OK, if the universe is expanding, exactly _where_ is it expanding? The usual 'blowing up a balloon' explanation says that it is expanding _everywhere_, so that everything is moving away from everything else at the same rate. OK, so does this mean that the Planck length gets bigger? That's the only way I can think of that allows 'everything' to move away from 'everything else' uniformly. Does this mean that a black hole gets bigger, merely by virtue of its being part of the expanding universe? Otherwise, the expansion of the universe would try to pull atoms & molecules apart, which would either _do work_, and provide for a source of power. This power might be tiny in any particular part of the universe, but as a whole, it's pretty big.