What is the simplest definition of time?

[Mystery111]

I'll get back to this. Defining time is hard, many different cases to consider than I have free at the moment.

 

Right now I have enough time... lol... mind the pun.

 

Let's start with Relativity. I've already spoken about timelessness arising as the time problem of uniting General Relativity with quantum mechanics in another thread, so time might not even exsit according to this theory.

 

Special relativity is a little more mundane; this theory allows clocks to be moving in a flat spacetime.

 

Essentially relativistic theories treat time as a ''dimension'' of space. Time actually has two very loose meanings in this context. One is a true real time description Real Time (or also known as imaginary space) or it can be called Real Space (which is imaginary time). Describing your universe or system in either context can be rewarding in physics when viewing the physical world. For instance timelike and spacelike movements are pivotal to understanding how a Bradyon and a Luxon and a Tachyon are all defined as speeds. Bradyons (''brady'' root word meaning slow, also known as tardyons) are spacelike whereas a tachyon (''tachy'' from the root word ''fast'' as in tachycardia) is timelike in nature (though not all tachyons require to be timelike according to some work).

 

Time in quantum mechanics has many descriptions, some of which are outdated. Newtonian physicists and a few quantum thinkers today still believe that time has a flow. This has been demonstrated in quantum mechanics to be false, there does not seem to be an arrow of time nor does there seem to be a flow associated to events. Instead time in quantum mechanics is more like a set of starts and stops. Tiny momentary fleeting flashing of physical existence which is not tied to any fundamental flow. Time is non-linear, and has a geometry. Time is not an arrow directly drawn from any center in space either because space does not contain your normal definition of ''up'', ''down'' ''left or right''. Nor did the big bang happen in one place alone, in fact big bang happened in all places at once.

 

So if you are looking for a nice, clean definition of time that is simple, you would certainly be leaving out a lot of details which may provide a clearer definition. A nice easy one would be ''Time is an instantaneous moment or short duration of an instantaneous moment.''

 

That would be the definition from physics. From Relativity, time may have two descriptions, actually one is a non-description:

 

1) Time does not exist

 

2) Time is a measurement of moving clocks

 

Of course, Relativity may permit a third

 

3) Time is an instrinsic degree of freedom

 

Where here ''degree of freedom'' is by definition a dimension.

Edited October 26, 2011 by Mystery111

[Appolinaria]

isn't it guaranteed that as time elapses, objects in space get further from each other?

 

shouldn't distance be incorporated in the definition of time somehow

[Mystery111]

Some might come to think this. I've often seen definitions where ''time is equated to the ability to change'', and ''time is a measurement of a change of space.''

 

I suppose you could. I probably wouldn't though, I don't like the idea of equating time to the ability to change because of the quantum mechanics principle of veiwing time as short beginnings and stops. Motion requires a linear notion of time when you measure events next to each other like that. But motion in General Relativity arises as a symmetry of the equations, so perhaps it can be faulty veiwing it directly like this if not careful.

Edited October 26, 2011 by Mystery111

[mooeypoo]

The person asking this question wanted the simplest definition of time, not the most clear in the eyes of a child.

I agree, I gave the child example as a bit of an extreme to make my point.

 

Still, a definition (even the 'simplest' one) should at least make it clear what the word it explains is. I don't dispute that making definitions is hard, i'm just saying I don't think "A to B" is sufficient.

 

Even your example:

If they wanted the simplest definition of the word "naked mole rat" I would give them;

 

"A warm-blooded vertebrate animal of a class" aka mammal

Is not quite sufficient. Like you admit yourself, that would define a mammal, not a "naked mole rat".

 

rather than "A rodent (Rattus and other genera, family Muridae) that resembles a large mouse" aka rat.

But that seems a better definition for the requested word, and it's not that complicated. We could make compromises on definitions, but I think that there's a point where the definition loses its purpose.

 

So seeing that this question was posted in the Physics section, I defined time according to the realm of physics, leaving no room for any controversial definitions, and concluded that A to B would seem an accurate, simple way of defining time.

I see your point, but I disagree. "A to B" is meaningless -- it requires you to explain what you mean, and therefore cannot be used as a definition.

 

I agree that the current definition of time is probably not sufficient, I'm just saying that if we go too simplistic, we lose clarity, and physics is also supposed to give some sort of clarity.

 

~mooey

[michel123456]

Too many definitions of time are circular. Not good.

"A to B" is a bit sybillic, but not so bad.

"To B" or not "to B", that's the question.

 

Sorry I couldn't resist.

[md65536]

The person asking this question wanted the simplest definition of time, not the most clear in the eyes of a child.

 

If they wanted the simplest definition of the word "naked mole rat" I would give them;

 

"A warm-blooded vertebrate animal of a class" aka mammal

Making something more defined or definite means to specify it more precisely, but you're doing the opposite and specifying it more generally.

I think you're literally undefining "naked mole rat" here, and undefining time with "A to B" (both by removing the meaning of time, and by not being specific about what A and B are).

 

 

Meanwhile a definition like "time is what clocks measure" specifies it precisely, but doesn't say much about its meaning, which is essentially what the thread is seeking.

That said, "simplest" and "most precise" might be mutually exclusive, in which case the simplest definition would only have to be precise enough to still be considered a definition at all.

[Appolinaria]

Making something more defined or definite means to specify it more precisely, but you're doing the opposite and specifying it more generally.

I think you're literally undefining "naked mole rat" here, and undefining time with "A to B" (both by removing the meaning of time, and by not being specific about what A and B are).

 

 

Meanwhile a definition like "time is what clocks measure" specifies it precisely, but doesn't say much about its meaning, which is essentially what the thread is seeking.

That said, "simplest" and "most precise" might be mutually exclusive, in which case the simplest definition would only have to be precise enough to still be considered a definition at all.

 

ok i see what youre saying in the first paragraph.

 

 

but what is the meaning of time im eluding, then? i thought it was a measurement or change... there is nothing specific about that.

[md65536]

but what is the meaning of time im eluding, then? i thought it was a measurement or change... there is nothing specific about that.

The answer to that is the answer to the thread and I don't think anyone knows.

 

"Time is (a measurement of) change" is also insufficient, because things can change slowly or quickly (the same amount of change can correspond to different amounts of time), and also it can't be "Time is (a measurement of) rate of change" because the same rate of change can be maintained over different amounts of time.

 

I don't think "change" is the essence of time. Entropy might be. The constancy of the speed of light certainly is related (but if time is defined based on light, it might be cyclical because distance is already defined based on time). If change is expressed in terms of the passing of information across distances, then a definition of time based on change might work.

 

Personally, I think (so please disregard this as anything more than just an idea) that "time is distance" is true, but as I mentioned distance is based on time. Also, the assumption of isotropic propagation of light makes it false. But if light was anisotropic and time and distance were equivalent, then a non-cyclical definition of time would be defined using something other than distance. My guess would be: Time and distance are emergent measurements of causality's consistency. Or instead of that, maybe something that even makes sense.

Edited October 27, 2011 by md65536

[Mystery111]

The answer to that is the answer to the thread and I don't think anyone knows.

 

"Time is (a measurement of) change" is also insufficient, because things can change slowly or quickly (the same amount of change can correspond to different amounts of time), and also it can't be "Time is (a measurement of) rate of change" because the same rate of change be maintained over different amounts of time.

 

I don't think "change" is the essence of time. Entropy might be. The constancy of the speed of light certainly is related (but if time is defined based on light, it might be cyclical because distance is already defined based on time). If change is expressed in terms of the passing of information across distances, then a definition of time based on change might work.

 

Personally, I think (so please disregard this as anything more than just an idea) that "time is distance" is true, but as I mentioned distance is based on time. Also, the assumption of isotropic propagation of light makes it false. But if light was anisotropic and time and distance were equivalent, then a non-cyclical definition of time would be defined using something other than distance. My guess would be: Time and distance are emergent measurements of causality's consistency . Or instead of that, maybe something that even makes sense.

 

Change means motion, Einstein's field equations generate motion in time that is a symmetry of the theory, not true time evolution. So there is a problem with believing the definition of time is change.

[DrRocket]

Time is what clocks measure.

 

No kidding. There is no more fundamental definition or deeper understanding. If you find one, publish it immediately.

[Mystery111]

Time is what clocks measure.

 

No kidding. There is no more fundamental definition or deeper understanding. If you find one, publish it immediately.

 

This is actually so true. To any definition brought forth yet, I bow down.

[md65536]

There is no more fundamental definition or deeper understanding. If you find one, publish it immediately.

That's what the thread is trying to figure out.

It's certainly helpful to realize that it's not a solved problem. We could even ask "Is there even a possible unknown greater meaning to time still to discover?"

 

If there's a "simple, deeper meaning" it's not going to be found simply in any likely way. But it's still worth contemplating.

 

 

 

I agree "Time is what clocks measure". It's simple, precise, and accurate.

[Appolinaria]

isnt that exactly what i said...

[Mystery111]

isnt that exactly what i said...

 

Well you said ''distance'' see. I think that is different to saying ''distance is what clocks measure...'' - or maybe not. I mean, we do move in time afterall, there is some quality to it that we may associate to a distance in time?

[Appolinaria]

Well you said ''distance'' see. I think that is different to saying ''distance is what clocks measure...'' - or maybe not. I mean, we do move in time afterall, there is some quality to it that we may associate to a distance in time?

 

i said a change. a to b. how can you have a clock without intervals?

 

in my previous post, the first thing i said was time is defined by its measurement. a clock measures time.

Edited October 28, 2011 by Appolinaria

[Mystery111]

i said a change. a to b. how can you have a clock without intervals?

 

As I said to someone else, not long ago:

 

''Change means motion, Einstein's field equations generate motion in time that is a symmetry of the theory, not true time evolution. So there is a problem with believing the definition of time is change.''

[Appolinaria]

As I said to someone else, not long ago:

 

''Change means motion, Einstein's field equations generate motion in time that is a symmetry of the theory, not true time evolution. So there is a problem with believing the definition of time is change.''

 

 

If there is a problem with believing the definition of time is change, how can you agree with DrRocket's statement, "Time is what clocks measure" ?

 

Can you have a clock without motion/change?

 

 

On the clock I have on my wall, the speed of the hand is the same between the distance of each number on the hand. It's in motion, it stops, it's in motion, it stops.

Shouldn't speed over distance, and motion, have SOME relationship with what we call "time" ?