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What’s in a black hole? Could we get into a spaceship in one of them? Jorge Luis Álvarez asked recently from Mexico when we invited the readers of BBC Mundo to send their scientific questions.
We rained questions from all over Latin America (thanks!).
The mathematician Hannah Fry and the geneticist Adam Rutherford plan to answer several in their program “The curious cases of Rutherford and Fry”, chose to start with this one.
“Sounds fun!” Exclaimed Fry.
” Nobody knows a lot about black holes, that’s why they are so fantastic,” said cosmologist Andrew Pontzen, which puzzled us a little because we had called him to contribute his knowledge … and ignorance, apparently.
“Not only do we not understand them well, but the little we understand exposes the strangest phenomena of physics,” he added.
Let’s do it
Let’s start with the most basic: what is a black hole.
“Essentially a black hole is a pile of stuff that is stuck in a space so small that nothing can come out, not even light, ” explains Pontzen.
“Imagine that you could pack in a space much more than you would think possible, until it becomes so dense that it has its own gravity.”
And the best ingredient we know to make a black hole are the stars that, at the end of their lives, suffer a gravitational collapse and reach a point of infinite density.
It is estimated that there are some 100 million black holes in the Milky Way.
The problem is that we can not see them …
But then, how did we discover that they existed?
The first person to conceive the idea was the English Reverend John Michell, geologist, astronomer and one of the great forgotten scientists in history.
In 1783, he proposed the existence of ” dark stars ” -the Newtonian version of the black hole-whose gravitational field was so large that even light could not escape.
But it was only thanks to mathematics that the presence of black holes began to be accepted.
While serving in the German army during the First World War, Karl Schwartzchild solved Albert Einstein’s equations and calculated how large the mass would have to be to have a gravitational force so strong as to prevent light from coming out.
However, astronomers continued to view the idea of black holes as ” absurd, ” with many refusing to accept that a dead star could produce an invisible but immense hole in the fabric of space and time.
Also, if by their nature they were invisible, how could they be sure that they really existed?
The movement of the stars
Are we talking about hypothetical entities that are claimed to exist because mathematics and physics confirm that they could be there?
” We have credible evidence that there are objects that behave exactly as black holes would,” the astrophysicist Sheila Rowan told the BBC.
“The observation of the way that stars and gas move in some regions of space tells us that there is a huge amount of mass squeezed into a small space with super strong gravitational effects,” Rowan added.
“It is true that we can not see them but the recent observations of LIGO (the Advanced Observatory of Gravitational Wave Laser Interferometry) have been able to detect gravitational waves in space created by mergers of immense black holes billions of years ago”, adds the expert.
Now, if we were to get on a spaceship and get into a black hole, what would happen?
“The first thing you would feel when diving into a black hole is that the tidal force is so powerful that they pull your head harder than the one that pulls your feet and you stretch until you’re ‘spaghetti’,” says Pontzen.
“If your body is very strong in theory you could survive that stretch and, assuming you are, there are several theories about what you would find in there,” he continues.
“One of the possibilities is ‘the wall of fire’ which, as the name suggests, you would find with a band of burning particles that would fry you like a potato.”
If you do not suffer such a scorching destiny, you could explore it, but only to satisfy your own curiosity because – remember – you can enter, but never leave.
Those of us who stayed on Earth
Those who did not get excited about traveling to the black hole but stayed watching, would see something completely different.
“If those in the ship say goodbye to us by moving their hand, we would see that the movement would become slower and slower until, upon reaching the event’s horizon – the entrance to the hole – the image would freeze and become less intense” explains Sheila Rowan.
“The gravitational force is so strong that it pulls up the information that is trying to get out, that’s why the image becomes paler, slower and smaller, until it freezes.”
And that is precisely what Relativity tells us: the same event seen by observers from different places may not look the same.
Inside, you keep exploring, but constantly the force pulls you towards the center of the black hole.
“That,” says Pontzen, is technically known as “singularity,” which is when everything that has fallen into the hole is piled up in the nucleus so that point is infinitely small but also infinitely dense. “
Also, when you finally become part of that very unique nucleus, you will probably no longer have the form of a human being, not even a spaghettiized or fried one.
“And the terrible news is that Physics is in serious trouble because eventually, all our numbers explode … we just do not know what happens when you get to the center of a black hole,” laments the cosmologist.
- What ‘s inside a black hole ?
- Everything that has entered into it
- The problem is that we do not know in what state all this is
- And we will never know until someone gets inside one of them
- But that trip is dangerous : you finish or return spaghetti or fried or crashed against the core or, perhaps, all of the above
- Although from the outside you will only see slower and blurrier.