What is this subjective experience, this awareness of existence, that we call consciousness? In tonight's episode, we will examine some of the aspects of this philosophical, scientific and spiritual question. Is consciousness a binary thing, or is it a kind of continuum with different "levels"? Do animals experience a degree of consciousness and how can it be infered of measured? Is it reductible to biology, is it the product of the treatment of information, is it something immaterial and detached from the physical world? Could an AI acquire consciousness from a silicon substrate, and if yes, what would be the pre-conditions and consequences? These are some of the questions we will try to answer, or at least understand better.

Our episode tonight takes us way back to 252 million years ago, at the end of the Permian geologic period. We will discover what marine life was like in the gigantic ocean called Panthalassa, as well as the flora and fauna of the supercontinent Pangea. In the last millions of years of the Permian, marine and land species began to go extinct in larger and larger numbers, culminating in the last million years in the most severe extinction event observed in the history of our planet. What are the possible causes of this extinction: volcanism, climate change, collision with a meteorite...?

For tonight, I take you to two "lost" cities, because they were deserted or replaced with another one, but their stories are windows on chapters of human history. First we will go to Mycenae, a city-state and palace from the second millenium BC, that represents well the rise of Bronze Age palatial culture in Greece, long before the more familiar periods of Classical or Hellenistic Greece. Then we will move to Mesoamerica and discover the history of Tenochtitlan, the capital of the Aztec Empire. Tenochtitlan was a marvel of urban planning and engineering, built on an island on lake Texcoco, just where Mexico City now is. With around 200,000 inhabitants, it was one of the largest cities in the world in the 15th century, until its fall to the Spanish Conquest of Mexico.

In this soft spoken ASMR video, I tell you about the Wars of the French Revolution and the Napoleonic Wars. We explore the transformation of society, politics, diplomacy and warfare that made Napoleon's destiny possible, and we follow him from his birthplace in Corsica to Toulon, Paris, Italy, Egypt until the coup that made him access to supreme power. But this was just a start: multiple conflicts saw him dominate Europe for a short time before a spectacular collapse.

Tonight's episode is an overview of the history of gold and other precious metals: how much is there on Earth? Where is it? How was gold discovered and how did it acquire its powerful symbolism as a symbol of wealth and power, that make it a store of value? From the tombs of ancient pharaohs to the reserves of central banks, let's delve into this history.

In this science talk for bedtime, I review the periodic table of the elements methodically and explain in simple terms plenty of phenomenons and concepts about chemistry and physics (the structure of atoms, valence and reactivity, isotopes, allotropes, ionic compounds, the definitions of metals, metalloids or noble gases, radioactivity...) as well as the industrial and economic relevance of some of these elements.

This episode will give you an overview of the concept of multiverse: where does it come from? What are the various meanings and ideas behind that term? I will detail different versions of this idea, coming from cosmology (the "Eternal Inflation Multiverse" or the "Cosmic Landscape Hypothesis", derived from String Theory), quantum mechanics (the "Many-Worlds Interpretation"), or the "Computational Multiverse" hypothesis. I will also tell you about thinkers such as Anaximander, Copernic or Giordano Bruno, who all contributed in their own ways to the intellectual revolutions necessary for this concept to emerge.

In this very long bedtime story, we explore every single planet of the Solar System and many of their satellites. I tell you about their formation history, what they are made of, what to expect at their surfaces, and plenty of other things about orbits, chemistry, rocketry, or concepts such as terraformation. Our journey will take us even beyond Pluto, in the Kuiper Belt and Oort Cloud.

In these new mystery stories set in New York City, we will travel through time at different periods of the history of the city, from its foundation as New Amsterdam to our days. Stories include: - Captain Kidd's Treasure, that could be hidden somewhere on Manhattan, Long Island or Gardiner's Island; - The wreck of the HMS Hussar in the East River with a big treasure on board during the American Revolution; - The Leatherman, a mysterious vagabond who travelled constantly on the same 365 miles loop in Connecticut and New York for more than 30 years, coming back to the same towns every five weeks; -The disappearance of Judge Joseph Crater, a Supreme Court judge who vanished into thin air in shady circumstances, that illustrate the intense corruption of the 1920's and 30's; - The existence and sometimes rediscovery of many hidden underground structures, such as the pneumatic tube mail system, the City Hall subway station, the Atlantic Avenue Tunnel or the maze of tracks, platforms and rooms under Grand Central Terminal.

This episode is a time travel to the Celtic era, to examine historical mysteries and discover more about Celtic culture. I will tell you about the druids: what we know of their emergence, their functions, their cultural importance, and also the many aspects of druidism that remain mysterious. We will also travel to the Hill of Tara in Ireland, examine the mystery of the vitrification of hillforts, and take a look at the enigmatic Gundestrup Cauldron.

This new space journey will take you to the mysterious and gigantic expanse that exists beyond the planet Neptune. We will discover different bodies from the Kuiper Belt, including its most famous resident: Pluto, its satellites like Charon, and other dwarf planets such as Haumea, Makemake and Eris. I will also tell you about tilted orbits and why they happen, tholins, regolith, the mysterious "Planet Nine", the Oort Cloud beyond the Kuiper Belt, and more things...

Tonight's episode takes us on a historical tour of monasticism, especially Catholic monasteries. I get that the topic of monasticism may sound at the same time random and particularly arid. But bear with me: I promise that if you are not familiar with it, you will discover a world of ideas, social experiments, spirituality, or controversies, that you did not realize you needed to know about. Give it a shot! You will learn what anchorites and cenobites are, how Christian monasticism appeared in the Third and Fourth Centuries AD, how monasteries became economic and intellectual centers in medieval times, what the rule of Saint Benedict is, and some of the most famous orders, such as the Benedictines, Cistercians and Trappists, Carthusians, Franciscans, Dominicans or Carmelites.

This is the compilation of the first 4 wonders of the Middle Ages I detailed in recent episodes (Mont Saint-Michel, Tower of London, Towers of Bologna, Charlemagne's palace in Aachen), with a new section at the beginning that explains how the medieval period is defined by historians. There will be more medieval wonders coming soon!

Tonight's episode takes us on a historical tour of salt: how much is there on Earth? Why did it start to be an important commodity for humans in the Neolithic? How was it extracted and transported in ancient times? We will explore all this, and more: how the taxation of salt helped early states to function, how salt was extracted and transported in medieval times, the history of various food preservation methods using salt, and how it was partially replaced with other techniques such as canning and refrigeration.

In tonight's episode, we take a look at two mysteries that keep sparking debates in their respective scientific communities: - The Cambrian Explosion: at the beginning of this period of our planet's history, the number of life forms and their complexity increased dramatically - both in terms of body plans and behaviours, with the emergence of ecological complexity, like predator-prey relationships. But why did it happen? - Dark Energy: like Dark Matter, Dark Energy is a hypothesis, a way of reconciling observations with the laws of physics, especially gravitation. The Dark Energy hypothesis arose with the observation that the expansion of the universe was accelerating instead of remaining constant or slowing down, and this theoretically requires energy. But what could this mysterious energy be: an unknown fundamental force, fields of particles, an energy of the vacuum, something else...?

Before the times of its decadence, the merchant republic of Venice was a great power of the Middle Ages. Its partnership with Byzantium, its shipbuilding and seafaring traditions and its trading capability made it powerful and respected. The building of the city of Venice, and its spectacular basilica (Saint Mark's) were extraordinary accomplishments for a city that began as a muddy outpost created by people fleeing the collapse of the late Western Roman Empire. In this episode, we explore this extraordinary chapter of history.

The Palatine Chapel that is part of Aachen's Cathedral is the best preserved remain of the palace that Charlemagne built when the city was his preferred residence. What is it like, and how was Charlemagne's empire? In tonight's story, we will explore this little known chapter of history and discover the rise of the Frankish Kingdom, the Merovingian and Carolingian dynasties, the attempts at creating a medieval successor to the Roman Empire, and how the seeds of feudality were planted.

In tonight's episode, we take a look at three topics that keep sparking debates in their respective scientific communities: - The existence of supermassive black holes at the center of galaxies, that are several million times more massive than "regular" black holes born from supernovas. Did these gigantic black holes appear as such, did they become so big by absorbing other bodies for billions of years, or is it something else? - Deep-Sea Gigantism, the fact that many species living deep under water become much bigger than their shallow waters relatives, despite living in an environment that offers much less food. - The climate on Venus: was it always as harsh, or did this planet once looked more like Earth before its atmosphere shifted dramatically?

The two towers that stand at the historical center of modern Bologna are some of the last remains of an 800 year old building craze, that saw the medieval city of Bologna covered in high and slender stone towers. Why did this happen? What where the towers like? This is what we will find out in this episode.

The Tower of London is a castle established in the Eleventh Century, shortly after the Norman invasion of England. It served as a royal residence, a fortress, a prison, a safe place for the Crown Jewels, a menagerie, and is now a World Heritage Site as well as one of the most popular tourist attractions in the UK. Join me on this journey to the past that will take us from medieval London to our time.