IF they could go AT the speed of light, which they can’t, the trip there would be instantaneous for them. But, you could get arbitrarily close to the speed of light in principle; i.e., you could make the trip in 1/100th of a second if you were impatient.
(No one in his right mind would want to do this, because there are all kinds of problems he’d encounter. But in principle, it could be done.)
Called Lorenz Contraction, another one of Einstein’s discoveries.
Um...”discoveries??? I think they are called theories, which tend to hold, until a better one comes along.