Penrose, Ghez, Genzel: Why Did They Win The Nobel Prize?

Every year, thousands of people wait for the Nobel Prize Award event. The Nobel Prize is an award of worldwide value awarded annually to living personalities who have distinguished themselves in the various fields of human knowledge, bringing the greatest benefits to humanity, for their research, discoveries and inventions for their literary work, for their commitment to world peace. The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics 2020 with one half to Roger Penrose, for the discovery that black hole formation is a robust prediction of the general theory of relativity, and the other half jointly to Reinhard Genzel and Andrea Ghez, for the discovery of a supermassive compact object at the center of our galaxy. It is crystal clear that we are living in the black hole era. But how did we get to this point? How did we prove that we existed? And what did it take to have the first observation of them? Why did some scientists' way of thinking become so important in our understanding of the universe? Follow me on this journey to know the answer of all of these questions and to take part in the black hole era! In classical physics, based on the principles of dynamics, it was theorized in the 18th century the possibility that a body has such a large mass as not to allow even light to exceed the escape velocity, that is, the minimum speed needed for a free, non-propelled object to escape from the gravitational influence of a massive body. That's why these bodies would have been invisible. Physics referred to these objects as dark stars. So why do we call them black holes? We call them black holes after physicist John Archibald Wheeler. The adjective black comes from the fact that it cannot emit light. The fact that no particles that were captured there can re-emerge, not even photons, is the reason for the term hole. After Einstein's theory of relativity, a concept of a black hole was theorized by scientist Carl Schwarzschild in 1916. Exploring some solutions to the equations of the theory, Schwarzschild calculated that a body hypothetically endowed with very high density would produce such deformation of spacetime in its vicinity that the light moving away from it would tend to undergo a gravitational red shift to infinity. Einstein didn't actually believe that black holes existed in physical reality, because his theory showed that they were a perfect spherical symmetry solution to his equations, and he thought that such a spherical object could not exist and give birth to a black hole. Nature would have found a way to avoid that creation. But then, in 1965, Sir Roger Penrose entered the game. Roger Penrose was born in Colchester, Great Britain, in 1931. He studied at the University College School in London and the St. John's College, Cambridge. In 1965, he came out with an article that showed that black holes existed as a natural consequence of the general theory of relativity. According to him, he started thinking about it on his own, and thinking about the problem more geometrically, not really solving equations because it was too complicated, and not making simple assumptions about symmetry because that was the point. You mustn't have that. So he produced arguments. Penrose made a huge effort to demonstrate mathematically that even chaotic geometries could have given birth to black holes. Ladies and gentlemen, his paper was awarded the 2020 Nobel Prize. He told the Nobel Prize interviewer Adam Smith this story, At that time I was at Birkbeck College, and a friend of mine, Ivor Robinson, who's an Englishman, but he was working in Dallas, Texas at the time, and he was talking to me. I forgot what it was. He was a very, he had a wonderful way with words, and so he was talking to me, and we got to this crossroad, and as we crossed the road, he stopped talking as we were watching it for traffic. We got to the other side, and then he started talking again, and then when he left I had this strange feeling of elation, and I couldn't quite work out why I was feeling like that, so I went through all the things that had happened to me during the day, you know, what I had for breakfast, and goodness knows what, and finally it came to this point when I was crossing the street, and I realized that I had a certain idea, and this idea was the crucial characterization of when a collapse had reached a point of no return, without assuming any symmetry or anything like that. So this is what I called a trapped surface, and this was the key thing. So I went back to my office, and I sketched out a proof of the collapse theorem. The paper I wrote was not that long afterwards, which went to Physical Review Letters, and it was published in 1965, I think. Roger Penrose tried to explain what is happening inside a black hole, going as deep as he could, reaching the so-called singularity. To understand more of this, let's do a small step back. We know that spacetime is curved, and that the Einstein curve equation describes how the deformation of spacetime is due to the mass existing at a certain point in space. The thing is that light itself gets curved by gravity. All of this has its consequences. If gravity can deflect light, the cause and effect bound between two events are influenced by gravity. And there is the possibility to have, in some points, a so curved spacetime that we couldn't have any effect on the outside. This is exactly what happens in black holes. Penrose studied the collapse of a star and how the system would evolve until reaching the singularity. We can't say what happens after that. Despite we know collapses happen, we won't be able to observe one of them until the end. That is, we won't ever be able to observe the formation of a black hole. That's because, as the black hole is forming, time slows more and more. In the end, the observer sees the black hole freezing one moment before his formation. For the observer, the formation of the black hole would take an infinite time. Furthermore, Penrose supposed the so-called Penrose process, a theory that tried to explain how a black hole could lose mass. In fact, he was trying to explain the formation of quasars in terms of supermassive black holes. Historically, the term quasar originated as a contraction of quasi-stellar radio source because quasars were first identified during the 1950s as sources of radio wave emission of unknown physical origin. We know today that a quasar is an extremely luminous active galactic nucleus, AGN, in which a supermassive black hole, with mass ranging from millions to billions the mass of the Sun, is surrounded by a gaseous accretion disk. But did we find them? Before finding out the answer to this question, be sure to like or dislike the video so that we can continue to improve and make these videos better for you the viewer. Plus, be sure to subscribe to the channel clicking the bell so that you don't miss any of our weekly videos. Observation over time lead to confirmed Penrose demonstrations. In the 60s, experimental scientists started to look around and search some traces of black holes. For example, they found that a black hole can eat a star, making it wind around inwards inside the black hole. This contributes to the creation of a so-called accretion disk that releases very hot X-radiation. That's how they found the Cygnus X-1 object. But the most important one was the case of Andrea Ghez and Reinhard Genzel. They wanted to study the region of our galactic center, where they detected a huge radio source, maybe a quasar, called Sagittarius A star. They carried their work for decades, trying to find a method to lead better observations of the galactic center. Developing new telescope technologies, adaptive optics, it was possible to make observations of our galactic center in which we can see many stars orbiting around something, even if we can't tell what that something is. But what is adaptive optics? According to Wikipedia, adaptive optics is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. When light from a star or another astronomical object enters the Earth's atmosphere, atmospheric turbulence, introduced, for example, by different temperature layers and different wind speeds interacting, can distort and move the image in various ways. Visual images produced by any telescope larger than approximately 20 centimeters are blurred by these distortions. An adaptive optics system tries to correct these distortions using a wavefront sensor, which takes some of the astronomical light, a deformable mirror that lies in the optical path, and a computer that receives input from the detector. The computer calculates the optimal mirror shape to correct the distortions and the surface of the deformable mirror is reshaped accordingly. Anyway, by studying those stars' velocity, for example, the so-called S2 star, that completes its orbit in 16 years around that object, we can tell how heavy that something should be. Its weight was estimated in 4.5 million solar masses. That huge object occupied the same point of Sagittarius A star radio source. And with the work done by Penrose that connected quasars and black holes, they concluded that they were facing a supermassive black hole. Ghez and Genzel Discovery was awarded the 2020 Nobel Prize that they shared with Roger Penrose. Their discovery led to a lot of questions. For example, why does the vast majority of the galaxies seem to have a black hole in its very center? But we still have a long way to go before we find the answers. This video ends here! Thanks for watching everyone! What would you ask them? Which discoveries do you think should be awarded the Nobel Prize in the future? Let us know in the comments below! See you on the channel!