Today is the 18th anniversary of the launch of the Hubble Space Telescope. When I mentioned that to my astronomy classes, a few of the students commented on the fact that they're eighteen years old, too. Most of my students don't remember a world before Hubble. I do. It was a quieter universe, beautiful and placid. We now know that is not the universe we live in, and I'm forever grateful to have seen the heavens through Hubble's eyes.
To commemorate today's anniversary, here are some colliding galaxies, from Hubble: