As space science develops, man has learned more and more about space. Space is not only amazing but also dangerous. While working in space, spacemen are facing danger as well as success. Scientists have found out that _ to spacemen in space. When spacemen are working in space, they are in danger of radiation from the sun and other stars, which is bad for their health. The damage  done by radiation won't be discovered until their children or even grandchildren are born. Some special medicine may work a little, but no really helpful medicine has been. Space junk is also thought _ It's reported that there are 9,000 man-made things flying in space. About 30% of these are satellites, 10% are spaceships, and the rest are space junk. An explosion  in 1996 made a cloud of 300,000. _ , each at least 4mm in size, and even a small piece of these knocked against a spaceship window and did some damage. Scientists are watching and reporting any possible danger all the time. They are working on helpful ways to do with space junk. Although space is really dangerous, it interests everyone on the earth. In the near future, it may become usual for people to spend a few days in a space hotel. We may even choose to leave the earth and live in space in a few years. So we should care for space and do something to help improve the space environment. Space junk and radiation in space are dangerous to  _   .
spacemen working in space people only on the earth all the people except children the old people on the earth