Which three people go on a secret expedition to the center of the earth?

Two of the three main characters of Journey to the Center of the Earth have different names, depending on the edition. In the original version there are Professor Otto Lidenbrock, Alex (his nephew), and Hans. In the 1871 English version, the names are changed to Professor Hardwigg and Harry Lawson. Hans is the same in both editions.

Professor Lidenbrock is a middle-aged professor in Hamburg, Germany. He is intelligent, short-tempered, and focused to the point...

Two of the three main characters of Journey to the Center of the Earth have different names, depending on the edition. In the original version there are Professor Otto Lidenbrock, Alex (his nephew), and Hans. In the 1871 English version, the names are changed to Professor Hardwigg and Harry Lawson. Hans is the same in both editions.

Professor Lidenbrock is a middle-aged professor in Hamburg, Germany. He is intelligent, short-tempered, and focused to the point of obsession. He gives little thought to the opinion (or well-being) of others on the expedition to the center of the earth. He refuses to give up.

His nephew, Alex, is a young adult living with his uncle Lidenbrock. He also is a student of geology and functions as his uncle’s assistant. He is more reasonable than his uncle, but he can be seen as cowardly in that he often tries to find a way out of what his uncle wants him to do. He changes partway into the expedition, once he sees that his uncle’s beliefs about the construction of the earth might be valid after all.

Hans is their servant, hired in Iceland. He does not speak German, so he communicates very little, and then only with Professor Lidenbrock. He is calm, strong, and incapable of being sidetracked. He does whatever the Professor asks of him and becomes a valuable member of the team.