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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."
"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.
That this whole universe as we see it is not an experiment in somebody's supercomputer?
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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...
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"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.
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.
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.
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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.
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.
Don't Bogart the fish sticks
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.
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