Day 10: Maison Poincaré and lots of rain

Today, the next day, was a lot easier. (We had only one more intense day but this was not it. That was tomorrow.)

We woke up tired. (No surprise.) After breakfast, we walked to the Maison Poincaré, a brand-new museum that had opened only about a month before, under the auspices of the Institut Henri Poincaré. Since the Institut is part of the Sorbonne and our hotel was in the Quartier Latin, it was in walking distance.

A lot of people would skip a place like this, if their time was limited. It's a math museum, for heaven's sake. But I knew Marie would love it. Back in the day, when we were both undergraduates, we both ended up majoring in math. We both loved the intellectual challenge and frisson that mathematics offers, even though neither of us ended up in a mathematical career. So I knew she would love the museum on those grounds. Also, while a place like this hardly sounds romantic to most people, I knew she would appreciate it as related to one thread of our common bond (viz., mathematical study). And finally, it had just opened. It wasn't in any of the tour guides, because it was too new. How could we pass it up?

So we went. And, sure enough, it was a lot of fun. Many of the exhibits were interactive.

• Here is a sphere: can you cover it completely with these shapes (all magnetized)?
• Here is a bunch of survey data represented as dots on a three-dimensional grid: can you find a slice through this space such that all the blue dots are on one side and all the red dots are on the other? (This one really did involve colored balls attached to strings under tension that ran from floor to ceiling, sprouting from a 10x10 grid on the floor.) 
• Here's a recording: play it and see what the graphical sound signature looks like. 
• Now do it at double-speed. 
• Now do it at half-speed. 
• Now do it, but filter out all the frequencies outside of the narrow range that cell phones transmit. (For this last one, the picture was indeed very abbreviated, and it sounded exactly like you were listening through a phone!)
• And so on. 

So we played there for a couple of hours. Then we went back to our hotel for a nap. (On our way back, we passed the house where Jean de Meun wrote his installment of the Roman de la Rose. I got a picture of Marie standing, grinning, under the plaque which proclaimed as much.)

After our nap, we went shopping. Marie wanted to visit the Abbey Bookshop (also in the Quartier Latin). So we went. Unusually, I didn't spend much time inside: the aisles were so narrow that they felt constricting to me, and I had the permanent sense of being in someone's way. So after a few minutes I made my way outside and found a place to sit. But Marie loved it. She even clambered down into the basement stacks, despite the general weakness of her knees.

Time for lunch! Or well past time, in fact. Down a side-street we found a small, family-owned Georgian restaurant and ate very well there.

After that, we wandered to a few other places, where Marie had specific things to buy that coworkers had asked her for. So we found our way to La Belle Iloise, and to Victor Richart. By then it was raining quite heavily and steadily. Since we had eaten a late lunch, we weren't very hungry for supper. So we made our way back to the hotel to rest and go to bed.

It stopped raining once we got there.