Today the whole scientific world is in mourning. Stephen Hawking died, one of the most brilliant minds that have ever walked on Earth.
The famous physicist was 76 years old and has fought almost all his life with a rare form of slow-moving SLA. Although doctors had given him a few years of life, Stephen Hawking never gave up and spent decades studying the origin and fate of the Universe, collaborating with many scientists and becoming one of the most famous icons in the scientific world.
He also appeared in many TV series, among which we remember Star Trek, the Simpsons and Futurama, has participated in various scientific transmissions and has also written several books on his theories, always using a simple language that has allowed even newbies to grasp the greatness of his ideas.
I confess that it is not easy to write an article about him. His work has ranged far and wide, without limits.
Surely theories for which it was best known were those on black holes.
In 1970 he postulated his second law of black holes, according to which the event horizon of a black hole can only increase but not diminish. And only four years later, he retracted his theory and showed that a black hole behaves like a black body and can therefore be described by the laws of thermodynamics: according to this new idea, a black hole should emit radiation, the Hawking radiation, and evaporate slowly in a variable time from 1066 to 10100 years.
Stephen Hawking has also worked all his life to solve the Black Hole Information Paradox: this derives from the fact that systems in quantum mechanics are described by different variables, while a black hole can be described only by mass, angular momentum and electric charge. If it’s correct that the black hole swallows up and destroys everything that enters it, then the information itself would be destroyed by violating the principle of conservation of information. The theory of the British physicist excludes at least in the first instance a conciliation between quantum mechanics and general relativity. Hawking proposed several solutions, the last of which very recently in 2015. According to this last solution, the black hole would preserve the information while erasing it and therefore allows it to survive, even if in a chaotic way. Later this re-coded information would be re-emitted in the Universe through the Hawking radiation.
Still on the subject of black holes, the physicist postulated the existence of small black holes in the beginnings of the Universe, that aren’t generated by the collapse of the stars but by fluctuations of space-time. Such black holes should be very hot and emit Hawking radiation more intense than the classic black holes present today, and a possible detection of this radiation would confirm Hawking’s theory. However, since the temperature of those black holes would be very close to absolute zero, detecting such radiation seems beyond our current possibilities.
The Hawking radiation unfortunately remains therefore only a theory, not yet been observed directly, however recently in the laboratory an experiment simulated the equivalent of black holes and it was observed the emission of waves, although acoustic. This demonstration, by Jeff Steinhauer, of the Israeli Technion Institute in Haifa, would therefore constitute a first indirect verification of the theories of Stephen Hawking.
Stephen Hawking was also very prolific in studying the geometry and evolution of the Universe, trying to apply quantum mechanics to the first moments of the Universe and coming to suppose that the Big Bang was nothing more than a singularity of behavior opposite to the black holes. and that the concept of time itself made no sense before a quantum fluctuation of the original singularity led to the birth of the Universe.
I want to conclude this article with one of his most famous phrases:
Remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist. Be curious. And however difficult life may seem, there is always something you can do and succeed at. It matters that you don’t just give up.