Can humans live forever even if the universe comes to an end?
We Found a Loophole to Survive the End of the Universe - YouTube
At the end of the universe, the last star will die, galaxies will dissolve, and black holes will evaporate. After that, the universe will continue to expand forever, becoming an empty void where nothing happens. This, Kurzgesagt described as 'a dull, depressing place without life, purpose, or meaning.'
However, there may be a loophole in the laws of physics that will allow future civilizations to survive the death of all things.
The loophole could be something like 'enjoying discussions on the Internet forever.'
'How to outlive the stars'
Imagine that 100 trillion years in the future, there is one last surviving civilization in a dying universe, and this future civilization has perfectly solved the laws of physics, achieving everything humanity could only dream of.
If this future being doesn't want to die with the last star and plans to maintain consciousness forever, is this even possible?
The first problem is energy: civilization requires a lot of minerals to sustain itself, but on a cosmic scale, there aren't that many.
If we harnessed all the energy emitted by the sun for five hours, we could power humanity today for approximately 10 billion years.
Therefore, if future humans were faced with a need to secure energy as the universe was about to come to an end, they would harvest the energy emitted by the last star and build a huge battery complex around their home planet. In principle, this amount of energy would be enough to keep future humans alive for hundreds of trillions of years, Kurzgesagt points out. However, while trillions of years is a long time, it is not eternal. Therefore, future humans would need to change the very nature of life.
'Ice-cold thinking'
Being alive means doing things - eating, playing video games, thinking, etc. - and these things require energy.
There's a famous paper called 'Dyson's Cold Thoughts,' which simply states that the cooler your body temperature is, the less energy it takes to do something.
The human brain requires more energy at higher temperatures, but at absolute zero the brain ceases to function.
For example, say your brain needs 20 joules of energy to come up with a simple thought like 'I'll wear a funny hat' in one second. If your brain could function at lower temperatures, a thought that requires 20 joules of energy in one second at 37 degrees Celsius would change to a thought that requires 10 joules of energy in two seconds at -118 degrees Celsius.
The colder it gets, the less energy it takes to think, so if your body temperature drops by a factor of 10, it might take you 10 times longer to think, but it will require 10 times less energy.
Kurzgesagt points out that by using this 'Dyson's cold thinking,' it would be possible to live forever. What is needed to do this is to cool the living body. However, simply putting it in a refrigerator would cause death from hypothermia. In other words, the body is an obstacle to realizing the plan of 'cooling the brain to save the amount of energy needed for thinking.'
If we need to abandon our physical bodies and transfer our brains to artificial ones, and connect these to a network, people in the future may be able to continue living in a digital world as beings of thought only.
Because it's quite a science fiction story, Kurzgesagt mentions, 'I don't know how to make the artificial brains and computers necessary to realize such a fantasy.' Still, if it's 100 trillion years in the future, it's quite possible that these technologies will be realized.
Even if we could obtain vast amounts of energy and successfully create a fuel-efficient artificial brain, how could it survive forever? Based on Dyson's 'cold thinking,' the lower the temperature, the less energy is needed to think. Therefore, if we could lower the temperature to the very limit of its operating temperature, it might be possible to survive for an almost infinite period of time.
When the last star dies and darkness descends upon the universe, the people of the future will activate the batteries they have prepared, begin cooling the artificial brain, turn off the brain, and enter hibernation. This will put the artificial brain into a state of no activity, no thought, and no dreams, and it will radiate heat and gradually cool down.
Once your brain has cooled down enough, you can turn it back on, and although your thinking speed will be slower because it's cold, it should require less energy to think.
Even after becoming an artificial brain, the brain will be turned on when it is active in the digital world and turned off when it is inactive. When the power is turned off, the brain will no longer dream and will become completely empty. This also helps cool the artificial brain.
It takes much less time for a temperature to cool from 300 degrees Celsius to 299 degrees Celsius than it does to cool from 100 degrees Celsius to 99 degrees Celsius, so the lower the temperature of the artificial brain, the longer it will take to cool down, i.e., to power it off.
What makes Dyson's 'cold thinking' so powerful is its sheer scale. Even if the power cycle continued for 100 trillion years, the artificial brain's temperature would only drop to about -43 degrees Celsius, above absolute zero. This would extend the time it takes to perform a simple thought from 1 second to 1.3 seconds. While this would mean the 'power-off time' for the artificial brain would be a whopping 400,000 years, a future human surviving with an artificial brain could still function with their brain powered on for the equivalent of 76 trillion years before the 100 trillion years had passed. This is more than 5,000 times the age of the universe at the time of writing.
Therefore, Kurzgesagt states, 'The only thing scarier than dying is living forever.' 'If a conscious being were to survive for that long, we have no idea how it would cope,' he says.
Millions of trillions of years after the end of the universe, white dwarfs, the remains of former stars, will continue to change color from yellow to orange to red to black.
Once all the galaxies have disappeared, the black hole will evaporate in a violent explosion.
Even so, future humans can continue to live in their artificial brains. However, because their artificial brains have cooled down too much, simple thoughts that previously took one second now take a trillion years to process. As a result, they spend 99.9999999999999999997% of their time in a completely blank state, powered off. Even though it takes longer to think, future humans living in a digital world still perceive time as fluid and vibrant.
After 4 quadrillion years, the battery finally runs out of power. However, the artificial brain's activity time is now shorter, so it no longer requires much energy.
The key to whether or not we can continue to live forever by repeating this cycle depends on whether the limits of the universe are reached first, or whether the artificial brain reaches absolute zero.
Dark energy could eventually cause the temperature of the universe to reach temperatures so close to absolute zero that the artificial brain would no longer be able to cool down any further and its battery would begin to die. At that point, quantum noise in the universe could destroy the artificial brain. Proton decay could destroy all atoms.
Even so, the artificial brain could last for as long as two and a half decades before it reaches its end.
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