Question

      Galaxies(星系) are made up of three main things: stars,clouds of gas and dark matter. Dark matter can not be seen and scientists only know that it

1. (存在) because of the influence its2. (重力) has on matter that can be seen. On earth,3. (physics) use particle acceleratora (粒子力口速器) to find out how different tiny particles are made up of by speeding them up until they 4. c into each other and looking at the pieces after they've broken up. Similarly,by using information from NASA’s Hubble Space Telescope and Chandra X-ray Observatory (线德拉X 射线天文台) ，scientists are looking forward

5. finding out more about what dark matter is by looking at what happens when dark matter bumps into things in groups of galaxies. Each bump,however,takes hundreds of millions of years to take place,so they only have a chance to look at one brief stage in the whole event. However,scientists are extremely hopeful that by watching many of these bumps they can get enough pieces of the 6.(谜) to create a more complete picture of what happens.

Answer 1

1. exists   2. gravity   3. physicists

4. crash   5. to   6. puzzle