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Astrophysicists Build Realistic Virtual Universe
sciencehabit writes "In the most detailed effort yet, astrophysicists and cosmologists have modeled the evolution of the universe right down to the formation of individual galaxies. The results of the mammoth computer simulation neatly match multiple astronomical observations, ranging from the distribution of galaxies in massive galaxy clusters to the amounts of neutral hydrogen gas in galaxies large and small (abstract). The findings once again neatly confirm cosmologists' standard theory of the basic ingredients of the universe and how it evolved—a result that may disappoint researchers hoping for new puzzles to solve."
Who ever thought slashdot would turn into a spam infested sneaky Malware Distributor.
I wanted to get a dollhouse for the kiddies, but a universe is even better.
Where the extra matter went and how the universe expanded faster than the speed of light, temporarily?
Because something tells me TFA is missing that bit or exaggerating in their last line about puzzles.
So, with a few words, the proposed theories, that are covering the existing KNOWN part of the universe, were used to simulate an universe, which resulted in exactly the same universe as expected.....Anyone else seeing what the problem is?
Meanwhile, all you ever needed to do was read Genesis to understand what really happened.
I hope they have a pretty accurate trading model with a good economic base. Need to buy and sell across multiple systems to save up for that bad-ass ship.
If you were me, you'd be good lookin'. - six string samurai
the big question is are entities in the simulation able to detect it is a simulation.
I was always confused by these simulations. Isn't it a tautology that the simulations correctly reproduce the universe we would expect as they were generated from laws derived from observations of this universe? If the results that were reproduced differed then wouldn't the simulation be a poor simulation? It's not like these simulations are a true experiment. Always seemed a bit like CS masturbation to me.
Choosing parameters that best simulate a model does not mean that model is correct.
A whole universe? What assumptions did they make?
42
My ism, it's full of beliefs.
So they know every thing about dark matter now, kudos.
Finally I'll be able to make an apple pie from scratch!
I love the part about "new questions to answer". As if "Where did the super dense mass the universe came from, come from, wouldn't be a good question to answer...
If there are no parameters for a model that allow the model to simulate reality, then the model must be incorrect.
If there are parameters for a model that allow the model to simulate reality, then the model may be correct, but may still be incorrect.
This work moves us from the first state to the second, at least when it comes to simulating rather large scale structure.
Not a sentence!
Here's one for you, and it's open source too: omegaverse.info
You mean my RC plane is not really governed by regression equations? Shit, there goes my Nobel!
Table-ized A.I.
Confirmation bias.
You wish to make an apple pie from scratch..
http://www.youtube.com/watch?v=9ssV79Qi7mM
are a feature of some other species' universe-simulation: high
but not the climate.
"What I’m convinced of is that we don’t understand climate." - Freeman Dyson
So when are they releasing it as a game?
I am anarch of all I survey.
When the parameters match observed conditions it does.
The simulation is uncanny! I noticed that there is only 1 planet with life on it!
Hint to /. editors and submitters: when talking about physics and astronomy papers, it's really helpfu to remember the existence of the arxiv, where the actual professionals go to find the papers.
http://uk.arxiv.org/abs/1405.1418
(Also, hint to commenters on cosmology articles: saying things like "simulations are pointless because they're confirmation bias" and "but they don't understand dark matter LOLOLOLOLOL" just make you look woefully ill-educated in the area, even to the level that a cursory skim of Wikipedia would give.)
This is a valid statement for any theory, not just a theory expressed in a simulation. Just because the theory works for some chosen values, it doesn't mean the theory is correct. Basicly yours is a null-statement, it doesn't yield any relevant information.
Science says you should be able to make predictions, so that the theory is valid. Matching observations in a model based on theories built to explain those same observations is circular reasoning.
This does not mean they are not on the right path, of course.
---- MISSING MISCELLANEOUS DATA SEGMENT --- [sigdash] trolololol
Now all it needs is a white arrow with the label "you are here".
Their parameters aren't simply chosen, though: most of them come from a disparate range of experimental observations, and the remainder are constrained to reasonable values. Getting experiment out with experiment in, particularly when it's a range of different experiment types in each case, is strong evidence that a model is accurate.
"The free parameters of our model are set to physically plausible values and have been adjusted within the allowed range to roughly reproduce the relation between mean stellar mass and halo mass inferred from abundance matching analysis. The resulting parameter settings have been tested on smaller-scale simulations and high-resolution zoom-in simulations of individual Milky Way-like haloes."
No kidding!!! What do you say at this point?
The observations their model makes are different from the observations used to construct the model.
No kidding!!! What do you say at this point?
It includes both normal matter and dark matter using 12 billion 3-D "pixels"
You mean 12billion Voxels.
If they had used an average desktop computer, the calculations would have taken more than 2,000 years to complete.
The problem with Java, right there ^^.
Probably a better one is "Simulation from the Big Bang results in output that looks like our universe at the galactic scale"
To suggest that this equals "Astrophysicists Build Realistic Virtual Universe" more than a touch hyperbolic.
-Styopa
Have they solved the problem with quantum theory and the big bang being mutually exclusive (other than saying the laws of physics changed somehow)? If not, there is still a really big problem to solve.
I think it would be quite fun to make a complete simulation of the events in Genesis. That'll make sure they were true!
Thank you Nat' for this!
Always seemed a bit like CS masturbation to me.
Nice troll, here's your cookie.
Next time you go to the airport think about the following. The skyscrapers you pass, the bridges you cross, the car you ride in, the multi-level car park you park in, the plane you board were all designed with CS masturbation. The fact that over the last 30yrs (about half of my life time) it's become virtually impossible to get finance for any engineering projects without first performing CS masturbation is testament to it's power and utility. Numerical integration is what these simulations are doing, and it's as valid as any other branch of mathematics for exploring the physical world. Simulation is how we find the results of solving the equations that comprise the so called "physical laws". Many (if not most) of the equations in those laws can only be solved through numerical integration since no analytical solution has been found. The laws themselves are just mathematical models that have been tested to a high level of confidence, they are no more or less "real" than the maths inside a well tested computer sim.
As an example there are no known analytical solutions to newtons laws of gravity when applied to a physical system such as the solar system (ie: the n-body problem). Since humans first started shooting rockets into space their trajectories have been planned using n-body simulations, such simulation are very accurate but not perfect, which is why we put small navigation rockets on space probes to correct it's course if it strays too far.
Isn't it a tautology that the simulations correctly reproduce the universe we would expect as they were generated from laws derived from observations of this universe?
No, simulations make predictions by solving the equations (laws) using numerical analysis. If the simulation does not match observations it could be a bug in the sim or a bug in the laws themselves (new knowledge), even better is when a sim predicts phenomena nobody has seen but is confirmed by later observations (new knowledge)
If the results that were reproduced differed then wouldn't the simulation be a poor simulation?
More often than not, yes. Things don't get interesting until the sim turns out to be correct when new observations are performed. For example the much maligned climate sims have discovered dozens of unknown phenomena that were later confirmed by observations. "polar amplification" and "stratospheric cooling" are two well documented examples.
It's not like these simulations are a true experiment.
As in they don't have a "control" and a "subject"? - Of course they don't, where do you get a "control" for a unique system such as the universe, the climate, the biosphere, the flow of molten metal in an engine block casting, a skyscraper that has yet to be built? Most practical problems in both nature and engineering have neither a control subject, or an analytical solution to the mathematical laws that (we think) govern them. In the modern world we attack those problems with a methodology known as systems science, we do that because it's track record says it works.. WP claims the field got started in the 50's but my CS degree covered the subject in depth, as such I think it can be more accurately traced back to the very first computer built during WW2, the first "real world" application of that computer was to run a numerical analysis of artillery fire to create artillery tables for use in the field, prior to this the tables were calculated by hand by thousands of people with adding machines and a note book. I very much doubt the WW2 generals and admirals would have used them if they had not provided a tangible military advantage.
What changed in the 50's was that well funded corporations and academics got to play
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Matching observations in a model based on theories built to explain those same observations is circular reasoning.
Even if this were the case (its not, as it is a different set of observations that give things like the fraction of dark matter), an important step in developing a theory is to check that it actually matches observations you're trying to match. They didn't know a priori the results would work out as they did, as if it could have just been solved analytically they wouldn't be doing more and more detailed numeric solutions. It isn't circular reasoning, it is checking consistency with the possibility that it comes out inconsistent and fails.
But it runs thousands of times faster than ours. Eventually they evolve intellignece, discover our universe, and break into it.
Yep, it took almost a century, several geniuses, the invention of telescopes and calculus, and years of painstaking observations, to refine the heliocentric model to a point where it outperformed the predictions of the ancient geocentric model. Now that we have space craft we can (finally?) determine which model is correct by observing the sun-earth system from an external viewpoint.
By definition there is no point in space outside the Universe, and we still can't even observe our home galaxy from the outside. For at least the last century the field of physics has been based on what Hawking has called model dependent reality.
Regardless of what Hawking thinks, you can always rely on Feynman to nail the root cause of the "problem" in layman's terms.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Observations use regression techniques, physical simulations do not. Two Nobel's in one day, that's gotta hurt!
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Parameters are inputs, physical constants such as the gravitational constant. The model OUTPUTS are what you compare to observations
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Do you just not understand what models are, how the work, and how to validate them? Is that why you just throw out that meaningless sentence?
The Kruger Dunning explains most post on
This does not mean they are not on the right path, of course
Indeed, when talking about the accuracy of any scientific theory (model) it should be noted that imperfect certainly does not imply useless.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
On what color pill they choose.
No, but if you can't find parameters that make a model behave similarly to reality, that's evidence that the model is incorrect. This is science: all we can do is try to find evidence that shows that models are incorrect and try to make new models.
The success of the simulation shows that the theories are consistent and may be complete (in the sense that other theories are not required) to the limits of the simulation, observation, and agreement. This is evidence that the theories aren't incorrect and that additional theories on top are. It's nowhere near conclusive, but it's useful.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes