河北省定州中学2017届高三下学期周练（1）英语试题

河北定州中学2016-2017学年第二学期高三英语周练试题(1) 一、阅读理解 If you look at the night sky, you’ll often see stars moving very quickly. In fact, they move much more quickly than they should according to their size and the laws of physics. Scientists do not completely understand why the speed of these stars is so high. But many believe the reason is that much of the universe is made of something called “dark matter”. Groups of stars called galaxies, such as the Milky Way, might even be made up of 90 percent dark matter. How much something weighs depends on where it is. The same object weighs only half as much on Mars as it does on Earth and almost three times as much on Jupiter. So scientists prefer to talk about the mass (质量) of something rather than how much it weighs, because mass does not change. They can work out the mass of galaxies by measuring the distance between them and the speed they move at. Recently, Jorge Peñarrubia, a senior academic at Edinburgh University, UK, and his team discovered someth