If you watch the fascinating popular science series “Cosmos: space and time”, then you know what a “ship of imagination” is – a spaceship traveling through the universe with the help of imagination. The host of the series, astrophysicist Neil Degrass Tyson, is at the helm of this ship and shows an inexperienced viewer a distant space. I really liked the idea with the ship of the imagination, so I hope Dr. Tyson will not mind if I borrow it for this article. So, let’s imagine that we are on board the ship of imagination and look at our planet from afar. But suddenly, at some point, a black hole appears out of nowhere. What will happen next?
What do we know about black holes?
Black holes excite and at the same time intrigue not only scientists. In the future, interest in these mysterious objects will only grow, especially after the discovery of gravitational waves and the first photo of a black hole. Let me remind you that the existence of gravitational waves was predicted in Albert Einstein’s General Theory of Relativity, but it was possible to prove their existence only in February 2016. Already in 2017, the scientists of the LIGO and VIRGO collaboration who made the discovery were awarded the Nobel Prize in Physics.
Gravitational waves are a curvature of the gravitational field that occurs due to the collision of massive objects, for example, two supermassive black holes. The curvature of the gravitational field propagates like waves, which is why we call this event gravitational waves.
Almost a year ago, on April 12, 2019, just on the day of astronautics, the world saw the first-ever photograph of a black hole, or rather, its event horizon. In addition to the most stunning fact – scientists photographed a black hole – this discovery proved the existence of mysterious space monsters. The fact is that all these years black holes were considered hypothetically existing objects. Then, a few months later, NASA presented the first visualization of a simulated black hole, which shows how the extreme gravitational forces created by these massive objects distort the light around them, creating the effect of a curved mirror. However, despite the fact that we were able to see black holes and even simulate their behavior, we do not know what lies beyond the event horizon. And it is unlikely to find out in the near future. But the good news is that science, armed with imagination, will help in finding an answer to this and other equally interesting questions.
Mass, angular momentum, and electric charge of a black hole
So, we know that black holes appear as a result of supernova explosions – this is a phenomenon in which massive stars dramatically change their brightness and then decay. Some of these stars immediately collapse into black holes, others go through all stages of stellar evolution – from a supernova they can become neutron stars – the densest objects in the Universe that collapse into black holes. But how do scientists measure the mass and properties of these space monsters?
There are three properties of a black hole that (in principle) can be measured: its mass, angular momentum (spin), and total electric charge. An outside observer, like you and me, from the side of the imagination ship, can only judge these three parameters, but all the information about what is behind the event horizon and what the composition of the black hole is unknown. Scientists call this the “hair-free theorem,” since all information about the source matter (called hair) is hidden behind the event horizon. Based on all three parameters, the mass is perhaps the most significant: it is the mass of the black hole – and the huge gravitational forces that it generates – that damage nearby objects.
If the ship of imagination comes too close to the black hole, then the ship itself and all its passengers will stretch out like spaghetti.
Imagine the bow of a ship looking directly at a black hole. Since it is physically closer to the black hole, it will be attracted to it more than the tail. Only the passengers of the spacecraft will be worse, simply because we have arms, legs and a head: since the hands are not in the center of the body, they will be attracted in a slightly different direction than the head. This will lead to the fact that the parts of the body closer to the black hole will be pulled inward. The end result will be not only lengthening of the body but also its thinning (compression) in the middle.
Thus, our bodies or the ship of imagination itself will begin to resemble spaghetti long before it reaches the center of the black hole. But what, then, will happen to the planet if a black hole hypothetically appears out of nowhere near the Earth?
Bad News for the Earth
The laws of gravity, as you know, are equally valid throughout the universe. Therefore, in the case of our planet, the same gravitational effects will act as with spaghettification: the side of the planet that is closer to the black hole will attract much more. In fact, the appearance of a black hole near our planet would mean the quick death of life on Earth and the planet itself. But, since we don’t know what lies beyond the event horizon of a black hole, an imagination ship falling into a black hole can move us to another part of the Universe or to another Universe – depending on the hypothesis that you like best. And you can watch the movie “Interstellar” in 2014 because it presents a rather interesting hypothesis that it might meet a lost space wanderer beyond the event horizon of a black hole.