Once I said "there is no such thing as time" in my high school physics class and got laughed at. I still don't understand how time can be anything "natural" though and I was wondering if someone could help me understand it. I get the concept of an arrow of time, and how our minds organise the sequence and structure of events and I get how it is asymmetrical. But I don't understand how time can be anything BUT a measurement of a change in entropy or sequence of events. When physicists talk about things like "spacetime" they talk about time as a dimension, in which events occur in a sequence. So, suddenly the time measuring the steps between events is part of space itself. When physicists talk about black holes, they say time "Freezes" once something crosses the event horizon. How can time freeze from one or any reference frame? And on that note how can it change at all? I get that there are schools of thought about what time is, but as a naive hobbyist it seems that time can be thrown into any old model, formula or theory and be bent to make it work. But to me I still don't see the effect of time being anything except something that we (as humans) need to have to understand things. So I guess the point I am getting at is that the definition of time seems to be retrofitted into different models and that the definition of time changes depending on the line of thinking it serves. My thought was, what if time is a concept invented by us/maths to help us understand things? In newtonian physics we have v = d/t - which is used just about everywhere. Can we define velocity without time? If we can't then that means things need time in order to move according to our models? Sorry for the long post, and I will sum it up in a tl;dr; question "Is there such thing as time, or is it just an invention of man?" Sorry if this is the wrong place to post this sort of thing.