Wormholes are standard fare in contemporary Science Fiction. The movie Stargate and its syndicated television spin-off series Stargate SG-1 were predicated on the idea that an advanced race of humans (the Ancients) were able to build a network of portals each of which was capable of establishing a stable wormhole to any other portal in the galaxy. This capability made it possible for people to travel from one side of the galaxy to the other in just a few seconds. The voyagers of Stargate SG-1 even discovered how to use the portal system to travel between galaxies.
Is time travel really plausible? Any discussion of time travel should begin with the observation that Kurt Gödel found a solution to the equations of Einstein's General Theory of Relativity that permits any observer to travel into either the past or the future. While this confirms that time travel is possible at least in principle, Gödel's solution involves an intrinsic rotation of space itself, and we know from direct observation that our universe has no such thing. Gödel's solution is important and quite interesting, but it doesn't apply to our universe.
The Economics of the Future
In the movie Star Trek: First Contact, Jean-Luc Picard comments to a woman of the 21st century that the economics of the future are very different from those of her own time. She was awed by the size and sophistication of the Enterprise and had asked about its cost. People of the 23rd century, Picard explained, no longer pursue wealth as a way of proving themselves. Instead they strive to improve themselves and all of mankind. The Enterprise was made possible by a completely different set of economic principles.
The Dyson "Sphere"
The great physicist and freethinker Freeman Dyson once proposed (circa 1960) that it would be possible for an advanced civilization to build a collection of independent satellites around a star, each of which would be capable of serving as a solar power generator. Such satellites, he imagined, might be built in a variety of configurations-- some habitable, some not. They could transmit energy to other satellites-- or planets-- via masers, thereby enabling the civilization to draw immense amounts of power from its star.
Captain Kirk of the starship Enterprise is standing on the surface of a planet that is crumbling beneath his very feet. He crash landed in his shuttle, he's bleeding profusely, and the shuttle is nothing more than a useless pile of mangled circuits and duranium alloy. He needs to get off the planet immediately. Fortunately he still has his communicator-- so he calls the Enterprise and asks to be beamed directly to Sick Bay.
Science Fiction vs. Science Fantasy
Science Fiction and Science Fantasy have long cohabited in the marketplace of written ideas, aspirations, hopes, and fears. One could go so far as to say that there is not really a clear distinction between the two-- that rather any story that turns on the possible implications of a scientific development must necessarily appear purely imaginary in some respect. There is perhaps only a matter of degree. Some stories are more concerned with relating the scientific facts, while others are more concerned with characters and their interactions. Every story about the impact of science on our daily lives necessarily requires a bit of both.