Scientists Illuminate the Nature of Dark Matter 揭开暗物质的神秘面纱
听力文稿 ( Transcript )
Morning Edition, More than 20 years ago, scientists discovered that most of the matter in the universe isn't made up of ordinary atoms but rather invisible material dubbed Dark Matter. New observations of nearby galaxies suggest that Dark Matter only comes in enormous clumps of particles that race through space faster than fighter jets.
Astronomers say they have some intriguing new clues about one of the biggest mysteries of the universe. More than 20 years ago, scientists discovered that most of the matter in the universe is not made up of ordinary atoms, it is something invisible called dark matter. New observations of nearby galaxies suggest that Dark Matter only comes in enormous clumps of particles that race through space faster than fighter jets. NPR's Richard Harris has the story.
Richard Harris: Of all the big mysteries in the universe, Dark Matter is surely one of the most alluring. Jerry Gillmore: Oh, well, it's impossible not to be interested in dark matter. Jerry Gillmore is a professor of experimental philosophy at the University of Cambridge. He has been fascinated by dark matter for his entire career. He says our very existence depends on it .
Jerry Gillmore: The Milky Way is full of dark matter, and it is the reason the sun is still in the Milky Way , it's the reason there are stars in the sky. All the stars in our sky would fly off into outer space if the weight of the dark matter wasn't holding them in.
Richard Harris: By its very nature, nobody can see dark matter, but that hasn't stopped scientists from trying to infer what it's made of. At first they thought it was made of ordinary atoms, maybe dead planets or black holes, simply stuff that couldn't been seen, because it's not glowing like stars. That proved not to be the case, Gillmore says, instead, dark matter seems to be made up of some sort of exotic particle.
Jerry Gillmore: The simplest expectation of these dark matter particles was that they were (are) all created in the Big Bang. And then therefore, they've just been expanding and cooling down, and moving slower and slower as universe got bigger and bigger. So the simplest explanation is they are really, look very slow moving, moving at millimeters per second .
Richard Harris: But Gillmore's new measurements suggest that it's not in fact the case. He is part of a team of astronomers that use telescopes around the world to study the motion of stars in nearby galaxies. The long and short of that study is that dark matter particles are moving at the speed of supersonic fighter jets.
Jerry Gillmore: So they are moving about million times faster than expected.
Richard Harris: Now, fast moving partiales can't be packed close together. That is why rapidly moving water molecules make up a diffused gas, steam. Likewise, these superfast partiales can not be jammed into a small space. Gillmore says the smallest possible clump of dark matter seems to be so vast, it would take you a thousand years to cross it traveling at the speed of light.
Jerry Gillmore: You just don't see the stuff compressed up on smaller scales. Now that's, that's still an astronomical number, but it's very very small compared to what it might have been, you know, very very big compared to what most theories had predicted!
Richard Harris: Obviously this clues don't reveal the true nature of dark matter, but they do appear to eliminate some theories and favor other ideas . Gillmore hasn't actually published these results anywhere. So other astronomers can't really evaluate how strong his new evidence is. Astronomer Marrine Atale, at the university of Michigan has been making similar measurements. He says there are so many uncertainties in these kinds of studies. It is hard to be too confident in the results. Even so, he is intrigued.
Marrine Atale: We are all actually starting to say something about the underlying nature of the particles, which I, you know, I find it fascinating when you are not doing it in a lab, here on the earth, you're doing it thousands of light years away.
Richard Harris: It is just possible that more clues about dark matter will eventually come from a lab on earth. Next year a giant particle accelerator in Switzerland is supposed to be up and running . Experiments there could at long last provide some tangible clues about this unearthly material which after all seems to make up 80% of our universe.