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Most Detailed View of Dark Matter Mapped By Hubble
astroengine writes "Building on previous studies by the Hubble Space Telescope, new analysis of gravitational lensing data has revealed the most detailed map of the distribution of dark matter yet. The distribution appears as a beautiful ghost-like or ethereal haze and could have serious ramifications on our understanding as to how galaxy clusters form and evolve."
Dynamical studies of our own galaxy show there's a lot of invisible matter in it. This means that something has to happen with gravitational theory within a region much smaller than the observable universe, at speeds of only a few hundred kilometers per hour. The modified theory also has to conform to the known motions of solar system objects, which are known to extremely high accuracy. These conditions are very hard to meet.
TFA is firewalled off, but I found a better FA -- straight from NASA's JPL. here is a hi-res photo of the "dark matter" lensing.
Free Martian Whores!
I just learned that Allan Sandage died this weekend. He was a giant among astronomers and did a lot of work with the Hubble. Take some time and learn about him if you care about astronomy http://en.wikipedia.org/wiki/Allan_Sandage
I'm just asking the question, because I don't have a great deal of knowledge about this, but could an alternative explanation be that our theory of gravity is wrong?
Yeah, that or a lot of other things. There was a popular explanation called MOND - Modification of Newtonian Dynamics - but AIUI the evidence shot it down. However, I think there's some MOND variants still out there. But most cosmologists apparently lean toward DM as the best explanation for the available observations.
Sheesh, evil *and* a jerk. -- Jade
but could an alternative explanation be that our theory of gravity is wrong?
Yea. The discovery is that, IF our theory of gravity is correct, this is more evidence for the existence of dark matter.
It is something more along the lines of this:
We have a good number of formulas and calculations that work properly with the things we can measure - planets, the sun, cars, planes, kitchen scales.
One of these might be:
y + 3 = 5
Nice and simple for this example. Lets say that the "y" here represents gravity and the formula has been proven in every experiment we have done.
We therefore assume that this calculation is correct and true. BUT when we try to use this calculation when looking at things like galaxies, we seem to find the wrong answer:
y + 3 = 7.2
This is clearly not correct, but as we don't want to throw out all the formulas and understanding we have about how things work, we add another variable to the formula like so:
y + 3 + x = 5
The "y" still represents gravity, but now we add the "x" which represents something we don't understand and we don't know where it came from. We call it Dark Matter because we can't see it, don't seem to be able to interact with it and have no real idea of what it is - but with this new addition to the formula, the answer once again comes out at what we know (think) to be true. We just now need to find what this x variable is.
THAT is why finding/understanding Dark Matter (and on that note, Dark Energy) is so important. We know (think we know) the right answers, but our formulas just don't seem to fit so well when applied to certain really, really, really big things (like clusters, superclusters etc). When we find this "x" in the formula, it will once again work perfectly for all our calculations.
Moved to http://soylentnews.org/. You are invited to join us too!
Long answer: Dark matter wasn't invented just because someone saw some anomalous behavior that didn't agree with theory, and said to themselves: "Oh, there has to be something mysterious at work here, we'll call it dark matter.". There are several reasons for believing in dark matter, for example that when measuring gravity we notice gravity coming from directions where we can't see any matter. However, the source of this gravity behaves a lot like matter would. For example we can observe these "invisible gravity sources" being thrown around when two galaxies collide. Because these "invisible gravity sources" acts a lot like matter, except for the fact that we can't see it, it's called dark matter.
If you're not yet convinced, take a look at this recent blogpost by a professional astrophysicist: http://scienceblogs.com/startswithabang/2010/11/the_simplest_argument_for_dark.php In this post, he basically explains how we can derive the existence of dark matter from: A) Assuming that the theory of general relativity is valid, B) assuming that the big bang theory is valid, and C) our observations of the cosmic microwave background.
With regards to your sig, it's not Apple you should thank, but the fine folks at KDE.org which did all the heavy lifting. Webkit is a modified version of khtml.
Just sayin'
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BMO