"Time moves forward; things exist in only one place at a time;"
I am not a physicist, so I'd like to ask one: Does it even make sense for time to 'move'? I don't know, but I imagined time to be some kind of - for us invisible - expansion of space (or... spacetime).
It's more of a philosophy question, or metaphysics, asking where time does objectively exist firstly and secondly, what it is. In physics we define it to be something convenient which works for our models. Within these models time can move forward and backward.
We may not even have a strict definition of time, and have to rely on our intuition. For example there's no way to define what reality is.
My grandpa contends that time is just that which we ascribe to motion in space, and if there were no motion, there would be no time.
That already explains a lot, thank you very much! I've read so many different definitions of time in physics - that was very confusing.
What your grandpa contends is exactly what I thought, too. I love the simplicity of that thought. But after reading about the relativity of time, I noticed that something must be missing. That's why I tried to imagine that space expansion I mentioned. In the end, it doesn't really make sense, but again the simplicity and thus the ease of imagining it is beautiful.
"Time moves forward; things exist in only one place at a time;"
I am not a physicist, so I'd like to ask one: Does it even make sense for time to 'move'? I don't know, but I imagined time to be some kind of - for us invisible - expansion of space (or... spacetime).