- [Narrator] Who would've believed that one day we'd be able to see this image?

A black hole in the universe, a strange star from which no light or person can escape.

This image was calculated using the equations of general relativity,

a scientific theory of space and time developed 100 years ago, a theory that was in turn praised, rejected, forgotten,

and then rediscovered, a theory that this black hole nearly killed,

my theory. (dramatic music)

- The theory of relativity is infamous for its difficulty.

I want to show that there's nothing peculiarly difficult about it.

- Let me illustrate this with an example here, let's imagine that this piece of jelly is the sapce and the presence of matter is to distort the space.

- Einstein's theory of relativity does lead us into very strange and unfamiliar paths. - Relativity is perfect intelligible

to anybody who is willing to think. (dramatic music)

- [Narrator] In the 20th century, I was known by the name of Albert Einstein and for my equation E = MC squared.

I sought to understand nature through mathematics. I had a new vision of the architecture of the universe

and I expressed it in a theory, general relativity.

General relativity is a theory about gravity, the mysterious force that attracts stars and planets to each other.

For 250 years before my theory, gravity was the realm of the great scientist Issac Newton.

My theory revolutionized the worlds of physics and mathematics.

(speaking in foreign language) - [Translator] Newton's theory of gravity, revolutionary in its scope and concision,

had held water since the end of the 17th century. It is fascinating to think

that to explain just a few changes to this law, everything had to be turned on its head.

And that is exactly what Einstein did. His theory of gravity involves several major modifications.

Space is no longer straight but curved depending on the matter inside.

Giving a position at a given time no longer makes sense.

Positions and times are intertwined and geometry now has to be seen in four dimensions

and we can't count on this equation here anymore. It needs to be replaced by one with a radically different form.

(dramatic music) - [Narrator] First of all, I discovered that space and time were actually connected,

working as one and matter such as stars and planets bends and curves the space-time.

That curvature is the gravitational field obliging the planets to rotate around the sun,

nothing, not even rays of light, can escape the curvature.

All these discoveries were based on a single observation, that of free fall, known since Galileo,

and which can even be observed on the moon. - Well in my left hand I have a feather,

in my right hand a hammer and I'll drop the two of them here and hopefully they'll hit the ground at the same time.

Galileo was correct. - [Narrator] I saw and understood free fall

differently from all other people. It guided me towards the curvature of space-time.

All I had to do was observe closely. - [Translator] Einstein himself

tells us about the moment when he understood that this was the tool that would allow him to form his theory.

(speaking in foreign language) In 1907 he wrote, "I was sitting at my desk

"in the patent office in Bern "when suddenly, I thought that if somebody was in free fall "they wouldn't feel their own weight and I was surprised."

He realized that gravity has the property and is the only force with this property of disappearing as a result of its own effect