My Podcast Interview on GLIMPSE


A few weeks ago, Alex Albanese interviewed me on the MIT post-doc GLIMPSE Podcast. We discussed populations, cakes, toilets, Google and many more topics. The podcast was released yesterday.

It was an awesome experience. Alex is a great interviewer. And, even though he is a biologist (I guess I can forgive that ;)), he was extremely sharp and quickly saw deep connections between the various mathematical topics I discussed. It was a real pleasure to interact with him, and I think that the podcast shows this very well. In fact, I highly recommend you to check his other GLIMPSE Podcasts.


What’s Einstein’s gravity? General relativity explained! Science4All 15


Last time, we saw that Einstein explains the falling of the apple by the upwards acceleration of the ground. This is Einstein’s happiest thought. But wouldn’t this imply that the surface of the Earth is expanding outwards? Well, no. Why? Because of spacetime curvature! At last, this video explains how Einstein’s gravity really works.

Warning! This video is a bit more technical than usual, and previous videos are prerequisites to fully grasp this one. They include:
Is special relativity relative? Time dilation and space contraction | Science4All 6
What’s wrong with that map? Spherical Geometry | Science4All 9
What’s a straight line? Curved-space geometry | Science4All 10
What’s the geometry of my underpants? Hyperbolic Geometry | Science4All 11
Are astronauts weightless? Einstein’s happiest thought | Science4All 14

More to understand general relativity…
Spacetime of General Relativity | Science4All Article
Is gravity acceleration or curvature? Follow-up clarifications | Science4All 16
Is Gravity An Illusion? | Space Time | PBS Digital Studios
General Relativity & Curved Spacetime Explained! | Space Time | PBS Digital Studios
What proved general relativity? Einstein’s heart palpitations | Science4All 17
What’s the destiny of the universe? Einstein’s biggest blunder | Science4All 18
What’s gravitational time dilation? Twin & Grandfather paradox | Science4All 20

Splash Report – My Best Teaching ever!


So good. I’ve just spent most of my week-end teaching as part of the MIT splash event, where high school students came in and took classes that went way beyond the high school curriculum. These guys are way smarter than I expected; and they were very, very curious. What a pleasure it was, just to get to interact with them!

On Saturday, I taught a 4-hour class on the math foundation crisis (which I kind of regarded as a warm-up my upcoming Youtube series). The 2 first hours were awesome. Both for me, and — I think — for them. The trouble was, they were way smarter and knowledgeable than I expected, so we went through all of what we prepared in just 2 hours. Seriously. They cracked the infinite hat problem with the axiom of choice in half a minute! So the last 2 hours were improvisation — and it turns out, I’m not comfortable with math foundation to improvise a class on this topic… At least so far.

Sunday was my marathon day. I first taught a 2-hour class on the mathematics of democracy — an field I have done research in. I had a class of hundreds of students — 138 were registered. So awesome. The students were very curious. They asked insightful questions, and proposed clever answers to the numerous questions I asked them. They also elected Batman as the Condorcet winner of superheroes! At the end, I proposed the voting system I have been designing in my research (which hopefully I’ll write and talk about on the Internet soon…). To my surprise, I even seemed to have convinced them that this was the right voting system… But that’s just a detail. What matters is that, for sure, they left pondering the legitimacy of all voting systems that are widely used these days… and that’s a big deal!

Next was a 2-hour class on cryptography and the theory of complexity. This was the only class that didn’t go as well as I had hoped. Somehow, I didn’t manage to connect with most of the students. Perhaps, the long historical introduction I presented was a bit too long. Perhaps, as well, the students started to get tired after over a day of advanced classes all over MIT…

At lunch, I must say, I was a bit afraid. While students started to get tired, I had become exhausted. Would I still find the energy and the voice to present another 4-hour class? Plus, by far, this 4-hour class was the one I prepared the least. Seriously, my slides were mostly pictures of physicists… But as it turned out, this last class would be the one I was actually the most prepared for, as it was about the theories of gravity I have been talking about in my recently finished series on general relativity.

This class was awesome! Step by step, I got the students to almost figure out by themselves the most brilliant thoughts of Galileo, Newton and Einstein. The climax was when I repeatedly asked them: “If gravity is not a force — which is what Einstein claimed — why do apples fall?” It took them a while. They proposed different ideas. Mostly wrong. But that’s okay. Einstein himself got mostly wrong ideas. But, slowly, they got warmer. And warmer. Until, all of sudden, one student said half convincingly: “the ground is accelerating upwards!” Yes! Yes, yes, yes! The ground is accelerating upwards!!!

I had several students thanking me for the classes. Many even said that my classes were the best classes they had attended… which, I guess, means that I’m not such a bad teacher when I don’t have to follow some stupid curriculum (which I had to when I was teaching in Montreal), and where students are not fully focused on some upcoming exam. I guess I actually love teaching. But the conditions need to be right… and I do know that conditions will hardly ever be as good as they were in this amazing Splash event…

I guess Youtube is the next best thing :p. Come on Final Cut, let’s talk logic and math foundation!

Are astronauts weightless? Einstein’s happiest thought | Science4All 14


Finally, here was my first video on general relativity per se. And it starts with a basic but incredibly deep question: Are astronauts weightless? Pondering similar questions (there were no astronauts back then) would lead Einstein to the happiest thought of his life… and for good reasons. It might be the most dramatic thought (in physics) I’ve ever encountered!

Despite a few technical issues and the smallness of the number of views, I still regard this video as my best one yet. Please let me know what you think 😛

How did Newton figure out gravity? On the shoulders of giants | Science4All 13


The theory of gravity did not fall from trees. It took a giant, standing on the shoulders of other giants. Building upon Descartes’ algebraic geometry, Galileo’s law of falling objects and Kepler’s law of planetary orbits, Newton would mark History, as he would infer the fundamental laws of motion and gravity.

Newton’s thoughts are so clear that they had to be true. And for centuries, they were to convince any scholar who would ponder them! Until came some unknown patent clerk…

Links to go further:
The Massive Puzzle of Gravity | Science4All Article
Don’t heavier objects fall faster? Galileo’s Thought Experiment | Science4All 12
Are astronauts weightless? Einstein’s happiest thought | Science4All 14
What’s Einstein’s gravity? General relativity explained! Science4All 15
Is gravity acceleration or curvature? Follow-up clarifications | Science4All 16
What proved general relativity? Einstein’s heart palpitations | Science4All 17

Don’t heavier objects fall faster? Galileo’s Thought Experiment | Science4All 12


Back to physics; back on tracks on our way to Einstein’s theory of general relativity… We start with Galileo’s brilliant insight into gravity, one of the greatest insights I’ve ever got to discover — and I discovered it only about a year ago!

In short, most of what you’ve learned about Galileo’s law of falling objects is, at best, misleading and deceptive… Does it annoy you, as it annoyed some viewers? Or does it clarify a lot of things and get you very excited about Galileo, as it did for me?