Scientists hunting an invisible form of matter that pervades the universe and holds galaxies together claim to have found it underneath a mountain in Italy.
--The Guardian (U.K.) (April 24, 2008) (opening paragraph)
Wouldn't you know it? Not only have those Eye-talians got the Pope, the Colosseum, Florence, lasagna, Chianti, the Mafia, half the world's cool operas, and Neapolitan ice cream -- we now learn that they've been hiding the Universe's "dark matter" under one of their mountains.
Dark matter is one of those hypothetical constructs that physicists like to imagine exist, because otherwise their calculations don't work out. Something's keeping the universe from expanding as fast as they think it should be. If it's gravity that's slowing the expansion, as seems likely, all the mass of the universe would have to weigh ten times as much to be holding back the expansion as much as it does . Therefore -- there must be something invisible that makes up 90 percent of the universe by weight. Something that doesn't give off light. Something that doesn't even reflect light. Dark matter.
A century ago, everyone "knew" that the entire universe was filled with a material called "ether" that couldn't be seen or felt. That's what science books said. It had to be there, because light was a wave, and you can't have a wave without something for the wave to move through. Ether. That theory quietly died with Einstein's special relativity theory, and the development of the idea that light (and everything else) had a dual wave-particle nature.
But who knows? Maybe dark matter really has been discovered deep in the Italian mountains. (The article did eventually clarify that scientists believe they've detected dark matter passing through the earth (like neutrinos), by use of underground detectors in Italy -- not that they've run across a large subterranean Italian lake of the stuff.) But maybe dark matter, like ether, is just another misguided solution to a problem that doesn't really exist.
Oh well. The Italians would still have the Vatican.
Saturday, April 26, 2008
Materia scura italiana
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2 comments:
If dark matter does exist, it will be an incredibly significant discovery. Most times something is discovered, it leads to a slight modification of the theories and models that make up the overall scientific explanation of everything. But this would be fundamentally in opposition to a lot of theories, and would throw everything off for a couple decades as scientists figure it all out.
Zachary, you may be interested in Wikipedia's article on the subject, if you haven't seen it already. I hadn't read the article before I posted this item. (My post was intended to be pretty light-hearted -- not heavy science, obviously!)
Wikipedia gives a pretty good summary of the kinds of particles that may make up dark matter, and mentions some other theories that don't involve dark matter -- relativistic effects on gravitation, quantum mechanical effects -- that might also explain the observed rate of expansion.
According to the article, the most likely candidates as constituents of dark matter are elementary particles in the same class as electrons, protons, neutrons, and neutrinos, but ones that have so far only been hypothesized (axions, sterile neutrinos, and "weakly interacting massive particles (WIMPS)), not yet detected. The article says that these light-weight particles are not part of the "standard model" of particle physics, but would be an extension of that model. In other words, dark matter would not be some bizarre unknown substance, like ether would have been, but something more or less understandable in terms of existing theory.
The Guardian article about the Italian discovery mentioned that the scientists were looking for axions.
This may all be stuff you've already read about, but I thought it was interesting. I guess "time will tell," as is usually the case!
Since you'll be jumping into science classes next year, you might want to take a look at the article.
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