Why does steam travel up instead of down?

It seems like water always falls down. Rain and snow fall down from the sky. Watering cans pour water down on plants. Waterfalls – well, the water falls down! But when water is steam, it rises up. Why is that? We asked aerospace engineer Nicole Sharp to help us find the answer. Got a question that’s weighing you down? Send it to us at BrainsOn.org/contact, and we’ll help find what’s up.   See omnystudio.com/listener for privacy information.