Time: A Scientific Exploration

[nitsuj]

There's an infinite number of directions, but every one of them is southwards.

Southwards=towards the South Pole, by definition
Northwards=towards the North Pole, by definition

Yup and nobody said southwards.

 

[Dale]

Cardinal directions have to be coordinated with something, that's always implied and is intuitive. Because you didn't explicitly mention what the cardinal directions were coordinated with I specifically assumed it was with the observer. So a north direction from the north pole is heading towards the south pole.

No, the poles are coordinated with the axis of rotation of the Earth with the north pole being the one where the star Polaris is overhead. North and south have nothing whatsoever to do with an observer.

Saying you can't travel in a north direction when at the north pole is nonsensical.

Huh? I can't believe you actually wrote this. You can only travel south from the north pole.

 

[Dale]

Yup and nobody said southwards.

That is a distinction without a difference. If you are traveling south you are going towards the south, hence southwards.

North and south have nothing to do with observers, the south pole is not north of the north pole, and an observer at the north pole cannot travel north, he can stay put or travel south.

 

[bobc2]

What is time??

I think the biggest problem with grappling with a concept of time is the tendency to try to think of time as some mixture of space and time. I think the biggest source of confusion has arisen from the use of the term, space-time--as though space and time are somehow mixed. The 4th dimension is not time, nor is it some kind of mixture of space and time.

So, one could first imagine the universe as a 4-dimensional space populated by 4-dimensional objects. The whole 4-dimensional universe is just there--all at once. Don't even bring time into the picture initially. This assures that you begin with a distinct separation of space and time into two separate concepts. This concept goes by the name of "Block Universe" and was suggested by Einstein's colleague, Kurt Godel (many physicists feel like Einstein embraced this concept--he just never liked to discuss it openly because of some of the bizarre implications).

Now, after envisioning a static 4-dimensional universe, then put in consciousness moving along the 4th dimension at the speed of light. So, in some sense--at least for us 4-D universe inhabitants/observers--the time comes in with consciousness.

Special relativity directly implies such a 4-dimensional block universe. Thus, the 4th dimension should not be thought of as a time dimension. It is a physical spatial dimension in the same sense as the other three spatial dimensions.

 

[N468989]

I think the biggest problem with grappling with a concept of time is the tendency to try to think of time as some mixture of space and time. I think the biggest source of confusion has arisen from the use of the term, space-time--as though space and time are somehow mixed. The 4th dimension is not time, nor is it some kind of mixture of space and time.

So, one could first imagine the universe as a 4-dimensional space populated by 4-dimensional objects. The whole 4-dimensional universe is just there--all at once. Don't even bring time into the picture initially. This assures that you begin with a distinct separation of space and time into two separate concepts. This concept goes by the name of "Block Universe" and was suggested by Einstein's colleague, Kurt Godel (many physicists feel like Einstein embraced this concept--he just never liked to discuss it openly because of some of the bizarre implications).

Now, after envisioning a static 4-dimensional universe, then put in consciousness moving along the 4th dimension at the speed of light. So, in some sense--at least for us 4-D universe inhabitants/observers--the time comes in with consciousness.

Special relativity directly implies such a 4-dimensional block universe. Thus, the 4th dimension should not be thought of as a time dimension. It is a physical spatial dimension in the same sense as the other three spatial dimensions.

To exist space there must exist time. Time is a consequence of space and vice-versa and they must coexist. For something to change in space there must be a time sequence associated, so we can assume that time is another dimension, sure.

Theoretical physicists suggest that there are parallel universes, I believe that there are other dimensions that we couldn't even begin to imagine. If we lived in a 2D world time would exist also but could we grasp the concept of 3D?

 

[bobc2]

To exist space there must exist time. Time is a consequence of space and vice-versa and they must coexist. For something to change in space there must be a time sequence associated, so we can assume that time is another dimension, sure.

But, the fundamental point was that there is no change. The full 4-dimensional spatial universe is just all there at once. The 4-dimensional objects in the 4-D universe do not move--there is no change.

Theoretical physicists suggest that there are parallel universes, I believe that there are other dimensions that we couldn't even begin to imagine. If we lived in a 2D world time would exist also but could we grasp the concept of 3D?

Parallel universes, perhaps. But that only compounds the problem, it doesn't take away in any sense the 4-D spatial universe that we inhabit.

 

[Dale]

For something to change in space there must be a time sequence associated

You can have dx/dy without any t.

 

[N468989]

You can have dx/dy without any t.

In math/calculus you may have anything you wish. Does that prove anything?

 

[harrylin]

What is time??

It's a measure of duration of physical processes, as well as keeping track of their progress (primarily by counting clock cycles).

Probably the best way to understand this human concept is to consider how it emerged. Evidently people started to count days (based on the Sun), months (based on the moon) and years (based on the Sun and the seasons). In other words, our concept of "time" is based on man's observation of natural clocks, and the application for making plans.

However, with the evolution of physics our understanding of how "time" works also evolved. You may appreciate an old discussion of the consequences of SR on our concepts of "time" and "space", here:

http://en.wikisource.org/wiki/The_Evolution_of_Space_and_Time

PS better: it's a measure of the progress of physical processes (primarily by counting clock cycles) as well as comparing the number of counts -see next

 

[Calimero]

It's a measure of duration of physical processes, as well as keeping track of their progress (primarily by counting clock cycles).

Well, ok, but what is duration? Saying that time is measure of time is not very helpful.

 

[harrylin]

Well, ok, but what is duration? Saying that time is measure of time is not very helpful.

Sorry for the glitch! I should have written comparison of the progress of physical processes, as may have been clear from the explanation that followed. Another way to look at it is to count how many cycles of a reference process something takes - for example how many days walking it is from A to B.

 

[Dale]

In math/calculus you may have anything you wish.

This is not true.

Does that prove anything?

Yes, it proves that you can have change in space without time. Your statement that change in space required time is incorrect.

 

[harrylin]

[..]Yes, it proves that you can have change in space without time. Your statement that change in space required time is incorrect.

Apparently you actually mean "difference", as expressed by dx/dy. However, that's not the proper (or at least, not the main) meaning of the word "change". The statement that change in space requires time is correct for the most common meanings of the words "change" and "time". - dictionary.com
There can be no "making" or "becoming" without "time" - those are related concepts.

PS: Of course we are very much used to say "a change of x as function of y". But that's mere figuratively speaking (only strictly correct if y stands for "time"), although it's easy to forget!

 

[nitsuj]

In math/calculus you may have anything you wish. Does that prove anything?

Nice retort, and well placed.

 

[Dale]

And untrue. You cannot just have anything you want in calculus.

 

[N468989]

And untrue. You cannot just have anything you want in calculus.

Well you can actually, assuming you prove it of course.

 

[Dale]

Of course we are very much used to say "a change of x as function of y". But that's mere figuratively speaking

I disagree, this is not just figurative. The derivative is the mathematical object that formalizes the concept of change, and change can be wrt any variable, not just variables representing time.

 

[Dale]

Well you can actually, assuming you prove it of course.

Wishing it does not make it provable and not wishing it does not stop it from being provable. The wishing is irrelevant, therefore it is simply false to say that you can have anything you wish in calculus.

 

[TrickyDicky]

I disagree, this is not just figurative. The derivative is the mathematical object that formalizes the concept of change, and change can be wrt any variable, not just variables representing time.

This is obviously true.

 

[1mmorta1]

You didn't get my point. Time, as you use the word, is not a rate, nor is there something like a "biological time constant" that measures elasped time.

Anyway, sure: elapsed time differs for different observers.

time doesn't move at any rate, it is a dimension which all things travel through.

The rate at which you travel through time is relative to your motion through the three spatial dimensions, in that (t being time, r being space) dt + dr = c.

 

[1mmorta1]

To exist space there must exist time. Time is a consequence of space and vice-versa and they must coexist. For something to change in space there must be a time sequence associated, so we can assume that time is another dimension, sure.

Theoretical physicists suggest that there are parallel universes, I believe that there are other dimensions that we couldn't even begin to imagine. If we lived in a 2D world time would exist also but could we grasp the concept of 3D?

If we lived in a 2d world, we would define our world as a 3D space time. And we would envision, and perform calculations on, n-dimensional areas, just as we do today.

 

[ghwellsjr]

What is time??

It's what is getting wasted on this thread.

 

[N468989]

Wishing it does not make it provable and not wishing it does not stop it from being provable. The wishing is irrelevant, therefore it is simply false to say that you can have anything you wish in calculus.

You are correct. I misused the term "wish", but was not meant in a supernatural way. Anyway math is only a tool for making the physical world more understandable, sometimes we must come up with something new. What is valid today might not be tomorrow.

 

[khemist]

You are correct. I misused the term "wish", but was not meant in a supernatural way. Anyway math is only a tool for making the physical world more understandable, sometimes we must come up with something new. What is valid today might not be tomorrow.

I disagree. Math is a tool to describe the universe. We might be able to come up with better approximations for particular systems, but valid math will not become obsolete over night.

 

[PAllen]

It's what is getting wasted on this thread.

Best.comment.ever.

 

[N468989]

I disagree. Math is a tool to describe the universe. We might be able to come up with better approximations for particular systems, but valid math will not become obsolete over night.

When we can't do something in math we just assume something, let's take division by zero, square root of minus 1. Assuming something always has an associated risk of being wrong. That is what I meant. Clearly 1+1=2 in any place or time.

 

[PAllen]

If someone is actually interested in seriously thinking about time, the link I provide in post #3 provides numerous essays on time, arguing virtually every conceivable point of view, at a level of sophistication exceeding anything posted on physicsforums. Several of them do not require advanced training to get the gist of the arguments. I seriously meant that it was pointless to navel gaze on time when many really great physicists and philosophers have had an awful lot to say about it already.

 

[Boy@n]

A eight-year old child asked: when a sand-clock is turned around does the time run our the sand?

 

[Boy@n]

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?

 

[harrylin]

This is obviously true.

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