1 . In a former gold mine a mile underground, inside a titanium tank(钛储罐)filled with a rare liquified gas, scientists have begun the search for what so far has been unfindable: dark matter.
Scientists are trying to understand why the universe is not what it seems. One part of the mystery is dark matter, which has by far most of the mass in the universe. Astronomers know it’s there even though it’s nowhere to be seen, because when they measure the stars and other regular matter in galaxies, they find that there is not nearly enough gravity to hold them together. If nothing else was out there, galaxies would be quickly flying apart.
The race to solve this enormous mystery has brought one team to the depths under Lead, South Dakota.
The idea is that a mile of dirt and rock, a giant tank, a second tank and the purest titanium in the world will block nearly all the cosmic rays and particles (粒子) around us every day. But dark matter particles, scientists think, can avoid all those obstacles. They hope one will fly into the liquid xenon (疝气) in the inner tank and smash into a xenon nucleus (原子核), revealing its existence in a flash of light seen by a device called “the time projection chamber.”
Scientists announced Thursday that the five-year, $60 million search finally got underway two months ago after a delay caused by the pandemic. So far the device has found...nothing. At least no dark matter.
And if all their calculations and theories are right, they figure they’ll see only a couple signs of dark matter a year. By the time the experiment finishes, the chance of finding dark matter with this device is probably less than 50% but more than 10%.
While that’s far from a sure thing, “you need a little enthusiasm,” said Kevin Lesko, a physicist at Lawrence Berkeley Naonal Laboratory. “You don’t go into rare search physics without some hope of finding something.”
These scientists tried to a similar, smaller experiment here years ago. After coming up empty, they figured they had to go much bigger. Another large-scale experiment is underway in Italy run by a rival team, but no results have been announced so far.
1. What do we know about dark matter?| A．It is a rare liquified gas. |
| B．It is invisible and hard to find. |
| C．It is unknown to scientists. |
| D．It is a form of gravity in the galaxies. |
| A．The result of the experiment. |
| B．The design of the experiment. |
| C．The reason for conducting the experiment. |
| D．The importance of the experiment. |
| A．Its success is guaranteed. |
| B．It is almost finished. |
| C．It has been fruitless so far. |
| D．It is the first attempt in the field. |
| A．Don’t count your chickens. |
| B．Two heads are better than one. |
| C．Strike while the iron is hot. |
| D．Every cloud has a silver lining. |
