In Animorphs the two species that have achieved faster than light travel both use the same method. They tunnel into some alternate form of our galaxy (not another dimension) called "Zero Space". If you went to the very edges of our universe, you would find blank white space (devoid of matter) that would bend your hand back if you reached into it (according to the Animorph series). This space, Zero Space, allows ships to travel at faster than light speeds, although nothing is said about how this is done. Space ships riding through Zero Space can collide with each other, although they cannot collide with planetary masses or stars, because Zero Space is not a mirror image of our universe -- it is the absence of our universe.

Zero Space is also used as a temporary depository for the mass that is "sucked away" in the process of morphing an animal that is smaller than yourself. It is known that Andalite, and probably Yeerk, ships are able to travel at very close to lightspeed velocity, but this does have the effect of warping their sense of time/space (as explained on the front page for lightspeed travel).