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### The Poincaré conjecture | Relativity 21

Could a universe without border, not go on and on forever?Poincaré not only gave an answer, he also proposed a fundamental conjecture...Poincaré Conjecture a...

### Is gravity acceleration or curvature? Relativity 16

Not many general relativity popularizations distinguish acceleration and curvature, and even suggest that gravity is... both. I know I did. Yet, these are ma...

### Curved-space geometry | Relativity 10

There's a fine line between straight and curved lines... Or is there not? What's a straight line (in a curved space)?What's wrong with that map? Spherical Ge...

### John Nash, a Beautiful Mind | Genius 1

Nobel prize winner John Nash passed away on May 23rd, 2015. He was 86. He had lived an amazing and difficult life. Early on, he was a mathematical prodigy wh...

### L'espace-temps de Minkowski | Relativité 7 + Défi Lê 1

Peut-on enfermer Sheldon Flash Cooper dans une cage qui fait sa taille au repos ? On semble devoir conclure oui et non, selon le référentiel dans lequel on r...

### Pourquoi π est-il si fou ? Relativité 1

π est la superstar des mathématiques. Mais pourquoi ? Qu'est-ce qui fait de π un nombre plus remarquable de 1, √2 ou i ? Voilà quelques éléments de réponse, ...

### How far can a pile of cards go? Logic 3

Take a pile of cards and try to get it leaning away from a table as far as possible. How far can that go? Can it go to infinity? What's pretty cool is that t...

### How big can numbers be? Logic 1

In the new series on math foundations, we'll be talking a lot about infinity. But before reaching the infinite, let's first go through the biggest numbers of...

### Twin & Grandfather Paradox | Science4All 20

Leave your twin on Earth while you travel across the universe. When you come back, will you be younger or older than your twin? The answer lies in (gravitati...

### Can't you "see" the Big Bang? Relativity 19

One of the most amazing thing about our universe is that we can see its baby picture by just looking up there. What's equally surprising is that it's only 50...

### Albert Einstein, the iconic figure of science | Genius 2

Will there ever even be another Einstein? Doubtful. Einstein not only is a great genius, he's also and most importantly the iconic figure of science, in its ...

### Einstein's biggest blunder | Relativity 18

Because the young Einstein couldn't accept the possibility of a universe with an end of time, he made obscure modifications to his equations... He would late...

### Einstein's heart palpitations | Relativity 17

This video retraces Einstein's footsteps towards worldwide celebrity. From his first steps into a theory of spacetime curvature to his epic dual with the gre...

### General relativity explained! Relativity 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'...

### Einstein's happiest thought | Relativity 14

In 1907, Einstein had the happiest thought of his life, the one that would initiate an 8-year-old seemingly impossible quest for a theory of gravity. While t...