请访问http://science.nasa.gov/ 。 大约四分之三宇航员因太空旅行而导致眼睛结构和功能發了变化。一项名为" 流体变化研究" 的实验正在调查这些问题。 http://www.nasa.gov/station 点击这里查看更多视频：https://alugha.com/NASA
Visit http://science.nasa.gov/ for more. Earth is surrounded by electrons that can be disruptive to our technology. NASA is using high-altitude balloons and spacecraft to monitor and understand these particles in the radiation belts surrounding our planet. Click here to see more videos: https://al
Explore how astronomers and scientists use astronomical units to measure distances in the solar system in this video adapted from NASA. The astronomical unit (au) -- equal to the average distance from Earth to the Sun -- is a convenient unit of measure when talking about distances in the solar syste
