Black holes disintegrating over time - really?!
I know it sounds strange, but as you're about to find out there really could be some credit to it (it's not that long either).
Hawking radiation is a theory proposed by none other than Stephen Hawking and attempts to reconcile QM (Quantum Mechanics) with the more relativistic black holes.
The theory of GR (General Relativity) was first proposed by Einstein in the 1900's, and has since become widely accepted in its ability to accurately predict the nature of gravity, in particular the existence and behaviour of black holes.
Make no mistake, GR is still exactly that - a theory, but it's definitely stood the test of time and more familiar individuals than myself will tell you that Einstein's many equations and principals relating to both Special and General Relativity are extremely robust.
Quantum Mechanics vs GR
However, the theory only works for gravity, and can't explain the other 3 fundamental forces that we now know of (strong nuclear force, weak nuclear force, and electromagnetism).
Since then, QM has been constructed by physicists from all over the world and has been extremely successful in providing clarity for the 3 fundamental forces that GR couldn't.
It was becoming more and more clear to us that we live in a quantum world, until the theory failed to account for gravity.
When you take the construct of gravity (particularly that it's a continuous field with infinite parameters) and apply it to the equations as set out by QFT (Quantum Field Theory), the conclusions drawn are completely non-sensical.
It's impossible to describe the environment behind the event horizon of a black hole observationally, for reasons that I cover in this article here, but suffice to say that since nothing can travel faster than the speed of light, and light itself is trapped within the black hole, all sources of information (besides 3 that we'll talk about in a minute) are lost in the black hole forever.
When people talk about black holes, probably the most mentioned feature is this concept of a singularity.
While often mistakenly portrayed as something that actually exists, singularities are non-sensical outcomes when we use our current models like classical physics to explain the compression of matter down to point in space of zero volume.
This point in space is a called a singularity, and with zero volume, its density is infinite - an obviously illogical result.
So what's the problem here?
Well, our current models of physics cannot properly explain the existence of black holes.
While it would be unrealistic to mention every way that our current models fail, let's take a look at an idea that I think is particularly interesting.
I mentioned earlier that 3 pieces of information of a black hole remain, and those 3 are:
mass
angular momentum (spin) and;
charge
Everything else, such as baryonic number, lepton number etc (all the neat quantum stuff) is lost forever.
The reason why this is significant is because it disobeys the quantum principal that information cannot be lost, but what do I even mean by information?
Well, it's just a general word that describes any characteristic - for example mass, charge, angular momentum, number of leptons, number of baryons etc... take it by face value - it's nothing crazy.
The problem is that black holes could theoretically form various different types of matter, like normal matter and anti-matter, but they all essentially produce the same result.
For example, let's say that there's a black hole that formed from the collapse of normal matter, and a black hole that formed from the collapse of anti-matter.
They would both produce the same result, and information about which matter the black hole came from would be completely lost - a principal that quantum physics simply doesn't allow.
But reality always supersedes theory (obviously), so something is clearly wrong with at least the current state of quantum physics.
The reason why I bring all of this up, while seeming somewhat unrelated to Hawking radiation, is because I want to make it clear that our current models of physics simply don't work with black holes, and Hawking radiation is Stephen Hawking's way of attempting to reconcile black holes with quantum physics.
But how, exactly?
In order to gauge a clear understanding of how Hawking radiation arises, it's paramount to have an understanding of some quantum concepts like virtual particles, but we won't go into detail of that here as you'll still be able to get an idea of what Hawking radiation is, where it comes from, and the effect it has on celestial objects like black holes.
Hawking Radiation
So for now, accept that in this universe pairs of particles seem to appear into existence from nowhere for a very short amount of time, during which the pair separate from each other, before recombining and essentially annihilating each-other.
I know that sounds a bit wild, and without serious evidence to back it up you'd probably never believe it could possible be true, but it's undergone thorough testing and the conclusion for now is that it does exist.
Well, these pairs of particles that come from nowhere are what's known as virtual particles.
And it's these particles that are responsible for Hawking radiation...
Stephen Hawking suggested that if this is happening everywhere in the universe, then it seems reasonable to say that it happens in and around black holes.
However, there becomes a point of interest in this idea when you combine it with the current understanding of a black hole, specifically that when particles pass the event horizon, which is essentially the boundary or cusp of a black hole (you can read more about that here), they cannot return - the gravitational pull of the black hole is so immense at this distance from the centre of mass that the escape velocity is higher than the speed of light.
It's when you combine this concept with the idea of virtual particles that you end up with the phenomena of Hawking Radiation.
If virtual particles were to exist along this boundary, the event horizon - ie if a pair of particles came into existence along this boundary - then upon separation, one particle would pass the boundary and never return, while the other particle would move away from the black hole.
Without being able to combine and annihilate each other, they're forced to self-annihilate, emitting a photon of radiation - Hawking Radiation.
Written like this, it seems like there's an obvious violation to the principle that energy cannot be created and cannot be destroyed, as we've just created radiation (energy) from nowhere.
This isn't the case though, which is why a deeper understanding of quantum physics is so beneficial, but I know how challenging those concepts can be.
But this means more than just, "black holes emit radiation".
This is where an understanding of quantum theory, however basic, can help to make things a bit clearer, as the idea of how these 2 particles can result in radiation being emitted and the decrease in mass of a black hole is extremely complicated.
At the time of writing this, I'm not sure as to whether to include a simpler version of how it works, which is what is most commonly done, or not because it really isn't how it works.
It's not simple by any means, and through conveying it in simpler terms, I'll end up losing clarity.
I'd highly advise you to invest some time into literature specific to quantum physics so that you can get the best understanding of this that's possible to date, but for now, take what I'm about to say with a pinch of salt just so that you can get a vague understanding of how it works.
The basic model
2 virtual particles come into existence - one is of negative energy, and negative mass, and the other is of positive energy and positive mass.
The negative particle moves past the event horizon, falling into the abyss of the black hole, while the other positive particle moves away from the black hole, before self-annihilating and essentially becoming radiation - Hawking Radiation.
Now, because the particle with negative mass becomes a part of the black hole, the black holes mass decreases accordingly.
What this means is that, according to Stephen Hawking and his theory, every black hole is slowly disintegrating in the vacuum of space and as they do so, will disintegrate increasingly quicker as they become smaller and smaller, until they disappear.
Now we are talking over extreme time-scales here, as a black hole with potentially millions to billions of solar masses (1 solar mass = mass of the Sun) would be "disintegrating" at an atomic level.
When I say an extreme time-scale, refer to this example if you ever find yourself curious of how long a black hole might survive for:
Ton-618, the largest known black hole, is approximately 10.4 billion light years away, and is suspected to have a mass of around 66 billion solar masses (remember that 1 solar mass is equivalent to the mass of the Sun, so this black hole is 66 billion times as massive as our star...)
As a quick side note - for fun - this black hole has a diameter of roughly 130 times the diameter of our entire solar system. Not the distance from the Sun to Earth (that's known as the AU, Astronomical Unit), but the distance from one side of our solar system to the other!
As this black hole is gradually disintegrating, it would take about 2^107 seconds to be rendered down to nothing!
That number doesn't really look like much, so try this instead.
2 billion billion billion billion billion billion billion billion billion billion billion billion seconds...
Although this is disregarding the fact that black holes often roam the universe pulling apart stars and combining with other black holes, which in both cases would cause drastic increases in mass, so the number is likely to be even higher than this in practice.
Especially when you consider that Ton-618 has an accretion disk, which is basically an aura or disc of gases and dust that swirl around a black hole at huge speeds (17000 kms^-1 in the case for TON-618) that's as large as our entire galaxy... so approximately 120,000 light years in diameter.
That's a heck of a lot of matter that's going to feed the black hole for all of eternity.
Additionally, remember that this black hole is 10.4 billion light years away, which means that the light from this black hole takes 10.4 billion years to get to us.
So by now, this black hole is likely far more massive than what our 10.4 billion-years-too-late prediction states.
I think that's all we'll cover in this particular article, as I don't want to get too caught up in the logistics of virtual particles and how they interact to form radiation while decreasing a black hole's mass.
As I said, it's not as black and white as it's made out to be here and in reality is an extremely complicated idea that involves quantum fluctuations and the like.
Hopefully the idea of black holes disintegrating was at least interesting though!
Thanks for reading, and consider sticking around here at Expansive!