Time: A Scientific Exploration

[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 derivitive (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.

 

[juanrga]

Whao, all of this are new information. thanks they help alot=D
But one more question, if time is (space ,other dimensions that things travel to one direction.), What is before time? If time is what is mention, anything that happen before that should not even happen. Hence if that did not happen how does time even start?

Since time is an evolution parameter, as said above. Asking «what is before y?» is like asking for some x(t) given y(t') where t<t'. Your question «What is before time?» is like asking for some x(t) given t where t<t, which makes no sense.

 

[ValenceE]

Hello all,

I would agree that dx/dy does not require time since the infinite number of possible ratios are all contained at ounce in this simple equation.

For me, Time is very real and is defined as the infinite realm in which space exists... it is the space of space and their common existence is spacetime.

In spacetime, Time enables fundamental energetic processes to evolve in space, interacting and becoming each and every structures we have so far named and included in the comprehension we developped of our magnificent Universe.

Our best (and current) comprehension culminates in Science and, since the beginning of its endeavour, Science uses Time in a quantitative manner providing a measure of duration that is usable in itself or in a relative way.

The actual quantization of Time is a product of basic arithmetics; 1 + 1 + 1... the accuracy to which it is measured depends on our current mastery of how fast we can resolve this basic repetitive addition.

For the human mind, Time remains a representation of duration, perceived in a mental creation stemming from both our environment, which itself is in a vast array of relative motion, and our knowledge of that basic arithmetic operation.


regards,

VE

 

[brettjor]

It's the thing that keeps everything from happening all at once.

 

[brettjor]

It's not a dimension per say. It's an unconstant constant constant.

 

[ranrod]

The OP's second post had an interesting question. When the universe was the size of a pin-head (or smaller), before expansion, shouldn't 'time' be frozen due to gravitational time dilation?

 

[ZapperZ]

Previous thread on this very issue has either been deleted or locked, due to several violations of the PF Rules, especially on speculative posts.

It looks like this thread will suffer the SAME fate. We have given it ample opportunity for people to discuss this on the basis of valid physics. However, it has now meander into personal opinions, speculation, and philosophy. That signifies the end of this thread.

Zz.