[s_m_t]

Let's do a thought experiment. Floating in an otherwise completely empty region of space is a bomb. It explodes. For quite some time after the explosion entropy will be decreasing in that region. I really don't see the mystery here.

[simiones]

The point is this: say we see a video of an otherwise completely empty region of space, with two masses orbiting each other for a while, that then fly off in different directions. We reverse the video and see two masses coming towards each other until they get into an orbit. Can we tell which of the two videos was the original and which was the reversed one? The answer is that we can't.

However, say we receive a video of a billion billion such masses all starting in a single point, staying more or less still for a few seconds, and then moving out at high speed away from each other. It is obvious that this video is almost certainly playing forward in time, since the reverse, a billion billion balls all coming together to form a single object, is very very unlikely.

[rrmm]

Coming together to form a single object sounds like the work of a gravitational force.