Change

[Resha Caner]

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?

 

[essentialsaltes]

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?

I hadn't heard of this. Wiki offers a little more, saying that Webb followed up with a second study in 2011 claiming a variation in alpha dependent on both redshift and direction. Webb's own website notes an unpublished paper from 2012, and then nothing. It's hard to judge the silence since then. Maybe he's dropped the issue, having become unconvinced of its reality.

But then, my second question would be: If it is possible some of these parameters change, what implications does that have?

At the level Webb was reporting, it wouldn't have much practical significance, but it would provide new insights into something more fundamental going on with the forces of the universe. The theorists would get busy trying to come up with explanations for how this might occur. Hard to say where that might lead.

 

[Resha Caner]

I hadn't heard of this.

That surprises me. That you were unaware does seem to speak to the "silence" though. The findings probably don't amount to much.

But are your comments specific to alpha or to the idea of changing universal parameters in general? Have you heard of evidence that other parameters might experience change?

At the level Webb was reporting, it wouldn't have much practical significance, but it would provide new insights into something more fundamental going on with the forces of the universe. The theorists would get busy trying to come up with explanations for how this might occur. Hard to say where that might lead.

OK. I was curious if it might have an impact on ideas of "time"?

 

[essentialsaltes]

But are your comments specific to alpha or to the idea of changing universal parameters in general? Have you heard of evidence that other parameters might experience change?

I can't say I'm super-knowledgeable about the topic, but as far as I know, physical constants seem to be constant in time and space on scales of billions of years and billions of light years. If you get real close to the Big Bang, there's not much evidence to go from, so it might be more of an open question.

OK. I was curious if it might have an impact on ideas of "time"?

I don't see how constants changing in time would affect our idea of time.

 

[lesliedellow]

If they are changing, cosmologists would have to do some big time rethinking. They might even manage to lose dark energy and dark matter along the way.

 

[Resha Caner]

I don't see how constants changing in time would affect our idea of time.

That's a good point. Philosophy of science would say a scientist is much more likely to challenge the instance than the principle - and it makes sense to do it that way.

But I wondered if indications of a parameter changing when that parameter is supposed to be constant would be enough to challenge a principle such as time. Maybe not.

 

[essentialsaltes]

But I wondered if indications of a parameter changing when that parameter is supposed to be constant would be enough to challenge a principle such as time. Maybe not.

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'.

 

[Resha Caner]

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'.

Then let me ask you 2 questions:
1) What is time?
2) How is time measured?

 

[essentialsaltes]

Then let me ask you 2 questions:
1) What is time?

May have to take that one to the philosophy section.

Time is one of the four coordinates used to locate events in space-time.

2) How is time measured?

With a clock?

We measure durations with a clock, just as we measure distances with a ruler. Hopefully, that's what you mean by measuring time.

We can generalize the idea of durations and distances into a space-time interval, which combines space and time. The negative sign in the equation picks out the time like coordinate (time) from the three space like coordinates (x, y, z). So another way to describe or define time is that it is the one coordinate of our four-dimensional universe that enters into the metric with a minus sign.

 

[Resha Caner]

May have to take that one to the philosophy section.

Nope. I wasn't asking the question in a philosophical sense.

Time is one of the four coordinates used to locate events in space-time.

All I wanted was a definition such as this. So, time is a coordinate in a "Space". That gets a bit convoluted when one names that "Space" as "space-time", but I think we can keep it straight if we use a capital S for the general mathematical concept and lower case s for the specific space-time ... or maybe you have some other synonym for Space that would work better.

Anyway, the definition is a mathematical one. Is there any connection to the material?

With a clock?

I'll assume that wasn't meant to be flippant. What is the definition of a second? (That's a somewhat rhetorical question as I expect we both know the definition, but let's throw it out there to give us a common reference.)

 

[lesliedellow]

So another way to describe or define time is that it is the one coordinate of our four-dimensional universe that enters into the metric with a minus sign.

Except that what physicists call a metric is no metric.

Hobby horse of mine.

 

[essentialsaltes]

Anyway, the definition is a mathematical one. Is there any connection to the material?

Looking about us, the material universe appears to have three spatial dimensions: length, breadth, height. Each of those can define an axis of a three dimensional space. Time also seems to have a single dimension. Things can be before or after, but events all happen in a sequence. So only one number is needed to denote time. So at least mathematically, we can easily tack on one numerical dimension of time to our three dimensions of space. Just as an abstract space.

But it certainly seems like there is more to this than just bookkeeping. Maxwell's equations are invariant under the Lorentz transformation, which mix space and time. Just as a rotation about the z-axis would mix x with y. Physics looks 'the same' whether you face north, or rotate 90 degrees and face east. And Physics also respects the symmetry of the Lorentz transformation. What this means, as Einstein showed, is that space and time do really mix together, and behave in the strange ways that relativity has revealed: shrinking rulers, and slowing clocks. So it seems that tacking on time to space is not just a bookkeeping exercise, but something that is really real about the world we live in.

What is the definition of a second? (That's a somewhat rhetorical question as I expect we both know the definition, but let's throw it out there to give us a common reference.)

Apparently, the second is defined as "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."

 

[essentialsaltes]

Except that what physicists call a metric is no metric.

 

[Resha Caner]

So it seems that tacking on time to space is not just a bookkeeping exercise, but something that is really real about the world we live in.

That's fine. The dimensions of space are no more real to me than the dimension of time, so if it is mathematically parsimonious to associate them, have at it.

... the material universe appears to have three spatial dimensions ...

However, I'll focus on this comment. There appear to be 3 dimensions. I guess I don't see any dimensions, though I know 3 is the convention. I think that convention comes from a Newtonian* heritage of working with independent bodies under a criteria for 1:1 correspondence between body and reference. However, as I learned in my sophomore engineering classes, for some machines it is more mathematically convenient to use something other than 3.

So, for some very real, very material things I can easily describe them with other than 3 dimensions. There is nothing that physically forces me to use 3.

Apparently, the second is defined as "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."

Yes, so clocks are material. Is there any way to measure time without a material clock? And why was cesium chosen? Maybe because it's stable? Constant?

- - -

* Rather than Newtonian, maybe it's a Cartesian heritage, or Aristolean. I'm not trying to argue a particular history here, but just that it is historically (rather than physically) based.

 

[essentialsaltes]

That's fine. The dimensions of space are no more real to me than the dimension of time...

However, I'll focus on this comment. There appear to be 3 dimensions. I guess I don't see any dimensions, though I know that is the convention.

This seems very peculiar to me. I mean, I take what you mean about Descartes laying coordinate axes over space to measure it, but really this idea that there are three spatial dimensions is quite intuitive. I hardly feel compelled to quote sources like Newton or Descartes or Euclid saying, "A solid is that which has length, breadth, and depth."

Don't apples and automobiles have length, breadth, and depth?

However, as I learned in my sophomore engineering classes, for some machines it is more mathematically convenient to use something other than 3.

So, for some very real, very material things I can easily describe them with other than 3 dimensions. There is nothing that physically forces me to use 3.

Nothing forces this description, no. We can use all sorts of 'coordinates' to describe things. But I was careful to say "three spatial dimensions". To locate a unique position in space requires no fewer than three coordinates (and using more than three would be redundant). This apple is at such and such a longitude, lattitude, and height above the ground. Or it's this far from the floor, this far from that wall, and this far from that other wall. Or to get that apple, turn 45 degrees to the right, walk 8 steps, and reach two feet above your head.

Yes, so clocks are material. Is there any way to measure time without a material clock?

You're sure you don't want to ask this in Philosophy? I really don't know what you mean. I can estimate the passage of time by counting out loud or in my head, but I need a material head to do that. We've established that we measure time with clocks, and if you have an immaterial clock, you don't actually have a clock. So a material clock would seem to be necessary.

And why was cesium chosen? Maybe because it's stable? Constant?

Yes. It's quite stable to the limits of our ability to test it (because that would require an even better clock). I think cesium is particularly suitable because it has only one valence electron, and several shells isolating it from any effects from the nucleus, but I don't know that cesium is the best element possible.[/quote][/quote]

 

[lesliedellow]

Yes. It's quite stable to the limits of our ability to test it (because that would require an even better clock). I think cesium is particularly suitable because it has only one valence electron, and several shells isolating it from any effects from the nucleus, but I don't know that cesium is the best element possible.

Assuming that it is not subjectively obvious that it is fluctuating wildly, you end up defining something to be 100% stable, don't you?

 

[Resha Caner]

This seems very peculiar to me.

My conception of space was formed by a father who taught geometry ... so, yes, I'm a little peculiar.

To locate a unique position in space requires no fewer than three coordinates (and using more than three would be redundant).

I changed the emphasis of your quote to highlight the point I am trying to make. If one includes orientation as essential to the idea of a "position" in space then the minimum is actually the 4 Euler parameters: http://mathworld.wolfram.com/EulerParameters.html

However, what if I don't care about a position in space? What if (as I did for my graduate thesis) I want to find an optimal path for a robot? The optimal path may cause certain parts of the robot to touch the same point in space more than once. As such, I am no longer concerned with some Cartesian Space. I am concerned with the degree-of-freedom space of the robot - something that is just as "real" as Cartesian Space. In such instances, it is often more mathematically efficient to use something other than 3 dimensions.

If I do that, the description of the path is no longer unique according to a Cartesian description, but it is unique from the perspective of the robot's space. And what do I care about? Well, in this case, the robot.

You're sure you don't want to ask this in Philosophy?

I'm sure. The examples I'm using here relate to science (and engineering).

So a material clock would seem to be necessary.

Yes, I would agree. So, 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.

If I am wrong, show me time apart from a measurement of it.

 

[Resha Caner]

Assuming that it is not subjectively obvious that it is fluctuating wildly, you end up defining something to be 100% stable, don't you?

Yep. Everything becomes dependent upon that assumption.

 

[FrumiousBandersnatch]

The current physical constant values, in conjunction with current big bang cosmology, do a pretty good job of predicting various observed features of the universe, particularly the distribution of the cosmic microwave background radiation, so there's no particular reason to suppose they've changed significantly. Perhaps there are other models that do an equally good or better job with varying 'constants', but I don't know of any.

In science, time is what clocks measure. The fundamental physical laws seem to be time reversible; the arrow of time, past-to-present-to-future, emerges as a result of an entropy gradient - the entropy of the universe was much lower in the past than it is now, and entropy tends to increase as a probabilistic statistical effect (very crudely, entropy is the measure of disorder in a system) as ordered systems tend to become disordered. In a sense, the universe unwinds... complexity is a feature of mid-range entropy, enabling maximum dissipation of energy and so rate of increase of entropy, until it dies away as the entropy gradient reduces towards equilibrium (maximum entropy).

We observe three spatial dimensions and one temporal dimension that are codependently linked as Einstein's 4D spacetime. There are theories that require additional spatial dimensions; these can be undetectable and inaccessible if they are curled up tightly at the smallest possible length (much as a 3D cylinder might appear to be a 1D line from far enough away).

 

[essentialsaltes]

Assuming that it is not subjectively obvious that it is fluctuating wildly, you end up defining something to be 100% stable, don't you?

Certainly not. All of these clocks are rated to particular accuracies.