NASA 的行星防御协调办公室正在努力保护地球免受来自深空中小行星和其他的危险侵害。 访问 http://science.nasa.gov/ 了解更多信息。 NASA 行星防御：http://www.nasa.gov/planetarydefense 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
