Whether in our daily lives or across our economies, services provided by satellites have become ubiquitous. However, they remain fragile and vulnerable. Indeed, at any time, their activity can be affected by a breakdown, a collision, malicious interference, or even a solar flare. What would happen if the world was, one day, deprived of its satellites? In an increasingly globalized and interconnected society, would this scenario be the starting point for gigantic chaos?

Ebola virus, H1N1, tuberculosis, cholera, botulism, listeriosis, malaria, nosocomial infections... For decades, viruses, bacteria, and other parasites have regularly made humanity tremble. Microbes are feared and fought relentlessly by the authorities and the scientific community. The objective: to defeat all these pathogenic micro-organisms that take up residence in our bodies and destroy our health. Everywhere, we vaccinate, we give antibiotics, we disinfect, we sterilize... This relentless struggle extends far beyond the medical field - where it is of course indispensable. Over the last two centuries, countless hygiene measures have played a fundamental role in the radical decrease in infant mortality and infectious diseases. And now, in our Western societies, life is increasingly sanitized. But is this a good thing? If nobody wants to protect the tuberculosis bacillus or the polio virus, are all microbes dangerous?

It measures between 0.5 and 1.5 cm and weighs only a few milligrams, yet it is also the number one serial killer in the world. Every year, it is the macabre countdown... 7 million deaths per year and tens of millions of patients affected. The mosquito is one of the worst predators in the world.

Sand is all around us. It is the main ingredient of concrete and we use it to build our homes and urban infrastructures. It is in fact the second most exploited natural resource ahead of oil and natural gas. If sand seems to be an infinite resource, a tiny part of the sand found on our planet is exploitable. To obtain this resource, some beaches and rivers are destroyed and the effect on the environment is devastating. With the help of geologists, engineers and conservationists, we explain why sand is such an important part of our lives and how to protect this precious resource.