[lisper]

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. :-)

[k_roy]

Reminds 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]

How 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?

[exfalso]

There'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??

[jobigoud]

It is counter intuitive but information can still travel between places that are so distant that expansion between them is faster than the speed of light. It's just extremely slow (so I still vote for going to the party at the highest density place).

We do see light from galaxies that are receding away from us faster than c. At first the photons going in our direction are moving away from us but as the universe expands over time at some point they find themselves in a region of space that is no longer receding faster than c, and they start approaching.

[zimzam]

I 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.

[chamomeal]

I think I sense a strange Battle Royale type game…

[kbelder]

Assuming these are advanced enough aliens, they'll also be bringing with them all the mass they can, to accentuate the effect? I'm imagining things like Niven's ringworld star propulsion.

[u1hcw9nx]

You must consider both time and locality.

From now until protons decay and matter does not exist anymore is only 10^56 nanoseconds.

[Sharlin]

If protons decay. There isn't really any reason to believe they're not stable.

[dheera]

Protons (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.

[Etheryte]

That's such an odd way to use units. Why would you do 10^56 * 10^-9 seconds?

[rubyn00bie]

I 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)?

[rbanffy]

If we think of the many worlds interpretation, how many universes will we be making every time we assign a CCUID to something?

[scotty79]

Proton decay is hypothetical.

[jl6]

Ah 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]

Sorry, your laptop was produced before FTL was invented, so its MAC address is only recognized in the Milky Way sector.

[SkyBelow]

If 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.

[RobotToaster]

Would 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.

[lisper]

I have to confess I have not actually done the math.

[9dev]

Oh no! We should immediately commence work on a new UUID version that addresses this use case.

[svnt]

Maybe 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]

:-)

[zeckalpha]

Don'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.

[ctoth]

Hanson's Grabby Aliens actually fits really well here if you're looking for some math to base off of.

[quijoteuniv]

The answer is 42. Have it from good source!