Ned Potter is the science correspondent for ABC's "World News with Charles Gibson." He has reported on such topics as space exploration, the human genome and climate change.
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A Dark, Dark Matter
May 15, 2007 5:57 PM
Take a look at the picture to the left of a galactic cluster called CL0024+17, and click on it to enlarge. (There's a high-resolution version HERE.) See the dark ring around the center? Astronomers say that's the best proof they've ever had of dark matter, the stuff they believe makes up 85 percent of the universe, even though it's invisible to us.
CL0024+17 is about 2.6 million light-years across, and 5 billion light-years from Earth. Conveniently for scientists, it was the site of a massive collision more than a billion years ago, which means there's stuff flying in all sorts of different directions.
But dark matter? Astronomers are pretty sure it exists, and they believe it exerts gravity on other things, such as the conventional matter of which we're made. But that's really the only sign they can see of it; they infer it exists mostly because various star formations would fly apart if there weren't something unseen pulling in on them.
In this case, they say the gravity is strong enough to bend light, much as Einstein, in his work on general relativity, predicted. The dark ring in this Hubble Telescope image is not dark matter--the stuff's invisible, not dark--it's a gap created by the dark matter bending the light from the galactic cluster.
Some helpful background can be found HERE and HERE.
M. James Jee is a member of the team at Johns Hopkins that found the ring, and NASA quotes him: "It took more than a year to convince myself that the ring was real. I have looked at a number of clusters, and I haven't seen anything like this."
His colleague, Holland Ford: "By studying this collision, we are seeing how dark matter responds to gravity. Nature is doing an experiment for us that we can't do in a lab, and it agrees with our theoretical models."
So what's dark matter made of? The best thinking at the moment, at least from the light-matter beings you find on our planet, is that dark matter is made of some sort of still-undefined elementary particles--the kinds of infinitesimal objects smaller than atoms.
If you figure them out, please send your name quickly to the committee that awards the Nobel Prize in Physics at the following address....
May 15, 2007 | Permalink | Share | User Comments (3)
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One still has to ask, "What are those particles made of?" I hope you all realize that all this is purely academic. The Mayan calendar, which science says is incredibly accurate, ends on December 21, 2012. I sure hope I'm alive to witness the Main Event, you know, when Nothing happens.
Posted by: Andy | May 15, 2007 9:38:40 PM
Very intriguing, but I don't think I'll be sending my name and address to the Nobel committee anytime soon. The detection and analysis of dark matter is clearly one of those instances of (ahem!) mind over matter.
Posted by: chuck | May 16, 2007 8:16:38 AM
I think the dark ring proves that the universe is shaped like a bathtub. :-))
Posted by: Andy | May 22, 2007 3:31:40 PM
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