How did you find PF?

I was looking for a way to ask questions about physics and cosmology.

I have no academic background in physics, so this is a question born out of curiosity rather than a formal theory. I'm hoping someone with a deeper understanding of relativity and the foundations of physics can help me explore it.

Einstein unified space and time into spacetime. I'm not questioning that framework or suggesting that relativity is wrong. What I'm curious about is something more fundamental: "why time, rather than physical change, as a basic ingredient in our description of the universe?"

My thinking is that, whenever we observe physical reality, we encounter things happening or changing. An atom changes its energy state, a field changes its value, particles interact, stars form and evolve. By change, I don't necessarily mean movement through space, but any physical process that alters the state of a system.

This makes me wonder whether we have the relationship between time and change the right way around conceptually.

We often describe change as something that happens *over time*. But we measure time itself through physical processes: the oscillations of an atomic clock, the rotation of the Earth, or other regular changes. In that sense, our measurements of time depend on change.

So why not consider whether physical change is more fundamental, with time emerging from the relationships between changes and processes?

There is another aspect to this that I find particularly interesting.

Imagine a hypothetical universe in which absolutely nothing changes. No particles interact, no fields vary, no clocks operate, and no physical state differs from one moment to another. Without any reference process or possible measurement, on what physical basis could we say that time was passing? We could mathematically describe time as continuing, but what would distinguish that universe from one in which no time passes at all?

I realise that this question doesn't, by itself, prove that time is emergent or that it can be eliminated from physics. I also understand that relativity describes proper time geometrically and that time plays an essential role in causal relationships and the mathematical structure of spacetime.

I'm simply wondering whether time might be a way of describing relationships between physical processes, rather than something that must exist independently of them.

My questions are:

1. Is this idea already explored in physics, particularly in relational approaches to time or theories in which time emerges from more fundamental relationships?
2. Is there a fundamental reason why physical change cannot serve as the starting point for understanding time, rather than the other way around?
3. If time were not fundamental, could the temporal structure of relativity, including proper time and causality, theoretically emerge from relationships between physical events and changes?

I'd appreciate any explanations, relevant research, or reading recommendations. I'm not proposing a new theory; I'm trying to understand whether this intuition has a meaningful counterpart in existing physics and, if so, what its limitations are.

Thank you, I hope this questions make sense.

Not everything remains relatively synchronous. Like how often it rains doesn't stay in relative synchronicity with the rotation of the Earth. We figure out the ones that are regular and the ones that are variable.

That's where the concept of time comes from. More specifically, that certain things in nature share a relative synchronicity. We use these to define units of time: day, month year. Then we make things like a pendulum or hourglass. Then we use things like a quartz crystal or a cesium atom.

Not everything remains relatively synchronous. Like how often it rains doesn't stay in relative synchronicity with the rotation of the Earth. We figure out the ones that are regular and the ones that are variable.

A philosopher might worry about that, but a physicist is only concerned with the relationship between time and change in physical systems. Which one is more fundamental is not a physics question - it doesn't matter.

Yes, two two are related as you say.

That's philosophy;not physics.

I understand your point, and I agree that physics is concerned with describing the relationship between time and physical change.

However, my question is more about the underlying assumption that time is fundamental and that physical change occurs within it.

We measure time through physical processes, but does that necessarily mean time exists independently of those processes? Or could time emerge from the relationships between physical changes?

I'm not suggesting that this changes the practical mathematics of physics, nor am I questioning the validity of our current theories. I'm trying to understand what justifies treating time as fundamental in the first place, rather than considering the possibility that it emerges from something more basic.

I realise this may ultimately be a philosophical question, but I'm curious whether physics offers any reason to favour one interpretation over the other, or whether both interpretations are equally compatible with our current understanding of the universe.

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I understand your point, and I agree that physics is concerned with describing the relationship between time and physical change.

Bunge M. Physical Time: The Objective and Relational Theory. Philosophy of Science. 1968;35(4):355-388. doi:10.1086/288228

and then go to later references that cite this one.

But we really try to focus on science here rather than philosophy, so we will leave this thread closed. From a scientific perspective there is no experimental or mathematical difference between the two. From a personal perspective I think that it is meaningless to look at ##df/dt## and wonder if ##df## or ##dt## is more fundamental.