Simulated Universe

anonymous lion writes "A story in the Guardian Unlimited reports on The Millennium Simulation saying that it is 'the biggest exercise of its kind'. It required 25 million megabytes of memory to take our universe's initial conditions along with the known laws of physics to create this simulated universe." From the article: "The simulated universe represents a cube of creation with sides that measure 2bn light years. It is home to 20m galaxies, large and small. It has been designed to answer questions about the past, but it offers the tantalising opportunity to fast-forward in time to the slow death of the galaxies, billions of years from now."

Comments

So where can I download it?

[Uppity Nigger]

I think my PC can handle it.

Re:25 TB? That's nothing.

[Seumas]

I'm pretty sure that they're talking about RAM. And yes, 23 terrabytes of RAM is a ton.

Re:I thought

[Anonymous Coward]

They have stuff like stars that are older than some estimates of the universe's age

No, they don't. This has happened a few times in the past, e.g., when they didn't know about the different populations of stars, but currently there isn't an age problem.

and missing matter in the form of dark matter that they can't account for

We don't know what dark matter is, but we know enough about its gravitational properties -- that's why it was postulated to exist, after all -- to simulate its effects on these scales.

How are they supposed to simulate the universe, if the model they have is so badly flawed.

The models we have are not as badly flawed as you think they are. But even if they are flawed, that's the point of the simulation: to test the validity of the model. If the simulation's results don't agree with observations, then that tells us about where the model fails.

Re:25 TB? That's nothing.

[andyh1978]

I figured they meant 25 TB of RAM. Which would be much more impressive.

This was on Newsnight a couple of days ago; the researcher said their machine had 1TB of RAM.

That's confirmed in page 18 of their paper: http://arxiv.org/PS_cache/astro-ph/pdf/0504/050409 7.pdf

The calculation was performed on 512 processors of an IBM p690 parallel computer at the Computing Centre of the Max-Planck Society in Garching, Germany. It utilised almost all the 1 TB of physically distributed memory available. It required about 350000 processor hours of CPU time, or 28 days of wall-clock time.
The mean sustained floating point performance (as measured by hardware counters) was about 0.2 TFlops, so the total number of floating point operations carried out was of order 5x10^17.

Re:Predicting the future

[Vellmont]

The uncertainty principle makes this an impossibility. Even if you could somehow simulate everything you could never get the exact initial conditions of even one particle. See http://en.wikipedia.org/wiki/Uncertainty_principle