While black holes have a great deal of theoretical and observational evidence to prove their existence, the theory of black holes is not without issue. For one, general relativity predicts that the mass compresses to an infinitely dense singularity where the laws of physics break down.
We can't see them, but we know that black holes can exist thanks to the groundwork laid by Einstein's General Theory of Relativity. A black hole forms when the mass of an object, like a star, suddenly collapses down to a tiny volume. A small object with a large mass causes a gaping dent in space-time.
Scientists have found proof that every large galaxy contains a supermassive black hole at its center. The supermassive black hole at the center of the Milky Way galaxy is called Sagittarius A. It has a mass equal to about 4 million suns and would fit inside a very large ball that could hold a few million Earths.
Technology has advanced enough that we've been able to spot one of these supermassive black holes in a nearby galaxy. In 2019, astronomers took the first-ever picture of a black hole in a galaxy called M87, which is about 55 million light-years away.
Binaries have revealed around 50 suspected or confirmed stellar-mass black holes in the Milky Way, but scientists think there may be as many as 100 million in our galaxy alone.
There is consensus that supermassive black holes exist in the centres of most galaxies. The presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as visible light.
Other studies have also suggested that the creation of a black hole can produce 'baby universes'. But, despite these theoretical oddities, none of these ideas has resulted in a testable prediction or any observable evidence. Hence, the question of whether we live inside a black hole can't yet be answered.
Problem is, no such thing has even been detected. Now part of the trouble is that these impacts would be rare. For the smallest PBH masses, there may only be one black hole hitting the earth every million years. For the Phobos-mass black holes or larger, you may only get one in the history of the earth.
The negative square root solution inside the horizon represents a white hole. A white hole is a black hole running backwards in time. Just as black holes swallow things irretrievably, so also do white holes spit them out. White holes cannot exist, since they violate the second law of thermodynamics.
The throat might be a straight stretch, but it could also wind around, taking a longer path than a more conventional route might require. Einstein's theory of general relativity mathematically predicts the existence of wormholes, but none have been discovered to date.
Black holes themselves are fundamentally unseeable. There's no way to bring back light from beyond the event horizon—the point at which light itself is irrecoverably lost to the object's gravity. The only way we know of their existence is to observe their effects on light and other objects.
So planets could potentially form around black holes, but that's no guarantee that they offer a life-friendly environment. On Earth, living things are hugely dependent on the light and warmth from the Sun to survive. Without the glow of a star, life around a black hole would likely need an alternative source of energy.
From the viewpoint of an observer outside the black hole, time stops. For example, an object falling into the hole would appear frozen in time at the edge of the hole. Inside a black hole is where the real mystery lies. According to Einstein's theory, time and space, in a way, trade places inside the hole.
The nearest known black hole is Gaia BH1, which was discovered in September 2022 by a team led by Kareem El-Badry. Gaia BH1 is 1,560 light-years away from Earth in the direction of the constellation Ophiuchus.
Stellar black holes are very cold: they have a temperature of nearly absolute zero – which is zero Kelvin, or −273.15 degrees Celsius. Supermassive black holes are even colder. But a black hole's event horizon is incredibly hot.
Has Anyone Ever Died in a Black Hole? No, no one has ever died in a black hole. At least not anyone human. The closest black hole we know of is still pretty far away and you couldn't get there if you wanted to.
New black hole simulations that incorporate quantum gravity indicate that when a black hole dies, it produces a gravitational shock wave that radiates information, a finding that could solve the information paradox. Perhaps the most enigmatic objects in the Universe, black holes embody many unsolved paradoxes.
There is no black hole near our Solar System, so there is no chance of Earth ever getting sucked into a black hole. In fact, the closest black hole to Earth is 1560 light years away from us. It would take us around 30 million years to travel there in a rocket!
Within any black hole is the central point, the singularity, which has infinite gravity and where mass is compressed into an infinitely small point. There, it is game over. There's no surviving. And therefore the idea of traveling through time and space, via black hole or wormhole, don't really register in reality.
When matter falls into or comes closer than the event horizon of a black hole, it becomes isolated from the rest of space-time. It can never leave that region. For all practical purposes the matter has disappeared from the universe.
It is possible for two black holes to collide. Once they come so close that they cannot escape each other's gravity, they will merge to become one bigger black hole. Such an event would be extremely violent. Even when simulating this event on powerful computers, we cannot fully understand it.
It was unclear at the time if these corresponded to real objects in the universe. Over time, as other end products of stellar death were detected, namely, neutron stars seen as pulsars it became clear that black holes were real and ought to exist.
'" Roger Penrose (left) proved black holes are real objects. Andrea Ghez (center) and Reinhard Genzel (right) showed that one weighing 4 million times as much as the Sun lurks in the heart of our galaxy. Since Penrose's advances, astronomers have found a wealth of evidence for black holes.
Despite their abundance, there is no reason to panic: black holes will not devour Earth nor the Universe. It is incredibly unlikely Earth would fall into a black hole because, at a distance, their gravitational pull is no more compelling than a star of the same mass.
