The lecture purposed that the three advantages of colonizing asteroids are over-glorified, on the contrary, there are lots of downsides and challenges.

Firstly, the low gravity allows spacecraft to land and take off easier, and requires lower energy to operate the spacecraft as well. But the low gravity impact people’s body rapidly, even though astronauts just stay in the spacecraft which is landing on the surface of asteroids, their muscle and bone density will permanently be decreased within minutes. It’s really risky for astronauts' health.

Secondly, moving rare minerals from asteroids to Earth, then selling them out at a high price seems a perfect strategy. But it’s necessary to consider the cost of transportation and exploration, maybe there is not a big profit after we count all the things in. Furthermore, no one can guarantee that after carrying these minerals back to Earth, the price will still remain high. With more and more minerals being transported to Earth, they will not be rare anymore, and the price will drop.

Thirdly, in the reading part, it says that the short distance makes colonization easier to achieve. However, we all know that asteroids are moving around all the time, and it is hard to predict where they will be after a while. So it might be cheap and easy to reach the asteroids at the beginning. But when it comes to returning to Earth, we don’t know how far we could be from the destination. The unpredictable movement of asteroids disillusions the asteroid colonization again.

These three reasons above indicate why the colonization of asteroids is unrealistic.