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Matej Velko
2016-May-05, 08:04 PM
Whenever I start thinking about length contraction and time dilation, at first I think I 'kinda' get it. Then, when I try to think about it in more detail I start noticing how I get it less than I did when I first started thinking about it. Also, I noticed that any deeper thinking about relativity leads me to fundamental questions: what are space and time? I mean, if I don't know precisely what those are, how can I even talk about relativity, or anything actually... So my question is, what is space and why does it make sense to talk about distances? What is the distance between two points in space? Is it simply what we read off of a meter stick, or is there more 'real' meaning? Likewise, what is time and why does it make sense to talk about time intervals? What is the time interval between two events? Is it simply what we read off of a clock, or is there more 'real' meaning? What is an event? :confused:

ShinAce
2016-May-05, 08:55 PM
There is no space and time. It is spacetime.

Remember the Pythagorean formula for right angle triangles? a^2 + b^2 = c^2

Well, if you have a triangle in 3D, it's a^2 + b^2 + c^2 = d^2

Well, if you have spacetime, you get, x^2 + y^2 + z^2 - (ct)^2 = ds^2

Space and time work like a triangle in 4D dimensions. Time is an inseparable 4th dimension.

Matej Velko
2016-May-05, 09:17 PM
If time is an inseparable 4th dimension, why do clocks exist and why do physicists use clocks to measure time intervals?

John Mendenhall
2016-May-05, 09:58 PM
Because, like Newtonian Mechanics for gravity, for most purposes they wotk just fine. At relativistic velocities or intense gravitational fields or precision GPS, not so good.

ShinAce
2016-May-07, 02:20 AM
If time is an inseparable 4th dimension, why do clocks exist and why do physicists use clocks to measure time intervals?

I don't know what to tell you. I can't figure out where you're coming from.

Do you want to know about the fringe limits of the theory of special relativity? Or do you want to know why we can safely ignore these limits in our daily lives? That second one is going to require some math.

Here's what you do. You calculate the contracted length of something according to special relativity (call it a). Now you've got the uncontracted length (call it b). Do ((b-a)/b) * 100. That is the percentage difference from using special relativity versus galillean relativity. Try it for something like a car, a plane, a spaceship. What you'll find is that you've wasted your time and it's only above 10% the speed of light that you should bother with these things.

How fast does the electron in hydrogen travel? Are you not surrounded by hydrogen(water)? Calculate the contracted circumference of the orbit. Would you use special relativity to calculate electronic hydrogen energy levels?

Matej Velko
2016-May-07, 09:17 AM
I don't know what fringe limits are and I understand the physics of length contraction and time dilation and their domain of application, my question is more philosophical than scientific, I'm just struggling with understanding fundamental notions of space and time.

Ken G
2016-May-07, 05:39 PM
If time is an inseparable 4th dimension, why do clocks exist and why do physicists use clocks to measure time intervals?
Yes, it is quite untrue to claim that just because space and time merge into a kind of manifold with various invariant properties, this means time and space are somehow "inseparable." Time and space are different, they have to be because otherwise there could be no invariant boundary between "timelike separated" and "spacelike separated" events. This is an irony in how relativity is often explained-- often it is claimed that having a universal speed limit (c) means that time and space are the same, because any space interval x can be turned into a time interval x/c (such as the concept of a "light year"). But actually, it's not that simple. If c were infinite (so we have Galilean relativity), then all events are timelike separated, and no events are spacelike separated-- any two events could be thought to have occurred at the same place by some possible observer. So Gailean relativity certainly enforces a huge difference between time and space-- everything that is invariant is timelike, and all observers agree on the time intervals involved. Einstein's relativity, on the other hand, creates a whole new category: spacelike separation. Now, for the first time, we have events that no observers could ever think happened at the same place, and no observers could ever think that one of those events could have been either a cause or an effect of the other. So relativity is not just about merging space and time, it is about rending spacetime apart, and creating a relationship between some events that we never even knew existed-- events that simply could never have any kind of direct bearing on each other. It is like opening up a category called "invariant spacelike separation", and pouring a bunch of events into that open hole. In that sense, it is a tearing open of time to put space in, but it is not saying time and space are the same thing-- causation only connects timelike separated events, and that's a difference.

ShinAce
2016-May-07, 09:52 PM
I don't know what fringe limits are and I understand the physics of length contraction and time dilation and their domain of application, my question is more philosophical than scientific, I'm just struggling with understanding fundamental notions of space and time.

Everyone struggles with the philosophy of time. We don't even have a decent definition of time. Anyone who claims to understand time is lying.

John Mendenhall
2016-May-08, 01:55 AM
Everyone struggles with the philosophy of time. We don't even have a decent definition of time. Anyone who claims to understand time is lying.

At the time. :D

Hornblower
2016-May-08, 02:38 AM
Everyone struggles with the philosophy of time. We don't even have a decent definition of time. Anyone who claims to understand time is lying.
I don't struggle with the "philosophy" of time because I couldn't care less about it. To me, time is a self-evident concept by which we evaluate how fast or slowly something changes. The fact that I cannot come up with a literal definition of time without getting into circular reasoning doesn't stand in the way of my understanding it. That is, unless I am missing a critical point about what "understanding" means. Likewise with points, lines and planes.

Matej Velko
2016-May-08, 12:21 PM
I don't struggle with the "philosophy" of time because I couldn't care less about it. To me, time is a self-evident concept by which we evaluate how fast or slowly something changes. The fact that I cannot come up with a literal definition of time without getting into circular reasoning doesn't stand in the way of my understanding it. That is, unless I am missing a critical point about what "understanding" means. Likewise with points, lines and planes.
I think time is not self-evident at all, if it were self-evident, it would be so to everyone. Time as a concept by which we evaluate how fast or slowly something changes makes sense to me and it is certainly useful to think that way about time. But why settle for ''understanding'' when we cannot even define it plausibly? The lack of plausible definition should make us question our understanding.

Robert Tulip
2016-May-08, 11:19 PM
deeper thinking about relativity leads me to fundamental questions: what are space and time? I mean, if I don't know precisely what those are, how can I even talk about relativity, or anything actually... So my question is, what is space and why does it make sense to talk about distances? What is the distance between two points in space? Is it simply what we read off of a meter stick, or is there more 'real' meaning? Likewise, what is time and why does it make sense to talk about time intervals? What is the time interval between two events? Is it simply what we read off of a clock, or is there more 'real' meaning? What is an event? :confused:
What science can say about the nature of space and time is a different question from what you call the ‘real’ meaning of these terms. The primary discussion on this board is about what science can say based on empirical observation. Your term “real meaning” is a philosophical concept. For example, it can be argued that meaning is a human construct based on our personal or social perspective, not something inherent in matter.

With time, the ‘real meaning’ given by the clock and calendar is rooted in our evolution as organisms within very long term stable cyclic patterns such as the day, the month, the year, and perhaps even the long slow orbital patterns that drive climate. The “real meaning” of time for us is defined by practical needs and effects, for which the objective findings of relativity are relevant but only distantly. Real meaning can even be psychological, with the speed of time seeming to vary according to our moods and situation.

The famous existential philosopher Martin Heidegger argued in his book Being and Time (1926) that understanding the real meaning of space and time must occur within the perspective of human being in the world. He argued this means that care is the meaning of being, and our constructed views about importance and value, what we care about, actually determine our sense of meaning. The objective data measurement and laws of science provide essential input to human construction of world, but real meaning is as much about relations, perspectives and values as about facts.

I mention this to illustrate that a call for a purely scientific meaning of space and time requires some agreed definition of meaning which is likely to depart from the usual sense.

Ken G has discussed how previous philosophies such as Kant were wrong to argue that space and time provide the absolute a priori necessary conditions of experience based on Newton’s assumption that matter obeys the axioms of Euclidean geometry.

Relativity has relativized our understanding. I fear that the philosophy of space and time still has some way to go to explain our seemingly earth-centred perspective on these fundamental realities against the scientific reality of the modern discovery of the nature of the universe. Our terrestrial units of temporal measurement solely apply on earth and are not relevant to any other cycles in the universe.

Saint Augustine famously said (http://www.brainyquote.com/quotes/authors/s/saint_augustine.html) that he understood time until he started to think about it. “What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know.”

ShinAce
2016-May-08, 11:41 PM
I think time is not self-evident at all, if it were self-evident, it would be so to everyone. Time as a concept by which we evaluate how fast or slowly something changes makes sense to me and it is certainly useful to think that way about time. But why settle for ''understanding'' when we cannot even define it plausibly? The lack of plausible definition should make us question our understanding.

There are three things we use often and yet I feel we might never understand. They are: time, energy, and information(in the physical sense).

Hornblower
2016-May-10, 12:55 AM
I think time is not self-evident at all, if it were self-evident, it would be so to everyone. Time as a concept by which we evaluate how fast or slowly something changes makes sense to me and it is certainly useful to think that way about time. But why settle for ''understanding'' when we cannot even define it plausibly? The lack of plausible definition should make us question our understanding.
My educated hunch is that some of us are overthinking the concept of time itself, as opposed to phenomena we evaluate in terms of it. I still have no grasp about what it is about time, if anything, that you think we don't understand.

Matej Velko
2016-May-10, 12:13 PM
My educated hunch is that some of us are overthinking the concept of time itself, as opposed to phenomena we evaluate in terms of it. I still have no grasp about what it is about time, if anything, that you think we don't understand.
You may be right... I think I may be overthinking it.. but then again if I leave time simply be a useful concept, I get a feeling like a might miss a great realization about time that would help me think more clearly about its properties. But I don't think that realization is likely, if possible, so I'll just leave it be :)

Ken G
2016-May-10, 01:58 PM
My educated hunch is that some of us are overthinking the concept of time itself, as opposed to phenomena we evaluate in terms of it. I still have no grasp about what it is about time, if anything, that you think we don't understand.
Yet, it is already a brand of personal philosophy to conclude that all questions that are not understood are therefore of no importance.

Ken G
2016-May-10, 02:06 PM
You may be right... I think I may be overthinking it.. but then again if I leave time simply be a useful concept, I get a feeling like a might miss a great realization about time that would help me think more clearly about its properties. But I don't think that realization is likely, if possible, so I'll just leave it be :)I would say that when a problem seems intractable, it needs to be broken down into smaller problems. If you cannot leap a stream, look for rocks in the stream that are only partially across. For example, on the issue of time, you might find it a more focused issue to ask, is it the passing of time that allows us to think, or is it our thinking that gives us a concept of the passing of time?

If you want my take on that one, I'd point to the fact that even a young child easily arrives at a concept of time, and uses that concept to organize their world. Yet to go beyond that basic functional approach, even the greatest physicists and philosophers struggle. So either time is a really simple concept that we are "overthinking" to try to get any further on, or it is so fundamental to how we think that we would need to understand ourselves better to make headway on. Perhaps we can only get so far when we regard time as something external to ourselves, and understanding ourselves is always the hardest thing. A telescope can resolve craters on the Moon and rings around Saturn, without the slightest concept of itself or how it does it.

Matej Velko
2016-May-10, 04:23 PM
I would say that when a problem seems intractable, it needs to be broken down into smaller problems. If you cannot leap a stream, look for rocks in the stream that are only partially across. For example, on the issue of time, you might find it a more focused issue to ask, is it the passing of time that allows us to think, or is it our thinking that gives us a concept of the passing of time?

If you want my take on that one, I'd point to the fact that even a young child easily arrives at a concept of time, and uses that concept to organize their world. Yet to go beyond that basic functional approach, even the greatest physicists and philosophers struggle. So either time is a really simple concept that we are "overthinking" to try to get any further on, or it is so fundamental to how we think that we would need to understand ourselves better to make headway on. Perhaps we can only get so far when we regard time as something external to ourselves, and understanding ourselves is always the hardest thing. A telescope can resolve craters on the Moon and rings around Saturn, without the slightest concept of itself or how it does it.
Thank you Ken G. I think it is our thinking that gives us a concept of the passing of time as well because everything that really exists is the present moment (in the everyday life at least) and past and future exist only in our minds.

kevin1981
2016-May-10, 08:02 PM
To me, space seems to be self replicating. It is expanding, getting bigger and bigger, so, it is either "stretching" or self replicating, making more of itself.

Ken G
2016-May-10, 09:18 PM
Thank you Ken G. I think it is our thinking that gives us a concept of the passing of time as well because everything that really exists is the present moment (in the everyday life at least) and past and future exist only in our minds.Our minds certainly play a key role in saying what has existed and what will exist, but it also plays a key role in saying what exists in the present as well! But I agree that the idea that "time passes" is one of the more obvious of our mental constructions. Einstein had something interesting to say along those lines:
"...for us physicists believe the separation between past, present, and future is only an illusion, although a convincing one."
One might wish to nitpick that when an illusion is sufficiently convincing, we don't call it an illusion any more, but I believe I understand what Einstein was getting at here-- though who knows the full measure of his point.

DALeffler
2016-May-10, 11:20 PM
If time stops for a photon, does time even exist for a photon?

Does it take a photon any amount of time to be reflected or absorbed and re-emitted?

Will the CMB eventually be zero?

Robert Tulip
2016-May-11, 11:46 AM
...Einstein had something interesting to say along those lines:
"...for us physicists believe the separation between past, present, and future is only an illusion, although a convincing one."

This idea implies that the past, present and future are equally real, opening the problem of how space-time could be considered an unchanging eternal unity. The various meanings of eternity include outside time, lasting forever within time, and having permanent value. An indigenous American saying is that you are surrounded by eternity.

Ken G
2016-May-11, 02:26 PM
If time stops for a photon, does time even exist for a photon?It's a singular limit, so it depends on how you take that limit. I would be inclined to imagine the state of a photon by taking a limit of faster and faster particles with smaller and smaller rest masses. After all, we don't even know that a photon rest mass is exactly zero. If you do that, you find something interesting-- time progresses for every hypothetical particle in that limiting series in exactly the same way it does for us. It's just proper time, it works the same for everyone at any speed. So by this reasoning, we should not say time stops for a photon, we should say time is completely normal for a photon-- but if the photon is created and later destroyed in some finite time from our point of view, it's life will be very short indeed from it's own point of view. It's not that time stops, it's that things happen very quickly! But a photon that is never reabsorbed, so exists for infinite time in our frame, can be seen by that limiting process I just described to also exist for an infinite time in its own frame.


Does it take a photon any amount of time to be reflected or absorbed and re-emitted?This is the key point. For photons, all the lengths that we regard as finite are length contracted into very short (or zero) distances for the photon. So it takes essentially no time in its own frame to cross these distances-- things happen fast for photons.


Will the CMB eventually be zero?It will redshift more and more, becoming effectively zero when we cannot detect a single photon from it any more, but there will still always be a nonzero probability of detecting a CMB photon in any finite timeframe. That said, I imagine that alien astronomers 100 billion years from now will have a very hard time indeed knowing that there is any CMB at all.

Ken G
2016-May-11, 02:31 PM
This idea implies that the past, present and future are equally real, opening the problem of how space-time could be considered an unchanging eternal unity. Yes, relativity inspires the concept of a "world line" that is in some sense "made of" a series of events, all equally important or real. The proper time along the world line is simply a kind of labeling system for ordering the events, but the event being perceived in the "now" is conveyed no special importance, nor any non-arbitrary way to match it up as being "simultaneous" with the events on other people's world lines except at the places where they cross. All that is invariant is the set of events that can affect my "now", and the set of events I can affect by what I do "now." In effect, if I claim that I "only exist in the now", it is like saying that all the other moments of my life were a different person, as different from my personal existence in the "now" as that of Abraham Lincoln. Alternatively, if I wish to maintain that all those "nows" are in some sense "also me", then it makes no sense to claim I exist only in the present.
An indigenous American saying is that you are surrounded by eternity.The ultimate total perspective vortex!

John Mendenhall
2016-May-11, 03:02 PM
And, since the Universe appears to be without bound and uniform in all directions, without a center, and each one of us has our own view of the Universe independent of others, each of us can consider ourselves to be the center of the universe for our own purposes.

As Feynman said, "What do you care what other people think?"

Matej Velko
2016-May-14, 05:25 PM
Yes, relativity inspires the concept of a "world line" that is in some sense "made of" a series of events, all equally important or real. The proper time along the world line is simply a kind of labeling system for ordering the events, but the event being perceived in the "now" is conveyed no special importance, nor any non-arbitrary way to match it up as being "simultaneous" with the events on other people's world lines except at the places where they cross. All that is invariant is the set of events that can affect my "now", and the set of events I can affect by what I do "now." In effect, if I claim that I "only exist in the now", it is like saying that all the other moments of my life were a different person, as different from my personal existence in the "now" as that of Abraham Lincoln. Alternatively, if I wish to maintain that all those "nows" are in some sense "also me", then it makes no sense to claim I exist only in the present. The ultimate total perspective vortex!
All the other moments of my life are a different person. What do you have in common with ''yourself'' 10 years ago? Only memories, and those are just constructs of our minds.

grapes
2016-May-14, 06:47 PM
All the other moments of my life are a different person. What do you have in common with ''yourself'' 10 years ago? Only memories, and those are just constructs of our minds.
And, legal obligations!

Personhood is fairly well established construct. You might need to coin a new phrase to describe the distinction you're making :)

Ken G
2016-May-14, 08:11 PM
For those who enjoy science fiction scenarios, it is fun (and potentially interesting) to devise situations where the concept of personhood is much more strained than the one we normally find applicable. Concepts like cloning or teleporter malfunctions can raise interesting issues that suggest personhood is more of a state of being than a claim on a stream of events. But then, we don't have clones or transporters in this day and age, so the question is currently more moot.

Matej Velko
2016-May-14, 08:11 PM
And, legal obligations!

Personhood is fairly well established construct. You might need to coin a new phrase to describe the distinction you're making :)
I agree it is fairly well established and it is because the great majority of people have established it that way. That most certainly does not mean they're right. I'm not saying I know for certain I'm right, but it seems fairly conclusive to me that personhood is an illusion, not having a way to objectively test this. Personhood is established in a way that people identify themselves with their thoughts. However, thoughts are only objects of one's consciousness and do not make up a person. I have not yet realized that personhood is an illusion, but the reason is I still lack needed concentration to do so. I know it may seem a little unscientific, but I think it will not be for long once neuroscience has developed more.

Hornblower
2016-May-15, 01:19 AM
I think time is not self-evident at all, if it were self-evident, it would be so to everyone.
Perhaps it is self-evident to everyone who does not overthink it.
Time as a concept by which we evaluate how fast or slowly something changes makes sense to me and it is certainly useful to think that way about time.That is a key point. It is useful for a wide range of purposes ranging from managing your everyday life to cutting-edge exercises in physics.
But why settle for ''understanding'' when we cannot even define it plausibly?Because that lack of a definition that would satisfy your standard of plausibility does not make it less useful for the aforementioned purposes.
The lack of plausible definition should make us question our understanding.All it makes me do is recognize some limitations of linguistic logic (alliteration intended). We develop an instinctive and useful grasp of time at a very young age, before learning the linguistic fine points of defining terms.

Flatland
2016-May-15, 11:36 AM
If time is an inseparable 4th dimension, why do clocks exist and why do physicists use clocks to measure time intervals?

Same reason we use rulers to measure space intervals.

Ken G
2016-May-15, 02:31 PM
What is clear is that our minds develop a concept of time. Whether that means time is anything other than a concept in our minds is quite unproven. What we get to know is that the concept has proven itself useful, and that's all we ever get to know, until some other concept proves more useful down the road-- which almost always happens in physics. To say anything other than that is to "overthink" the evidence.

George
2016-May-16, 03:45 AM
What is clear is that our minds develop a concept of time. Whether that means time is anything other than a concept in our minds is quite unproven. What we get to know is that the concept has proven itself useful, and that's all we ever get to know, until some other concept proves more useful down the road-- which almost always happens in physics. To say anything other than that is to "overthink" the evidence.This seems a little too clinical and a lot like how mathematics is treated, but time seems to be more in the physics realm which some like to call "reality", which is the word, if taken too seriously, becomes too unclinical as words like "absolute" become attached yet they never stick very well if one looks closely.

Ken G
2016-May-18, 04:49 AM
This seems a little too clinical and a lot like how mathematics is treated, but time seems to be more in the physics realm which some like to call "reality", which is the word, if taken too seriously, becomes too unclinical as words like "absolute" become attached yet they never stick very well if one looks closely.The main thing to keep coming back to, in all that is actually scientific and not something else, is that we make models, test them, and modify them as necessary. That's it, that's the beginning of the story, the middle of the story, and the end of the story. Reality is just another one of those-- in science, anyway.

George
2016-May-18, 01:40 PM
The main thing to keep coming back to, in all that is actually scientific and not something else, is that we make models, test them, and modify them as necessary. That's it, that's the beginning of the story, the middle of the story, and the end of the story. Reality is just another one of those-- in science, anyway.For a general audience, if you had to use one word to make a distinction between math and physics, would reality be it? Further explanation would be helpful to this audience so that absolutes don't become too entangled, along with other aspects such as probabilities, but perhaps "reality" would serve fairly well. I have seen it used by physicist authors (e.g Aczel).

Fiery Phoenix
2016-May-18, 06:43 PM
For a general audience, if you had to use one word to make a distinction between math and physics, would reality be it? Further explanation would be helpful to this audience so that absolutes don't become too entangled, along with other aspects such as probabilities, but perhaps "reality" would serve fairly well. I have seen it used by physicist authors (e.g Aczel).
As a general rule, my understanding is that physics is a description of reality, whereas math is a formal abstraction of the concepts of reality described by physics (which can be generalized across a wider spectrum of theoretical and practical purposes).

So, I guess you could use reality as the word, but then again it's a matter of semantics and what makes sense to one subset of the general audience may not necessarily make sense to another.

Ken G
2016-May-19, 01:27 AM
For a general audience, if you had to use one word to make a distinction between math and physics, would reality be it?That's a toughy! The problem is, it really depends on your preconceived view of what reality is all about. For many of us, physics more closely aligns with reality, and math with "pure thought", because in physics you cannot know the "right answer" without looking at nature, but in math you can know what passes for the right answer using pure logic. But still, there are those who would say that looking invokes the illusions of your senses in ways that pure logic does not. They would point to the fact that our senses told us that Galilean relativity made perfect sense, but the axioms of special relativity are in some sense more elegant and more closely connected with pure logic. So they would say the "reality" was special relativity, not Galilean relativity, for reasons that have nothing to do with how we perceive our surroundings, but rather reasons of elegance of structure. Are they right? I don't know, but I do know that Einstein himself said he never cared much for the observations that showed general relativity made correct predictions-- he already knew it would, said he, purely because of its mathematical and conceptual elegance.


Further explanation would be helpful to this audience so that absolutes don't become too entangled, along with other aspects such as probabilities, but perhaps "reality" would serve fairly well. It would likely serve most people well-- just not the rationalists who think that what is must be what makes the most sense, moreso than what we come to believe based on our observations. After all, rationalists may tend to think that every time you do an observation, all the possible outcomes actually occur, and it is only a kind of illusion of perception that you think only one did.

Robert Tulip
2016-May-19, 10:42 AM
What is clear is that our minds develop a concept of time. Whether that means time is anything other than a concept in our minds is quite unproven. What we get to know is that the concept has proven itself useful, and that's all we ever get to know, until some other concept proves more useful down the road-- which almost always happens in physics. To say anything other than that is to "overthink" the evidence.

KenG, your comment is a great example of more mind-dependent reality "overthinking". The mean tropical year on January 1, 2000 was 365.2421897 days. The exactness of this measurement of terrestrial time illustrates that the likelihood of "some other more useful concept" is precisely nil, and the ratio between spin and orbit really exists independently of our knowledge of it. Orbital dynamics are well enough understood to provide accurate measurements of time.

George
2016-May-19, 02:27 PM
As a general rule, my understanding is that physics is a description of reality, whereas math is a formal abstraction of the concepts of reality described by physics (which can be generalized across a wider spectrum of theoretical and practical purposes). The idea of description was one I was considering. "Descriptive" addresses the work done in physics and implies purpose, whereas math more of a tool used for that purpose. But reality is likely the better word since it goes to what it is you are attempting to describe.


So, I guess you could use reality as the word, but then again it's a matter of semantics and what makes sense to one subset of the general audience may not necessarily make sense to another.Yes and it can get abused in order to advance ideas that are short in merit.


That's a toughy! The problem is, it really depends on your preconceived view of what reality is all about. For many of us, physics more closely aligns with reality, and math with "pure thought", because in physics you cannot know the "right answer" without looking at nature, but in math you can know what passes for the right answer using pure logic. Yes, but the latter is internalized -- it doesn't need a reality and in some cases it is false with reality but true to itself -- and the former is just the opposite (or strives to be), I think.


... So they would say the "reality" was special relativity, not Galilean relativity, for reasons that have nothing to do with how we perceive our surroundings, but rather reasons of elegance of structure. Are they right?I would assume these are few in number within a general audience, but even they would recognize the caveat assigned to any one word use and would be tolerant, I suppose. I thought of Galileo when I asked the question since he said math is the language of physics ("Nature"?). I think you have aptly described physics as a conversation with Nature so that word should make the short list as well.


I don't know, but I do know that Einstein himself said he never cared much for the observations that showed general relativity made correct predictions-- he already knew it would, said he, purely because of its mathematical and conceptual elegance. Yet he did have heart palpitations when he applied his theory to the Mercury anomaly. :) The excitement of such a result with such a complex theory is not hard to believe.

"Time" may yet be another one-word approach for delineation. It's lack of accuracy (as a one-word separator) may be offset by its sizzle impact, important to keeping a general audience attentive. Physics, per the Greeks, is a word for motion, IIRC, and time is the key ingredient. Math provides the accounting process for something in motion. But things like mass and charge are independent of motion, though things change when they are set in motion, so "motion" might not cut it, perhaps ironically.

George
2016-May-19, 02:42 PM
KenG, your comment is a great example of more mind-dependent reality "overthinking". The mean tropical year on January 1, 2000 was 365.2421897 days. The exactness of this measurement of terrestrial time illustrates that the likelihood of "some other more useful concept" is precisely nil, and the ratio between spin and orbit really exists independently of our knowledge of it. Orbital dynamics are well enough understood to provide accurate measurements of time. Yet this value is not exact but an approximation or average. Each digit in the last decimal place represents about 8.5 milliseconds, but atmospheric changes and other mass motions change the last two digits every day. But is the Earth's rotation rate changing daily or is the universe spinning around us changing, or both? GR, at least the mathematical aspects of it, doesn't distinguish much between the two, though it might with time (pun given a future resolution to Mach's ideas, I think).

Ken G
2016-May-19, 04:10 PM
KenG, your comment is a great example of more mind-dependent reality "overthinking". The mean tropical year on January 1, 2000 was 365.2421897 days. I think you are mistaking a number for something more than a number. I certainly see no argument here that our ability to create a concept of a mean tropical year proves that there is not some more useful notion we have not yet come up with. For example, the rate of change of the mean tropical year is already a more advanced notion that can be added to the concept of a mean tropical year. Of course most people (clearly not George) wouldn't even know that the mean tropical year does change, such is the problem with underthinking.


The exactness of this measurement of terrestrial time illustrates that the likelihood of "some other more useful concept" is precisely nil, and the ratio between spin and orbit really exists independently of our knowledge of it. We already know there are some other more useful concepts than the duration of a mean tropical year. Even the word "mean" in that phrase proves quite clearly it is not something fundamental, but rather a choice of the human mind to compute. As with all bad arguments in science, one only needs to look more closely.

Robert Tulip
2016-May-20, 07:38 AM
I certainly see no argument here that our ability to create a concept of a mean tropical year proves that there is not some more useful notion we have not yet come up with. That misses the point. My response was to your comment “What is clear is that our minds develop a concept of time. Whether that means time is anything other than a concept in our minds is quite unproven. What we get to know is that the concept has proven itself useful, and that's all we ever get to know, until some other concept proves more useful down the road-- which almost always happens in physics. To say anything other than that is to "overthink" the evidence.”

The inference I drew from your comment was that the “some other concept down the road” would affect the point at issue, your claim that “Whether time is anything other than a concept in our minds is quite unproven.”

A new concept of time can only “prove more useful” in these terms if it shows that our current concept of time has some error. Just showing that a future measurement is more exact is immaterial to whether our current concept is soundly based on observation of objective reality.

The millisecond precision obtained by current measurement illustrates that it is a correct measurement, not just a possibly wrong mental concept.


For example, the rate of change of the mean tropical year is already a more advanced notion that can be added to the concept of a mean tropical year.
That is not relevant to whether the mean figure is more than just a concept in our minds.

the word "mean" in that phrase proves quite clearly it is not something fundamental.
That is nonsense. The existence of such precise calculation of the mean illustrates that it is based on fundamental and accurate celestial mechanics.

Ken G
2016-May-22, 03:33 PM
The inference I drew from your comment was that the “some other concept down the road” would affect the point at issue, your claim that “Whether time is anything other than a concept in our minds is quite unproven.” Yes, that is a correct inference, but I still don't see how our minds' ability to generate a calculation we call a "mean tropical year" informs that inference. Perhaps your other comments will clarify your intention there.


A new concept of time can only “prove more useful” in these terms if it shows that our current concept of time has some error."Error" is a strong word, but you are basically correct. And of course, that will indeed be the case. In fact, to some degree we already know the concept of a "mean tropical year" does contain errors, which is why it is an approximate number-- for the reasons pointed out by George and myself.


Just showing that a future measurement is more exact is immaterial to whether our current concept is soundly based on observation of objective reality.
Now you are equivocating. Before you said the concept had to contain an error, yet now you claim that's the same thing as it not being "soundly based on observation." Of course that's wrong, we need only look at the many other examples we already have. The force of gravity? The location of a particle? The individual identity of an electron? All things that we now view as containing significant errors, yet all are also quite "soundly based on observation," to the extent that they are all used all the time in physics-- in the appropriate contexts. Our theories are always soundly based on observation, and they also always turn out to have significant errors. That's just how science works.

Robert Tulip
2016-May-23, 07:06 AM
I still don't see how our minds' ability to generate a calculation we call a "mean tropical year" informs that inference [that future science might show our theory of time is only a concept].
The difference between “only a concept” and “something objectively real” is that there is no way the latter could be proved wrong, in that it is absolutely and indubitably true and lacks the provisionality of mere concepts.

How does our knowledge of the ratio between earth’s orbit and spin periods fit this high goal of true knowledge? Quite well really.

The exactness of prediction of orbital motion is so good that astronomers have routinely added in leap seconds to fine-tune the match between spin and orbit, at the level of something like one part in fifty million. The 2012 status was explained at http://www.nature.com/news/leap-second-granted-extra-time-1.9865

Only if the leap seconds created unexplained changes as happened with the application of classical mechanics would the spectre of a paradigm shift be relevant. In paradigm theory, we are used to seeing how anomalies in classical mechanics or geocentrism built up until they were resolved in the shift to a new paradigm. With terrestrial time, that emergence of anomalies is just not going to happen.

The ratio under analysis is not between our concepts of the day and the year, but between the actual day and year periods. We could make a conscious decision to shift to atomic clock time rather than orbital time, and wait until we needed leap minutes rather than the inconvenience of leap seconds, but either way our concepts are true because they match to and derive from a reality that is reliably independent of our concepts.



the concept of a "mean tropical year" does contain errors, which is why it is an approximate number
The uncertainty is about one part in a hundred million, and does not constitute a theoretical anomaly. It does not make sense to call such an accurate prediction approximate.



The force of gravity? The location of a particle? The individual identity of an electron? All things that we now view as containing significant errors, yet all are also quite "soundly based on observation," to the extent that they are all used all the time in physics-- in the appropriate contexts. Our theories are always soundly based on observation, and they also always turn out to have significant errors. That's just how science works.

Uncertainty of a few parts per billion in orbital prediction is not a “significant error.” Advice to generals includes to avoid fighting the last war. In this case, that means the scepticism produced by past paradigm shifts may simply not be justified in cases where our knowledge is absolutely true. In the theory of time, we are better off to accept that our current astronomy is highly accurate, given its excellent predictive record, which is completely different from the examples you provide of significant errors.

Agreeing that the understanding of time is incomplete is very different from your argument that current measurement may have significant error. If future new knowledge about time turns out to only build on current knowledge, rather than show that our current knowledge is wrong, then your theory that time is only a concept will be proved wrong. One swallow does not make a summer, and nor does the inductive argument from one or two paradigm shifts create a general law about the provisionality of all knowledge.

Ken G
2016-May-23, 01:41 PM
The difference between “only a concept” and “something objectively real” is that there is no way the latter could be proved wrong, in that it is absolutely and indubitably true and lacks the provisionality of mere concepts. First of all, as I have said many times, I would avoid the overly leading term "only a concept." That's like when people who don't like evolution call it "only a theory." Time is a concept, evolution is a theory. We need not shy from these basic facts, and neither of those basic facts subtracts from time or evolution. It's just what they are, the scientist should always deal in the truth. Second of all, I have no idea what you mean that some things can be proved wrong and other cannot. Science has never been about any of that, it has always been about testing theories.


How does our knowledge of the ratio between earth’s orbit and spin periods fit this high goal of true knowledge? Quite well really. Of course, as did Newton's gravity, classical particle locations, and the concept of the identity of an electron. That's why I supplied that list of things that fit a high goal of "true knowledge", but are wrong. I'm not sure you quite get science, or what "true knowledge" constitutes in science. You should look more closely at the history of that pursuit, and being to see it for what it is, not what you might like it to be. For example:

Uncertainty of a few parts per billion in orbital prediction is not a “significant error.” Of course that's wrong, it all depends on the context what is a "significant error." You seem to imagine that term has some absolute meaning, but you shouldn't imagine that. Science certainly doesn't work that way, great discoveries in science can be based in smaller deviations from expectation than that. The point is, the problem with the mean year is not it's "uncertainty", it is the simple certainty that the concept is approximate. It's not that we don't know if it is correct, it is that we do know it is incorrect as some kind of absolute "true knowledge." I'm afraid that's just not what scientific "true knowledge" is, because in science, true knowledge is always approximate. If someone said that the energy of the Lyman alpha line in hydrogen had a certain "true" value, and that value was shown to be wrong to one part in a billion, no good scientist would ever say "ah, but that's not a significant error, so it's still true knowledge of the energy of that transition." No, any good scientist would say "well, we obviously have one very good theory that gets the answer right to a part in a billion, and now we need to go out and find an even better theory that does not have that significant error."

Hornblower
2016-May-23, 03:03 PM
The ratio under analysis is not between our concepts of the day and the year, but between the actual day and year periods. We could make a conscious decision to shift to atomic clock time rather than orbital time, and wait until we needed leap minutes rather than the inconvenience of leap seconds, but either way our concepts are true because they match to and derive from a reality that is reliably independent of our concepts. The ratio under analysis is between our best estimates of the day and year periods for some specified date, which you have not stated. In addition you have not defined "day" for the purposes of this post. As a matter of fact we shifted to atomic time as the master timekeeper several decades ago, and for cultural reasons we are jiggering the official expression of atomic time with leap seconds to keep it roughly in step with Earth's spin, which is fluctuating irregularly in the short term and gradually slowing down in the long term. We started doing this when we concluded from exercises in nuclear physics that the cesium clock is a more reliable timekeeper than the unsteadily spinning Earth. For reasons which are a mystery to me, for better or worse, we set the SI second as 1/86,400 of a mean solar day that prevailed sometime in the 1800s instead of a more recent value. We have lucked out in recent decades as short term speed-ups in the spin rate have reduced the need for frequent leap seconds, but eventually the tidal drag will prevail and the need for some sort of adjustment will become more frequent. I personally know an astronomer in the Naval Observatory timekeeping department who wishes the powers that be would abolish the atomic time leap seconds and let the civil authorities worry about defining civil time and date benchmarks. This could be done far in the future when mean solar noon at Greenwich gets more than 30 minutes out of step with atomic noon. The basis of civil time could be changed by an hour by appropriate legislation, which in principle would be no different from what we already do in making switches between standard and daylight saving time. Of course there would be some technical and perhaps legal challenges, but that would be a people problem, not a scientific or technological problem.

As I see it, none of this addresses the OP's concern about "concept of time" or "understanding of time", whatever those concerns are supposed to mean. All we are discussing here is a matter of our technological skill in creating what we consider a reliable timekeeper (the cesium clock), and measuring the rates of the periodic motions of the Earth in comparison with it.

Ken G
2016-May-23, 05:30 PM
As I see it, none of this addresses the OP's concern about "concept of time" or "understanding of time", whatever those concerns are supposed to mean. Right, it's the difference between the concepts of "time" and "timekeeping", which are necessarily two different concepts. That's the flaw in the above argument that we are "overthinking" time when we ask what it actually is, in some sense, or when we wonder if some better concept will come along. Robert Tulip argued that if there were any surprises in the time concept, timekeeping would not be so simple. You showed just how incredibly not simple timekeeping is, so poof goes that argument!

George
2016-May-23, 10:53 PM
Freshman mechanical engineering student to astronomer, “They sent me to get the exact time in one year.”

Astronomer, “Ah, so this time it’s you they have sent. What year would you like?”

ME, “This year.”

Astronomer, “No. Do you want the sidereal, mean tropical, or anomalistic year?”

ME, “Just the year we use. One trip around the Sun. That’s what’s happening, right?”

Physicist, “Revolving around the Sun is a useful concept, but it isn’t quite the most accurate picture.”

ME, “What could be better?”

Astronomer, “Well, a better picture is the Earth revolving about the barycenter of the Solar System and not about the center of the Sun. The c.g. of the Solar System is the term you would use. This point varies due to all the other masses and motions, especially Jupiter’s.”

ME, “Ok, I hear you, but at the end of the day, the time of one year is always the same because time and Earth’s orbit is constant.”

Physicist, “Time should not be considered, actually, as an absolute. It varies depending on things like relative motion of inertial frames, for instance.”

ME, “Sure, on Mars a year is longer.”

Astronomer, “No. That’s not what he is saying. Though the difference in the rate of time is extremely small -- so comparing an atomic clock there with one here is likely required – the rate of time on Mars is not the same as here.”

ME, “Oh, I get it, because we are traveling faster through space than Mars. I think I read about time dilation once. At least, however, what Newton discovered about gravity gave us most of the laws (statics and dynamics) I will likely need to know, which should give me my answer for the length in time of Earth’s year – the normal one.”

Physicist, “Newton stated that he had no clue as to what gravity is. His laws are indeed useful for most engineering work, but his laws were derived from the effects observed from what we call gravity, namely the inverse square law.”

ME, “Ok, but at least we know today, since Copernicus, that we do go around the Sun, or some point near its center, and not the other way around.”

Physicist, “That is a very useful concept, assuming that's not a pun, but it would not be false to state that any point in the universe could be taken as a central point, though things often get more complicated doing so.”

Astronomer, “Interestingly, NASA, for closer orbits, will use the center of the Earth, and not the Sun, as a center point since it’s both simpler and effective.”

ME, “That’s logical and how an m.e., I assume, would handle it. At least space close to Earth is known.”

Physicist, “Yet it is not an absolute either. Space and time go hand in hand, and space is altered by mass, or gravity if you prefer. Mass bends space, and time is affected as well and is well defined in Einstein’s General Relativity.”

ME, “Oh yeah. Thanks for reminding me why I chose engineering! I’ll come back later with the year they want me to get from you. BTW, what happened to the guy last year who came?”

Astronomer, “He switched to psychology.”

[Note: The ME is me, an m.e., though not a freshman]

Robert Tulip
2016-May-24, 06:34 AM
I would avoid the overly leading term "only a concept." That's like when people who don't like evolution call it "only a theory." No, that analogy is completely invalid. When creationists say evolution is only a theory, they are arguing that evolution is untrue. When I question your argument that time is only a concept, I am saying that your symbolic representation of time is a different thing from time itself, that the map (your concept) is not the territory (time itself). I have no doubt that your concept of time is far more accurate than most people have.

Time is a concept, evolution is a theory. We need not shy from these basic facts, and neither of those basic facts subtracts from time or evolution. They both subtract massively by claiming that the concept/theory is all there is, and that therefore time and evolution are only in our heads and words. Evolution is far more than a theory, for example it includes the actual reality of how our genes have changed over four billion years of life on earth.
It's just what they are, the scientist should always deal in the truth. I understand you won’t change your opinion on the epistemology of whether reality is dependent on the mind, since your views are abundantly clear on that. However, saying there is no more to reality than just concepts and theories remains a debatable point about the OP questions, such as “Is time simply what we read off of a clock, or is there more 'real' meaning?” There is far more to time than what we read off a clock, which solely reflects interpretation of the relation between the earth and the sun.
Second of all, I have no idea what you mean that some things can be proved wrong and other cannot. Science has never been about any of that, it has always been about testing theories. Let me give some examples. Epicycles were proved wrong. Classical mechanics was proved wrong. Current scientific consensus may be proved wrong in the future, but at the moment it cannot be proved wrong. The fact that science has accurately measured the number of seconds in a year and its rate of change cannot be proved wrong because it is true.

Of course, as did Newton's gravity, classical particle locations, and the concept of the identity of an electron. That's why I supplied that list of things that fit a high goal of "true knowledge", but are wrong. I'm not sure you quite get science, or what "true knowledge" constitutes in science. You should look more closely at the history of that pursuit, and being to see it for what it is, not what you might like it to be. You are fighting the last war. Anomalies like those that led to change of consensus about these topics are most unlikely to arise in calculating the ratio of earth’s spin and orbit. There is a difference between settled science and uncertain frontiers.
great discoveries in science can be based in smaller deviations from expectation than that. Do you really imagine the uncertainty about the timing of leap seconds is going to bring great discoveries in science? Great discoveries only happen where the deviation can’t be explained by the old paradigm. That is not the case for terrestrial time measurement at the day/year scale.
The problem with the mean year is that we do know it is incorrect as some kind of absolute "true knowledge." https://en.wikipedia.org/wiki/Tropical_year states “The mean tropical year on January 1, 2000, was about 365.2421897 ephemeris days according to the calculation of Laskar (1986); each ephemeris day lasting 86,400 SI seconds.[1] By 2010 this had decreased to 365.2421891 (365 ephemeris days, 5 hours, 48 minutes and 45.14 seconds).” These are absolute calculations.
any good scientist would say "well, we obviously have one very good theory that gets the answer right to a part in a billion, and now we need to go out and find an even better theory that does not have that significant error."
The general principle of scepticism that you use here to say there will be more accurate calculations of the mean year than those I quoted is a good example of a sound method taken to absurdity.

Ken G
2016-May-24, 02:16 PM
No, that analogy is completely invalid. When creationists say evolution is only a theory, they are arguing that evolution is untrue.No, the whole reason they use the "only" argument is that they cannot argue that evolution is untrue, so they fall back on hyperbole. They are arguing that evolution is not known to be true, is not proven, so it is "only" a way for us to model or think about the situation. And that is of course entirely true, except for the incorrect implication of inserting the word "only." So the situation is precisely the same when someone says that reality is "only" a model, or time is "only" a concept. It is a perfect analogy, and to see it, simply rewrite the following three sentences without the "only:"
Evolution is only a theory ---> Evolution is a theory
What the scientist means by the word reality is only a model ---> What the scientist means by the word reality is a model
Time is only a concept ---> Time is a concept.
See? It's the same principle, all three times. All the statements are perfectly correct, their only problem is the false insinuation that if something is "only" something, then it is somehow invalid or able to be dismissed. Remove the hyperbole, the "only" that was serving no logical purpose in the sentence, and the sentence is just fine.

When I question your argument that time is only a concept, I am saying that your symbolic representation of time is a different thing from time itself, that the map (your concept) is not the territory (time itself). So let's play that little game again-- remove the hyperbole, take out the "only" in your last sentence. What does it say any different now? I mean, is it not perfectly clear that a "concept" already carries the implication you follow it with, that of a "symbolic representation" that is "different from the thing itself"? So what was the "only" doing there? It's just the same as "only a theory." The real problem here is the unscientific concept of "the thing itself", which science does not deal in. Science deals in concepts and experiments, not "things in themselves", pick up any science book to see this.


Evolution is far more than a theory, for example it includes the actual reality of how our genes have changed over four billion years of life on earth. Certainly not, evolution is not more than a theory, it is precisely a theory. The evidence that supports any theory is never part of a theory, it is always part of why we use that theory. That's science.


However, saying there is no more to reality than just concepts and theories remains a debatable point about the OP questions, such as “Is time simply what we read off of a clock, or is there more 'real' meaning?” My personal opinion about what time is is of no consequence, my entire argument centers on what science is, not what time is (outside of the concept of it that is actually used in science). And then we need only look at how science uses the concept of time, and sure enough, the empirical evidence is abundant: time is a concept, that is just precisely what it is, and that is just precisely how it is used in science. You are free to believe, if you choose, that it is something "more than a concept", but you cannot cite any scientific evidence that it is more than a concept. You tried once already, with the mean solar year, and were shown exactly why that is a concept too. The same thing will happen again if you try again, that is my scientific prediction.
Do you really imagine the uncertainty about the timing of leap seconds is going to bring great discoveries in science? I expect it to, yes. (I try to always keep beliefs away from science, but expectations based on evidence are something quite different.) I expect the study of how the rotation and orbit of the Earth change over time to bring great discoveries in science, yes. Indeed, I expect looking closer at things that nonscientists regard as absolute truths will always bring great discoveries in science, that's more or less just how scientific discoveries occur.

Hornblower
2016-May-24, 05:26 PM
In my opinion Ken G is hitting the nail on the head squarely. I do not share Robert Tulip's apparent conviction that precise determination of Earth's orbital and spin rates at a particular epoch are of any special importance in the practice of physics. All we have done here is to determine the ratio of those two rates, and in recent decades the ratios between them and the oscillation rate of an atomic cesium clock. By careful observation, along with some exercises in nuclear physics theory, we have concluded that the clock is the steadiest timekeeper, and we can test theories of orbital mechanics and geophysics against observations of changes in Earth's motions. As I see it, none of this addresses the OP's misgivings about our alleged lack of "understanding of time", whatever that is supposed to mean. I still don't understand what it is that he doesn't understand and thinks we don't understand. I still think of time as nothing more than a self-evident coordinate that is mathematically useful, along with space coordinates, for evaluating our observations of change in the universe around us.

Ken G
2016-May-24, 06:13 PM
Perhaps the OP issue is attempting to build a bridge between that clear and scientifically solid version of what time is, and another version that seems more inevitably true or more fundamentally real. The desire to build bridges like that motivate a lot of philosophical thinking, and can even inform interpretations of scientific theories, but is still an endeavor that is quite clearly separate from objective science. So I'd say that the question quoted in the OP would need to have its goals more clearly established, as to whether or not it is something scientific that they seek, or something beyond science. I think they are basically asking, if time and space are unified into a single manifold in the "true reality", then how can it be that we measure them differently? I'd say the answer is, the fact that we measure them differently means that we regard them as different things, but they can still be mathematically unified in an important way. What that mathematical unification "means" is a very deep issue of relativity, and gets into personal interpretations.

NonMember
2016-May-24, 09:20 PM
Time and space are different

+1

I hate descriptions of relativity that say time is just another dimension. The "c" in the extended Pythagorean formula is just a matter of units, but the negative sign makes a big difference.

Robert Tulip
2016-May-24, 09:25 PM
No, the whole reason they use the "only" argument is that they cannot argue that evolution is untrue, so they fall back on hyperbole. They are arguing that evolution is not known to be true, is not proven, so it is "only" a way for us to model or think about the situation. That is a surprising description of creationist fundamentalists, who mostly do not know quite so much about Popperian falsificationism. They tend to say that evolution is only a theory because God created the universe and they see these theories as incompatible. That deprecation of theory is completely different from my point here that time is actually more than the scientific concept.
Anything that is more than a scientific concept by definition cannot be analysed with the methods of science, so any quest for a “real meaning” of time would require philosophy rather than just science. In looking for philosophical methods, one good theme in relation to the study of time is the distinction used by Kant between “a posteriori” truth, based on evidence, and “a priori” truth, based on logic. A posteriori, after the event, collects our observations under theoretical frameworks into orderly concepts, and is the empirical method of science. A priori, prior to the event, seeks to use pure logic to discern necessary truths that form the universal conditions of experience.
Efforts to define a priori truths are unreliable, as the example of creationism raised by Ken G illustrates, with its a priori use of the concept of God. Similarly Kant thought that space and time are Euclidean absolutes, as a priori necessary conditions of experience, a theory proved wrong by relativity.


the false insinuation that if something is "only" something, then it is somehow invalid or able to be dismissed. Remove the hyperbole, the "only" that was serving no logical purpose in the sentence, and the sentence is just fine. No, that logic is completely wrong. Saying that time is only a concept means that time is not anything else as well as a concept. It does not at all dismiss the concept as invalid, it simply asserts that our concept does not exhaust the reality.
And again, the comparison between creationism and realism is fallacious. Creationism says that evolution is not a true theory at all, while realism says time is more than our descriptions of it.
a "concept" already carries the implication you follow it with, that of a "symbolic representation" that is "different from the thing itself"? So what was the "only" doing there? It's just the same as "only a theory." The real problem here is the unscientific concept of "the thing itself", which science does not deal in. Science deals in concepts and experiments, not "things in themselves", pick up any science book to see this.
Yes, all correct, but the question in this thread is about the “real meaning” of time as distinct from our scientific descriptions. There is an old view in the logical positivism of Rudolph Carnap of the Vienna School that there is no meaning outside science. That is an opinion which has a logical elegance and beauty, but is quite hard to sustain against common sense opinions which routinely see meaning other than the pure scientific description. If we say the real meaning of time is only the scientific description, we are ignoring time itself, and time itself, as Ken G has said “is the unscientific concept of "the thing itself", science does not deal in.”

evolution is not more than a theory
Your comment produces a fallacious elision.
“The science of evolution is not more than a theory” is a true statement.
“The thing itself of evolution is not more than a theory” is a false statement.
In assessing what we can know of the thing itself except through science, philosophy could generate some a priori claims, such as that evolution actually happened, that material causality is universal, that time flows forward, that matter obeys consistent universal laws, that the universe actually exists. The logic of such axiomatic claims is that our scientific experience would not be possible if the claim were false.


empirical evidence is abundant: time is a concept, that is just precisely what it is, and that is just precisely how it is used in science. You are free to believe, if you choose, that it is something "more than a concept", but you cannot cite any scientific evidence that it is more than a concept. “What it is” (ie the thing itself) is not “how it is used in science” (ie the thing as it appears to us). You are now reduced to the contradiction of arguing that a thing itself is not what it is, against the central logical axiom of identity. That is a simple logical proof that there is more to reality than science.
You tried once already, with the mean solar year, and were shown exactly why that is a concept too. The same thing will happen again if you try again, that is my scientific prediction. My point regarding the year was that science has measured the rate of change with such extreme accuracy and precision and reliability and coherence that the opinion that this description may not be knowledge of the thing itself is of a piece with the radical skeptical opinion that the sun may not rise tomorrow. But such opinion can only be refuted a priori, not a posteriori, by philosophy rather than by science, by logic rather than by observation.
I expect the study of how the rotation and orbit of the Earth change over time to bring great discoveries in science, yes. My point was that the tiny deviations between prediction and observation of time could be the result of inaccurate measurement rather than theoretical error, in which case the theory would be absolutely true. But I hope you are right that time will tell to be a fertile research topic.

Ken G
2016-May-25, 02:35 AM
I hate descriptions of relativity that say time is just another dimension. The "c" in the extended Pythagorean formula is just a matter of units, but the negative sign makes a big difference.Right you are, that pesky minus sign has some pretty important ramifications! Indeed, it is arbitrary whether we give the minus sign to the space or to the time, but it must be there somewhere. The way I look at it is, spacetime is threaded with world lines, much like how threads run along a rope. All any individual observer an experience is one of those threads, with all others being inferred from the reports of others and the requirements of reason. So in that sense, the difference between time and space is much like the difference between one thread and another, in a rope. We can say the rope is made of threads, but that doesn't mean the threads can't be distinguished.

Ken G
2016-May-25, 02:41 AM
No, that logic is completely wrong. Saying that time is only a concept means that time is not anything else as well as a concept.Of course that's wrong. Everyone already knows that "time" is lots of things that are not concepts-- it is a word made of four letters, it is the name of a magazine, it is what you say when you want to stop the clock in a sports game, and on and on. Saying "time is only a concept" does not mean we don't understand all those other things that time is. What I've told you is that it is rather silly to say "time is only a concept" because the "only" is pure hyperbole, playing no important role at all. Say it without the "only."

My point was that the tiny deviations between prediction and observation of time could be the result of inaccurate measurement rather than theoretical error, in which case the theory would be absolutely true.Yet for the reasons given above, we know that your hope is in vain. We already know we have both measurement errors, and theoretical errors in naive descriptions of timekeeping.
But I hope you are right that time will tell to be a fertile research topic.It already is, as people who build GPS satellites know quite well. It's almost like you haven't heard of general relativity or Gravity Probe B! Did you see the movie Interstellar? There is much we have yet to understand about time.

Robert Tulip
2016-May-25, 07:36 AM
"time" is lots of things that are not concepts-- it is a word made of four letters, it is the name of a magazine, it is what you say when you want to stop the clock in a sports game, and on and on. Your claim that time is a concept was made in an exclusive way, to imply that the scientific concept exhausts “just precisely” what time actually is. That is not true. The rhetorical examples you provide are not relevant to the relation between the concept of time and what time actually is.
Saying "time is only a concept" does not mean we don't understand all those other things that time is. What I've told you is that it is rather silly to say "time is only a concept" because the "only" is pure hyperbole, playing no important role at all. Say it without the "only." Saying "time is only a concept" means time is not anything else other than a concept. You added in the “only”, for example when you said reality is just another model and time is just a concept. Discussion on whether there is more to time than our models addresses whether anything beyond scientific models has meaning, which is part of what the OP asked about.

You have several times here made statements about what is known as true by science and then illogically extended that to all of reality, such as your claim that “time is a concept, that is just precisely what it is”. Your phrase “just precisely” here is a good example of hyperbole.
There is much we have yet to understand about time.Indeed, but the point was whether the reasons for why the duration of the year is changing contain much that is not understood, or whether that is something that celestial mechanics understands fairly well.

What I really don’t get is how you can reconcile your argument that time is just a concept with your observation that there is much we don’t yet understand about time. Surely things that are not understood cannot be called concepts?

Ken G
2016-May-25, 12:51 PM
Your claim that time is a concept was made in an exclusive way, to imply that the scientific concept exhausts “just precisely” what time actually is.Perhaps you have not understood. I said that time is a concept. That means that in scientific thinking (which I restrict to in my comments in this forum), it is important to recognize that we don't get access to anything that could be called "time itself", we only get our concept, as that is all we can test. I regard that as completely obvious, but for anyone who does not yet know that, the evidence is quite abundant-- they need only pick up a random science book and start reading. That is just how science works, a fact that I wish more people could accept and move on from because I get awfully tired of having to repeat it every time I find someone failing to recognize it.

Hornblower
2016-May-25, 02:02 PM
I can imagine that the current dialog could continue until doomsday without ever being resolved, with no adverse scientific consequences. I remain at ease with everything I have said so far in this thread.