I really don't see how anybody can say anything is impossible. 100 years ago the idea of humans flying was thought to be impossible, now we have an orbiting space station, and robot rovers on Mars, and where's the first Explorer now...way out past Pluto right?
The speed of sound was thought to be a "wall" that would destroy you when you hit it...now we have land vehicles that have pushed through the "wall".
If we did not have the fossils, and bones to prove it, would you have ever believed that a few hundred-thousand years ago the Earth was ruled by dinasaurs?
Light is the limit of what we can understand now. That does not mean that there is not another realm of understanding just waiting to be discovered.
I say it's possible. Whether or not we'll see it in our lifetime is another story. Maybe it's technology brought to us by other means.....