[bno1]

It's because distances and time durations contract the faster you travel. The passangers don't experience faster than light speeds, just shorter distances.

This is how the twin paradox gets solved. The twin that leaves earth sees the trip as if it was shorter in both directions, so from their perspective it makes sense that they aged less than the twin that remained on earth.

Also, if you had infinite energy and you could travel at the speed of light you wouldn't feel any movement or time passing during your trip, it would feel like instantly teleporting from one place to another. Photons wouldn't feel their existence if they could. From their perspective they are produced in one place and instantly absorbed in another place.