Given that his work on black holes during the 1960s finally made him half of the 2020 Nobel Physics Prize laureate, has Roger Penrose’s trailblazing work advanced theoretical physics to what it is today?
By: Ringo Bones
His work on black holes in the 1960s was very influential – not just for established theoretical physics academics – but also in the science fiction universe as well. Since his knighting, Sir Roger Penrose, together with the late, great Prof. Stephen Hawking were often seen as the rock-star scientists of the 1990s post-Thatcher Britain. Penrose shares the 2020 Nobel physics Prize with Andrea Ghez – one of the only four women who were awarded the Nobel Physics Prize since 1901 - and Reinhard Genzhel. But what is it that makes their work fascinating?
A black hole is an object so compact that nothing can escape its gravitational pull – not even light. They are formed when stars die and start collapsing under own weight. Deep inside the black hole resides an infinitely hot and dense object called a singularity. Black holes are perhaps the most mysterious objects in nature because they warp space and time in extreme ways and contain a mathematical impossibility – often referred to by theoretical physicists as a “singularity” – an infinitely hot and dense object within. But if black holes exist and are truly black, how can exactly we be able to observe one?
Sir Roger Penrose won half of the 2020 Nobel physics Prize for his seminal work in 1965 which proved, using a series of mathematical arguments, that under Einstein’s General Relativity, collapsing matter would trigger the formation of a black hole. Penrose’s mathematical results at the time opened up the possibility that the astrophysical process of gravitational collapse – which occurs when a star runs out of its nuclear fuel – would lead to the formation of black holes in nature. Penrose was also able to show that at the heart of a black hole must reside a physical singularity – an object of infinite density where the laws of physics simply break down. At the singularity, our very concept of space, time and matter fall apart and resolving this issue is perhaps the biggest open problem in theoretical physics today.
Penrose managed to invent new mathematical concepts and techniques while developing this proof. Those equations that Penrose derived in 1965 have since been used by physicists studying black holes. In fact, just a few years later, Stephen Hawking, alongside Penrose, used the same mathematical tools to prove that the Big Bang cosmological model – our current best model for how the entire Universe came into existence – had a singularity at the very initial moment. These are results from the celebrated Penrose-Hawking Singularity Theorem. The fact that mathematics demonstrated that astrophysical black holes may exactly exist in nature is exactly what has energized the quest to search for them using astronomical techniques. Indeed, since Penrose’s work in the 1960s, numerous black holes have been identified.
The remaining half of the 2020 Nobel Physics Prize was awarded to Reinhard Genzhel and Andrea Ghez, who each lead a team that discovered the presence of a supermassive black hole, 4 million times more massive than our Sun at the center of our Milky Way galaxy. Genzhel is an astrophysicist at the Max Planck Institute for Extraterrestrial Physics, Germany and the University of California, Berkeley. Ghez is an astronomer at the University of California, Los Angeles. Genzhel and Ghez used the world’s largest telescopes – the Keck Observatory and the Very Large Telescope – and studies the movement of stars in a region called Sagittarius A at the center of our galaxy. They both independently discovered that an extremely massive – 4 million times more massive than our Sun – invisible object is pulling on these stars, making them move in very unusual ways. This is considered the most convincing evidence of a black hole at the center of our galaxy. The topic of the 2020 Nobel Physics Prize – which follows on the heels of the 2017 Nobel Physics Prize for the discovery of gravitational waves from black holes, and other recent stunning discoveries in the field – such as the 2019 image of a black hole horizon captured by the Event Horizon Telescope – serves as a great recognition and inspiration for all humankind.
