after listening to audio book of Project Hail Mary and thinking of Relativity.

This is Rocky's problem. So if mass and length increases as velocity increases , and when velocity is very high, at least 50% of the speed of light, then distance to target increases and newtonian physics becomes too inaccurate ti use, so how is velocity measured at all? ( I think )

am now in reading more on relativity 😵‍💫