[nyrath]

Originally Posted by Steven Lyle Jordan

Sci-fi-acceptable technology that, in all honesty, we will probably never crack:

FTL drives

Anti-gravity

Immortality

Universal Translators

Hard science SF stories generally do not have any of those EXCEPT for FTL drives. The author thinks "You want it, they want it, everybody is doing it..."

So even though it is probably forbidden by the laws of physics, a hard science author will use it, or be faced with the grim prospect of setting their story in the limited confines of the solar system.