Time: A Scientific Exploration

[harrylin]

Best.comment.ever.

Yes indeed - after a first exchange of thoughts, there's only a waste of something that we can't agree on.

So... I'm out of this thread - good luck!

 

[TrickyDicky]

It is obviously wrong if you just check the dictionary - which I even linked and cited.

Yeah, too bad the english dictionary is basically useless as a reliable guide on math and physics, but as long as you believe it...enjoy!

 

[1mmorta1]

I don't think time exists, neither does space, but spacetime does.

What is spacetime? A human concept.

A spacetime exists in human awareness. What reality is really made of we don't know. My view is that everything existing is of same essence, based on two fundamental elements, somethings and nothingness, and countless configurations of these two make countless appearances of unique forms (like patterns of 1 and 0 in computers can produce infinite amount of information).

Perception of time is merely a by-product of how our awareness functions, which is quite limited. If our awareness could have much higher, say wider, ability of perception, e.g. if what we percieve as moment of now would expand so we would percieve now for whole minute as intensively as we percieve now for a second, would the time itself change? Sure not, only our perception would... Imagine our perception to experience now lasting an hour, can you? A year? Timeless?

An anology: I see human perception as a simple scanner which scans a photo dot by dot, line by line, and slowly it captures whole photo. Photo in this case represents existence... Got a visual?

Have you gone to school for physics at all? That sounds like pseudo religion

 

[Boy@n]

Immortal, might be, no idea how pseudo religion looks like.

Human awareness and perception are not as special as we humans like to think, both are very narrow...

Ponder on about your own awareness for a bit and what is experience of now... I wonder where it takes you...?

 

[khemist]

Immortal, might be, no idea how pseudo religion looks like.

Human awareness and perception are not as special as we humans like to think, both are very narrow...

Ponder on about your own awareness for a bit and what is experience of now... I wonder where it takes you...?

Thats more philosophy, not physics.

 

[Dale]

You are correct. I misused the term "wish", but was not meant in a supernatural way.

It was meant to justify ignoring the math. The math was simply my wish, of no more consequence than a personal opinion.

The fact remains that there is no logical need to have a time sequence in order to have something change in space. Do you understand that now?

What is valid today might not be tomorrow.

Nonsense.

 

[Dale]

check the dictionary - which I even linked and cited.

No you didn't.

More relevant is a reference on derivatives, which clearly explains that in math the derivative captures the idea of change:
http://www.whitman.edu/mathematics/...aneous_Rate_of_Change-_The_Derivative_2up.pdf

There is nothing about change that requires all change to be wrt time.

 

[1mmorta1]

No you didn't.

More relevant is a reference on derivatives, which clearly explains that in math the derivative captures the idea of change:
http://www.whitman.edu/mathematics/...aneous_Rate_of_Change-_The_Derivative_2up.pdf

There is nothing about change that requires all change to be wrt time.

Mathematicaly, y and x can be anything. In the real world, change is calculated with respect to time.

Unless you are calculating something like the slope of an object, which can change with respect to another object or to the surrounding space...but this is not "change" in your daily use of the word.

Within the local area nothing actually occurs, even though you can use derivative to calculate "change"

My point is that, physically, yes, it should be true that time is a necessity for change. That extra degree of freedom must be there for, within an n dimensional bound, change to occur from the perspective n-1 dimensions.

 

[1mmorta1]

To be more clear, if a square exists in R3, it is unchanging. If something happens, the square turns to a rectangle or grows larger, a time coordinate(or whatever you choose to name the extra degree of freedom) becomes necessary to define the cube's entirety..at t=0, before the change, and t=1, after. Or however you choose to label your timeline...

 

[bahamagreen]

Time is the comparison between changes; one of these changes takes the form of a clock (whose physical changes we suppose change regularly), the other changes are compared to that clock, and these other changes may be either more clocks or changes in some other quantities.

It is not necessary to imagine time as another dimension; ultimately, all clocks' changes are three dimensional physical changes, most often just simple changes in length, or other common quantities that break down ultimately to lengths.

So, time is (change in physical quantity of interest)/(change in physical clock quantity), which if you take all the way down to simplest units becomes some form of (distance/distance).

Time is not the fourth dimension, it is the three dimensional world self referencing comparisons of itself.

 

[Dale]

Mathematicaly, y and x can be anything. In the real world, change is calculated with respect to time.

Often, yes, but not always. In the real world change can be wrt space as well, or even wrt other real world quantities.

Have you any mainstream scientific reference which states explicitly that change must only ever be calculated wrt time?

 

[1mmorta1]

I suggest you observe how you quote more carefully, you have taken mine out of context. I went on to describe how change can be measured against other local properties, but that this does not really apply in the situation at hand.

 

[harrylin]

Often, yes, but not always. In the real world change can be wrt space as well, or even wrt other real world quantities.

Have you any mainstream scientific reference which states explicitly that change must only ever be calculated wrt time?

Oops I forgot to unsubscribe, so here a last comment.

"change" isn't a parameter and this isn't Wikipedia. Anyway, that discussion drifted away from the starting sentence: "For something to change in space there must be a time sequence associated".

Evidently the referral was to a physical change, and that concept is related to time. Time is in a certain way a measure of change.


Harald

 

[Boy@n]

Thats more philosophy, not physics.

So, can you, or anyone, answer this honest child's question via physics:

When a sand-clock is turned around does the time run our the sand?

You could say both, but really? I don't think you can answer "what's time?" very well with current physics alone, philosophy certainly can add to better understanding.

 

[Boy@n]

Again, if we humans had a different perception of time and experience of present moment (now) we'd also deal with it differently, even in mathematics. Of course I might be wrong, I don't have different (expanded) perception to know it.

 

[1mmorta1]

Again, if we humans had a different perception of time and experience of present moment (now) we'd also deal with it differently, even in mathematics. Of course I might be wrong, I don't have different (expanded) perception to know it.

This forum answers questions using physics, and yes, physics can answer the question.

If you view time as part of an entirety, an extra degree of freedom in a four dimensional, static space-time, the hour glass changes from t=x to t=x+1.

Time doesn't CHANGE anything in the hourglass, it gives the grains of sand the opportunity to be in different locations within R3, at differing time coordinates.

 

[1mmorta1]

not the fourth dimension, it is the three dimensional world self referencing comparisons of itself.[/QUOTE]

That is fully incorrect.

 

[Dale]

Boy@n, there is a philosophy sub-forum that would be more appropriate for your comments which thus far have 0 physics content. The psychological aspects of the sensation of time are not relevant to physics, only whether or not the mathematical models developed accurately predict the result of experiments, which they do.

 

[Dale]

"change" isn't a parameter and this isn't Wikipedia.

I don't know what this comment is in reference to. Is this simply your way of declining to provide a reference supporting your position?

Anyway, that discussion drifted away from the starting sentence: "For something to change in space there must be a time sequence associated".

Evidently the referral was to a physical change, and that concept is related to time. Time is in a certain way a measure of change.

I agree that time is in a certain way a measure of change since it always shows up in a derivative (dt). But it is not the only measure of change, hence the obvious fact that you can differentiate wrt other quantities besides time (e.g. dx).

The sentence you cited, the one that sparked this whole diversion, specifically referred to changes in space. A change in space (d/dx) in no way logically implies a time sequence, as claimed.

 

[Dale]

I suggest you observe how you quote more carefully, you have taken mine out of context. I went on to describe how change can be measured against other local properties, but that this does not really apply in the situation at hand.

Actually, I thought your comments didn't apply, which is why I didn't quote them.

We are concerned with physics usage of the term change, not "daily usage". Asserting that we are interested in "daily usage" is off-topic for the forum, and furthermore you cannot by fiat simply declare that "daily usage" only refers to changes wrt time for your convenience.

This approach is simply an attempt to turn this into a petitio principii argument:
Change always refers only to changes wrt time
Therefore any change implies time

I do not accept the premise. I will ask you again for a mainstream scientific reference that supports it. Otherwise there is no point in continuing to assert it.

 

[1mmorta1]

Time is ONLY used as a reference of change.

You can take a derivative, mathematically, of change in a system that, physically, is unchanging.

In PHYSICS, change requires time. As I said, if you are differentiating the slope of, say, a car hood, this is mathematically sound. It does not mean though, that the system(the hood) is changing. It just means that curvature is a property of the hood, any PHYSICAL change(burning, denting, etc) is shown wrt time.

 

[ghwellsjr]

Time is ONLY used as a reference of change.

You can take a derivative, mathematically, of change in a system that, physically, is unchanging.

In PHYSICS, change requires time. As I said, if you are differentiating the slope of, say, a car hood, this is mathematically sound. It does not mean though, that the system(the hood) is changing. It just means that curvature is a property of the hood, any PHYSICAL change(burning, denting, etc) is shown wrt time.

Maxwell's equations contain two spatial derivatives, the curl and the divergence, which are vector operators, along with the gradient which calculate changes in vector fields that do not involve time. Wikipedia says the gradient "Measures the rate and direction of change in a scalar field". Maybe you should edit the wikipedia article so the world can be in line with your opinion.

 

[1mmorta1]

Yes, the curl and divergence are inherent properties of the local space time, much like the curvature of the cars hood.

I suppose perhaps I'm being too aggressive in my word choice.

I know you can take the derivative, and thus demonstrate change, within nearly any system.

There is a difference between change in three degrees of freedom and in four.

 

[Dale]

In PHYSICS, change requires time.

Please provide a mainstream reference to that.

As I said, if you are differentiating the slope of, say, a car hood, this is mathematically sound. It does not mean though, that the system(the hood) is changing.

If the derivative is non-zero then it does mean that the slope is changing wrt position. You are simply assuming that change means only change wrt time. Your assumption is unjustified.

 

[khemist]

A physical change would be the temperature in the room (from one point to the next), but the gradient of the temperature does not require a change in time.

 

[Boy@n]

Time doesn't CHANGE anything in the hourglass, it gives the grains of sand the opportunity to be in different locations within R3, at differing time coordinates.

If you say that time enables something to change you make time real, almost like some kind of hidden force, and it sounds as if time is necessary for change to happen...

Why would time be needed at all for change to happen? If we have a hourglass and gravity then sand shall fall down without the need of time. Time is just representing the changes... it's not giving sand opportunity to move, it's not enabling that change.

Time is just something we use to "measure" changes. Time is what clock shows. OK, but it doesn't make the clock tick, mechanics in clock do that (powered by hand or battery or whatever).

I'd say time could be real, well, as much as the three spatial dimensions are, if time is a true forth dimension. And we are back to perception, we perceive three dimensions differently than the forth, while they might be all equal in what they are.

 

[digi99]

I think lightspeed represents our understanding of time.

See this topic https://www.physicsforums.com/showthread.php?t=536987", answer #18.

 

[GrayGhost]

Time is just something we use to "measure" changes. Time is what clock shows. OK, but it doesn't make the clock tick, mechanics in clock do that (powered by hand or battery or whatever).

I'd say time could be real, well, as much as the three spatial dimensions are, if time is a true forth dimension. And we are back to perception, we perceive three dimensions differently than the forth, while they might be all equal in what they are.

Well, some of your points seem valid enough. The special theory tells us that a luminally moving clock's hands must be bent, as well as the clock being length contracted. IOWs, each point along the clock's length axis exists in a different era of the clock's own proper time, per the observer who moves relatively in his own instant of time. That's "why" the hands are bent, because moving bodies desycnhronise. This suggests that different eras of the clock's proper time coexist, even though an observer carrying the clock never realizes it from his own casual experience. Same for all observers. So in my view, the question is not so much whether time is the 4th dimension, or a 4th spatial dimension that we interpret as time. But rather as to whether time is the progression from event to event, within a 4 dimensional continuum. Even on a Minkowski spacetime diagram, lines-of-simultaneity advance seemingly steadily within a 4-space.

It's a chicken versus the egg deal. Is time a man made notion to quantity change in space, whereby time is an illusionary effect, and where space and motion are all there really is? Or, is time that which allows for the progression of events, ie a progression thru the 4d continuum?

GrayGhost

 

[logics]

Time is the rate at which things change.. .

If we want to understand the concept of "time" in English, we ought to consider the word "tempo" [from Latin: tempus = time] defined : "the rate of movement, motion, activity".

Being, that is: "what exists", "reality","the world" can be conceived as static [Parmenides] or dynamic [Heraclitus].
The static world of Parmenides is timeless as it is unchanging. The categories of being [Aristotle, Kant: basic concepts] we need to describe such a world are :

substance [ens, essence, what is/exists]
quality [because substance has qualities],
quantity [of substance and quality],
space [because substance/ matter takes up, occupies space]

If we accept that our world is dynamic, we need another basic concept : change. Its most evident manifestation is motion, displacement, "change" of place, but there is also invisible, microscopic change, and change without displacement: internal transformation.

Any regular, reliable phenomenon is idoneous to measure "time", we used distance traveled by the Sun, mass (water or sand) with clepsydra, we counted oscillation with pendulum and quartz crystals, now we count invisible "transitions ... in caesium"

We must be careful when we talk of time being absolute or relative, of time elapsing and so on: "time" has no properties. We should always consider and remember what we are actually measuring. Kant goes to the extreme of saying that it is just an apriori intuition of human mind, a tool we need to categorize, understand and describe the world.

 

[Dale]

Is time a man made notion to quantity change in space, whereby time is an illusionary effect, and where space and motion are all there really is?

Time is a created by us, the observers of space.

Kant goes to the extreme of saying that it is just an apriori intuition of human mind, a tool we need to categorize, understand and describe the world.

The idea that time is a product of the human mind is silly. It is the height of egocentrism to think that the universe popped into existence the moment the first human appeared, and that it is only because we are around that planets orbit and isotopes decay, and that everything will stop again when the last man dies.