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How Cosmological Supercomputers Evolve the Universe All Over Again

Soulskill posted about 2 years ago | from the just-don't-let-it-escape dept.

NASA 144

the_newsbeagle writes "To study the mysterious phenomena of dark matter and dark energy, astronomers are turning to supercomputers that can simulate the entire evolution of the universe. One such simulation, the Bolshoi projection, recently did a complete run-through. It started with the state the universe was in around 13.7 billion years ago (not long after the Big Bang) and modeled the evolution of dark matter and energy up to the present day. The run used 14,000 CPUs on NASA's fastest supercomputer."

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I call (1, Funny)

Anonymous Coward | about 2 years ago | (#41534331)

Bolshoit!

Re:I call (0)

Anonymous Coward | about 2 years ago | (#41535627)

"Bolshoi" means Big in russian.

How long until... (2, Interesting)

bejiitas_wrath (825021) | about 2 years ago | (#41534353)

How long will it be until we can build a supercomputer that can span the Universe and if the Universe suffers a heat death it could just remake the whole Universe as it stored the state of everything within? Therefore humanity could survive even the end of the whole Universe in 100,000,000,000,000 years time. The short story the Last Question made quite an impression on me and surely with the current evolution in technology we could create a God computer eventually that would exist outside of anything we could comprehend. That would be mind-blowing.

Re:How long until... (1)

Anonymous Coward | about 2 years ago | (#41534365)

You should probably also read The Last Answer, also freely available online. An equally thought-provoking short story.

Re:How long until... (0)

Anonymous Coward | about 2 years ago | (#41534511)

More to the point, you might want to read Frank Tipler's "The Physics of Immortality".

Re:How long until... (1)

progician (2451300) | about 2 years ago | (#41535717)

The Last Question is better. This whole Omega Point crap is nothing but extrapolating the claim of theism of the Intelligent Design argument not that of the currently known science.

Re:How long until... (1)

YttriumOxide (837412) | about 2 years ago | (#41534975)

You should probably also read The Last Answer, also freely available online. An equally thought-provoking short story.

I believe the story you're referring to is "The Last Question" by Isaac Asimov.

Re:How long until... (1)

erraticus (2461588) | about 2 years ago | (#41535029)

I've read it. I'm looking for sci-fi books like this. Do you guys remember anyone related to these matters?

Re:How long until... (1)

yahwotqa (817672) | about 2 years ago | (#41535299)

Frederick Pohl's "The World at the End of Time" deals tangentially with heat death of the universe, and also has superbeings tossing stars at each other. Can't miss it. :)

Re:How long until... (2)

maxwell demon (590494) | about 2 years ago | (#41535233)

You should probably also read The Last Answer, also freely available online. An equally thought-provoking short story.

I believe the story you're referring to is "The Last Question" by Isaac Asimov.

https://en.wikipedia.org/wiki/The_Last_Answer [wikipedia.org]

Re:How long until... (2)

wonkey_monkey (2592601) | about 2 years ago | (#41535711)

The GGP mentioned The Last Question, so I think the AC really was referring to The Last Answer [thrivenotes.com] .

Re:How long until... (1)

YttriumOxide (837412) | about 2 years ago | (#41535827)

You're right... it's my fault for not reading the GGP fully. I only skimmed it, saw the premise of "The Last Question" and assumed that's what the GP meant. I am aware of the story "The Last Answer", but don't think it has much at all to do with the topic at hand, so assumed the AC suggesting it really meant The Last Question.

Re:How long until... (1)

dissy (172727) | about 2 years ago | (#41535849)

Twice now it has been posted "Not only should you read The Last Question, but you should ALSO read The Last Answer"

And twice now you have attempted to claim they intended to say "You should not only read The Last Question, but also read a totally different story called The Last Question"

Why do you refuse to believe there are two stories by the same author with different names?

The Last Question: http://filer.case.edu/dts8/thelastq.htm [case.edu]
The Last Answer: http://www.thrivenotes.com/the-last-answer/ [thrivenotes.com]

Perhaps you should make yourself aware of both of them, before attempting to correct others who know what they mean to say :P

Re:How long until... (1)

YttriumOxide (837412) | about 2 years ago | (#41535867)

Perhaps you should make yourself aware of both of them, before attempting to correct others who know what they mean to say

Perhaps you should read that I apologised twice for my mistakes already - it was due to reading comprehension failure (which I attribute to nicotine withdrawal - I'm quitting smoking) and not due to a lack of knowledge of the books. Regardless of the cause, it was my failure though, and I apologised for it.

Re:How long until... (0)

Anonymous Coward | about 2 years ago | (#41534381)

Would we have the power to change the code so that Justin Bieber was never born?

Re:How long until... (1)

binarylarry (1338699) | about 2 years ago | (#41534423)

According to this post [slashdot.org] , no.

Re:How long until... (2)

Tablizer (95088) | about 2 years ago | (#41534561)

Could be worse: in one of the variants, Justin Bieber's mom had quintuplets.

Re:How long until... (3, Funny)

Nyder (754090) | about 2 years ago | (#41534399)

How long will it be until we can build a supercomputer that can span the Universe and if the Universe suffers a heat death it could just remake the whole Universe as it stored the state of everything within? Therefore humanity could survive even the end of the whole Universe in 100,000,000,000,000 years time. The short story the Last Question made quite an impression on me and surely with the current evolution in technology we could create a God computer eventually that would exist outside of anything we could comprehend. That would be mind-blowing.

I'm pretty sure Douglas Adams covered all that.

Re:How long until... (1)

stressclq (881842) | about 2 years ago | (#41534597)

And we still don't know how it ends... Darn those Vogons and their hyperspatial express route!

Re:How long until... (1)

binarylarry (1338699) | about 2 years ago | (#41534401)

Someone better call the Dixie Flatline!

Re:How long until... (2, Insightful)

Yvanhoe (564877) | about 2 years ago | (#41534435)

There is not enough energy in the universe to store all the informations of the universe in a computer.
If you focus on some information (human minds for instance) of special interest to you, on the other hand...

Re:How long until... (2, Insightful)

Black Parrot (19622) | about 2 years ago | (#41534705)

There is not enough energy in the universe to store all the informations of the universe in a computer.

I subscribe to the view that the universe is computing its own final state.

Or more precisely, always computing its next state; apparently there isn't going to be a final one.

Re:How long until... (1)

19thNervousBreakdown (768619) | about 2 years ago | (#41534875)

The Planck constant just get bigger as you go.

Or we could just ... (1)

PPH (736903) | about 2 years ago | (#41534481)

... run Windows 9 with it.

Re:How long until... (1)

thej1nx (763573) | about 2 years ago | (#41534537)

That will in all likelihood be much, much longer than human kind's likely survival odds. So, the answer is never.

Re:How long until... (1)

Tablizer (95088) | about 2 years ago | (#41534549)

Maybe that's what we actually are, and "God" is really a lonely Linux admin (equivalent) playing with his human ant farm.

Re:How long until... (1)

Anonymous Coward | about 2 years ago | (#41535155)

You jest, but that is actually one possible solution to the Fermi Paradox / Drake Equation... The longer we go without discovering other life in the universe, the more likely this is all a simulation.

Re:How long until... (1)

DigiShaman (671371) | about 2 years ago | (#41534759)

And this ultra-mega-super-computer will run on...what exactly? Once the real Universe cools down, so will this computer that requires a constant feed of energy.

Re:How long until... (1)

die standing (2626663) | about 2 years ago | (#41534847)

so many people these days are throwing the concept around so easily eg. Google "itself," the iPhone "itself", Internet "itself," Earth "itself," the Law "itself," money "itself..."

so it's really quite simple: it will just run on "itself" ;-)

Re:How long until... (2)

sFurbo (1361249) | about 2 years ago | (#41535189)

If there were no dark energy, the temperature difference between a heat storage and an ever cooling universe would allow you to do infinitely many calculations, at an ever slowing rate. It seems that there is dark energy though, so the point where space-time recedes faster than c from you moves closer and closer. This is, essentially, an event horizon, so it will have Hawking radiation, meaning that the visible universe will not get arbitrarily cold, so only finitely many calculations can be done. It also becomes hard to do calculations when the electrons around a nucleus recedes from the nucleus faster than c. Dark energy is really a bummer when it comes to living forever.

Re:How long until... (1)

tchi.keufte (1154325) | about 2 years ago | (#41535393)

In "The Last Question", the "God computer" you're talking about is composed of... humans. (Humanity IS the computer) What I mean is that, in real life, *maybe* (or maybe not) there's nothing to be built except running the Good (or God) software in people's brains.

What about next month? (0)

Todd Palin (1402501) | about 2 years ago | (#41534357)

I wonder who they say will win the election next month.

Simulation Variant #85472721 (3, Funny)

Tablizer (95088) | about 2 years ago | (#41534585)

I wonder who they say will win the election next month.

Mitt Obamney: He taxes the rich to pay for birth certificate forgeries and dog racks on top of all GM cars. He told the UK Olympians that their skeet shooters are bitter gun clingers.

Re:Simulation Variant #85472721 (2)

Black Parrot (19622) | about 2 years ago | (#41534725)

Mitt O['B]amney

Not a Kenyan, not a Mormon, but an Irishman!

Re:Simulation Variant #85472721 (0)

Anonymous Coward | about 2 years ago | (#41534815)

Not a Kenyan, not a Mormon...

Shouldn't that be "Not a Kenyan, not a Mexican..." for consistency?

Re:Simulation Variant #85472721 (0)

Anonymous Coward | about 2 years ago | (#41535023)

not when the axis of measure is bigotry.

Re:Simulation Variant #85472721 (0)

Anonymous Coward | about 2 years ago | (#41535243)

not when the axis of measure is bigotry.

You can't be bigoted against Irishmen, they aren't human.

the simulation can never end (4, Funny)

catmistake (814204) | about 2 years ago | (#41534373)

It started with the state the universe was in around 13.7 billion years ago (not long after the Big Bang) and modeled the evolution of dark matter and energy up to the present day.

so... what happened when it reached the simulation of the simulation, and then eventually the simulation of the simulation of the simulation? I've long been told that it's turtles all the way down, but I'd like to see a citation.

Re:the simulation can never end (5, Funny)

olsmeister (1488789) | about 2 years ago | (#41534447)

so... what happened

A stack overflow.

Re:the simulation can never end (4, Funny)

Cryacin (657549) | about 2 years ago | (#41534531)

No, it's not turtles all the way down. Eventually you hit tortoise and a SVN repository.

Re:the simulation can never end (0)

Anonymous Coward | about 2 years ago | (#41534461)

It started with the state the universe was in around 13.7 billion years ago (not long after the Big Bang) and modeled the evolution of dark matter and energy up to the present day.

so... what happened when it reached the simulation of the simulation, and then eventually the simulation of the simulation of the simulation? I've long been told that it's turtles all the way down, but I'd like to see a citation.

Unfortunately it's in turtle-ease.

Re:the simulation can never end (4, Funny)

GodfatherofSoul (174979) | about 2 years ago | (#41534483)

42

Re:the simulation can never end (4, Funny)

ctrl-alt-canc (977108) | about 2 years ago | (#41535087)

Given the amount of floating point calculations involved in the project, the result will be 41.999999

Re:the simulation can never end (0)

Anonymous Coward | about 2 years ago | (#41534877)

so... what happened when it reached the simulation of the simulation, and then eventually the simulation of the simulation of the simulation? I've long been told that it's turtles all the way down, but I'd like to see a citation.

It might be turtles all the way down, but I'm pretty sure Xzibit is going to be in there somewhere. I mean, we do like to simulate.

Re:the simulation can never end (1)

jmerlin (1010641) | about 2 years ago | (#41534897)

Well if there's a simulation within a simulation ad infinitum, the 'simulation' starts off in a real universe (sort of like how there's a smallest element in the set of natural numbers). But then the probability that we're in the real universe is therefore infinitesimally small.

Re:the simulation can never end (2)

brisk0 (2644101) | about 2 years ago | (#41535041)

Not infinitesimally, each universe would probably have to be significantly simpler [smbc-comics.com] than the one it's already in, until the point that a universal simulation is too complex for the universe. Of course any one universe could spawn [very large number] of simulated worlds in a tree structure.
So if we assume mediocrity (and assume I'm not just spouting bull), we exist in one of the simpler universes... the original must have been nuts.

Re:the simulation can never end (0)

Anonymous Coward | about 2 years ago | (#41535503)

GIGO happened, it still invented merkins

False advertising (1)

Cyphase (907627) | about 2 years ago | (#41534375)

Did anyone else think this was going to be about some sort of Universe-scale natural phenomenon being modeled as a supercomputer?

Let's qualify that sentence just a bit... (3, Informative)

Empiric (675968) | about 2 years ago | (#41534387)

...astronomers are turning to supercomputers that can simulate the entire evolution of the universe.

I'm thinking the intent here is to mean this qualified "up to a certain point in time", as I'm pretty sure that to say this as a general, even theoretical, possibility is a Godelian-type logical impossibility. Since the supercomputers would be part of the universe you are simulating, you have to simulate the simulation of the supercomputer, which requires simulating the simulation of the computer simulating the computer... ad infinitum.

But then again, I may be wrong. Best simulate my thought processes to be sure.

Re:Let's qualify that sentence just a bit... (1)

bejiitas_wrath (825021) | about 2 years ago | (#41534547)

But what if you build the computer outside the Universe so it is not part of the Universe. The AC was in hyperspace... BTW, is the One in the Last Answer story the cosmic AC?

Re:Let's qualify that sentence just a bit... (1)

YttriumOxide (837412) | about 2 years ago | (#41535015)

But what if you build the computer outside the Universe so it is not part of the Universe. The AC was in hyperspace... BTW, is the One in the Last Answer story the cosmic AC?

The story is called "The Last Question ", not "The Last Answer"... seems to be a common mistake; but completely defeats the point of the story. The point is that the question remains the same throughout the ages and is always answered the same way; until the very end when there is finally a way to answer to the last question - however the answer is never given since only through demonstration of the answer can there be someone to give the answer to.

As for the name of the computer, it changes for each "time period"... "AC" is the only stable part. The first one is "Multivac", the very last one is just "AC". "Cosmic AC" is, IIRC, the second last one.

Re:Let's qualify that sentence just a bit... (1)

Maritz (1829006) | about 2 years ago | (#41535367)

The story is called "The Last Question ", not "The Last Answer"... seems to be a common mistake; but completely defeats the point of the story.

I hadn't heard of it until reading these comments but there is a 'last answer' by Asimov as well. The common mistake seems to be people correcting those who mention it..!

Re:Let's qualify that sentence just a bit... (1)

YttriumOxide (837412) | about 2 years ago | (#41535855)

I hadn't heard of it until reading these comments but there is a 'last answer' by Asimov as well. The common mistake seems to be people correcting those who mention it..!

I am aware of the story "The Last Answer", but didn't think it has much at all to do with the topic at hand, and had just replied to someone else about "The Last Question" so mistakenly assumed the reference here should also be to it. Totally my fault on lack of comprehension, since re-reading the GP post; he clearly did mean "The Last Answer" and was wondering about the relationship between the stories...

Re:Let's qualify that sentence just a bit... (1)

Sique (173459) | about 2 years ago | (#41535373)

There are two stories, one is The Last Answer and the other The Last Question. Both are by Isaac Asimov.

Re:Let's qualify that sentence just a bit... (0)

Anonymous Coward | about 2 years ago | (#41534571)

Since the supercomputers would be part of the universe you are simulating, you have to simulate the simulation of the supercomputer, which requires simulating the simulation of the computer simulating the computer... ad infinitum.

You're naively assuming the simulation is perfect. It isn't and could never be, even if you used all the matter in the Universe to build the machine. It'd be great if everything could be perfect, but even when possible often the costs are too high so a good enough solution is... well, good enough.

Re:Let's qualify that sentence just a bit... (0)

Anonymous Coward | about 2 years ago | (#41534629)

I always laugh at this genius bit of journalism

"...simulate the entire evolution of the universe..." :D

Just to add some clarity amd intrigue, the simulation concerns large-scale structure of the Universe: The models in principle include dark matter, dark energy and standard matter (i.e. stars and such stuff...), but the point is that they use a simplified description which is valid only over VAST distances. It turns out that, e.g. the 'standard matter' can be modeled as a fluid --- basically all the stars, dust, galaxies, etc., when 'smeared' in space, behave as a fluid. Imagine a sand storm, where all sand particles are stars.

So, there are equations describing how fluids flow, including the gravitational and electromagnetic forces through them (which are the only ones relevant at long distances). As the 'Universe evolves' in the model, the fluid of dark matter clumps together into a network of fibres, and since it gravitationally attracts normal matter, it clumps too, forming filaments of higher density. Indeed, astronomers observe galaxies clumping into filament-like structures.

To add inslut to injury, such hydridynamic simulations are actually done by using "effective particles", meaning that the fluid itself is not modeled as a continuous medium but is modeled by a bunch of 'particles' which interact in specific ways. But these particles represent bits of fluid contining billions of solar masses.

Resulting pictures and videos (follow also http://en.wikipedia.org/wiki/Millennium_Run ) make me calm and blisful.

Re:Let's qualify that sentence just a bit... (1)

Joe_Dragon (2206452) | about 2 years ago | (#41534643)

what about it becoming a feed back loop where the simulation of the computer simulating ends ends powering the simulation of the computer simulating

Re:Let's qualify that sentence just a bit... (1)

Yetihehe (971185) | about 2 years ago | (#41535011)

This was answered in Permutation_City [wikipedia.org] by Greg Egan. You just start new simulation.

Re:Let's qualify that sentence just a bit... (2)

JWW (79176) | about 2 years ago | (#41534689)

What part of "turtles all the way down" don't you understand?

Re:Let's qualify that sentence just a bit... (1)

Empiric (675968) | about 2 years ago | (#41534779)

Good question. What part of the relative timestamps of that post and mine don't you understand?

Re:Let's qualify that sentence just a bit... (1)

Anonymous Coward | about 2 years ago | (#41535359)

Good question. What part of quantum tachyon dynamics do I need to understand to follow the jokes on this thread?

Re:Let's qualify that sentence just a bit... (2)

Black Parrot (19622) | about 2 years ago | (#41534745)

...astronomers are turning to supercomputers that can simulate the entire evolution of the universe.
I'm thinking the intent here is to mean this qualified "up to a certain point in time", as I'm pretty sure that to say this as a general, even theoretical, possibility is a Godelian-type logical impossibility. Since the supercomputers would be part of the universe you are simulating, you have to simulate the simulation of the supercomputer, which requires simulating the simulation of the computer simulating the computer... ad infinitum.

Almost without exception, simulations are simpler than the thing being simulated. You use simulations when the real thing would be impossible, or too dangerous or expensive.

Re:Let's qualify that sentence just a bit... (1)

Empiric (675968) | about 2 years ago | (#41534805)

Indeed. And without the qualifier "entire", I wouldn't have commented. That suggests complete algorithmic, rather than heuristic, simulation.

Re:Let's qualify that sentence just a bit... (0)

Anonymous Coward | about 2 years ago | (#41535491)

When they say "entire", they mean the entire universe as opposed to some subset of it (like a single galaxy). In the same way, I could write a simulation of my home city's entire traffic network rather than some subset of it (like a single intersection). It doesn't mean that I'm calculating the vibration of every atom in every fleck of paint on every vehicle on the roads.

Re:Let's qualify that sentence just a bit... (2, Insightful)

Anonymous Coward | about 2 years ago | (#41535215)

You fail to realize something. If the reality we are experiencing is in fact a simulation, then it doesn't matter if one plank-step of the simulation takes an hour or a Universe worth of time to compute -- To us within the simulation, time remains locally constant. Likewise, The super computers can simulate the entire evolution of the universe by imposing acceptable error rates (epsilon).

A very low resolution simulation would simply count down from 1.0 (max Universal energy) to 0.0 (heat death) over one universe worth of time steps, the fastest of such simulation is a single constant approximation: .42

A higher resolution simulation could produce a more detailed simulation using much more than a single time step. Interestingly, the quantum error rate can be predicted from within the simulation via observation. Heisenberg has calculated the epsilon of our Universe... Plank calculated the physics step size.

In short: One can indeed calculate an entire Universe within another if one allows a high enough "acceptable" error rate and low enough resolution. Quantum Uncertainty may be proof such corner cutting has already happened at a higher dimension.

Re:Let's qualify that sentence just a bit... (1)

Anonymous Coward | about 2 years ago | (#41535317)

Wow. In case you missed it, an AC just provided both the Ultimate Answer to Life the Universe and Everything, AND demonstrated the Ultimate Question too. Protip, The U.Q. seems to be something like: "What is 'normal', anyway?" -- Deep Thought simply used a scale of 100 to 0 instead of 1.0 to 0.0

There may be hope for humanity yet!

Re:Let's qualify that sentence just a bit... (0)

Anonymous Coward | about 2 years ago | (#41535617)

Simulation inherently involves abstracting away from the real world, so there is no problem with this sentence.

The most depressing thing (-1)

Anonymous Coward | about 2 years ago | (#41534417)

The most depressing thing about this simulation was that after simulating 13.7 billion years of galactic evolution using 14000 high-end CPUs for months on end, the end result was that in the simulated universe, just as in our own, Justin Bieber made it big.

GIGO (-1, Flamebait)

slashmydots (2189826) | about 2 years ago | (#41534449)

As soon as they feed data in, they realize they were wrong about some part of physics or particles or total universe mass and start over. There are hundreds of pure assumptions and estimations put in to the point where the accuracy is terrible. Then when the result doesn't match, they sort of BS it until it does match but the numbers barely make sense. Not exactly the best use of supercomputing. They'd probably get more money than that science grant money baiting if they ran a bitcoin miner on it instead, lol.

Re:GIGO (2)

steppedleader (2490064) | about 2 years ago | (#41534681)

It appears that the model reproduces some large scale statistical properties of the universe with reasonable accuracy. That seems reasonable. It's a far cry from being able to say "the model reproduced the Milky Way", but the statistical information by itself could very well be useful as a tool for developing new hypotheses. Of course, if the model is all wrong those hypotheses will be useless, but let's see what they can do with the data before we make that conclusion.

Re:GIGO (1)

TapeCutter (624760) | about 2 years ago | (#41534701)

The only garbage here is your post, I suspect what you are doing is projecting your own personality flaws onto others.

Re:GIGO (0)

Anonymous Coward | about 2 years ago | (#41534777)

So, as you seem to be saying, they take a model and use it to make predictions about the observable universe, then compared those predictions to actual observations, tossing out the model if it doesn't match. And this is wrong?

You could be trying to make a subtler point about over-fitting, where they have freedom to choose so many parameters they can find whole classes of models that would work. But do you actually know how many input parameters they have control over, and how many independent data points they are comparing this to? Or are you just assuming their actions happen to match your preconceived notions, resulting in you having horrible accuracy due to assumptions?

Re:GIGO (1)

Maritz (1829006) | about 2 years ago | (#41535383)

There are hundreds of pure assumptions and estimations put in to the point where the accuracy is terrible.

You sound like you know what you're talking about; able to point us in the direction of a few dozen of those hundreds of assumptions?

Or we could ... (3, Funny)

PPH (736903) | about 2 years ago | (#41534495)

... put this supercomputer to work generating all possible Slashdot logos.

Did it find out who killed JFK? (0)

Anonymous Coward | about 2 years ago | (#41534527)

Maybe my expectations are too high.

Re:Did it find out who killed JFK? (2)

Tablizer (95088) | about 2 years ago | (#41534611)

We all did, in at least one variant. My avatar slipped on Marilyn Monroe's used tampon in a grassy knoll, setting off a guard's gun. Sorry 'bout that.

Re:Did it find out who killed JFK? (1, Insightful)

Black Parrot (19622) | about 2 years ago | (#41534763)

We all did

I shouted out Who killed the Kennedys?, when after all... It was you and me.

Re:Did it find out who killed JFK? (0)

Anonymous Coward | about 2 years ago | (#41534845)

You bastards!

Re:Did it find out who killed JFK? (1)

wbr1 (2538558) | about 2 years ago | (#41536275)

Pleased to meet you! Won't you guess my name?

Oy Vey (0)

Tablizer (95088) | about 2 years ago | (#41534535)

If you think slashdotters are tired of First Posts....

Any Cosmologists Here? (2)

steppedleader (2490064) | about 2 years ago | (#41534593)

First off, "entire evolution of the universe" should obviously be qualified with "on cosmological scales", unless they've built the matrix. That said, how big is the domain? Is it just set to match the observable universe? 2048 grid points across the entire universe (or just the observable universe) seems rather... low-res. The TFA mentions an adaptive grid, but fails to mention what factor that can increase the local resolution by.

Also, how exactly do we model dark matter when we don't really know WTF it is beyond the fact that it has gravitational mass? Does it work because gravitational effects are the only thing that really matters on cosmological scales?

I must say I like the use of periodic boundary conditions, though, simply because it makes their simulated universe conform to the Modest Mouse lyric "The universe is shaped exactly like the earth, if you go straight long enough you end up where you were".

Re:Any Cosmologists Here? (5, Informative)

mendelrat (2490762) | about 2 years ago | (#41534981)

I'm not a cosmologist, but I am an astronomer. Most of the questions you ask are in the papers associated with Bolshoi, but science writers just leave them out because the numbers are so huge and hard to relate with -- I'm going to use megaparsecs for distances; 1 megaparsec = 1 million parsecs = 3.26 million light years = 200 billion astronomical units. 1 astronomical unit is ~93 million miles, the distance from the Earth to the Sun.

First off, "entire evolution of the universe" should obviously be qualified with "on cosmological scales", unless they've built the matrix. That said, how big is the domain? Is it just set to match the observable universe? 2048 grid points across the entire universe (or just the observable universe) seems rather... low-res. The TFA mentions an adaptive grid, but fails to mention what factor that can increase the local resolution by.

As you point out, the 'entire evolution ...' phrase is a bad way of saying that the simulated volume and mass is large enough to be statistically representative of the large scale structure and evolution of the entire universe. It's 2048^3 particles total, which is a heck of a lot. 8,589,934,592 particles total, each pushing and pulling on each other simultaneously. It's an enormous computational problem. The particles are put into a box ~250 megaparsecs on a side; the Milky Way is ~0.03 megaparsecs in diameter, and it's ~0.8 megaparsecs from here to the Andromeda galaxy, our nearest large galaxy. 250 megaparsecs is a huge slice and more than enough to ensure that local variations (galaxies) won't dominate the statistics. The ART code starts with a grid covering 256^3 points, but can subdivide to higher resolutions if some threshold is passed up to 10 times if I remember correctly, giving a limit of around 0.001 megaparsecs. My memory is hazy, and the distances are scaled according to the hubble constant at any given point, but they're in the ballpark I think.

Also, how exactly do we model dark matter when we don't really know WTF it is beyond the fact that it has gravitational mass? Does it work because gravitational effects are the only thing that really matters on cosmological scales?

Essentially, yes; gravity absolutely dominates at these scales compared to all other forces considered. The role of stellar and galactic feedback into their environment when forming (and as they evolve) changes lots of important things, but simulations like Bolshoi seek to simulate the largest scale structures in the universe. Smaller subsections of the simulation can be picked out to run detailed N-body simulations of Milky Way type galaxies, or to statically match the dark matter clumps (which will form galaxies) to huge databases like the Sloan Digital Sky Survey. Both of those are pretty active things-to-do in cosmology now.

Re:Any Cosmologists Here? (1)

steppedleader (2490064) | about 2 years ago | (#41535357)

Ah, thank you. I'm a numerical modeler myself, but I'm studying meteorology and thus generally focus on things that happen a bit more nearby and in a fluid medium. Good to know my physics BS allows me to at least ask somewhat intelligent questions about this sort of stuff, though!

Reminds me of that old joke (2)

khelms (772692) | about 2 years ago | (#41534615)

Scientists build the ultimate computer. The first thing they ask it is, "is there a god?". The computer answers "there is now!"

Re:Reminds me of that old joke .. the answer is 42 (-1)

Anonymous Coward | about 2 years ago | (#41535091)

Actually, it's no joke, just a blasphemy. The simulation was based upon faulty input -- GIGO rules.


First, there was no Big Bang. The universes are eternal. These universes are connected by white holes (Garbage In) and black holes (Garbage Out). Black holes destabilize matter into energy which is drawn into an alternate parallel universe. In that alternate universe white holes spew energy out into a cacophony of frequencies that astronomers now identify as dark matter/dark energy. This dark matter/dark energy is the basic building block of all perceived matter in each universe before it has coalesced into self-organized symphonies of frequencies. Matter is merely the interference pattern of energy that has self-organized into stable symphonies of frequencies that exhibit specific perceived physical properties. It is possible to alter these interference patterns, which will coincidentally alter matter, gravity, and time.


These alterations allow the transmutation of matter, known by ancient alchemists but lost to humanity and rediscovered numerous times with each rise and fall of advanced civilizations. These alterations also allow for access to free energy, plus interstellar, inter-dimensional, and time travel. These physical properties can and do vary in each each universe, along with the laws of physics, which are symphony dependent. From the smallest subatomic particle to the largest galaxy in each universe, all are the equivalent of a Mandelbrot Set of energy that vibrates in resonant symphonies of frequencies. Only two things are eternal, energy and time, although time has a different rate of speed in each universe. Energy is immutable, but matter is not, nor is gravity.


Einstein was knowingly wrong, and left out many components in his famous "E = mc^2" formula. So too was Lorenz, with his modifications of that formula. Components of the true formula have not been completely revealed, although Nikoli Tesla came the closest thus far in the modern age of man. The knowledge imparted to Tesla was via his psychic connection to the universal consciousness, through which all knowledge may be gained for the truly worthy. My inter-dimensional spirit guide imparted this rudimentary knowledge to me with the understanding that I must pass this knowledge on to others. Slashdot appeared to be the ideal medium for this transmission. When this basic understanding of the nature of our universes is quantified and codified, NASA's Pleiades Supercomputer will find the answers to zero point energy, anti-gravity, the transmutation of matter, interstellar and inter-dimensional travel, and time travel.


These discoveries must be shared with the entire world for the benefit of the entire world, and not withheld to empower an elite few.

Ironically, my Slashdot validation code is "repress"

A complete run-through? (0)

Anonymous Coward | about 2 years ago | (#41534641)

A complete run-through of the universe up to present day? It's not a complete run-through, then, is it? I would imagine it should include a heat death or a big freeze to be considered anywhere near complete.

Re:A complete run-through? (0)

Anonymous Coward | about 2 years ago | (#41534789)

Do you not understand what a grammatical qualifier is and how it can modify meaning to be specific to a narrower context?

Re:A complete run-through? (0)

Anonymous Coward | about 2 years ago | (#41535067)

Yes, but this is /. and I like to nitpick. The summary talks about simulating the entire evolution of the universe. It's not like the universe won't evolve beyond present day.

Seeing (at least) the next few steps might be interesting and also relevant in evaluating the strength of the model. This is beyond my nitpick, though.

This is really creepy (1)

GodfatherofSoul (174979) | about 2 years ago | (#41534741)

Or maybe I just watch to many sci-fi movies. Feels like one of those "knowledge man was not yet ready to possess" storylines in the works.

Re:This is really creepy (1)

noobermin (1950642) | about 2 years ago | (#41534811)

General Relativity has been around for almost a century and it's been understood pretty well since the 60's.

Epistemological Weakness (4, Interesting)

Required Snark (1702878) | about 2 years ago | (#41534893)

This is clearly good work, but I believe that the article glosses over real problems with these kinds of simulations. The short version of the problem is that the agreement between the model and the observations doesn't provide a huge degree of confidence in the model being tested. It appears that both the model and the starting setup are per-disposed to produce results that match observations.

There has been no perturbation testing of the model. It does not seem that they did any runs that were intended to produce a result that did not match observations. They have no idea what range of input or modeling change produce a result that matches observations.

The greatest utility of these simulations is when they don't match observations. This opens the possibility that the current ideas are incorrect, and that new ideas are needed.

I also wonder about scaling issues. The three simulations at different scales are unconnected. There is no way to see how events at one scale effect events at other scales.

The author also said one specific thing that bothered me:

Astrophysicists can model the growth of density fluctuations at these early times easily enough using simple linear equations to approximate the relevant gravitational effects.

I am not a physicist or cosmologist, but that seems to be a huge assumption. We have no idea what dark energy or dark matter are, but they can be modeled by "simple linear equations."

I know that the shear cost and complexity of these computational experiments means that they are hard to accomplish. Even so, I will be less skeptical about their value when they are done in ways that test how the simulations fail, as well as how they verify current ideas.

Re:Epistemological Weakness (2, Insightful)

Anonymous Coward | about 2 years ago | (#41535227)

Yes, Bolshoi's initial conditions were in some sense designed to match observations. Specifically, the five main parameters which describe cosmology (including the abundance of dark energy and dark matter) were derived from observations of the cosmic microwave background, supernovae, and galaxy clustering. These five numbers were used to generate the initial conditions for Bolshoi; a supercomputer spent the time to figure out how the universe should evolve from several million years after the Big Bang to the present day. Thus, Bolshoi serves as a giant consistency check of the model: i.e., it tests whether the five parameters are enough to explain everything we observe about the evolution of the universe, as well as whether observers calculated them correctly.

However, the fact that Bolshoi matches observations now is no guarantee that a future observation won't come along and break things. The previous large simulation (the Millennium Simulation), which was run in 2005, was also designed to match all observations up to that point. However, since then, we've made observations which contradicted results from that previous simulation, which have indeed taught us new things.

Finally, to address the specific point that you raise: we don't know what dark matter and dark energy are, but to our knowledge, gravity doesn't care about the type of matter/energy involved. This assumption could be wrong, of course. So far, however, making that assumption has led to predictions which seem to match observations. (So it would definitely be interesting if someone made an observation that proved otherwise!) The "linear equations" the author is referring to are simply Taylor expansions of the gravitational potential. Since the density fluctuations in the early universe are tiny (variations of +/- 0.001% even 300,000 years after the Big Bang), using a linear approximation doesn't introduce significant errors. However, once the density fluctuations grow to +/- 10% or so, then the linear approximation is no longer as useful; that's when the supercomputer takes over to do more accurate computations of gravity.

Re:Epistemological Weakness (1)

Anonymous Coward | about 2 years ago | (#41535519)

We have no idea what dark energy or dark matter are, but they can be modeled by "simple linear equations."

That bit's fine. Dark matter and dark energy are fudge factors in the equations that make them generate answers corresponding to what we see. (This isn't a bad thing: an electron is also a fudge factor that makes lots of different equations produce results that correspond to experimental results.) At the moment, simple linear terms for dark matter and energy are enough to produce results consistent with observations. If they weren't, that would tell us that our simple concepts of dark matter and energy are wrong. Until then, though, by Occam's razor, we'll stick with the simple linear representation.

(I'm an astrophysicist, but not a cosmologist.)

Re:Epistemological Weakness (0)

Anonymous Coward | about 2 years ago | (#41536139)

We'll know the worth of this model in the future, when we have new observations.
If the new observations fit the model, that's good.
If they don't, that's great. That's the place to search for new stuff.

Models, models, models.... (1)

macraig (621737) | about 2 years ago | (#41534915)

And if the beginning parameters of the model were off from actual history by even the tiniest fraction, the extrapolated results won't be worth much. We pretend otherwise, but we really still don't know the current state and composition of the universe, much less how it started... assuming it started. There's a reason that they're called theories.

Re:Models, models, models.... (1)

brisk0 (2644101) | about 2 years ago | (#41535135)

There's a reason that they're called theories.

Because they have been repeatedly confirmed through observation and experiment [wikipedia.org] ?

As far as I know your point is still valid, I'm just nitpicking.

Sing Along With Me Folks (1)

Crypto Gnome (651401) | about 2 years ago | (#41535183)

I'm sure eventually we'll get enough size and resolution:

It's the simulation that doesn't end.
Yes, it goes on and on my friend.
Someone started running it not knowing what it was,
And they'll continue singing it forever just because...

Well to be perfectly honest:
(1) Most people don't realise they're in a simulation
(2) The few with "suspicions" have no idea where the off switch is

Can it tell me what happened in the future? (0)

Anonymous Coward | about 2 years ago | (#41535219)

I'd like to know stock prices next week, next month, next year, etc. Who won the Super Bowl, etc...

Bolshoi, you say? (0)

leromarinvit (1462031) | about 2 years ago | (#41535405)

I recommend you get rid of this Stalin fella in the next iteration. He's up to no good.

Pretty sure their model didn't come close (0)

Anonymous Coward | about 2 years ago | (#41536137)

How foolish to think that any number of modern CPUs, in their current state, could come close to being an accurate model of the universe. Our field of vision of the universe is but a miniscule slice and it is quite clear that though we will always "know more than we ever have before", the model is nothing but a model of our thoughts on what small parts we know of, not any real representation of what our universe really is.

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