Disclaimer: The following is my analysis based on dozens of books and magazines I have read and pieced together over the years. Most of the concepts I’ve never seen related together before. Most of it I think I understand pretty well, but I have been wrong before. Some of it I know I don’t understand. Input and corrections are welcome.
No one likes to die. Humans take grand steps to avoid being killed. Most religions hold that some form of consciousness outlasts the death of the body and that the soul lives for eternity. How might such a thing work? It would seem to violate physics.
Medical science may one day progress to the point that the physical body can be protected from aging and almost any disease or injury. It might also be possible to upload copies of our minds onto more durable, artificial bodies, or onto multiple, wirelessly connected bodies in case one of them is completely obliterated by a bomb or something. To avoid supernova-sized catastrophes, our bodies could be spread across multiple star systems. This way, something of us would always survive.
If possible, these methods might keep us alive for billions of years. However, we would eventually run into the problem of entropy and heat death. One day, all useable energy will be gone; everything will be homogenous and uniformly heated. Then nothing will ever happen again. By carefully slowing our rate of energy consumption, we could theoretically extend our lives indefinitely – but could our state then legitimately be called life? Awareness requires thoughts, and thinking uses energy. Slowing our energy consumption also slows our thinking. It is not enough for us to live forever in time on a finite amount of energy if our thoughts also become finite.
No one really knows how consciousness works, but one Scientific American article I read long ago suggested that thought rate was proportional to the volume of the brain, while energy use was proportional to the surface area, meaning that we could in fact experience an infinite number of thoughts on a finite reservoir or energy – albeit at a progressively retarded rate. This is very encouraging.
Unfortunately, there was a catch. Heat loss is also proportional to the surface area, meaning that a continually-running brain will heat up. It must be periodically shut down so it can cool. Since the rate of heat dispersion depends on the difference in temperature with the surrounding environment, as the brain uses up energy, the universe will become even closer to equilibrium, and the cooling time will become progressively longer. This requires some sort of “alarm clock” to wake the brain at the appropriate time and no such mechanism is 100% reliable. Given an infinite amount of time, it would eventually fail us and we would never wake again.
There are other limits on time as well. In accordance with the Heisenberg Uncertainty Principle, there is always a non-zero probability of measuring any object to be in a different position than where it was previously measured to be. On the scale of atoms, this manifests as a lot of “jumpiness.” On the scale of people, planets, and galaxies, it means that given enough time there is a statistical certainty that one day they will simply leap across the universe far away. It is much more likely still that only small parts of them will be similarly transported, which in the case of humans can be deadly (imagine if your heart suddenly vanished). This is called quantum tunneling. On infinite timescales, the entire universe could suddenly pop into a different configuration, with a new arrangement of matter and new laws of physics. There would be no way to survive.
There are also limits on space. It is not good enough that we have an infinite number of thoughts if we do not retain them as memories. Is it really life to just have the same two thoughts over and over? What are we if not our unique path through history? If the original body is not important, and memory is not important, what is to separate us as individuals? Otherwise it could be said that we have survived so long as someone else survives. Who is to say it isn’t us? Memory storage requires space. Even with combinatorics, infinite memory storage requires infinite space.
Even assuming the universe to be infinite in volume, we know from observation that it is expanding. Matter is thinning. The farther away a galaxy is, the faster it recedes. Galaxies far enough away recede faster than the speed of light. Light from those galaxies can never reach us even in principle. Nothing can go faster than light in space (the receding galaxies are following the flow of space, not moving in it). This means that an infinitely-sized (or at least continually-growing) brain will eventually be pulled apart by the expansion of the universe and its various parts will lose contact with each other. The only ways around this problem are to use faster-than-light communication (impossible), reverse the expansion of space (good luck with that), or to find ways to store ever-more information in an ever-smaller volume.
Unfortunately, there is a maximum limit on how much information can be packed into a given space. Counterintuitively, this limit is proportional not to the volume it is packed into, but to the surface area of a sphere with that volume. It is called the holographic bound. Holograms have some weird properties. Information in holograms is spread around such that a small part of the hologram can be used to recreate the whole picture – though at a lower resolution. They are also able to hold in only two dimensions the information to recreate a three-dimensional image. I don’t understand very well myself how this works, but it is made possible by quantum entanglement. Since every particle in the universe has interacted directly or indirectly with every other part, in a sense the entire universe is entangled and therefore should also have holographic properties. This is why some physicists have suggested that our four-dimensional spacetime might be a “simulation” running on a computer in a three-dimensional spacetime. Thus, the amount of storage space available is proportional to a two-dimensional area and not a three-dimensional volume.
Probably not coincidentally, the holographic bound of a cache of information is the same as its Schwarzschild radius. Information is stored on matter and increasing the information density to its maximum can only be done by increasing the density of the material. Squash a material enough, and it will collapse into a black hole. The volume of a black hole is not proportional to its mass, but rather needs to be ever larger with every addition to still be called a black hole. A black hole with the mass of the Earth needs to be roughly the size of a golf ball and therefore very dense, but a black hole the size of the solar system need be only as dense as water. The observable universe is so big that to be a black hole it need be only as dense as roughly what we measure it to be. We might be inside a black hole now! To retain an infinite memory, we must grow an ever-larger brain that also grows ever-thinner to prevent gravitational collapse.
Even assuming we find a way to halt the expansion of the universe or a way to send signals faster than light in order to keep different parts of our brain in constant communication (or both), we will eventually run into a math problem. Any finite set of matter only has so many possible configurations. Given an infinite amount of time, something must repeat. Given an infinite extension in space, this means our superbrain will be filled with copies of the same sequence over and over. Some of these sequences will be whole universes just like ours and contain fully functioning organisms with brains themselves – believing themselves individuals distinct from their surroundings. Maybe that’s what we are. Maybe we are already part of a superbrain that has already lived forever.
Related Post: Where Is Heaven?
My name is Dan. I am an author, artist, explorer, and contemplator of subjects large and small.