In the midst of a global pandemic and economic woes around the world, we have the glimmer of optimism known as the Nobel Prize. It was first created to focus the world's attention on the great progresses of mankind in scientific and social fields instead of on the negatives in the world, and it seems that we need it today more than ever.

But enough of the doom and gloom, it is time to focus on what is really important - physics!

This year's award was split equally between theoretical physics and observational astronomy, with Roger Penrose receiving a long overdue award for his brilliant work in the theory of black holes in the 1960s, and Reinhard Genzel and Andrea Ghez sharing the other half for their equally brilliant work in observing the properties of the supermassive black hole at the center of our own galaxy. 

The idea that there could be objects in space whose gravity was so strong that even light could not escape goes back several centuries, but the real study of black holes began in 1916 with the Schwarzschild solution of Einstein's equations of general relativity. Less than a year after the publication of Einstein's theory, Schwarzschild solved the equations for a spherical mass - such as a planet or a star. What he discovered was that if matter become dense enough, then there would be a spherical shell around it that nothing could ever escape from. Even light would be trapped within this event horizon forever. 

However at the time, no one took it seriously. Einstein assumed it was just a mathematical oddity of this particular solution, with no physical meaning. Other physicists assumed that some mechanism prevent matter from reaching such high densities. Black holes were dismissed as a flaw in the equations and nothing more.

Then in 1965 Roger Penrose published what many considered to be the most important research in general relativity since Einstein first proposed the theory. Penrose showed how a realistic star or dust cloud could collapse into a singularity that was hidden by an event horizon. He showed the world that in theory at least, black holes really could exist.

Nearly forty years later, Genzel and Ghez entered the story. Each leads a team of astronomers that have been studying the region around Sagittarius A*, which happens to be the center of our own galaxy. For close to thirty years they have carefully mapped the positions of the brightest stars at the center of the Milky Way, and have used these precise measurements to map out the gravitational field in that region. This is not like watching the stars from your backyard either - this part of the galaxy has dense clouds of dust and gas that block out the light from the stars. And the precision needed means that even distortions in the Earth's atmosphere could change their apparent positions enough overwhelm the tiny movements of these stars over the decades that they have been observed.

Using pioneering methods and equipment to make these observations, both teams independently proved that something exists at the center of the galaxy with a mass equal to four million stars like our own Sun, but in a region smaller than our solar system. And the only thing we know of with that density is a supermassive black hole.

And so that is the 2020 Nobel Prize in Physics in a nutshell. Half the prize for proving that a black hole could form, and the other half for the astronomers who went looking for it in our own galaxy.

Congratulations to the recipients of the 2020 Nobel Prize in Physics!