Why You Might Live Inside a Black Hole
Imagine for a moment that you are falling towards a black hole. Or to be more exact an event horizon. All holidays need a good scare. If you could, you’d look outward to see a sky full of stars fading away to oblivion. You’d feel the forces of gravity rapidly multiply around you, stretching you apart violently into a string of atoms until the event horizon consumed you. Once you fall behind the horizon, and it is an abstract place, where you and nothing else can escape without exceeding the speed of light, you are lost to this universe forever.
Still if the hole is bigger, in the billions of solar masses. These beasts live inside galaxies. One solar mass equals the mass of our sun. Then it is entirely possible that you could (in theory) survive the fall into the hole and cross the event horizon. From there it could be an eternity (really no one knows) when you’d meet your final oblivion at the singularity.
Yet black holes are not completely black. They leak radiation in a process known as Hawking Radiation. A half century ago Stephen Hawking wed Quantum Mechanics to Relativity. He did this by computing the heat of quantum fluctuations. This is a constant stream of virtual particles that pop into existence for a brief moment before evaporating. Hawking interpreted this radiation as the heat or temperature of the hole, taking the temperature as the average heat. The Unruh effect. Hawking’s wisdom was to compute this heat at infinity and this implied that some of the particles escaped.
Across immense expanses of time, this heat steals away the mass of the hole. Einstein said that mass and energy are equivalent with the equation E=Mc^2. A black hole with the mass of the sun should evaporate in 10^64 years and this is longer than the current age of the universe.
The Light Cone and the Particle Horizon
But what if the observable universe is inside an event horizon? An event horizon is again, any boundary where escape is mathematically impossible. A quarter century ago astronomers discovered that the universe is inflating, and this expansion is accelerating on account of dark energy. Don’t ask me to explain dark energy, since it is still an unsolved problem in physics. Plus this energy is driving the growth of the observable universe. The boundary of the observable universe is occasionally known as the particle horizon and this defines the light cone of the cosmos.
The light cone is an invention of Einstein’s Relativity and it defines the spatial limits of light. This cone specifically states the regions in the cosmos that light can reach in its 13.7 billion year lifetime and it varies by the observer. Our horizon reaches outward to about 16 billion light years. Any photons from any Sasquatch, Werewolves, or aliens that exist beyond this boundary are lost to our sight forever. They might as well be in another universe.
But shouldn’t this event horizon emit Hawking Radiation? Yes it should. In theory this energy does leak across the boundary and yet our cosmos isn’t shrinking. Quite to the contrary it is growing (dark energy). Our particle horizon or light cone is predicted to reabsorb this radiated energy.
In the epilogue, the event horizon of a black hole and the particle horizon of the cosmos are imaginary constructs of mathematics. Still this boundary presents real consequences for the longevity of black holes and our long term understanding of the universe.