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If time is, as you say, a property of the motion of material things, then an apple 'experiences' time whether you measure it or not, as, even in isolation, its material constituents are vibrating, behaving like tiny clocks. You will have noticed this (particularly with pears) as fruit often goes off when you're not observing it.... it seems to me time is a property of the motion of material things. The apple you mentioned is present whether I measure its dimensions or not. It's an apple. But time isn't present unless I measure it - only the material motion is present apart from the measurement.
However, what if I don't care about a position in space?
If I am wrong, show me time apart from a measurement of it.
It always seemed to me that, for the master clock, they're aiming at increased precision rather than accuracy - they want to get minimum variability of the frequency, whatever it may be. [/pedant] I may have this wrong...Certainly not. All of these clocks are rated to particular accuracies.
Then you are not interested in the number of spatial dimensions.
Well, time is certainly not material in the usual sense.
If time is, as you say, a property of the motion of material things, then an apple 'experiences' time whether you measure it or not, as, even in isolation, its material constituents are vibrating, behaving like tiny clocks. You will have noticed this (particularly with pears) as fruit often goes off when you're not observing it.
So it's spiritual? That's a joke. I realize you didn't meant that. But if it's not material, what is it? Does physics deal with things that aren't material?
What is time?
It deals with things that are physical.
Let's try a different question.
What is weight?
Ah, OK; in that case, I don't really know what you meant. Can you rephrase it?Touche' ... though you cast my post differently than I meant it.
You seem to reinforce my point with this, so I must be missing what you're getting at. I don't think weight is a thing either. It is, as you say, a measured property of the apple ... a description of how particular things interact.
Seems to me a distance measures the separation of two positions in space - which may be abstract, i.e. not relate to any physical (interacting) thing.Time does not interact with the apple, but is a measure of the motion of the apple with respect to some other thing (cesium). Likewise, distance is not a measure of space, but a measure that relates 2 things.
Such measures often have two meanings, the value that we measure, and the corresponding property or relationship that can be measured.I don't think weight is a thing either. It is, as you say, a measured property of the apple.
Or a label for a particular kind of interaction.If I use a scale, weight is a measurement of the distance traveled by the supporting plate as the gravitational force of the apple acts against a spring. Weight is not a thing in itself, but a description of how particular things interact.
Not really seeing where this is going...
No, I think we're in agreement, but maybe have different ideas of what 'real' or 'physical' means, as opposed to material.
I know this is somewhat old news, so my first question is whether there have been any recent developments in the discussion on possible variations in certain physical parameters (fine structure constant, alpha) etc.
https://www.newscientist.com/article/dn19429-laws-of-physics-may-change-across-the-universe/
https://www.newscientist.com/article/mg18324541-100-if-the-speed-of-light-can-change/
Has this idea been largely accepted or rejected? Or is it still something that is unfolding?
But then, my second question would be: If it is possible some of these parameters change, what implications does that have?
I can't show you them if they're abstract; clearly there has to be some initial physical referent, but the points between which the distance is being measured don't have to represent anything physical. For example, a point 3 miles above the centre of the White House is a distance x from a point a mile above the North Pole. A distance can be calculated between any two designated points in space without having to specify anything particular at each point... if distance is a measure between 2 points in space, show me those points or that space independently of anything material.
The observed time is dependent on the position and/or motion of the observer; observers in different inertial frames will measure time outside their frames differently.If, however, time is contingent on the material ... and if the parameters associated with those things (alpha, c, etc.) could possibly change, then time would change with them.
That is contradicted by more recent work: Decay rates of radioactive substances are constant.I see nothing problematic in this. being that we also are beginning to suspect none of the constants are constant.
http://news.stanford.edu/news/2010/august/sun-082310.html
A distance can be calculated between any two designated points in space without having to specify anything particular at each point.
The observed time is dependent on the position and/or motion of the observer; observers in different inertial frames will measure time outside their frames differently.
Care to elaborate on where you think we differ on "physical"?
When is a parameter 'supposed to be' constant? I don't think we have any a priori reason to suppose that anything is constant. But when the evidence rolls in, those determinations can be made. We might suppose that the temperature is constant, but then we see it goes up and down. Not a constant after all. Finding that alpha varies would be more interesting (and unexpected) than finding that the temperature varies, but I don't see how it would be connected to 'our ideas of time'.
No, because I fear it will turn into philosophy, and I'm unarmed. After a tiny amount of google-fu, all I've learned is that "a property is physical if and only if it either is the sort of property that physical theory tells us about or else is a property which metaphysically (or logically) supervenes on the sort of property that physical theory tells us about".
Glad to hear that. Haven't you already forgot the argument on the decay constant of radiometric element?
No, quite. Is that what this is about, whether space is 'real'?That you can abstract the concept of measurement doesn't make space real.
True, people misjudge things; I don't see the relevance.Have you ever been in a boat with no land in sight on a cloudy day? No sun. No stars. No instruments. No GPS. It's an eerie feeling as you realize you have no way to determine whether you're drifting, in what direction, or how fast. People in such situations misjudge all the time.
I don't know what you're getting at. Care to explain?That's not the type of change I'm talking about. You can still calculate how those inertial frames will relate. And what parameter is key to that calculation?
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