Scientists Complete Universe Millennium Simulation

james tech writes "The Virgo Consortium recently completed its massive "Millennium Simulation", tracing the universe's evolution from its early origins to present day. To simplify the computations, they considered only dark matter which composes most of the universe. Using a 512-node cluster with IBM processors, the group produced over 20 terabytes of data with some of the most breathtaking images of the universe never seen. A visible matter simulation is underway, at a lower resolution."

Comments

impressive

[Anonymous Coward]

Wow, this is some impressive stuff indeed.... Of course I'm talking about their "not yet slashdotted" webserver that's probably handling a lot of big 50MB downloads right now.

Re:impressive

[LucidBeast]

Well, what did you think they did with that super computer after they were done simulating the whole universe.

Total Millenium Vortex

[Anonymous Coward]

The scientists are working on future versions of the software that will exptrapolate the whole Millenium simulation from a piece of pie.

Talk about bloat

[sygin]

"20 terabytes of data" This has to be the most bloated screensaver ever!

Re:Talk about bloat

[AndroidCat]

There's talk of Google buying them out and offering it as Google Everything.

Caveat -- cosmology not far from understood

[helioquake]

"It doesn't matter how beautiful your theory is, it doesn't matter how smart you are -- if it doesn't agree with experiment, it's wrong." -- R.P. Feynman

I feel that this quote is appropriate, as I believe this type of simulation possibly cannot contain every essential physics that governs the evolution of the Universe. Some oversimplification must be present and some tweaks (e.g. dark matter) may go into the modeling to match whatever we see it today.

This isn't the end of the study of cosmology. That's all I'm trying to say.

Re: Caveat -- cosmology not far from understood

[Black Parrot]

> > "It doesn't matter how beautiful your theory is, it doesn't matter how smart you are -- if it doesn't agree with experiment, it's wrong." -- R.P. Feynman

> I feel that this quote is appropriate, as I believe this type of simulation possibly cannot contain every essential physics that governs the evolution of the Universe. Some oversimplification must be present and some tweaks (e.g. dark matter) may go into the modeling to match whatever we see it today.

Yes, and figuring out why your model doesn't reproduce what you see is where the potential for real discoveries lies.

evidence

[resistfascism]

Besides the argument that stars orbiting around the fringes of galaxies appear to be moving too fast to stay in orbit without extra mass, what other observable evidence of dark matter is there?

Re:evidence

[Use Psychology]

a good one is gravitational lensing by massive clusters -- a lens analysis of all the arcs seen in, for example, a cluster, can be used to infer the mass of the cluster, and hence see that it is inconsistent with the mass of all the luminous matter. i.e. dark matter

Re:evidence

[gilzreid]

Also, by measuring the expansion rate of the universe over a very long time (ie. billions of years), and making observations of the Cosmic Microwave Backgound (CMB, the left over radiation from around 300000 years after the Big Bang) we can calculate the amount of matter it must contain. Then from models of the Big Bang and the CMB observations we can also find the amount of 'normal' matter (ie atoms), which comes to about 4% of the so called 'critical density', which is the amount of matter/energy required to have the universe be spatially flat (expands forever but tends toward zero expansion rate as time goes to infinity)

Since the amount of matter is measured to be around 25% this means dark matter must be around 20% of the critical density.

Incidentally, this also means that 75% of the energy/matter in the universe is 'dark energy', since the cosmic microwave background indicates the universe is almost exactly flat.

However, the importance of each constituent changes over time because essentially the dark energy is proportional to the size of the universe and when it was much smaller the matter was more concentrated so it had a far greater influence. Therefore for studies of the early evolution of the universe the dark energy is unimportant, and since dark matter is most of the total matter the models can just use dark matter alone. At present, however, the dark energy appears to be causing an acceleration of the expansion rate, which is seen using distant supernovae. This is how the 75% figure is worked out.

NB: Nobody can explain what the dark matter or dark energy is right now! This is by far the most important problem in Cosmology, and there are many , many competing theories.

Re:evidence

[gr8_phk]

"Besides the argument that stars orbiting around the fringes of galaxies appear to be moving too fast to stay in orbit without extra mass, what other observable evidence of dark matter is there?"

I looked into that whole thing. Most of the people who make that claim refer to Keplers laws of motion for orbiting bodies. If you assume the stars orbit a heavy core and don't interact with each other you get a galactic rotation curve that tapers off with radius. Real measured curves are nearly flat, so they conclude some "dark matter" that has some really unintuitive properties (see below). My own calculations of a rotation curve for a uniform flat disk of stars using interactions between all stars shows velocity increasing roughly linearly all the way out, and increasing even faster toward the edge. I don't think we should be suprised that observation lies somewhere between these two models. My distribution of stars is not accurate.

Stupid properties of dark matter: The interaction with regular matter must be asymetric. Why? Because they model it as a sphere of dark matter enclosing a disk shaped galaxy to get the expected rotation curve. If dark matter interacted with itself and visible matter in the same way visible matter interacts with itself, they should have the same distribution. I think they just observed that a big sphere of stuff would make their flawed model match reality and said "oh there must be this goofy thing here". Remember, there are NO direct observations of dark matter (or energy).

The tragedy of Einstein is that he convinced physicists that strange nonintuitive things are a part of the universe. This encourages the promotion of nifty off-the-wall sounding theories that make headlines to get funding.

I've said it here before: The only dark matter is between the astrophisicists ears.

Re:evidence

[lgw]

Stupid properties of dark matter: The interaction with regular matter must be asymetric. Why? Because they model it as a sphere of dark matter enclosing a disk shaped galaxy to get the expected rotation curve. If dark matter interacted with itself and visible matter in the same way visible matter interacts with itself, they should have the same distribution. I think they just observed that a big sphere of stuff would make their flawed model match reality and said "oh there must be this goofy thing here". Remember, there are NO direct observations of dark matter (or energy).

This argument has several flaws. There is direct evidence for dark matter in the cosmic microwave background data, which is why dark matter is now the preferred theory for explaining galactic rotation rates.

It's not actually the theory that all of the "normal matter" in our galaxy is visible in a disk, and all of the "dark matter" is distributed in a sphere - a significant percentage of the dark matter in our galaxy is thought to be normal matter that just didn't clump enough to form (many) stars - that is, disperse hydrogen gas.

For the remaining "exotic dark matter", the one thing we know about it (from the CMB data) is that it interacts weakly with normal matter. There's no reason to assume that whatever caused most "normal" matter to clump and eventually become stars would cause "exotic" matter to have a similar distribution. A disk makes sense for matter that tends to form clumps as a result of collisions, and a sphere makes perfect sense for matter that doesn't. It's not all that unintuitive or surprising, given the data now in hand.

Big bang

[Xoknit]

After the images of the simulation were released, a second big bang was reported by the scientists of the project, originating from the server room.

Apparently all the packets on the internet condensed in one of their servers and created a second universe, from now on to be referred to as "cyberspace".

Comment removed

[account_deleted]

Comment removed based on user account deletion

MirrorDot

[HateBreeder]

http://www.mirrordot.org/stories/bdfc0ad7cef604a1a f6b98722b0f530f/index.html

About those authors...

[Black Parrot]

> Authors: Volker Springel (1), Simon D. M. White (1), Adrian Jenkins (2), Carlos S. Frenk (2), Naoki Yoshida (3), Liang Gao (1), Julio Navarro (4), Robert Thacker (5), Darren Croton (1), John Helly (2), John A. Peacock (6), Shaun Cole (2), Peter Thomas (7), Hugh Couchman (5), August Evrard (8), Joerg Colberg (9), Frazer Pearce (10) ((1) MPA, (2) Durham, (3) Nagoya, (4) UVic, (5) McMaster, (6) Edinburgh, (7) Sussex, (8) Michigan, (9) Pittsburgh, (10) Nottingham)

Now you know why "et al." is one of the most important concepts in the natural sciences.

Typical

[CleverNickedName]

The Virgo Consortium recently completed its massive "Millennium Simulation", tracing the universe's evolution from its early origins to present day. To simplify the computations, they considered only dark matter...

Reminds me of a joke:
A rich oil-baron hires a veterinarian, a statistician and a physicist to develop a method for predicting the outcome of a horse race. The three scientists disappear for a week and each returns with a different method; The vet states "I have studied the form, health and blood-lines of all the horses for the next race and can confidently say that number 7 is the best of the lot. Whether he wins on the day, is another question". The Statistician boasts "I have studied the race histories of all the horses in the next race and all the races ran on this track and can definitely say that horse number 3 has a 85% chance of coming in the top 3". The physicist then strides up to the baron and boldly proclaims "I have developed a way to predict the outcome of any race with 100% accuracy! First, one assumes that the horses are perfectly spherical and moving through a vacuum...".

Re:Typical

[syntaxglitch]

Bah.

I generally find that joke is found to be funny in direct proportion to the audience's scientific illiteracy. "Har har, look at those silly scientists, spouting their nonsense. I'll just sit here and laugh at them while I enjoy all the lovely modern technology their work has made possible."

While mildly amusing, it betrays a deep failure of understanding the value of analytical simplification. Just because something sounds silly to the uninformed does not mean it has no value.

As pitiful as the current public understanding of science is (as evidenced by such things as the rampant belief in nonsense like 'creationism'), it'd be nice if the problem not further exacerbated.

Re:Typical

[jfengel]

Actually, I think only a scientist would find that joke funny. A nonscientist is just going to give you dumb stares.

It's an exaggeration for comic effect. Every good scientist recognizes in it some silly oversimplification he or she has made at some point in the past, because that's the way science gets done. The nonscientist doesn't get it precisely because he doesn't know how science gets done.

Public misunderstanding of science has little to do with the jokes of scientists poking fun at themselves. In fact, one of the best ways to convince the general public that science is simply wrong is to be humorless about it. Lighten up.

Who is to say...

[seti]

That this whole universe as we see it is not an experiment in somebody's supercomputer?

Re:Who is to say...

[indifferent children]

"Evolution vs Intelligent Design", it seems to me that the two aren't mutually exclusive.

Actually, I-D does preclude evolution (at least macro evolution). I-D proponents claim that complex structures (they love to pick on the eye and protozoan flagella) must have been designed, and could not have evolved. Many try to bastardize the concept of entropy, and claim that complexity arising out of less complex structure violates the laws of Physics. If you try to posit complex structures coming into existence through evolution, then you remove their entire argument for I-D (watch needs a watchmaker).

There are many people who believe that a god created the Universe, and created life, but then that life evolved into the diversity that exists today. This is not I-D.

Suspicious

[Arthur B.]

I cannot access the article at this moment but I am very suspicious of how accurate / scientific this simulation is. It surely is an amazing artistic work but heck, we don't even know the mass density of the universe (related to its curvature). Yet that sounds like a required data to make a simulation. This simulation should be ruled by the equations of general relativity which is still drafty. Most equations lead to cahotic behavior... we have trouble simulating three bodies because of the unstability of the system...

So, to quickly simulate everything that exists...

[kahei]

...they left out everything that is actually known to exist.

Yay!

But they can't run it into the future...

[haakondahl]

Because then the machine would have to simulate itself on earth, and could cause the program to crash. Think of the simulated /.ers!

Re:Breathtaking indeed.

[Xaositecte]

"Just a theory" is a phrase that should never be used in the context of Scientific discussions. It shows a misunderstanding of what the word theory means in Science. A Theory, put simply, is an explaination for observed phenominon which can be experimentally disproven, and is capable of being used to make predictions. Mathmatical theory applies to the real world only insofar as it correctly explains real-world phenomina, and predicts the actions of the real universe. Current theories on the creation of the Universe are anything but simplistic, and are accurate according to the data we've collected so far. When more data comes along that proves the theory false or inadequate, the theory will have to change, creating a stronger theory. The idea that it's somehow worthless because it's incomplete is ridiculous.

And the Answer is

[dankasfuk]

Forty-two.

Ok, Let me get this straight...

[mritunjai]

I'm sleep deprieved, but have a fundamental question... the article said they only simulated 'dark matter' and produced 'breath-taking images'!!

Breath-taking images of *DARK MATTER* ??? WTF

Re:Breathtaking indeed.

[syntaxglitch]

Your question is meaningless. There is no "before" the big bang, because time AND space began at that point. "Prior" to the big bang is about as meaningful as asking what point on the Earth's surface is the center of the world.

There is no known way--and likely never will be--to know anything about existance outside of the post-big bang observable universe, other than indulging in wild and baseless speculation.

Re:Mod parent up Insightful

[saider]

Dark matter is "observed" indirectly through gravitational effects. It is not that the scientists doubt its existence, it is just that they cannot observe it directly, hence the name "dark".

A crude example would be if you were looking out your window at a lake. You might see waves caused by fish swimming below, but you would not be able to describe the fish, because you only saw the wave.

Re:Seems like a waste of time

[Mt._Honkey]

The fact is, this generates pretty pictures, maybe a nice paper in some backwater of journal land, and not much else beyond froth.

Some backwater journal like Nature?

I've done some work in the past couple of years on simulations of galaxy collisions, and can speak a little on the value of this type of research.

Large-scale structure simulations such as this one do have specific uses. They do not claim to reproduce the current universe in all its complexity, but can be used to test theories on its composition. When doing simulations like these, one makes certain assumptions in order to test them. They seem to have assumed that dark matter is made of non-relativistic (cold) particles that only interact gravitationally. They also would have had to assume an initial distribution of dark matter that has small density fluctuations. So by comparing the results of this simulation with observations of the real universe, one can get an idea of how accurate our theories of dark matter behavior and initial conditions are.

A common theory that is often assumed to be true is the Cold Dark Matter (CDM) cosmology, where all dark matter is assumed to be relatively heavy particles that are moving much more slowly than the speed of light. When you do this kind of simulation, a large number of dwarf galaxies are created, several times more than are observed in the real universe. This is a strong indication that the CDM assumption is flawed, that there is at least small portion of the dark matter that is "hot", or relativistic, as if there were a large number of high energy neutrinos, or some similar particle.

Well, rumor has it that...

[alien-alien]

After 6 days of calculation, they took the next day off.