It's been a while since we've been to the Museum - since at least before we moved - but Asa led me directly to the dinosaurs. And then to the trains.

As he gets older, though, there is more to explore in this place of miracles. Like an exhibit on solar energy, in which one can use mirrors to focus light onto a sensor, and thereby make a machine whirr. Totally engrossed.
Cause and effect again: the happy land of the three-and-a-half (!) year old. Light and levers and simple machines and oh, the cogs were spinning, not just on the wall but in his mind. "That one's like a train, Mummy, see, when the piston pumps?" (Who knew he was paying attention to those segments of Thomas and Dinosaur Train? Thank you, PBS.)
Kinetics seems to be the order of the day. This sculpture was surrounded by young people, entranced by probability and motion. Science as art: perfection.
Of course, there are always the lessons that we didn't plan on learning... Look closely.
The official reason for the trip was to "see stars". Asa is finally big enough that the planetarium seats don't fold up on him, but he's decided that the dark is too scary to face alone, so I got to snuggle my big boy anyway. Such an amazing show; a journey out of Boston, through the Solar system, past the Oort cloud and out into interstellar space - views of our galaxy and représentations of the known universe. I think both of our minds were sufficiently blown.
Of course, a trip to the museum store was in order - Asa wanted to get something for Elias. At least, he did right up until we reached the book section. Needless to say, this book now lives at our house, beloved possession of our little scientist, along with glow-in-the-dark stars and planets that now hang from the boys' room ceiling.