[00:00] Can we survive the heat death of the universe?  One day, the last star will die, galaxies will dissolve and black holes will evaporate. The cosmos will become a forever expanding, empty void where nothing happens. Forever.
[00:16] A place without life, purpose, or meaning. But there might be a loophole in the laws of physics for a future civilization to survive the death of everything.
[00:31] And go on having fun and internet arguments for googols of years, maybe even forever. so strap in if you want  consciousness to live forever.
[00:44] Let’s travel 100 trillion years into the future, when the last stars are about to die Here, in this dying universe we find the Noxans, the last civilization still alive.
[01:01] Compared to them we are cave dwellers, they have solved physics and can do things we can only dream of. Still, the same rules of reality apply to them as to us. The Noxans like being alive and don’t want to vanish with the last stars.
[01:16] So they are enacting the plan to keep consciousness around forever. If you want  to keep a civilization running you need a lot of it – but actually not that much in cosmic terms.
[01:29] With five hours of the full energy emitted by the Sun, we could power present day humanity for about 10 billion years. So the Noxans harvest the last stars and build a gigantic complex of batteries around their home star.
[01:45] In principle, this energy could keep them alive for a few hundred trillion years, So now the hard part of the plan begins. The Noxans need to change the nature of life itself.
[02:00] Being alive means doing things – eating,  playing video games and very importantly: thinking. But how much energy?
[02:12] There is an idea from a famous paper we’ll mercilessly simplify and call Dyson's Cold Thoughts – In a nutshell the idea is that the lower your temperature,  the less energy it takes to do something.
[02:24] Your brain runs at a temperature of 310 degrees above absolute zero. At 310 degrees your brain needs 20 joules of energy to think a simple thought
[02:37] that takes one second to think, like “I should wear a funny hat”. If your brain worked at colder temperatures, say 155 kelvin instead of 310, a few things would change.
[02:49] First of all, you’d think at half the speed and the same thought would now take two seconds. But in return, the energy you’d need to think the thought, now halves from 20 joules to only 10.
[03:01] If Dyson's Cold Thoughts are correct, then the colder you go, the less energy you need to think a thought. At one tenth your current temperature, the same thought would take 10 seconds but only require 2 joules.
[03:13] Because it means that we actually might be able to play this game forever. Cooling down a living organism isn’t easy. The reality is that this plan will be  impossible to do with flesh and blood,
[03:31] Before we cool anything down, consider this: Maybe the real trick is stepping back and seeing ideas from different perspectives. Because even with more efficient brains, we’re still prone to the same biases we face today.
[03:45] Thankfully, Ground News, the sponsor of this video, is working to confront these issues. They’re a website and app designed to help you think critically about the information you consume
[03:57] For each news story, they gather articles from around the world, with details on political bias, reliability, ownership, and summaries  that show what each side leaves out. Luckily, it seems both sides agree that robots still have a long way to go.
[04:15] Thinking critically about the news we consume has become a necessity since information bubbles have become the norm. To get 40% off their Vantage Plan,  with unlimited access to all features,
[04:28] go to ground.news/nutshell, or scan the QR code on the screen. Using this link supports our channel and helps make the media landscape a more transparent place. They have to leave biology behind and transfer  their minds into some kind of artificial brain.
[04:45] Or even better, become completely virtual minds and build a digital world as good or better than the real one. This is getting pretty sci-fi, so to be fair we don’t know how to build such brains or computers.
[04:58] the Noxans are desperate and the  laws of physics should allow this. So now we have a pretty big battery with a huge, but finite, amount of energy. And a lot of brains or a computer that can cool down.
[05:14] Ok this is great and all, but how do you stay around with limited energy, forever? Well, this is at the core of the plan: Each time the  Noxans get colder, they need less energy to stay alive So from the Noxan's perspective, as long as they can keep getting colder fast enough,
[05:32] their battery's energy is growing proportionally and could keep them alive forever. Cooling Down As the last star in the universe goes  out and the universe turns dark forever,
[05:45] the Noxans activate their batteries  and start cooling down their brains. The way they do it is extremely simple.  How do you cool down a light bulb? Well, you unplug it so it can radiate away its heat.
[05:57] They enter a state with no activity, thoughts or even dreams, and let their “bodies” radiate heat away to cool down a bit. When they activate again after some time, they are now colder than before.
[06:12] They think slower and each thought uses up less energy from their battery. They enter into a new cycle of  cosmic days and cosmic nights. During the days they are alive and awake,  doing all the stuff they want to do,
[06:24] hanging out with friends, thinking about things, eating virtual cheeseburgers, simulating universes And during the night they are switched  off, lost in dreamless non-existence.
[06:38] Not even noticing anything isn’t happening  while cooling down their brains even more. At the beginning the nights will be  very short and the days extremely long. A day can last a million years while night is only a few hours.
[06:52] But warm things shed heat  much faster than cold ones – cooling from 300 to 299 degrees takes much less time than going from 100 to 99. So as the Noxan brains become colder,  the nights will have to grow longer and longer.
[07:08] So, how long could they actually do this  and how is this a way to live forever? The reason Dyson's Cold Thoughts are so  incredibly powerful is how incredibly they scale.
[07:21] As eons pass in the dying universe, the Noxans keep cooling down and waking up. After a 100 trillion years of this cycle, their temperature  has only dropped to 230 degrees above absolute zero.
[07:34] A simple thought now takes 1.3 seconds instead of 1. Each cosmic night is now 400,000 years long. But even accounting for their slower speeds and  long hibernations, the Noxans have experienced
[07:47] the equivalent of 76 trillion years of life. Over 5000 times the age of the current universe. What is way scarier than being dead?
[08:01] So we need to detach ourselves a little bit –  we simply have no concept how conscious beings   Maybe our Noxans delete their memories regularly, maybe they create new worlds and new life,
[08:16] Maybe they just activate their pleasure  centers and experience perfect bliss forever. As time keeps passing and the Noxans keep going  through their cycle of day and night and cooling down,
[08:30] After quadrillions of years, the corpses of former stars,  white dwarfs, turn yellow, then orange, then red, then black. Trillions of trillions of years later: All galaxies have dissolved like dandelions.
[08:46] Decillions of decillions of years later: The first black holes evaporate in bursts of light like sad fireworks. At a chilling 10 quintillionths degrees above zero.
[09:01] They’ve become so slow that a simple thought takes a trillion years. They spend 99.999999999999999997% of the time hibernating.
[09:17] Their conscious experience is just as fluid and vibrant as on the first day. As they got colder and colder their thoughts got slower and slower.
[09:31] But if you and the world around you slow down at the same pace, you don’t notice anything. Your conversations, thoughts, adventures and experiences feel exactly the same as before. And while the cosmic nights are now a quattuordecillion years long,
[09:45] it doesn’t matter to them, because during the  nights the Noxans don’t experience anything. So no matter how long the nights are, they pass in an instant. Only that with each night they use up even less energy than before.
[10:02] At this point, they have lived, felt and experienced the equivalent of 4,000 trillion trillion years. but the Noxans now need so little energy that it seems larger than ever before.
[10:17] True eternity has just begun. Or has it? Whether Dyson's Cold Thoughts can make you live forever depends on one thing:
[10:29] can you keep cooling forever, or does the universe force you to hit a true limit? There are a few problems – dark energy might  eventually make the universe hit a temperature limit of one nonillionth degrees above absolute zero.
[10:42] but then they can’t cool any further and their battery will begin to run out. And after this much time, the universe will make going on impossible in other weird ways.
[10:54] All matter may decay into iron  or proton decay may destroy all atoms. But even if the Noxans don’t get a true forever – if Dyson's Cold Thoughts work, then within these googol years,
[11:12] their consciousness would experience  the equivalent of two trillion, trillion, trillion years. But the amazing thing about it is that, for all we know, the laws of physics don’t forbid life to adapt
[11:27] And it would mean that life and consciousness  aren’t a brief accident in cosmic history, but the final chapter of existence itself – giving the universe meaning, purpose and hope.
[11:42] Here is your special connection to kurzgesagt! our newsletter delivers the latest updates  straight from the Birbs Nest to your inbox.
[11:57] You’ll be the first to access limited releases and deals, learn about new product drops before the rest, and get fascinating, snackable  science facts about our favorite topics. Of course we’ll also let you know of new video releases and updates from our game department
[12:13] – plus you’ll get exclusive  freebies – like this cosmic diorama. And don’t miss the very special product drop coming soon.