When we envision black holes, we think of an object of infinite density, a singularity,
with gravity so great that it creates an event horizon from which even light cannot escape,
often surrounded by a brightly glowing accretion disk of very high speed matter spiraling around
the black hole.
One of the best depictions of this in science fiction is the black hole Gargantua featured
in the movie interstellar, a depiction that was originally conceived of for the film by
physicist Kip Thorne.
And while that’s certainly true for some black holes in the universe, it isn’t a
hard and fast rule for them all.
Indeed there are black holes that are simply that, an event horizon with no accretion disk
for lack of material to devour.
But no matter the circumstances of black holes, they all share one characteristic.
An event horizon, from which no light or information can escape.
This means that the singularity at the center of the black hole cannot ever be seen.
Except in one hypothetical instance that if we ever saw it, it could fundamentally revolutionize
our understanding of the universe.
This involves rotating black holes.
Rotating black holes are going to be the predominant type of black hole in the universe, given
that whatever formed it, such as a star going supernova, would have been rotating as well.
There is a type of hypothetical black hole known as a Schwarzschild black hole that isn’t
charged, and does not rotate, but that’s really more of a concept thought experiment
than something that’s going to be encountered in the universe.
But Schwarzschild black holes hold some interesting possibilities themselves, if one could exist
or be made to exist, more on that in a different video.
But while rotating black holes are probably the rule of the universe, there is a possibility
that some portion of them, probably rare, are spinning very rapidly, such as those formed
from rapidly rotating stars that go supernova.
We know that stars like this exist that rotate so rapidly that they flirt with the speeds
that would destroy them, such as the star Regulus A which rotates at 86% of the speed
needed to rip itself apart, leaving the star in a badly squashed oval shape.
If that indeed translates to rapidly spinning black holes that form during supernovas of
these types of stars, then we end up with a very interesting animal indeed.
A naked singularity.
These have not yet been seen in nature, and if they do indeed exist, they will rank amongst
the universe’s strangest phenomena.
Essentially what happens in a very rapidly spinning black hole is that the singularity
can form a ring instead of a point.
This would have the effect of creating two event horizons, and as the spin increases
the event horizons are predicted to shrink towards the singularity until finally they
match it and thus expose the singularity to the universe.
The heart of a black hole out there for all to see.
There are huge questions here, first and foremost is why we don’t see these.
It’s been suggested that naked singularities would be highly unstable, and may not exist
for long.
And that may be a good thing, because encountering such a thing would be beyond bad.
The immediate area around a naked singularity would be inherently unpredictable.
The laws of physics in this environment break down, specifically General Relativity, due
to the extreme distortions of space and time near the singularity.
Any star or planet passing through the environs of a naked singularity would very likely be
destroyed in a very visible manner.
But where this gets really strange is in the physics of the matter, a conundrum involving
the two competing sets of laws of physics used in this case, quantum mechanics and General
Relativity.
In the case of the interior of black holes, or near a naked singularity, they give two
incompatible predictions.
With a black hole, this discrepancy is easy to deal with, you just view anything beyond
the event horizon as not really a part of our universe any longer.
This similarly goes for the singularity that is thought to have given rise to the big bang,
you can’t see before a certain period in the big bang, so you don’t have to worry
about spotting the singularity that caused the universe, if indeed that model is correct.
But in the case of naked singularities, you are forced to reckon with the discrepancies
because they are no longer hidden.
No one is certain just what we would see if we did spot a naked singularity.
It’s assumed however that naked singularities, like black holes, rotate and that may offer
a clue on just how to detect naked singularities should they exist, and differentiate them
from black holes, which are clothed singularities.
But it may just as easily be that quantum effects regarding naked singularities always
clothe them, just as in the case of black holes, where the event horizon conveniently
hides the singularity, or in the big bang where the opaqueness of the early universe
before about 300 to 400 thousand years after the big bang obscures the singularity there.
It may simply be that nature doesn’t allow us to see singularities and always pulls some
sort of trick to hide them.
And this is where it gets spooky.
An event horizon, an opaque early universe, and a hand wavey invocation of quantum effects
would seemingly be three separate ways of concealing a singularity.
That seems somewhat contrived in a simulation theory sort of way in that it just seems like
a convenient, if patchy way to hide things that violate the laws of physics.
But it may be how the universe works and that’s that.
But if naked singularities do exist and we can freely observe them, the promise is bright.
We’d literally be able to watch the collapse of a star to become infinitely dense and directly
study some of the conditions of black holes that are obscured to us in normal black holes
with event horizons.
It might also yield clues on why general relativity breaks down under these conditions and give
us a significantly more complete picture of how the universe works.
But one other possibility is that black holes simply cannot, for whatever reason, rotate
rapidly enough to produce a naked singularity.
But that seems odd, and there is one black hole known that spins very rapidly, though
not enough to produce the phenomenon.
Another type of singularity is even more mysterious because it may bear some implications on the
birth of the universe itself.
Physics tends to like opposites, and they are often seen in nature.
You simply reverse the equations describing something like a black hole, and you get the
opposite effect, a prediction of a white hole.
A white hole is a singularity that does draw you in as it has mass and gravity, but you
can’t ever reach the singularity and the event horizon of the white hole spews out
matter.
You literally cannot enter a white hole, at least until it becomes a black hole.
But it would release light, information, matter and energy in the opposite way from how a
black hole takes them all in.
Yet we see huge amounts of evidence for the existence of black holes, but nothing solid
for white holes.
It’s unknown why this is, but one possibility is that we are seeing them in the form of
gamma ray bursts, which might make sense given that it’s been suggested that white holes
would be inherently unstable and collapse on themselves almost immediately through their
own gravity and become a black hole.
They would appear randomly in the universe, release energy for only a short time, and
then disappear, and the emissions would fit the profile of a gamma ray burst.
And there is a candidate for this.
Gamma ray bursts tend to fall into several categories, essentially long and short and
have been associated with neutron star mergers and supernovae.
But there is an oddball.
Known as GRB 060614, this burst was detected on June 14, 2006, and it was a long burst
so a corresponding supernova was expected.
It never happened, this burst has no association with a supernova at all, and features of the
signal suggested that it wasn’t a normal gamma ray burst, but part of a new category
of its own.
Subsequently, it was suggested in a paper by Retter and Heller, link in the description
below, that it may in fact have been an observation of a white hole’s brief existence.
But there is one other instance that looks very suspiciously like a white hole.
It’s the big bang itself, where something happened, an initial singularity that may
have existed just before the dawn of the universe that contained all the energy and spacetime
we see today, that erupted in the expulsion of a huge amount of energy that led to the
formation of matter.
It essentially meets the criteria.
If it was indeed a white hole, then it begs certain questions.
One model of white holes is that they represent the “other side” of a black hole.
Matter enters a black hole, only to be expelled out the other side.
Where it goes is unknown, but there are some ideas.
One is that black holes serve as gateways to other universes, and that each black hole
on the other side represents a big bang of its own and a daughter universe is spawned.
This could also be the case for time, a black hole might exist at one time, but its counterpart
white hole exists at another.
But if the big bang were a white hole, then the black hole that spawned it had to be beyond
supermassive, but at the same time we don’t know what the universe it existed in would
be like.
A lot of mass may not have been a problem for it.
But whenever you get into the idea of other universes, all with differing laws of physics,
the possibilities for those universes becomes dizzying.
One interesting idea comes from physicist Lee Smolin known as the Fecund universes theory.
This works something like natural selection in biology, but instead is applicable to universes.
So you have a collapsing black hole, that causes a white hole that forms another universe
on the other side.
Since its fundamental properties may be different from the original universe, different things
can happen.
These universes may contain varying amounts of black holes of their own, or potentially
none at all.
If none, then you have a universe that cannot spawn other universes.
If it has few, it produces less universes.
But if it has a lot of black holes, like our own universe does, then it will spawn immense
amounts of new offspring universes.
This starts looking eerily like natural selection and evolution at that point.
This would mean that successful universes, if you want to call it that, spawn more similar
universes that have more chances for having similar laws of physics to the original.
The new universe may even be defined by the universe that spawned it much like a child
looks like its parent.
You can apply all kinds of familiar words to this in science, but in a very different,
very strange setting including reproduction, mutation, natural selection and so on.
This is not to say that universes themselves are alive, only that in some highly theoretical
ways they mimic aspects of life, but fundamentally they are ultimately what allows for life,
and intelligence to exist at all.
And that’s where this gets interesting.
The concept of fecund universes populating the multiverse with successful offspring universes
actually offers a ready explanation for the fine-tuning problem.
The fine tuning problem is that a whole set of parameters had to be just right, or closely
so, to allow the emergence of life in our universe.
Mess with those parameters even a little bit and bad things happen, and there are a whole
slew of them and we’re not far enough along to know what all of them are in order to arrive
at us.
Some of these parameters are very fundamental, such as mess with a number in the big bang
and the result is that matter itself can’t exist, or the laws of physics are different
and motion doesn’t behave like it does, or chemistry is completely different not allowing
for complex organic interactions for life to operate on, and so on.
You can make arguments here all day long about parameters ranging from the big bang to the
formation of the earth, that if the rules had been slightly different, the chain would
have been broken and we would not be here.
Yet it happened.
But with the fecund universe hypothesis, it simply becomes a natural result of how the
multiverse works.
A successful universe that has lots of black holes that create other universes similar
to it, and every now and again, perhaps even commonly, you will get a universe that allows
for intelligent life as we know it.
Lesser universes remain dead, or nearly so and reproduce less, and only branches of the
successful universes get anywhere as far as reproduction.
Interestingly, this hypothesis which was published back in 1992 offered some predictions that
seemed testable, but it’s debated as to whether they’ve held up and in once instance
may not have.
But, only time will tell if this little known theory is correct, and black holes represent
new universes, our own included, or if the similarities between the big bang and white
holes is merely superficial.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently glad we live in a
nice universe, but dismayed that it’s so secretive about its singularities.
And then there’s dark matter and dark energy and plenty of other things it’s openly hiding.
I suspect a shenanigan and be sure to check out my books at your favorite online book
retailer and subscribe to my channels for regular, in-depth explorations into the interesting,
weird and unknown aspects of this amazing universe in which we live.