9 ms·
This analysis is not quite fair. It takes into account locality (i.e. the speed of light) when designing UUID schemes but not when computing the odds of a coll
by lisper 8mo ago
This analysis is not quite fair. It takes into account locality (i.e. the speed of light) when designing UUID schemes but not when computing the odds of a collision. Collisions only matter if the colliding UUIDs actually come into causal contact with each other after being generated. So just as you have to take locality into account when designing UUID trees, you also have to take it into account when computing the odds of an actual local collision. So a naive application of the birthday paradox is not applicable because that ignores locality. So an actual fair calculation of the required size of a random UUID is going to be a lot smaller than the ~800 bits the article comes up with. I haven't done the math, but I'd be surprised if the actual answer is more than 256 bits.
(Gotta say here that I love HN. It's one of the very few places where a comment that geeky and pedantic can nonetheless be on point. :-)
- u1hcw9nx 8mo agoYou must consider both time and locality. From now until protons decay and matter does not exist anymore is only 10^56 nanoseconds.
- rbanffy 8mo agoIf we think of the many worlds interpretation, how many universes will we be making every time we assign a CCUID to something?
- antonvs 8mo agoWe don't "make" universes in the MWI. The universal wavefunction evolves to include all reachable quantum states. It's deterministic, because it encompasses all allowed possibilities.
- petcat 8mo ago> many worlds interpretation These are only namespaces. Many worlds can have all the same (many) random numbers and they will never conflict with each other!
- shiandow 8mo agoIn that interpretation the total number of worlds does not change.
- rubyn00bie 8mo agoI got a big laugh at the “only” part of that. I do have a sincere question about that number though, isn’t time relative? How would we know that number to be true or consistent? My incredibly naive assumption would be that with less matter time moves faster sort of accelerating; so, as matter “evaporates” the process accelerates and converges on that number (or close it)?
- zamadatix 8mo agoTimes for things like "age of the universe" are usually given as "cosmic time" for this reason. If it's about a specific object (e.g. "how long until a day on Earth lasts 25 hours") it's usually given in "proper time" for that object. Other observers/reference frames may perceive time differently, but in the normal relativistic sense rather than a "it all needs to wind itself back up to be equal in the end" sense.
- idiotsecant 8mo agoThe local reference frame (which is what matters for proton decay) doesn't see an outside world moving slower or faster depending on how much mass is around it to any significant degree until you start adding a lot of mass very close around.
- scotty79 8mo agoProton decay is hypothetical.
- hamdingers 8mo agoSo is the need for cosmologically unique IDs. We're having fun.
- Etheryte 8mo agoThat's such an odd way to use units. Why would you do 10^56 * 10^-9 seconds?
- lisper 8mo agoThis was my thought. Nanoseconds are an eternity. You want to be using Planck units for your worst-case analysis.
- u1hcw9nx 8mo agoIf you go far beyond nanoseconds, energy becomes a limiting factor. You can only achieve ultra-fast processing if you dedicate vast amounts of matter to heat dissipation and energy generation. Think on a galactic scale: you cannot have even have molecular reaction speeds occurring at femtosecond or attosecond speeds constantly and everywhere without overheating everything.
- lisper 8mo agoMaybe. It's not clear whether these are fundamental limits or merely technological ones. Reversible (i.e. infinitely efficient) computing is theoretically possible.
- adrian_b 8mo agoReversible computing is not infinitely efficient, because irreversible operations, e.g. memory erasing, cannot be completely avoided. However, the computing efficiency could be greatly increased by employing reversible operations whenever possible and there are chances that this will be done in the future, but the efficiency will remain far from infinite.
- UltraSane 8mo agoIf you have a black hole as an infinite heat sink this helps a great deal.
- 8mo ago
- Sharlin 8mo agoIf protons decay. There isn't really any reason to believe they're not stable.
- hnuser123456 8mo agoAnd recent DESI data suggests that dark energy is not constant and the universe will experience a big crunch in a little more than double its current age, for a total lifespan of 33 billion years, no need to get wild with the orders of magnitude on years into the future. The infinite expansion to heat death over 10^100 years is looking less likely, 10^11 years should be plenty. https://www.sciencedaily.com/releases/2026/02/260215225537.htm https://www.sciencedaily.com/releases/2026/02/260215225537.h...
- disconcision 8mo agonot obvious to me this makes things better as opposed to worse? sure, the time bound helps but in the runup to a crunch won't we get vastly more devices in causal range at an asymptotically increasing rate?
- Towaway69 8mo agoWho’s there doing the counting? I would assume the temperatures at those extremes won’t support life in its known forms. Perhaps some Adamesque (as in douglas adams) creature whose sole purpose is to collect all unique UUIDs and give them names.
- throwaway290 8mo agoRunup to the crunch is a looong time lots of which is probably very habitable. in 5 billion years life can arise from scratch become conscious and exterminate itself
- frikit 8mo agoProtons can decay because the distinction between matter and energy isn't permanent. Two quarks inside the proton interact via a massive messenger particle. This exchange flips their identity, turning the proton into a positron and a neutral pion. The pion then immediately converts into gamma rays. Proton decayed!
- dheera 8mo agoProtons (and mass and energy) could also potentially be created. If this happens, the heat death could be avoided. Conservation of mass and energy is an empirical observation, there is no theoretical basis for it. We just don't know any process we can implement that violates it, but that doesn't mean it doesn't exist.
- dinosaurdynasty 8mo agoConservation laws result from continuous symmetries in the laws of physics, as proven by Noether's theorem.
- dheera 8mo agoTime translation symmetry implies energy conservation, but time translation symmetry is only an empirical observation on a local scale and has not been shown to be true on a global universe scale.
- adrianN 8mo agoAll of physics is „just“ based on empirical observation. It’s still a pretty good tool for prediction.
- svnt 8mo agoMaybe the definitions are shifting, but in my experience “on point” is typically an endorsement in the area of “really/precisely good” — so I think what you mean is “on topic” or similar. Pedantry ftw.
- lisper 8mo ago:-)
- RobotToaster 8mo agoWould this take into account IDs generated by objects moving at relativistic speeds? It would be a right pain to travel for a year to another planet, arrive 10,000 years late, and have a bunch of id collisions.
- ctoth 8mo agoHanson's Grabby Aliens actually fits really well here if you're looking for some math to base off of.
- k_roy 8mo agoReminds me of a time many years ago when I received a whole case of Intel NICs all with the same MAC address. It was an interesting couple of days before we figured it out.
- imglorp 8mo agoHow does that happen? Was it an OEM bulk kind of deal where you were expected to write a new MAC for each NIC when deploying them?
- fdefitte 8mo ago[dead]
- quijoteuniv 8mo agoThe answer is 42. Have it from good source!
- jl6 8mo agoAh but if we are considering near-infinitesimal probabilities, we should metagame and consider the very low probability that our understanding of cosmology is flawed and light cones aren’t actually a limiting factor on causal contact.
- missingdays 8mo agoSorry, your laptop was produced before FTL was invented, so its MAC address is only recognized in the Milky Way sector.
- SkyBelow 8mo agoIf we allow FTL information exchange, don't we run into the possibility that the FTL accessible universe is infinite, so unique IDs are fundamnetally not possible? Physics doesn't really do much with this because the observable universe is all that 'exists' in a Russel's Teapot sense.
- exfalso 8mo agoThere's a fun hypothesis I've read about somewhere, goes something like this: As the universe expands the gap between galaxies widens until they start "disappearing" as no information can travel anymore between them. Therefore, if we assume that intelligent lifeforms exist out there, it is likely that these will slowly converge to the place in the universe with the highest mass density for survival. IIRC we even know approximately where this is. This means a sort of "grand meeting of alien advanced cultures" before the heat death. Which in turn also means that previously uncollided UUIDs may start to collide. Those damned Vogons thrashing all our stats with their gazillion documents. Why do they have a UUID for each xml tag??
- zimzam 8mo agoI think I missed something: how do galaxies getting further away (divergence) imply that intelligent species will converge anywhere? It isn’t like one galaxy getting out of range of another on the other side of the universe is going to affect things in a meaningful way… A galaxy has enough resources to be self-reliant, there’s no need for a species to escape one that is getting too far away from another one.
- jobigoud 8mo agoSocial aspect. There is no need but it's more fun to spend the end of the Universe with other intelligences than each in its own place.
- wat10000 8mo agoYou'll run out of resources eventually. Moving to the place with the most mass gives you the most time before you run out.
- exfalso 8mo agoYes that's the idea. The expansion simply means that the window of migration will close. Once it's closed, your galaxy is cut off and will run out of fuel sooner than the high-density area.
- 8mo ago
- zeckalpha 8mo agoDon't forget that today's observable universe includes places that will never be able to see us because of the expansion of the universe being faster than the speed of light. There's a smaller sphere for the portion of the universe that we can influence.