guide you're thinking. so it turns out if the sun turns into black hole, everything would be okay. you know why the sun's round? you know why the earth's round? you know why the planets are round? because if there are great, big cubes the corners could be pulled in by gravity, gravity pulls everything in until it gets round. the whole universe, it turns out the idea of gravity underlies our thinking about the universe. you guys hear about the big bang theory? the idea that about 14 to 20 billion years ago the whole universe was in one point and exploded out, all flying out. let's look at that in terms of the gravity bit here. let's suppose, here's the big bang and all these pieces are flying. now let's suppose that we knock the whole universe into four halves just to make the thinking easy. if we can understand the simple examples then maybe we can deal with complexities. here's part of the universe here, here's part of the universe here, part of the universe here and all are flying apart. there's nothing else that exist just this and there they go. any force of attraction between these phases? how many say, yeah? it turns out this would be attracted to here, this wo