The difference is, of course, infinitesimal at human speeds. However, when approaching the speed of light, not only does time slow down significantly but objects also become smaller and their mass increases.
Inimlikest mõõdetest lähtudes on see erinevus muidugi kaduvväike, ent kui on tegemist valguse kiirusega, siis lisaks sellele, et aeg märkimisväärselt aeglustub, muutuvad objektid ka väiksemaks ning nende mass kasvab.