Great for both kids and adults! We went at 2pm on ...

Great for both kids and adults! We went at 2pm on one of the five free days a year, and we were pleasantly surprised by how uncrowded it was. There were lots of people, but with so many exhibits, we never had to wait in line. Highlights: the theory graveyard, the camera obscura, and the exhibit where you could see the trails left by muons and other subatomic particles.