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# Define time

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Has no one used the definition I have heard alot on this forum before: Time is that which a clock measures. Measures is the key word in that definition.

That is exactly what TAI is. Well, almost. TAI is what a bunch of clocks measure, about 300 or so atomic clocks around the world.

It is the measurement of movement of an object from one point in space to another relative to a constant.

That is not what atomic clocks measure. If it was, there would be a fundamental problem in the definition of a meter. That the speed of light is constant means that it can be used as a basis for defining either time or distance, but not both. The second is defined in terms of the frequency of the electromagnetic radiation that results from a specific transition. The frequency distribution of the radiation that results from this transition has an incredibly high Q (incredibly narrow bell curve). This high Q means that this frequency can be used as to drive a clock with incredibly accuracy.

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Time is more profound than its measurement.

To me time is a phenomenon.

IOW when time flows, something is going on. Simply we don't know what is going on.

Some people believe its the other way round: time emerges because something is going on. Under this point of vue, time is a way to measure change.

Personally I am not satisfied with this explanation because that explains nothing. I prefer to consider time as an unexplained phenomenon.

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If clocks had never been invented, even if no intelligent life had ever evolved, everything in the natural cosmos, on all scales, would still be moving. "It takes time" for that to happen, to move from point A to point B. There is your time; any/all event duration. It's not all about who sees what from where (different frames of reference) with clocks ticking at different rates because of relativity effects. Sure, they speed up or slow down relative to each other, but what is time but the longer or shorter period between 'ticks'... or movement from here to there in a cosmos with or without clocks?

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Time is simple

Let's say we have a particle,

If it's timeless, then it just have a position in space (x,y,z), which is the same at all times

Otherwise, it has a position (x,y,z, t), which means that at time t its position in space is (x,y,z)

You can see from the second line, that particles bound with time, can have two different positions in space at two different times, this show progress

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Time is simple

Let's say we have a particle,

If it's timeless, then it just have a position in space (x,y,z), which is the same at all times

Otherwise, it has a position (x,y,z, t), which means that at time t its position in space is (x,y,z)

You can see from the second line, that particles bound with time, can have two different positions in space at two different times, this show progress

"two different positions in space at two different times" shows motion.

The mystery of time, if "mystery", is that a particle can have the same position in space at 2 different times. Or not?

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Time is simple

Let's say we have a particle,

If it's timeless, then it just have a position in space (x,y,z), which is the same at all times

Otherwise, it has a position (x,y,z, t), which means that at time t its position in space is (x,y,z)

You can see from the second line, that particles bound with time, can have two different positions in space at two different times, this show progress

There are some problems here.

- You used time to define time. This is a huge problem in and of itself.

- You are conflating a process in which time is the independent variable with time. The process is not time.

- This is a very Newtonian view of time. Time is anything but simple in relativity and in quantum mechanics.

"two different positions in space at two different times" shows motion.

Correct. Motion is not time. Motion is a process in which time is the independent variable. Big difference.

The mystery of time, if "mystery", is that a particle can have the same position in space at 2 different times. Or not?

I would say "or not." That a particle can have the same position in space at two different times begs the question, "what is time", and also ignores that what you are talking about is observer dependent.

There are several mysteries of time.

- Why does time have an arrow? This is partially, but not completely, answered by thermodynamics.

- Are there quantum violations of CPT symmetry? There are some signs that time has an arrow even at the quantum level.

- Is time fundamental or is it an emergent property? This is a big open question.

- What exactly is "time"? This is an even bigger open question.

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You're right .. It seems that time is one big question, I've heard many things from media, some:

- "in a timeless reality, where 'beginning' and 'end' are meaningless" --Final Fantasy XIII-2 (Game)

- "Observers, they exist at all times simultaneously" --Fringe (TV Series)

- "What is Eternity ? Define Time." --unknown scientific quote

- "Imagine humans are swimming through the river of time, Imagine there is someone who is watching on the riverside." --unknown

Edited by khaled

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