[kadoban]

What advances in physics are necessary? I understand it to be an engineering, economics and political question.

[dikei]

Well, if you want to colonized planets in other solar systems, FTL travel or Cryonics technology might be necessary.

[brohee]

People willing to breed and die during the trip would work too. At which point it's a pure engineering challenge, albeit a hard one...

Sending humans to outside the solar system doesn't mean they have to be the same humans that departed.

[hobofromabroad]

But then the question becomes what generation +1 wants?

This is probably going to be nearly as big a problem as the engineering one.