B Why do we Experience a 'Flow' of Time?

[Sorcerer]

I don't really see the relevance of that. In fact, information technology in general is a human endeavour which has a time parameter, but no recognisable map to spacetime.

For example, a computer program, is not a physical object, has no spacetime coordinates - the physical location of the program is largely irrelevant - but it does have a history. Both as a logical object, it has a version history, and as a run time object it has a usage history, say.

Time, but not space, is very much a factor in IT systems. Especially in any sort of logical rather than physical view of a system.

Yeah but computers only work because electric signals move around inside them, right?

 

[Arman777]

As in post #97, you could, theoretically, use spin precession of an electron in a uniform magnetic field to measure time.

In general, the state of a quantum system changes with time.

Okay then can you show mathematically for us how you do that ? Build a clock for us.

 

[Arman777]

therefore can be used to justify your (now meaningless) claim.

I don't see how can you do that ?

None of that is motion. After the decay then the decay products move, but the decay itself is not motion.

The usual hyperfine transition used in standard atomic clocks is not motion, and in fact must be corrected for any motion that does occur.

If, after decay particles don't move, then how can you possibly understand that decay "happened". I am really curious about that.

I am not sure you guys understand me. Motion happens at any level in the universe. Theres has to be change in the system so we can understand the change but the change happens also in the space. Becasue that's where we live in and it can be count as motion.

The usual hyperfine transition used in standard atomic clocks is not motion, and in fact must be corrected for any motion that does occur.

So the atoms in the clock don't move at all (also the electrons) and we can perfectly know their position and nothing happens to them or etc right ? They are not excited or we don't measure things. Well Of course not there's no such thing as not moving particle. Your definiton doesn't make sense at all actually.

Motion is everywhere. Everything is in motion respect to something at any level. And to measure the time you need motion.

 

[PeterDonis]

as soon as you start to do physics it's the time derivatives (of spatial coordinates among other things) that appear

Careful. We're in the relativity forum here, where there is no such thing as a "time derivative" in any coordinate-independent sense. There are only "spacetime derivatives". This is a "B" level thread so it's hard to get too technical about this, but I don't think it's useful to focus on just time coordinate derivatives in a relativistic context.

 

[PeterDonis]

What I was trying to say was along the lines that change, as in the evolution of the system is absolute. Something either changes or it doesn’t. So in that sense evolution is one directional.

Sorry, you're contradicting yourself again. If you had left out the last sentence I would probably have let it pass; but if you insist on using the word "directional" you can't get away from the fact that there are two "time" directions, past and future. More generally, any time you have an ordered set--and the proper times along any worldline are an ordered set--there are always two "directions" to the ordering.

As it’s impossible for a system not to change

This is wrong. A system in an energy eigenstate does not change. The fact that it does not have a definite value for all observables does not make that false. If you measure an observable of the system that does not commute with energy, then you change the state of the system so it's no longer in an energy eigenstate; yes, at that point you can say the system will "change", but that's because you changed the state when you measured it, not because it was changing before you measured it.

all systems are constantly evolving forward. Which is how I understood that the flow of time was always forward.

"Forward" is not an inherent property of time, it's a choice we make; we label one of the two directions of time the "forward" direction because that's the direction we can only predict, not remember. Ultimately this is because of the second law of thermodynamics and the fact that our universe started out in a very low entropy state. The underlying laws of physics are time symmetric; they don't pick out either direction of time as "forward"--both directions are the same as far as the underlying laws are concerned. The fact that our universe started out in a very low entropy state is a contingent fact about the particular solution of the laws that we live in, not about the laws themselves.

 

[PeterDonis]

Thread closed for moderation.

 

[PeterDonis]

This thread has run its course and will remain closed.