manaman said:
The more we learn the more it seems traveling the galaxy faster then the speed of light in the style of sci-fi always will be fiction. There may come a day when we make engines that are powerful and efficient enough that we can start sending ships out to distant places, but that day is far in the future, and will only be possible due to time dilation effects. It will still take hundreds of years to travel, but to the occupants it will have only been years.
Our current knowledge says this ^
Even with limitless energy (and it WILL require near limitless energy) we could travel to the galaxy, but coming home would mean that everyone you ever knew or loved would be long dead, perhaps even the human race itself.
Any other theory about instant space travel breaks the other holy grail of science and is thus extremely likely to be impossible. Newtons law of conservation of energy/matter. Or the "no such thing as a free lunch" law as I like to call it.
Think of a technology that somehow allowed us to get around the huge energy requirements of relativistic travel. Use it to raise a mass into high orbit, let it drop, harness the energy of the impact, raise it again, rinse and repeat for free energy. A clear break of the conservation law a thus almost definitely impossible.
Two of Arthur C. Clarke's saying are relevant here.
One as already mentioned,
"Any significantly advanced technology would be indistinguishable from magic"
and the other
"If a scientist tell you something is impossible he is most definitely wrong. If he tells you something is possible he is quite probably right."
You never know, Higgs bosons, Zero Point energy or extra dimensions, you never know. Here's hoping.