What would happen if you fell into a black hole? You have probably already asked yourself this question. And NASA has decided to give you an answer. A challenge even for astrophysicistsastrophysicists. But a way for them, by simulating processes that are difficult even to imagine, to practice working on connecting the complex mathematics of relativity to their consequences in the real world.
A supercomputer to simulate a supermassive black hole
This is thanks to the capabilities of the supercomputer Discover of Center for Climate Simulation from NASA that engineers have managed to reveal what happens at the heart of a black hole. Their project generated some 10 terabytes of data over about 5 days. A computercomputer classic would have needed over a decade. To do what, exactly? To simulate a camera – but the result would be the same for a daring astronaut – crossing the event horizon of a black hole.
To make the experiment more spectacular, the researchers chose a supermassive black hole. 4.3 million times the mass of our SunSun. Consider a black hole similar to the one that lies at the center of the Milky WayMilky Way. More modest black holes, of a few dozen solar masses, in fact produce tidal forcestidal forces stronger ones that can tear apart approaching objects before they even reach their event horizon. Astrophysicists talk about spaghettification.
The tragic fate of a camera that falls on a black hole
The event horizon of the simulated black hole extends about 25 million kilometers. This is just over 15% of the distance between Earth and the Sun. A cloudcloud flat and swirling gasgas hot and incandescentincandescentTHE accretion diskaccretion disk, surrounds it and serves as a visual reference during the fall towards the black hole. The same goes for luminous structures called rings of light. photonsphotonswhich form closer to the black hole from the lightlight which circled around him one or more times. A starry sky background seen from Earth completes the scene.
The videos begin when the camera is some 640 million kilometers away. As it approaches the black hole, the camera accelerates to speeds closer and closer to the speed of light. Like the sound of a carcar of oncoming racing, the glow of the accretion disk and starsstars in the background is amplified. Everything distorts more and more, giving rise to multiple images as their light passes through a space-timespace-time more and more distorted.
In real time, the camera takes about three hours to reach the event horizon. She performs almost two orbitsorbits complete along the way. But for anyone observing from afar, the camera would never reach the event horizon. Indeed, as space-time distorts, the camera image would slow down and then appear to freeze just before. This is why the astronomersastronomers first called black holes “frozen stars”.
Once the event horizon is reached, even space-time flows inward at the speed of lightspeed of light. Then the camera and the spacetime it moves through rush toward the center of the black hole – a one-dimensional point called the singularity, where the laws of physicalphysical as we know them stop working. Destruction of the camera by spaghettification then takes no more than 12.8 seconds. And he only has 128,000 kilometers left to go in the blink of an eye.eyeeye to singularity.
Discover the surrounding cosmos seen from inside a giant black hole with a 360° representation. © J. Schnittman, B. Powell, Goddard Space Flight Center, NASA
Time no longer passes in the same way when approaching a black hole
An alternative scenario is proposed by NASA engineers. The one in which the camera missedmissed narrowly past the event horizon of the black hole. And the physicistsphysicists explain that if an astronaut had accompanied the camera and then returned to the mother ship, remaining sheltered from the black hole, he would have returned 36 minutes younger than his colleagues. Because time passes more slowly near a strong gravitational Source and when moving at close to the speed of light.
The experiment repeated with a black hole that rotates as quickly as the one in the film “Interstellar” would even allow the daring astronaut to return a few years younger than those who remained far away.
