单词：
单词： 相关文章
By measuring how fast these stars were moving, he could prove if there really was a black hole at the center of an active galaxy. I picked a galaxy nearby which is called NGC 1068, an active galaxy, w
超大质量黑洞
Gravity 重力 What happens if you drop a book? 如果你丢一本书会发生什么？ Absolutely, it will fall down to the floor. This is called gravity. 很显然，书会掉到地上。这就叫做重力。 Gravity pulls from the center of the Ea
与美国小学生一起学英文第6册
Orbit 轨道 Do you know what an orbit is? 你知道什么是轨道吗？ An orbit is the path of a planet when it moves around the sun. 轨道是行星围绕太阳运动的轨迹。 It is similar to a cycling track. 它类似于自行车赛道。 As
与美国小学生一起学英文第12册
JIUQUAN, Oct. 26 (Xinhua) -- China will launch the spacecraft Shenzhou-8 in early November at the Jiuquan Satellite Launch Center in northwest deseart area. The unmanned spacecraft is expected to perform China's first space docking with Tiangong-1, o
英语新闻
Did you ever dream of digging a hole so deep it came out the other side of the earth? Let's play that game again, using a little physics. First we have to imagine that our tunnel is lined with super-heat-resistant material so we can pass through laye
英语时差8，16
Last time we imagined a tunnel through the center of the earth. If such a thing existed, you could step into one end, fall all the way to the other side, and step out. Gravity would cause you to pick up almost exactly as much speed on the way down as
英语时差8，16