Regardless of the sun, which is subject to entropy, ergo, waning effect upon earth as time proceeds, everything is a closed system, from earth to the farthest star.
All are subject to entropy in varying states of decay.
Also, is gravity a mass thing, as Einstein theorized, or is it an electrical bond between atoms?
It’s a mass thing.
And entropy can be staved off for a time by energy input.
What’s so hard to understand about that?