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In the Dark

Where are we in our exploration of the gravitational Universe? Inflation has uncovered for us the secrets of the Universe 10-38 seconds after the Big Bang! But among the predictions …

Dark matter

Let me tell the saga of dark matter, this non-luminous form of matter, from its identification in the 1930s by Fred Zwicky in the Coma cluster to the realization that …

An interview with George Smoot

In this interview, George Smoot gives us a recollection of the moments of his discovery of fluctuations in the Cosmic Microwave Background, what was his personal reaction, and how the …

The Story of Planck

The Planck mission has achieved maps of the Cosmic Microwave Background to a level of details that had never been reached before. This has allowed to measure a certain number …

First light on the horizon

We now proceed to identify the first light which could travel through the Universe: this light which was emitted 380 000 years after the Big Bang can still be detected …

From horizon to inflation

It is now time to introduce the scenario of cosmic inflation, a period of very fast expansion which took place right after the Big Bang. Theorists identified this stage of …

Where do we stand?

It is time to summarize what we have learned so far about gravity, and to realize what it means to say that “gravity is the engine of the Universe”. This …

An evolving Universe

Because the Universe is expanding, it is dynamical and thus it has a history. How do we follow this history? We review the many parameters that may help to describe …

Big Bang theory

It is time now to describe what is known as the Big Bang theory. What is the Big Bang itself? How does the Universe evolve from this primordial moment? Is …

Static or expanding universe

Einstein tries to apply his equation to the whole Universe, but what is the Universe? It turns out that it is more complex than anticipated. Henri Lemaître and Edwin Hubble …

Experimenting with gravity

Nobel Prize winner George Smoot, with Marie and Thierry, reproduce with old-fashioned balls and board but modern stopwatches the inclined plane experiment of Galileo, which marked the foundation of modern …

First encounter with relativity

Continue with Galileo, focusing on the notions of inertia and mass. And discover the principle of relativity, as expressed by the same Galileo. This will lead us smoothly to Einstein’s …