Because of the increase in solar radiation, the surface of the earth will soon be unable to sustain life, and people will need to move to the ground in the future. Therefore, scientists have developed high-tech trains that can shuttle underground efficiently.

Because of the increase in solar radiation, the surface of the earth will soon be unable to sustain life, and people will need to move to the ground in the future. Therefore, scientists have developed high-tech trains that can shuttle underground efficiently.