The concept of "hyperspace" is often used in science fiction to describe a hypothetical higher-dimensional space or an alternate dimension through which faster-than-light travel might be possible. However, according to our current understanding of physics, there is no evidence to support the existence of hyperspace or the ability to achieve faster-than-light travel.
If we consider a hypothetical scenario where we could somehow travel at speeds near the speed of light and then return to normal spacetime, several effects predicted by Einstein's theory of relativity would come into play. These effects include time dilation and length contraction.
Time dilation means that time appears to pass more slowly for objects moving relative to an observer at rest. As an object approaches the speed of light, time dilation becomes increasingly significant. If someone were to travel at near-light speeds and then return to normal spacetime, they would experience time passing slower than for someone who remained in normal spacetime. This means that, from their perspective, less time would have elapsed compared to the people they left behind. This effect is known as time dilation.
Length contraction, on the other hand, predicts that objects in motion appear to be shorter in the direction of their motion as observed by a stationary observer. So, if someone were traveling at near-light speeds and returned to normal spacetime, they might perceive objects in normal spacetime as contracted or compressed in the direction of their travel.
It's important to note that traveling at speeds approaching the speed of light would require an enormous amount of energy and would involve overcoming many technological challenges that are currently beyond our capabilities. Additionally, our current understanding of physics does not provide a clear framework for how one could transition between hyperspace and normal spacetime or achieve faster-than-light travel.