Black holes have a bad reputation but they are actually very simple. They are all about gravity. Gravity can bend light. It can shorten or increase, redshift, its wavelength. With enough gravity it can stop it coming out at all. We don't know what happens to the mass within the core of the black hole but the force of gravity is so strong but nothing not even light can escape. That often quoted statement is not true. Gravity escapes from a black hole. Now that may seem like nonsense but there is an essential truth in there somewhere. A bit of history cos I love black holes. The idea of a body so massive that even light could not escape was briefly proposed by astronomical pioneer and English clergyman John Michell in a letter published in November 1784. Albert Einstein first predicted black holes in 1916 with his general theory of relativity. The term "black hole" was coined in 1967 by American astronomer John Wheeler, and the first one was discovered in 1972.
Since then black holes have gone from strength to strength. Today more and more, bigger and bigger black beauties are being discovered. Millions of black holes in our galaxy. Supermassive black holes of 21 million sun masses and rising. Black holes at the center of almost every galaxy. Primordial black holes proposed as Dark Matter candidates.
So where do they come from?
Well stellar mass black holes are easy, from collapsing old stars.
As for the rest, nobody knows.
Although not exactly engines of destruction that remove from our universe, they do grow by pulling in dust, stars and other black holes. But you need a voracious appetite to get to 20 million solar masses.
But all this stuff is on the net.
Black holes are the future. All the bright shiny stars will collapse into a black hole or be absorbed by one eventually. We will all end up in a black hole one day.
What are they made of? Well neutron stars show us how dense things can get. A star of several sun masses can collapse to a neutron star only few kilometres across. That's 1 million earth masses in a 10 mile sphere. Or if you like 1 cubic centimetre would weigh 1 million tons, the size of Mount Everest. Now that is what gravity does to atoms. Who says that gravity is the weak force!
So what happens when the star is big enough to form a black hole rather than a neutron star. Over 3 sun masses the neutron star collapses to a stellar black hole.
One distinct possibility is that it's just like a big neutron star but the event horizon is now outside the radius of the mass. No change in the structure of the core. The only difference is you can’t see it. No light can escape.
Note on event horizons. Don't worry about them. They're not real things. Just the crossover point where light can escape. There's an assumption that when stuff crosses the event horizon it is sucked into an infinitely dense singularity. I don’t think so.
More likely inside the event horizon matter looks pretty much like outside of it. Only difference is, you can't see it. Remember, just cos you can't see it doesn’t mean it's not there.
Now stellar mass black holes may have the same core structure as neutron stars, but what about supermassive black holes? Under the enormous forces of gravity inside 20,000,000 sun masses what further structural collapse is possible. Some kind of quark soup or a complete change of phase to produce a particle much denser and with no interaction other than gravity. Not a singularity, but where the particles and forces we see in the Standard Model are crushed by the massive force of gravity. Not unified but destroyed leaving only gravity and the base substance of the cosmos.Could it be Dark Matter?
Whether it is a stellar mass black hole, a binary of 20 or 30 solar masses, primordial black hole formed at the beginning of time, intermediary black hole or super or even ultra massive black hole the arrow of time only points to black holes.
Nature or if you prefer, science doesn't like beginnings and ends. It works in cycles.
So are we all going to end up in black holes? Is that the end of the story?
Rather surprisingly the given version of the universe says that it all started 14 billion years ago and it will all dissipate into the black void eventually. Now 14 billion years sounds like a long time but in cosmic terms it's tiny. The black dark end is about a 10 to the power 140 away so by this reckoning we are just at the start of time.
Just as with Dark Energy they’ve got it wrong.
So what is the cycle of the cosmos? We can see where the arrow of time is pointing but where did it start? What really happened in the Big Bang?
That's a story for another day. 😎
