Ralph: Oh, Ralph, I heard it is very dangerous traveling in space. Disasters have happened before. If the spaceship were out of order. . .
Joanna: You should be optimistic about this. Things have taken a good turn. You should remember that less than two centuries ago the dangers of train travel seemed similarly terrible.
Ralph: But is it possible that travelers could be hit by meteors?
Joanna: It's once in blue moon.
Ralph: What do you think is the real danger man faced in space?
Joanna: The main one is radiation. There are two sorts of radiation man must fear in space. The first is radiation from the sun, and this is particularly dangerous when the sun is very active and explosions are occurring on its surface. The second, less harmful, comes from the so-called Van Allen Belts.
Ralph is more optimistic than Ralph about traveling in space. Ralph thinks the real danger is radiation and Van Allen Belts.