How is this done in practice? I know that in GR the gravity is believed to curve not only space, but also time, and this prediction has been confirmed somehow in practice. How can we measure that? Because as far as i know, there is no device that actually measures time, but instead measures a mechanically created intervals (such as a pocket watch ticking) that we humans then use to measure the time we experience. Also what sounds very strange to my ear is, that if the time experienced by one object could differ from another object, then how would they still exist in same present moment? Shouldn't the slower running clock just dissappear from my present moment if it actually would be living in in slower running time for even a short period of time?