I think you won't gain anything from conflating "detectable change" and "awareness". We kind of already had this discussion in Quantum mechanics with "observations" and the "consciousness" of an observer. Nowadays the information theoretic point of view is prevalent among physicists and an observation is often seen as just a correlation between the observer system and the measured quantum system. No consciousness needed.

Nevertheless I agree, that it is interesting to think about time as an series of changes or events instead of just as a dimension of 4D spacetime. I didn't watch the video yet (I prefer text), though, so I refrain from bothering you with may opinion on this topic.

Right, we could instead say “sensation” as in “sensor.”

Nevertheless, I like that “time” and “experience” are often synonymous—eg, “I had a good time.”

You would need memory as well. Without memory you wouldn't be able to detect change over time, and hence not the existence of time. And without that you can't have awareness (as I understand the word).

The past light cone of an object constrains what past events can affect an object regardless of whether the object has awareness of not. So you don’t need memory to experience time, even if you need memory to understand it.

That's a very interesting point. I had never considered it. I have always conflated the perception of change with change itself.

What you wrote was quite profound to me! Thanks.

Indeed. And the direction of memory is one of the things that determines the arrow of time, perhaps the most important one.

If I remembered tomorrow yesterday, then today exists to make it true.

Measurement, awareness, and memory, are not required for time to exist. These are all things that make observation possible, but time could still exist even if the universe were just a fog of loose atoms bouncing around with no self awareness.

Of course. I was just trying to point out time is a necessary but not sufficient condition for awareness.

If you're on a space ship travelling at 0.86c, your Lorentz factor is 2, and so time is moving half as fast for you. Yet if you measure the speed of light it will be the same. Then if you look out the window you will see the universe is 1/2 the size it used to be in the direction you are travelling.

I don’t see why space should be required for a change to occur. Now, particle spin may be associated with a physical direction, but I don’t see why it needs to be. Why not say “we have a unit vector in C^n evolving unitarily” (Where C^n is n-tuples of complex number) ?

In my philosophy, times would merely be various signal clocks. Time in this sense, then, will be the instantenous unit that relates one's environment-embedded consciousness' clockrate to the clockrate of the clock. Consequently, one can have at every moment multiple, changing times. One builds foundations of embedded agency partly on this, signal theoretic, interpretation—without confusing it with the physics notation which has uses elsewhere.

If you take the quantum field of view.. its the start of interaction between two particle-permutations forcing a breakdown into a observable and measurable interaction?

Time is the expansion of the involved while simultaneously collapsing complexity permanently.

If the universe has only a single particle, is time even possible?

I think a universe with one particle is the same as one with none. As soon as you have two particles they can move toward each other, and spin can be observed.

I think that's gonna depend heavily on your definition of particle.

It seems most likely that our current universe is a singularity, a single point that contains the entirety of space and time, such as they are. Viewed through a certain lens this could be considered a particle, but I'm not sure that it checks all the boxes for properties you associate with one.

I'd say yes to time with one particle, as its position within the universe, or the universe's size in relation to the particle, can change.

If a universe only contains a single particle, then there can be no "position" within the universe as how could you possibly measure it? Similarly, how would you be able to determine if it was static or moving without comparing it to something else?

Wouldn't a single particle still change, move, experience time? There is just no way to measure time.

There is no way to tell if it is moving.

Yes, but that is irrelevant. Change happens, even if you can't recognize it. Recognizing change is a shortterm-problem. But longterm it can be relevant, if the particle some day will break down, disappear, burn out, or whatever happens to them.

> If the universe has only a single particle, is time even possible?

space is constantly expanding. particles have energy. energy decays. eventually into photos. colors shift red due to increasing wavelength and decreasing energy.

We don't know if space is expanding. The models and observations appear to support expansion.

This was just a thought experiment with a theoretical single partical in a universe of unknown size to demonstrate that the universe changes in non-obvious ways as you add energy/matter.