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What life could be like for civilizations 1 trillion years from now (phys.org)
209 points by tosh on June 30, 2018 | hide | past | favorite | 158 comments



Isaac Arthur made a compendium called Civilizations at the End of Time [1] that goes into this territory. This guy, in my opinion, goes above and beyond even your typical hard scifi. Can't recommend highly enough.

[1] https://www.youtube.com/watch?v=p58yFf7aZsM&list=PLIIOUpOge0...


I just gave this a go. It's amazing, thank you for putting it on my radar.

At first his speech impediment makes it harder to follow, but 5 minutes in you're used to it and you're just riveted by the content and the clear communication style.

This is quality stuff.


I guess it’s more fun to dream about the world millions of years in the future, but wouldn’t we gain so much more if we spent all of our energy trying to optimize acquiring knowing more rapidly in the next few decades?

For example, supply 9 billion humans with clean, renewable energy by 2050. Accelerate cures for cancers, heart disease, malaria, etc. Large colony on Mars within 20 years, ...


It is not how science works. You can't predict what might be useful.

  1940 Hardy labels number theory (his own area of mathematics) as useless
  1977 RSA
You can't imagine the modern internet without cryptography.


Hardy's statement was philosophical, not a scientific prediction. Encryption was already an important science by 1940


My favorite example of the unexpected practical benefits of primary research is the first paragraph from the original proposal for the web: https://www.w3.org/History/1989/proposal.html

> This proposal concerns the management of general information about accelerators and experiments at CERN. It discusses the problems of loss of information about complex evolving systems and derives a solution based on a distributed hypertext system.


You can have imagination without implementation.


Are these endeavors so separate? The curiosity, thirst for understanding, and drive for mastery and improvement that brings advances in engineering, medicine, and science seems to also cause people to gaze longingly at the cosmos.

Not to say we shouldn't be pushing to make even more progress on those difficult, pressing issues.


These long range time horizons may help us calibrate ourselves in the right direction. Imagine you’re traveling to Jupiter, off by a couple degrees and you’ll miss your mark by millions of miles.


don't be a killjoy - thinking about these timescales doesn't gore your ox. In fact, putting effort into long-term thinking of any kind is probably going to help prioritizing on any scale.


Thankfully, Isaac Arthur makes many videos about the very near future. I recommend the “Upward Bound” series. His work is the inspiration and optimism I need to put my best efforts toward building a better future in my own way.


You are under the assumption that we aren't already trying to doing all these things?


When the brightest minds of our generation have dedicated themselves to optimizing advertising networks, you can be sure we aren't emphasizing these things.


Are we sure the brightest minds of our generation really are simply devoting themselves to optimizing advertising? To be sure, some are - but folks like the author of the original paper the article is based on are the counter example to the common refrain. I see brilliant folks laboring in all sort of fascinating endeavors. They’ve yet to achieve publicity because their work is either not complete or they prefer obscurity.


I've considered the possibility that while seemingly pervasive and inescapable, ad tech is widely ineffective.

There's the perception that it's part of some deep state panopticon, and that there's more than one, and the other one fucked up the 2018 election, or something like that.

But I'd take a wild guess that in reality the effectiveness is something akin to anti-virus software. It only seems to catch the low hanging fruit.

With that in mind, I think this narrative is basing the underlying theme on things that were happening in the early 2000's when Google started buying up companies like Urchin and DoubleClick.

We're way past those days, and while ad tech does still pose a pervasive privacy hazard, I think newer more powerful technologies can passively track pretty much everyone by sniffing all the signals in the air for every wireless and mobile device in everyone's pockets.

I'd wager that the coverage is so dense that it even exposes the identities of people not carrying devices at all, and the facial recognition analysis of security video is just the icing on the cake to confirm exactly that.

So, really, now you have to wonder what the new awful thing is, that our brightest minds are working on.

Probably killbots.

Flying, driving, walking, talking killbots. That's my guess.


Well, I am under the certainty that we aren't already trying _enough_ to doing all these things...


If more people had a long-term perspective, we might not be in the mess we're in today.

I support The Long Now foundation and others who try to think and plan far ahead in to the future.


And you think this is possible without art and creativity to inspire?


Or oppression, pain, suffering, and something against which to push back.


Interesting. What's up with his pronunciation of the words earth and stars? Everything else is perfectly pronounced.


rhotic speech defect. you get used to it (and turn on subtitles)


I think Oliver Sacks (RIP) had the same impediment. It’s very pleasing to my ears for some reason.


This goes together nicely with the Aestivation Hypothesis (https://arxiv.org/abs/1705.03394).

If a civilisation puts itself on hold for a trillion years, just waiting around doing nothing, then when it wakes up the universe is much colder and it can do computations 10^30 times more efficiently. If the civilization consists of minds running on computers then they've increased their own lifespans by the same factor.


You might enjoy "The Last Question" by Issac Asimov:

http://www.multivax.com/last_question.html


Having the possibility to ask this question to Google Now, Siri or Alexa and getting a real answer would be a cool Easter Egg.


WolframAlpha does this.


One of my favorite quick reads! I probably re-read about once a year when some random train of thought leads me to it.


It's not like entropy will halt in that time. Worrying about efficiency of each individual calculation is a little ridiculous when you are wasting billions of years for the ambient temperature to drop.


Even in a trillion years, a star won't burn up so much of its energy that less than 10^-30 of it remains. So the wait is worth it.


I'd argue the opposite: it only takes one non-hibernating species out to dominate and it will hunt down every sleeping civilizations data center and annihilate them - so that they remain the most dominant species. Such a "hibernation data center" must thus be the most well guarded / hidden place in the galaxy...


Imagine if humans decided to hibernate en masse on Earth (maybe because of an ice age or fallout or something). We'd almost certainly set up alarms so if one hibernation center were damaged or destroyed another one nearby would thaw out some people (or machines) to go investigate. If the damn dirty apes really had become an existential threat to our sleepers, I'm sure we'd wake everyone up to reassert our planetary dominance before returning to a secure slumber.

Same thing would make sense on larger scales.


It's possible that there's a physical principle by which you can aestivate without being accessibly annihilable.

Some principle like "the only way to annihilate something in aestivating space is to annihilate the entire universe it's aestivating in."

Guess we won't know for a while.


This is certainly a possibility. It's also possible that one civilisation will attain dominance and then aestivate. It's also possible that there are no other civilisations within range of us (if there are other aggressive civilisations nearby why haven't they have wiped us out already?).


The background temperature of the universe now an trillion years from now is not significantly different. It's 2.73 Kelvins today. Even if it goes very close to zero, that's not a big difference.


If you halve the temperature in kelvin, you double the number of calculations you can do.


Here's my take on the future: We'll upload ourselves and use much less energy. As uploaded agents we'll have all the advantages of software - forking multiple instances of ourselves, backup for assured immortality, plugins and upgrades, changing our appearance at will, slowing down or speeding up, becoming part of a collective - everything. It will be Life 2.0, very different from our life.

We've already "uploaded" parts of the brain - visual processing, voice, simple communication and some interaction skills like playing game, moving about and handling objects.

Our age is the first where massive storage, worldwide communication and cheap cameras exist. So we will be an interesting case for the future uploaded agents - we'll be revived based on our digital traces in order to study the origins of Life 2.0 - digital archeology.


Yeah, and we could set the clock speed really low and we wouldn't even notice the difference ;)


I'm finding it difficult to understand what you mean by 'uploading'. Do you mean in some kind of Mixed Reality scenario where we are interacting with virtual assets?



Check out the book Accelerando by fellow HNer cstross. It goes pretty deep into this premise and I found it incredibly thought provoking.

You can read free here:

www.antipope.org/charlie/blog-static/fiction/accelerando/accelerando-intro.html


I assume he means digitally simulating your entire mind on a computer. Basically trading your biological brain for software.


To accelerate stars, you squeeze them until a jet of matter comes out in the opposing direction. For ideas on getting matter out of stars, see "star lifting".

Furthermore, most of the useful energy in stars is not their nuclear binding energy, it is their potential as gravitational fuel, for example when added into a black hole via the Penrose process. It makes sense to accelerate stars toward the central dwelling place of intelligent life, even if the stars have burned out by the time they get there.


How silly. Saying we don't know how to move a star is exactly the same as saying "you just squeeze it", right up until the point you actually go out there and actually fucking squeeze it.


I was on mobile so didn't have the time to post a link to more than "search on star lifting", but now that I'm off mobile, have a link.

https://en.wikipedia.org/wiki/Star_lifting

EDIT: more material directly on moving stars:

https://en.wikipedia.org/wiki/Stellar_engine https://www.dynamical-systems.org/zwicky/stellarengines.pdf


You've also removed the part where you called those pontifications "engineering".

edit: No, seriously, the initial comment shat on the author of the link for not knowing anything about mega-engineering. That's what I was calling silly.


People need to stop abusing the term “engineering.” This is dungeons and dragons fantasy with s bit of math for color.


If you like, you can reserve the term "engineering" for detailed currently-implementable designs (or for work by a licensed professional engineer, or whatever). But that doesn't mean it's impossible or useless to explore what's conservatively doable within the laws of physics using resources we don't yet have.


But, please, go squeeze some other star


"A chemistry is performed..."—Elizabeth Holmes


These are really mind-blowing szenarios. While they might appear as rather theoretical in nature, as they are in such a far distant future, the most striking part was the one of direct practical consequence: based on the theoretical models we can now and today watch for any indication of other civilizations preparing for the far future. And that is pretty cool, even if we might just not see anything interesting.


There simply is no way to predict what life will be like in 1 trillion years. We are still riding horses in many parts of the world, we are still killing each other..

its like asking a caveman what the next update to windows will look like.

We simply have no capacity to think yet.


I think tools 1 trillion years from now that stumble across that headline will wonder what humanity was.


> I think tools 1 trillion years from now that stumble across that headline will wonder what humanity was.

We will be lucky to still be here in 100 years.


We've already come this far, we probably will be here for a while longer


We're kind of like rats.


I think that, a trillion years from now, any trace of humanity's existence will have long since vanished from the universe, and nothing that comes after us will know that we were ever here, there or anywhere.


Chances are we'll have self-annihilated or been beaten by disease within 10K years. After that, it will only take millions of years for all traces of humanity's existence to vanish. Cement structures, plastics, garbage, etc. will mostly be gone in tens of thousands of years.


Diseases have evolutionary pressure to not wipe out their hosts. While it’s not impossible, I literally don’t expect anything that bad in a million years.


More on this?


If a disease wipes out their hosts, they usually go extinct as a direct consequence because species jumping is a rare trait.

Rare, but not unheard of. With only one exception that I am aware of, really nasty human diseases are those which only infect humans by accident and have a different main host. The exception, HIV, is already evolving into a various strains, at least one of which is much less dangerous than the original.

However, if we ever consider a disease to be an existential threat, wiping out the other host species isn’t something we would have much practical difficulty with these days. We’re already considering that with Malaria, and that’s not an existential threat.


They'll probably wonder why all the fragments they find seem to indicate we preferred damaging technologies over benign.

Then like archaeologists everywhere will conclude it was of religious significance.


Are you saying that we shouldn't have had the industrial revolution, because burning coal and oil was very polluting?


Not at all. A little glibness aside, I do think we should have replaced many things with better or less polluting alternatives far, far earlier than we do. The market is the wrong tool for many of these choices as shown by some of the current global issues.

At such a vast time distance there's likely nothing whatsoever left of us - except in the geological record as a few rare fossilised artefacts and environmental clues. We have a hard enough time understanding life a couple of thousand years back and religion is all too often trotted out as easy explanation for "we don't know why".


Yeah I'm getting huge nihlistic vibes from a few comments in this thread...


I suppose sibling comments were downvoted because they didn't address (a) the probable truth of the parent and (b) it's comedic nature.

I'm curious if any natural being could ever last so long. To stand that sort of test of time would require an environmental design to withstand everything the cosmos can throw at a species. Humans won't last that long, but if they did it would be because they augmented themselves.


Or indeed why any sentient alien should care.

“Apes became conscious, heated up and destroyed their environment, forced back to wilderness, evolved out. Meh... who cares.”


Have we ruled out the possibility that a future civilization could slow or stop the expansion of the universe before all the stars disappear from view forever?


For all we know expansion is their plan to eliminate the competition.


Kurzgesagt had some nice summaries of: 1) Why white dwarves might be the last home for life in the universe - https://www.youtube.com/watch?v=qsN1LglrX9s 2) ...or maybe it will be black holes - https://www.youtube.com/watch?v=ulCdoCfw-bY


all stars outside the Local Group of galaxies will no be accessible to us since they will be receding away faster than the speed of light.

Can anyone explain what this means?


Space is expanding, pushing all the stuff in the universe apart. But "pushing" is not really the right word, because the objects aren't actually being accelerated.

Instead, new space is being created between all objects. This can cause the distance between two objects to increase "faster" than the speed of light, without either of the objects actually moving.


The first few paragraphs of https://en.m.wikipedia.org/wiki/Expansion_of_the_universe do a reasonably good job at describing what I assume is the source of your puzzlement (namely how can something recede faster than the speed of light)


Due to the big bang the universe is expanding... but you’d expect the expansion to be slowing down due to the drag of gravity. However, since the 1990s we’ve observed that the universe’s expansion is accelerating - the theory is that a force called “dark energy” is causing this acceleration. If the acceleration continues, there will be a point where distant galaxies will be accelerating away from each other at the speed of light. Since light is the universe’s “speed limit”, we would not be able to travel to these galaxies with known physics because even traveling at light-speed the galaxy we’re going to would be stretching away faster. Locally, however, due to gravity, it sounds like the paper is saying we would have regions of dense galaxies that stay closer together. Islands of matter in a sea of dark energy.


The idea that humanity will ever travel even to the nearest star is pure fiction.

Anyone who thinks otherwise just fails to grasp the distances involved. They are so large as to be beyond understanding.


The idea that humanity won't ever travel even to the nearest star is pure fiction.

Anyone who thinks otherwise just fails to grasp exponential growth. They are so large as to be beyond understanding.


"...won't ever... is pure fiction"

Do you mean to say humanity certainly could travel to the nearest star?

I'm skeptical that anything resembling humanity could because everlasting exponential growth requires infinite resources. And humanity evolved on an abundant--but far from infinite--gravity well.


I was mostly making a point that grandiose statements can be rebutted by similar (in this case, changing 3 words) grandiose statements.

To answer your question though, the main problem with space travel isn't physics (assuming you are ok with long travel times), it's economics. We have sent astronauts to the moon and probes all across the solar system. The main reason we don't do more though is because of how expensive it is. However, a thousand years of 2% growth (not a given but again, grandiose) means we would have 400 million times more money to possibly spend on space travel. A NASA budget 400 million times larger could certainly build and send a spaceship 4 light years to alpha centauri.

Now how long will we sustain exponential growth? Well that's anyones guess but I don't see us becoming resource constrained for a long long time. The sun produces 10^13 more energy than the world used in 2013 according to [0] and we have plenty of resources in the solar system to build with (and we can recycle more).

[0]: https://www.quora.com/How-much-energy-does-the-sun-produce-p...


> To answer your question though, the main problem with space travel isn't physics (assuming you are ok with long travel times), it's economics.

I'd argue it's biology, not physics. Sending a rock to another star is easy. Sending a rock that can send back data is probably possible with our technology, but it's unlikely it would retain data transmission capabilities long enough to actually report back from another star. Sending a bunch of humans and keeping them alive the entire journey? It's not clear we can do that for a round trip to Mars, let alone an interstellar journey.


The 2 biggest health problems that I am aware of with spaceflight are due to weightlessness and radiation. However, both can be probably be solved with enough money (make the spaceship a rotating one with artificial gravity and add more shielding). There might be others but I am pretty confident you could engineer your way past each and every one given a large enough budget.


You're sort of missing the biggest health problem of all: how do you make a self-sustaining closed ecosystem?


True, I was thinking more in the context of the mars trip you mentioned where you can generally take the resources you need for the trip. For intersteller travel, you would need to make it self sustaining since the travel times are so long and that would be extremely expensive.


The article suggests moving stars.


Let's be a bit more positive on Humanity's progress eh?

Humanity is on the cusp of three major technological breakthroughs that will quite literally change everything.

1) AI. Even if we don't reach ASI in the near term, we'll have ANI to help us research new technologies in months/years rather than decades.

2) Asteroid Mining. Whether it's Musk/Bezos/A. N. Other, the very first time someone brings down an asteroid. It will herald the dawn of abundance for precious metals. What will happen to prices is another topic. But this will allow researchers to develop even more exotic materials.

With better materials resistant to heat, more conductive elements, etc, etc. Humanity be able to build what can only be dreamt of.

3) 7 Billion (now). 13 Billion with Mars, 50+ Billion with Europa, Titan, Ganymede, etc, etc, etc. There will be a time where Humans will stretch beyond this solar system. Imagine how many breakthroughs will be possible with 100m researchers and AI trying to crack something?

What will make this possible? With 1 and 2, we'll be able to finally crack fusion reactors. This will enable faster space travel than with current engines. Habitats will evolve from those initial Mars missions and will sprawl into mega cities. Who knows, there may even be Luxury apartments hovering in the upper atmosphere of Venus.

All this progress is exponential and if you stop to look around. The seeds are being sewn right now. By 2050, some things we consider Sci-fi will be reality.

Oh and I'll just throw this one in.

4) Nasa has been doing some work on the Alcubierre drive. Who is to say, that the issues that cannot be surmounted now, will be in the future? For those that want to know more. I'll leave a channel that goes into such things [0].

[0]: https://www.youtube.com/channel/UC2kkCGRqZWaSIK3BmLC8vaw/vid...


> 2) Asteroid Mining. Whether it's Musk/Bezos/A. N. Other, the very first time someone brings down an asteroid. It will herald the dawn of abundance for precious metals. What will happen to prices is another topic. But this will allow researchers to develop even more exotic materials.

Say what? The idea that asteroid mining will enable material science revolutions is fanciful. We're not exactly short on metals (even precious metals). And interplanetary space is less extreme than environments we can create in terrestrial situations, so we're not going to find weird new stuff by poking around asteroids.


>We're not exactly short on metals (even precious metals).

Last I checked, the price of most metals was greater than zero. They're commodity markets, so that means they're scarce. If you mean "available at any price," then we were not short on iron during the Bronze age or short on Aluminum during the early 1800s.


Well, it is possible that if rare and expensive metals become dirt cheap, new exotic alloys may be developed that were previously economically inconceivable.

I don't know how likely this is. I imagine plenty of research has already been done on exotic alloys, however I wonder how much that research has been affected by economic constraints.


Alcubierre drives require exotic matter which is not quite ruled out by the laws of physics. Hopefully they don't require Jupiter-sized masses of the stuff, although some have suggested as much. However, that solved, there are two slight problems with this idea. One is that FTL inherently violates causality, which is sort of a problem. The other is that the spacecraft is expected to pick up and accelerate with it basically any matter it runs into along its superluminal path, releasing these as a spectacular shower of near-c particles whenever it stops. Your other speculations have their own defects, but I'll let others address them.


The distance to the moon is already beyond intuition, but you can still understand how to get there by doing calculations. If the numbers say that it's possible then it's possible.


My vote is still with the brain in a jar (or something close to it). Fewer resources, less area, and much of the life support equipment could be shared between many individuals. There's reason to believe it would extend lifespans as well, provided that an entirely virtual life could be made worth living.

I honestly think we'll achieve this long before we're able to properly or effectively simulate a brain with computers of any kind.


the _nearest_ star is actually quiet close :-]


thats pretty accurate as far as current technology goes, but then again with a few additional centuries of research we never know what we end up achieving.


We could just about do interstellar now if an existential threat called for it. Project Orion or a nuclear salt water rocket are both possible already.


There is a theory that the universe is expanding faster and faster. At some point in the future, stars would be moving away faster than the speed of light and we couldn't ever see them again or reach them.


How could they be moving faster than the speed of light?


Imagine two RC cars driving in opposite directions on a crumpled up, (virtually) infinitely large blanket with an uncountable number of ripples. The cars' top speeds are 10 MPH. On top of each car is an ant watching the other car.

Both cars start driving off at 10 MPH in opposite directions. From an ant's perspective on top of one car, the other car looks to be going 20 MPH away from it. Then someone starts pulling the blanket underneath the cars from opposite ends at 5 MPH. Now it looks like the other car is going 30 MPH. Now imagine for each ripple on that blanket, another hand appears and starts to pull, and the outer edges are pulled at 5MPH from the reference point of the nearest ripple.

From the perspective of an ant on one end, it can eventually get to the point that the other car is warping off at 100MPH or more. And as this blanket spreads out more and more, things speed up more and more as well. The cars never technically exceed their speed limits of 10 MPH, but the space that they occupy is being pulled apart in a way that they seem to be exceeding 10 MPH from each other's perspectives.


Anything which moves through space-time is restricted to moving at the speed of light. Space-time itself can warp causing objects to "move" away from each other faster than the speed of light.

Think of ants crawling on the surface and a balloon which is being blown up.


Because while matter cannot move faster than the speed of light the universe itself is allowed to expand faster than the speed of light. Think of the spacetime fabric stretching so fast light cannot cover the increased distance. The universe is essentially creating more distance between objects.

Another way to think of it is velocity of an object is derivative of position in space over time. If space itself is moving your position relative to it isn't changing.


I still can't intuitively understand this. If two objects ar stationary relative to each other, the expansion implies that at some point, the distance between those two objects will increase (without either of those objects having moved).

So space is being somehow created?! What if i have a large object, will the length of that object increase? Or will it break up?


The object is bound together by electromagnetic forces, and the local group is bound together by gravity. These forces are much stronger than the expansion of the universe (cosmological constant), but the expansion of the universe manifests as a tiny tiny outward pressure term (too small for us to detect). It makes every atom/orbit a little bigger by changing the equilibrium point, but they don't to grow in size because the force isn't increasing.

If the cosmological constant were much larger than it is, atoms would have never formed at all.


I think you are using a concept of space-time that is quite limited. You are at most using concepts from Einstein's Special Relativity. Everything changed with General Relativity.

Space is not "created", space-time is warped. Gravity is the deformation of space-time by mass/energy. The distance from point A to point B is measured by the time it takes for a light ray to get from A to B using the shortest path. But if you move objects with mass (or with energy) near A and B, the shortest path will change. Also, it's easy to measure distance in seconds when you know the speed of light.


If I understand this correctly, you're talking about something similar to Star Trek's Warp Drive (or the Alcubierre drive, for something less fictional). Instead of stars and galaxies moving at the speed of light, the space around them expands and the expansion accelerates at a rate that will eventually make the speed of expansion larger than the speed of light. Or in other words, stars and galaxies will continue to move at their sub-luminar speed, but the space in which they exist will expand so fast that the expansion will cause the distance between them to increase at such a rate that light will not be able to keep up.

[Edit: and, er, all that has something to do with dark energy?]

OK, but in that case, and if we still exist as a technological civilisation at that time (very doubtful) we might be able to use the effect for our own benefit. By building warp drives and er, not-quite-travelling faster than light, by expanding space around a ship, etc.


Warp drive solves a plot problem, it doesn't do anything to mitigate violating causality.


And if they can, why can’t we and catch them? I mean we are in spacetime. If it stretches we stretch too!


Right now the only serious effort to consider how to do so is the Alcubierre metric and its variations. Nobody knows how to build one, or what matrials could build one, or how to turn it on or off. Unless you have a cunning way to cheat, such as making the inside bigger than the outside, it requires in excess of minus the rest mass of the observable universe for a plausible sized object. There are further objections, but above my level.


So would the light from those stars also be moving outward faster than the speed of light?


No. In fact, if two objects are far enough apart, then the amount of new space created between them will be so great that light will never be able to travel between them. Neither object will ever be able to see the other.


It's really hard for me to imagine how a flashlight on a distance plant could be moving away from me faster than the speed of light but the emitted light is going slower.



Just like the sound of an ambulance.


the universe is expanding and the expansion is accelerating


How would this scenario change, if there was a Big Bounce? And how would we potentially recognize alien civilizations preparing for that? And finally: in order to find out which of the two cosmological models is actually the correct one, we just set up SETI to find signs as to which of those two hyper-engineering projects have been undertaken - by civilizations that are a bit further in their cosmological understanding ;-)


Then, there will be a post on HN about it, marked [2018 FE (First Era)]. "Ancients knew all this would happen [2018 FE]"


And below that, a post about how this will be the year of Linux on the desktop?

Sorry, couldn't resist :-)


"What you need to know about the Windows 10 Star Squeezer's Update"


this assumes that civilizations will be able to use energy from sources other then their own star (or galaxy) or that it will be possible to get a significant number of their individuals to other stars. unlikely. just hang on until your own star dies then its over.


By this time in the future I hope we have worked out wormholes.


Highly unlikely. Unless wormholes are setup with strange restrictive configurations they allow sending messages back in time, without needing any new physics.

Once you have a wormhole, if you use gravity to accelerate one of the ends away then bring it back near the other end, they will have a time difference, due to general relativity. If you bring them close enough, that time difference will be greater than it takes to travel between them in normal space, allowing you to travel to your own past.

This video gives a quick explanation of the problem:

https://www.youtube.com/watch?v=sUqxzH0652w&t=186s


I’ve recently become dissatisfied with the two standard ways to make closed timelike curves.

Gravity: that’s treating gravity like it doesn’t go through the wormhole. I expect it would. If it does, both sides are time dilated equally.

Acceleration: what, exactly, are you accelerating? If it’s made of stuff, you time dilate the stuff. If it’s not made of stuff… can you even move it in any meaningful sense, or is that like trying to move a patch of curved space from here to the moon to create artificial gravity?


You are accelerating the space which contains the wormhole. It doesn't matter if it's "stuff" or not.


The patch of space is directly attached to the other end of the wormhole. GR assumes stacetime is differentiable, you just put a discontinuity in it somewhere inside the wormhole.


Doesn’t that just put bounds on which wormholes are possible, rather than proving no wormhole is possible?


It doesn't prove they are impossible, but what it shows is if they are possible, the universe is conspiratorial. Because it restricts your free will so you don't create time travel paradoxes.


As the maxim says, "relativity, causality, or FTL... pick two."

The bounds on which wormholes are possible are likely bounds which make the transmission of information (including matter) impossible, because we live in a universe in which relativity and causality exist, and cannot (as far as we know) be violated.


Something wrong with that site. Crashed my browser.


What a fascinating read. Thanks for posting this.


Errr. I think by 2400 we’ve got every chance of living in the ruins of a past grand human civilization.

Trillion is nice sci fi. 10,000 years in the future with any recognizable civilization is even more of a stretch.


A stretch indeed but interesting to think about nonetheless:

10,000 years in the future is the premise of Frank Herbert‘s Dune.

The novel (or rather the series) depicts a mankind that on one hand in some ways has evolved way beyond humanity’s current capabilities.

On the other hand, society has devolved into a feudal state.

Some technologies are shunned and outlawed for their destructive potential, most notably nuclear weapons and “thinking machines” (there’s some room for interpretation if this just means AI or computers in general), which have been replaced by “mentats” (basically human computers).


400 years is nothing. I mean, climate change is real and could be very damaging, but what aside from that and war - why do you think we’ll be living amongst ruins? That seems overly pessimistic to me.


Water is already running out in many areas of the world. Rains are failing worldwide.

No water = no food. Where millions perhaps billions of people are on the move, societies will break down. Look what is happening on the European and US borders and the hysteria it generates when the migration is but a trickle of what is to come.

Yes humanity and technology is moving forward at record speeds, but at what cost to the world majority? To the environment.

I think by 2400 is a rather optimistic figure, it is likely to be much sooner


Fresh water is running out. If you have enough cheap energy, desalination solves that problem.


400 years is enough time for us to nuke ourselves out of being able to sustain our society, and climate change is a classic cause of wars.


30 years ago there was a very real prospect of a Worldwide nuclear war -- my mother was, in the UK, involved in creation of shelters to allow some kernel to survive the ensuing nuclear winter. Apocalyptic films were portending doom and in school we watched films about what to do if there was a nuclear blast.

There have been massive wars/killings, massive famines, massive epidemics.

We're in what may well be a local maxima, or perhaps an overall maxima. There are a lot of challenges to face that we need to unify to fight, like water poverty, food security, avoiding escalation of conflict - and not much sign of greater unification (quite the opposite AFAICT).

IMO we can turn it around, but we're going to have to have a sudden outbreak of altruism.


> water poverty, food security, avoiding escalation of conflict

Two out of three of those problems are getting easier with technology (renewable energy for desalination and smart agriculture). If we leave this maxima, it will be because we permitted nuclear proliferation. Even that isn’t inescapable, however.


Thats a pretty pessimistic view to have when we live in an era of ongoing progress in almost every area.


A pessimistic or at least skeptical dialectic counterpart to the optimistic/progressive worldview is a valuable thing to have, I think.

You can't reach into people's brains and change their temperament (yet! say the optimists) but I don't think we should want to. And not allpessimism/skepticism is based on temperament, though certainly some is.


That's a very anthropocentric view. We have a single point of failure. It's not likely to drastically change in any reasonable time-frame.



Speaking of pessimism, i just hope we humans destroy each other before we destroy earth to pave way to species which is not so hell bent on personal over society.


I don't get it. I mean this is the premise of many sci-fi stories, but humanity has made pretty steady civilized progress since its inferred inception. There isn't much of a reason to believe this pessimism.


Prior civilizations collapsed after over-exploiting their environment, and we're making the same mistake on a global scale. Our complex supply chains based on fossil fuels are rather fragile - we will likely survive a collapse at reduced quality of a life, however total recovery may be slow or impossible depending on remaining resources.


We can produce more food than ever with less energy. Knowledge transfer is always improving, and with computer programs it will be even easier to transfer knowledge.

You guys need to clarify what "a collapse" is. Not eating as much meat? Do you really think that we would not be able to power our computers or not be able to produce rice/wheat on any industrial scale?

The amount of FUD spread without any foundation for it is maddening.


> We can produce more food than ever with less energy. Knowledge transfer is always improving...

I imagine that's what people said before the Dark Ages too. It's not as if empires and civilizations haven't ever fallen before.


Yes, but civilizations and empires are not representative of the progress of humanity as a whole. Besides, isn't Dark Ages a rejected term by historians now? In addition, what is 200-400 years in the history of civilization? Of course there will be volatility - just like life on an individual level, the stock market, annual crop yields, etc.


An abrupt, significant, and wide-spread regression in quality of life, coupled with cultural and technological stagnation. Something like the Late Bronze age collapse ( https://en.wikipedia.org/wiki/Late_Bronze_Age_collapse )

It is a reasonable low-probability high-risk concern, given (unordered):

* Depleting fossil fuel reserves: most obvious risk; dominant fuel source for transportation and agriculture, dominant energy source for industries, dominant material in many consumer goods.

* Climate change: threatens some regions' agricultural and ocean productivity, pressuring human migration, spreading diseases.

* Exhausted oceans: oceanic deadzones are spreading, loss of fishing as a food source is a serious risk for parts of Asia, which will put additional pressures on agriculture and motivate economic migration.

* Over-use of antibiotics and vaccines: risk of super-bacteria/virus plagues, mostly in agriculture and 3rd world nations.

* Depletion of aquifers: imminent risk amplified by climate change. America's food production is heavily reliant on effectively non-renewable aquifers, depletion or poisoning through fracking are serious risks.

* Globalized economy/supply chains: coupling economies improves efficiency but introduces the risk of cascade failures.

No one of these problems are an existential risk by themselves... but they are all interrelated and poorly understood, which impacts our ability to effectively preempt wide-spread impact.

Humanity will recover should the worst happen, but I think it's better to avoid the set back in the first place.


Have you met humans?


I started reading this and then thought "what a waste of time". This pertains in no way to my life or the life of anyone for the foreseeable future. I read it just after the one about taking pictures preventing people from experiencing things and remembering them. Putting these together reminded me that reading some of these things on HN is preventing me from living. And with that, I'm gonna close this laptop and go do something rather than worry what people a trillion years hence will be doing.


The people who actually take humanity to the stars (if it happens) will likely be motivated, in part at least, by this and other grand, cosmic ideas. I personally find it motivating and invigorating in a certain sense.

But, of course, if it is bumming you out, then definitely go do something else :)


Oh, I agree with you. SpaceX is awesome and I'm excited about the idea of colonizing Mars. The difference is that Mars is attainable now. Lots of unknowns but it's within reach.


I mean, it's at least plausible that the first immortal has already been born. Whether that immortality is physical or digital, I'll leave up to the Westworld writers.

Alternate Westworld themed hypothesis: It's already a trillion years in the future, we're all living in the valley beyond and don't realize it.


What you find boring, other people find interesting, and thus not a waste of time. I’m curious about why you bothered to post a rant about how these discussions are “preventing you from living”, followed by a public announcement of how you’re “gonna close this laptop and go do something”. It comes across as bizarre and a bit narcissistic.


There is a lot of weird downvoting in these threads, can anybody explain what is going on?


I'm not sure what you're referring to, but could you please email hn@ycombinator.com with details so we can take a look instead of posting a meta comment?


It was curiosity. Essentially what looks to be reasonable comments are being downvoted, not sure if there is anything nefarious.


I wish I could still see people and nations with the optimism of youth.

But now I am going to point out that someone will probably weaponize fusion and that will be the end of that.

We're not making it off this planet as a civilization, and honestly that may be for the best.

(but I still think The Expanse may be the best show since Babylon 5)


Are you not familiar with the hydrogen bomb, or are you speculating about unphysical weapons?


I think the movie Interstellar closely depicts how life on Earth may turn out. Climate change is never going to stop, humans except few just don't care. Instead they will try to create more machines which will try to use carbon engineering to reduce CO2(as one discussed few days back on HN). With less need for trees and more need to fulfill population demand, if this technology becomes successful, it can be a doomsday scenario for trees and land everywhere will slowly start to erode resulting in greater imbalance in the ecosystem and eventually worldwide famines. Add to that, thawning of permafrost will release large amount of methane along with bacteria which were inactive since ages and for which humans may have no cure.

Most of CO2 is absorbed by oceans, and humans may never be able to find a way to tame CO2 there, this will result in much faster melting of ice in Arctic and Antarctica than anticipated.

No, humans aren't going to find an alternative habitable planet anytime soon where they can travel.


In the '70s, movies like Soylent Green depicted how people thought Earth may turn out: more and more people supported by limited resources, food riots, etc. e.g. China introduced the one child policy to head this off.

In the '80s, movies like War Games and The Day After depicted how people thought Earth may turn out: nuclear war triggered through Mutually Assured Destruction. (Source: I lived through the '80s.)

you get the idea.


This is a good contender for the next Ig Noble prize.

My knee reaction with such articles is "I am glad that the guy is not payed with my taxes" but then I wonder how many of such useless papers where actually trampolines for useful ones (by bootstrapping ideas, suggesting "some uses of vibranium which, in that specific case could be replaced with titanium", etc.).

This extends to topics like astrophysics of galaxies far away (which we will not reach within 7000 years), particle physics (which work at energies which cannot be replicated outside of the lab), ... I am well aware that things which happen around these topics (say, the need to better understand magnetism in accelerators which can lead to better tomography or something) but are these money pits really needed as catalyzers?




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