A definition of time

[Greg H.]

I'm posting this here because the material I'm reading deals with cosmology and the origin of the universe. If the topic belongs in a more appropriate location, please advise me, and I'll ask the mods to move it.

 

I've been reading The Origin of the Universe by John Barrow and I'm starting this thread to discuss an idea he puts forward that I have to disagree with. I'll quote the salient passage here and then put forth my counter-argument.

 

Our everyday experience of time measures it in terms of sequences of natural events: swings of a pendulum in the gravitational field of the earth; the shadow cast by the sun on a sundial as the Earth rotates; or the vibrations of a cesium atom. We have no way of talking about what time "is" except in terms of how we measure it. [emphasis added]

 

The last line is the part that I take issue with. From my understanding, what Professor Barrow seems to be saying is that we cannot define time unless we append some concrete units to it - pendulum swings, seconds, vibrations, etc.

 

It seems to me that we can arrive at a more abstract definition of time by thinking of it as a separation, in much the same way that distance is, in an abstract fashion a separation. Where distance is a separation of two points, can we not think of time as a separation of two events? Or is that simply redefining the more concrete definition of time using different "units"?

[swansont]

Physics is not in the business of telling us what things are — that's ontology. In science we like falsifiability, i.e. testing that your thought actually describes how nature behaves, and that involves a measurement of some sort. So he's absolutely right — any science discussion of what time is has to involve how we measure it.

[studiot]

Physics is not in the business of telling us what things are — that's ontology. In science we like falsifiability, i.e. testing that your thought actually describes how nature behaves, and that involves a measurement of some sort. So he's absolutely right — any science discussion of what time is has to involve how we measure it.

 

Excuse me, are you suggesting that Science in general and Physics in particular can only define or describe things in terms of measurement?

 

Surely this is a bit restrictive?

[ydoaPs]

I'm posting this here because the material I'm reading deals with cosmology and the origin of the universe. If the topic belongs in a more appropriate location, please advise me, and I'll ask the mods to move it.

 

I've been reading The Origin of the Universe by John Barrow and I'm starting this thread to discuss an idea he puts forward that I have to disagree with. I'll quote the salient passage here and then put forth my counter-argument.

 

 

 

The last line is the part that I take issue with. From my understanding, what Professor Barrow seems to be saying is that we cannot define time unless we append some concrete units to it - pendulum swings, seconds, vibrations, etc.

 

It seems to me that we can arrive at a more abstract definition of time by thinking of it as a separation, in much the same way that distance is, in an abstract fashion a separation. Where distance is a separation of two points, can we not think of time as a separation of two events? Or is that simply redefining the more concrete definition of time using different "units"?

 

It's the same exact way with literally everything. All of our knowledge is derived from measurements. It's just that some people only see this as an issue when time is the subject being studied.

 

Physics is not in the business of telling us what things are — that's ontology. In science we like falsifiability, i.e. testing that your thought actually describes how nature behaves, and that involves a measurement of some sort. So he's absolutely right — any science discussion of what time is has to involve how we measure it.

 

Ontological discussions are bound by the same restriction.

[Greg H.]

Physics is not in the business of telling us what things are — that's ontology. In science we like falsifiability, i.e. testing that your thought actually describes how nature behaves, and that involves a measurement of some sort. So he's absolutely right — any science discussion of what time is has to involve how we measure it.

Ok, so the context of the discussion is the gist of the argument. What's he's really getting at is the measurement of this thing we call time, as opposed to the concept of time itself, at least in this context.

 

It's the same exact way with literally everything. All of our knowledge is derived from measurements. It's just that some people only see this as an issue when time is the subject being studied.

 

 

So I wonder why that is? What is about time that makes it seemingly so much harder to quantify and understand than length (for example). They both (to borrow my earlier example) describe a separation that can be quantified into measurable units.

[swansont]

Excuse me, are you suggesting that Science in general and Physics in particular can only define or describe things in terms of measurement?

 

Surely this is a bit restrictive?

 

Science can't tell you what it is. It can only tell you how it behaves, which means models; you can define things, but those definitions will ultimately be mathematical in nature. Testing the models inherently involves measurement.

[studiot]

you can define things, but those definitions will ultimately be mathematical in nature.

 

I'm sorry but I can't agree with this view.

 

What is the mathematical definition of 'rock'?

 

What is the mathematical definition of a 'leaf'?

 

What is the mathematical definition of 'concrete'?

 

What is the mathematical definition of a 'support'?

 

What is the mathematical definition of 'foam'?

 

All these and many, many more have precise definitions in some branch of science or another.

 

I think the issue is worth discussing.

[owl]

...

It seems to me that we can arrive at a more abstract definition of time by thinking of it as a separation, in much the same way that distance is, in an abstract fashion a separation. Where distance is a separation of two points, can we not think of time as a separation of two events?

...

(My italics)

Sure, why not? "Tick"... "tick"... Time is that which elapses ... between "ticks." Make the clock travel faster or go deeper into a "gravity well" and there will be more time between the ticks.

It takes time... we call it "a year" for earth to orbit the sun, whether or not there were any humans measuring it.

 

Likewise, even if there were no clocks measuring it (or no intelligent life in the universe for that matter,) the elapsed time since the Big Bang would still be nearly 14 billion of the above naturally occurring units of time.

 

Everything moves and it all "takes time" whether it is measured or not.

[Greg H.]

Just for the heck of it, I went and looked up the definitions of time and distance.

 

Distance is defined fairly simply and straightforward:

An amount of space between two things or people.

Nice and abstract, but still useful. It explains the concept of what distance is, without going into the measurements or the math of how we determine distance.

Then we look at time

The indefinite continued progress of existence and events in the past, present, and future regarded as a whole.

What the...? So distance as a concept is restrained, finite, with a definite beginning and end. Time, on the other hand, is infinite, and encompasses every when that ever was or ever will be all at once. Is that because we, as humans, have limitations in envisioning time as being limited in the same ways we can limit distance?

[ydoaPs]

Just for the heck of it, I went and looked up the definitions of time and distance.

 

Distance is defined fairly simply and straightforward:

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Nice and abstract, but still useful. It explains the concept of what distance is, without going into the measurements or the math of how we determine distance.

 

You spelled "circular" wrong. There's no "s", "f", or "e" in it, and there's only one "u".

[swansont]

I'm sorry but I can't agree with this view.

 

What is the mathematical definition of 'rock'?

 

What is the mathematical definition of a 'leaf'?

 

What is the mathematical definition of 'concrete'?

 

What is the mathematical definition of a 'support'?

 

What is the mathematical definition of 'foam'?

 

All these and many, many more have precise definitions in some branch of science or another.

 

I think the issue is worth discussing.

 

I'm not familiar with these physics terms.

 

Nice and abstract, but still useful. It explains the concept of what distance is, without going into the measurements or the math of how we determine distance.

 

Make your case that "amount of space" is unrelated to measurement.

[Greg H.]

You spelled "circular" wrong. There's no "s", "f", or "e" in it, and there's only one "u".

 

Not to be obtuse, but you lost me.

 

 

 

 

 

Make your case that "amount of space" is unrelated to measurement.

 

I see your point, but aren't you assuming that we care about the amount as a concrete quantity? It is possible to acknowledge the presence of some intervening space without quantifying it in terms of fixed units?

 

To your original point up the thread a bit, though, in scientific terms, the concrete measurement is what is useful, and what will be used and discussed in those contexts.

[ydoaPs]

Not to be obtuse, but you lost me.

 

Your definition of "distance" was essentially "length is how long something is". Rather than being useful, it was entirely circular.

[swansont]

I see your point, but aren't you assuming that we care about the amount as a concrete quantity? It is possible to acknowledge the presence of some intervening space without quantifying it in terms of fixed units?

 

No, it works for relative amounts as well. The gist of it is that you are quantifying something; that's a measurement.

[Bill Angel]

Excuse me, are you suggesting that Science in general and Physics in particular can only define or describe things in terms of measurement?

 

Surely this is a bit restrictive?

I would also consider myself an Empiricist, meaning that I also believe that a valid scientific theory should make predictions that can be verified or refuted. But who pays attention to Empiricists anymore? The area of physics I have in mind is String Theory, which has been criticised as being useless for physical explainations as there is no basis in the theory for offering concrete predictions.

[michel123456]

I'd like to support Greg's point.

 

After all, the constancy of Speed Of Light authorizes to express distances in terms of time interval, and reversally time intervals to be expressed in terms of distance.

IMHO if you scratch the surface, there should be no fundamental difference between a distance and a time interval. IMVHO of course.

[studiot]

I'm not familiar with these physics terms.

 

 

I was so taken aback by the approach from a forum mentor that I thought I would not bother further.

 

However the original statement did say 'science' not just physics so I included examples form several sciences.

 

One of these was indeed physics, perhaps if I tell you that a support is very well defined in a branch of physics called mechanics?

 

However I have thought of some more physics examples.

 

What is the measurement necessary to define a crystal?

 

I maintain that there is something non measureable that is particularly relevent to Greg's quesition. That something is order (not as in statmech) but order as in

 

Let us suppose I have a fence comprised of posts set in at random intervals. Let me now walk along that fence painting the numbers 1, 2 , 3 etc on the posts as I pass them.

 

To avoid being accused of counting them say I do not finish.

 

Now let there also be a gateway in this fence and when I come to post 11 it is the first gatepost.

 

What number do I paint on the second gatepost and where is the measurement?

[Klaynos]

I was so taken aback by the approach from a forum mentor that I thought I would not bother further.

 

However the original statement did say 'science' not just physics so I included examples form several sciences.

 

One of these was indeed physics, perhaps if I tell you that a support is very well defined in a branch of physics called mechanics?

 

However I have thought of some more physics examples.

 

What is the measurement necessary to define a crystal?

 

 

I'd say that all of your above can be defined by a set of measurable physical quantities. Hardness, constituent materials etc...

 

Crystals are an easy one, crystals have to have a high order parameter and the lattice and basis is clearly mathematically defined.

[studiot]

Go on then, what measurements, are necessary to distinguish

 

the geological term 'rock', the biological term 'leaf', the materials science term concrete, the mechanical term 'support' and the chemistry term 'foam'

 

By 'necessary' they have to be necessary and sufficient in the strict logical sense. In other words they have to be the only way to arrive at a conclusion that an object or idea is one of these.

Edited June 5, 2012 by studiot

[Klaynos]

Well rock, is a very generic term, I suspect you'd have to have a series of specifications and then have the sum of all of them as rock.

 

I would propose that for each one you would have a hardness, a constituent chemical make up, and some description of the lattice of the I suspect partially ordered material.

 

Leaf is again chemical make up, and a description of the locations/lattice of the cells, probably also a map to show they are at the ends not joining parts.

 

Concrete you'd use similar terms to rock.

 

Support you'd have to consider the forces along the system, their directions etc...

 

Foam I would go towards filling fractions and a model of the thin layers you get. Bubble densities may also be helpful.

 

I'm not an expert in any of these so couldn't provide you with specifics, but it seems very reasonable to me that this is all very possible.

[studiot]

I did say necessary.

 

Of course measurement add much to the description but necessary?

 

Let us go through them.

 

rock

Geologically rock is all the material that makes up the earth below the atmosphere, even water is a 'rock'.

You have hard rocks and soft rocks, rocks tha flow and so on and so forth.

 

leaf

Well I'm not a biologist but I do believe there is something to do with ' an outgrowth of a stem of a plant which engages in transpiration and photsynthesis'

 

concrete

A mixture of aggregates that form a structural shape due to particle interlock, held together by a binding medium.

 

support

Well I don't need a single measurement to note that a table supports a book resting on it.

 

foam

A gas entrained in a liquid.

 

I think that suggesting physics is only measurement is a bit like suggesting that Euclids geometry is only the five axioms or postulates.

With Euclid there are 23 definitions and a further five 'common notions'

So it is with other sciences.

 

I have suggested several abstract 'common notions' such as sequencing and interlock which also play a part in science and even physics.

I am sure ther are many more.

 

Finally I return again to sequencing or ordering as it is directly relevent to Greg's question.

Edited June 5, 2012 by studiot

[swansont]

However the original statement did say 'science' not just physics so I included examples form several sciences.

 

"Science in general and Physics in particular" was the claim to which I responded.

 

One of these was indeed physics, perhaps if I tell you that a support is very well defined in a branch of physics called mechanics?

 

There are forces, e.g. tensions, stresses and strains, all of which have mathematically-based definitions. F=ma

 

However I have thought of some more physics examples.

 

What is the measurement necessary to define a crystal?

 

The claim was that the definitions would be related to math, not measurement — measurement was in regard to testing of models. A crystal has a regular pattern to its structure, that would be given mathematically.

[studiot]

"Science in general and Physics in particular" was the claim to which I responded.

 

 

Which means both Science and Physics in my book.

 

In fact the full question was

 

Excuse me, are you suggesting that Science in general and Physics in particular can only define or describe things in terms of measurement?

 

Only = exclusively.

 

To which your reply was

 

Science can't tell you what it is. It can only tell you how it behaves, which means models; you can define things, but those definitions will ultimately be mathematical in nature. Testing the models inherently involves measurement.

 

Since that post was a direct reply to my question aboveI took the emboldened part to mean yes.

Edited June 6, 2012 by studiot

[Greg H.]

Your definition of "distance" was essentially "length is how long something is". Rather than being useful, it was entirely circular.

 

It's not my fault if the dictionary is occasionally redundant, is it?

 

 

 

[owl]

Regarding my statement on 6/4 about the definition of time:

 

"Everything moves and it all "takes time" whether it is measured or not."

This is a broader, all inclusive concept of time than the standard physics definition, "Time is that which clocks measure," even if any given movement is a "clock" in the broadest sense.

 

In "a galaxy far, far away" things still move around and that takes time whether clocked and assigned "units of time" or not.