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."

I thought

[CastrTroy]

I thought that they really hadn't even figured out how the universe worked. They have stuff like stars that are older than some estimates of the universe's age, and missing matter in the form of dark matter that they can't account for. How are they supposed to simulate the universe, if the model they have is so badly flawed.

Predicting the future

[XXIstCenturyBoy]

I always though that a computer large enough to handle a simulation of the universe would allow us to predict the future, even at individual level if the simulation was advanced enough.

And then I realized that the smallest simulation of the universe would probably be the size of the universe.

It got very confusing at that point.

Re:Google Maps

[FleaPlus]

In all seriousness, the interface used by Google Maps seems like it would be well-suited for dealing with astronomical imaging data.

Re:25 Million Megabytes

[turkeyphant]

I use SI units - tebibytes [nist.gov].

Re:25 TB? That's nothing.

[daveschroeder]

Jeez.

Yeah, I can point out more that that too in our facilities.

After all, UW-Madison is one of the largest research universities in the world.

The point is that:

- They were talking about 25TB of disk, not RAM
- 200TB in a single installation for a single project is hardly "peanuts"; it's actually quite a bit by enterprise storage standards, but that's neither here nor there
- Oracle is doing press releases on things like using *50 TB* of disk for a project
- 200TB of Xserve RAIDs in one place is, I believe, the largest Xserve RAID installation at a single site (save perhaps Apple), and that was really the thrust of the article anyway

So, even if you do see 200TB of disk as "peanuts", then 25TB of disk is a peanut shell fragment. The comparison is still apt because the submission and the press release and articles are talking about 25TB of disk like it's a shitload, and I'm just pointing out that it's not in this environment (particle physics).

Re:I thought

[mindstrm]

They haven't, that's why you build a simulator.. to explore various ideas.

A flight simulator does not perfectly simulate flight, but it does let you see what effect different changes have based on your mathematical models. Same idea here..

Not even enough to hold "Spider-Man 2"

[Apotsy]

According to this [colorfront.com], "Spider-Man 2" employed a 4K digital intermediate, resulting in nearly 40 terabytes of data for just the completed footage (without sound).

25TB ain't enough to even hold a single feature film, let alone the universe.

Re:Dudes...

[Feyr]

have you read neal stephenson's "diamond age"? he has one of those, they do computation by fucking wildly (and i mean that quite literally)

Re:How about giving me an accurate weather report?

[fbform]

We can put together enough hardware to simulate the universe, YET WE ARE UNABLE TO PREDICT THE FREAKING WEATHER.

Not sure if you were trolling, but simulating the universe requires only the equations for gravity and relativity to be simulated (physicists, please correct me if quantum mech is also required). Either way, those are non-chaotic systems. Weather prediction (fluid mechanics) involves solving the Navier-Stokes equations, which is computationally difficult.

You can however make better predictions regarding the climate (the average weather over longer time periods in a particular place). You can say with high certainty that it won't snow in Singapore this winter, but you don't know if it will rain there on Dec 24 at 2 PM. The universe simulation is somewhat like that - simple equations over reasonably large time steps. Weather prediction is not like that - difficult equations over short time steps.

Re:25 TB? That's nothing.

[Pxtl]

No, seriously - all trolling aside, it's a really good paper. I'm a left-wing atheist and I respect it's journalistic integrity. The fact that it has that name was an explicit wish if it's founder, and it really is unrelated to the actual content of the paper.