[theemathas]

Reversing time on an attracting force still gives you an attractive force. Velocity is reversed, but acceleration isn't.

Imagine a ball being thrown up and then falling down, in a parabola. Reversing a video of that still gives you a video of a ball in a normal parabola trajectory.

[pixl97]

The history of the universe channel on YouTube has an episode called 'what is time' that goes over symmetries like this. Lots of atomic/quantum scale interactions are time reversible like this, but not quote all, and that may be where time arrives from.

Well worth watching that episode as it does far better explaining than I do.