of light and
the difficulties involved in trying to exceed it. You can't. Nothing travels faster than the speed of light with the possible exception of bad news, which obeys its own special laws. The Hingefreel people of Arkintoofle Minor did try to build spaceships that were powered by bad news but they didn't work particularly well and were so extremely unwelcome whenever they arrived anywhere that there wasn't really any point in being there.
So, by and large, the peoples of the Galaxy tended to languish in their own local muddles and the history of the Galaxy itself was, for a long time, largely cosmological.
Which is not to say that people weren't trying. They tried sending off fleets of spaceships to do battle or business in distant parts, but these usually took thousands of years to get anywhere. By the time they eventually arrived, other forms of travel had been discovered which made use of hyperspace to circumvent the speed of light, so that whatever battles it was that the slower-than-light fleets had been sent to fight had already been taken care of centuries earlier by the time they actually got there. This didn't, of course, deter their crews from wanting to fight the battles anyway. They were trained, they were ready, they'd had a couple of thousand years' sleep, they'd come a long way to do a tough job and by Zarquon they were going to do it.
This was when the first major muddles of Galactic history set in, with battles continually re-erupting centuries after the issues they had been fought over had supposedly been settled. However, these muddles were as nothing to the ones which historians had to try and unravel once time-travel was discovered and battles started pre-erupting hundreds of years before the issues even arose. When the Infinite Improbability Drive arrived and whole planets started turning unexpectedly into banana fruitcake, the great history faculty of the University of MaxiMegalon finally gave up, closed itself down and surrendered its buildings to the rapidly growing joint faculty of Divinity and Water Polo, which had been after them for years.
Which is all very well, of course, but it almost certainly means that no one will ever know for sure where, for instance, the Grebulons came from, or exactly what it was they wanted. And this is a pity, because if anybody had known anything about them, it is just possible that a most terrible catastrophe would have been averted - or at least would have had to find a different way to happen.
