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The Science of Time and Gravity
It seems like a really basic thing, but time and space, and space/time, and the effects of mass on them are actually really complex when you get into the math of it.

Not that we need to do that. Gravity itself is actually really complicated math that people with degrees have trouble understanding, at least for the big stuff like the sun, something the size of a person or an average space ship can be approximated with a fairly simple calculation, that I don't remember at the moment; Calculating acceleration by gravity is easier though.

The Earth has a gravitational force resulting in an acceleration of 9.8m/s^2, meaning for every second an object is falling towards the earth it goes 9.8m/s^2 faster then the second before, up to the point where wind resistance equals the force of Earth's gravity, otherwise known as terminal velocity.

So that's a crash course on how gravity works, now a tricky bit everybody knows but nobody realizes

E=MC^2; Energy is equal to the object's Mass, times the Speed of Light(C) Squared. This means many different things, but the point here is that Energy and Mass are equivalent, even in Gravity. Though, it does take considerably more energy to produce the same amount of gravity as a unit of mass. This is useful because it's a scientific basis for artificial gravity and makes plausible gravitational weaponry and shielding should you be able to produce enough energy.

Space/time is a trickier matter. think of space/time like a film reel, except instead of there being sixty to a hundred frames per second, there's a theoretically infinite number in every moment. Throwing in the multi-planar models it get's worse. One of the major theories is that every time the universe moves onto the next frame, it splits into trillions of trillions of alternate univii, one for each possible set of options of all the different things happening in the universe at that moment. This is sort of akin to Schrodinger's Box.

In the thought experiment Schrodinger's Box you have a box (obviously), in the box there is a cat and a device, the device contains an unstable isotope, that is going to decay at a time in the future that can't be predicted, and a tank of nerve gas. The nerve gas will be released into the box and kill the cat if and when the isotope decays, but as long as the box remains closed there's no way to detect if this has happened yet. So as long as the box remains closed the cat is just as likely alive as it is dead, creating a situation of what's called Super Position, where two self exclusive facts are true, the cat is dead and the cat is alive.

with 'Tree' style temporal physics it's sort of like this, as I said every possible outcome of every possible decision to be made between this 'frame' and the next spawns a new universe, so there's universe A where the cat actually is dead, and universe B where the cat actually is alive, and universe C where the cat fell through a wormhole into universe D, where there is not a living cat and a dead cat, as apposed to Universe E where both of them are alive, not even mentioning universe F where the cat is a dog.

There's also unified time stream style where there is only one universe with an indefinite number of possible futures, and the destiny theory, where the past and the future are fixed lines that we are only traveling through.

Then the space part of it.

Space is basically a three dimensional mesh , but it's easier to ignore the third dimension so you just have a plane, with a grid on it for your own reference. The effect of mass on this grid is to distort it, by stretching it, the only directions it has to move is down; but it's not really down, it's just useful to think of it like that because your brain will understand the effect of gravity better