studiot

So it is not constant in all cases ?

Nor is it an invariant of the system.

17 minutes ago, Markus Hanke said:

I think it depends exactly what you mean by determinism. What is stochastic about QM is only the outcome of specific measurements - but given some quantum state of a system, plus necessary boundary conditions, its evolution is entirely deterministic.

17 minutes ago, joigus said:

Can prediction be extended indefinitely in principle without appealing to cosmic events?

Both good thoughts, hopefully my response will add some clarification.

There is a cause and effect connection to determinism so if we can consider the very last cause before the effect Joigus comment of how far back can we go along the chain of cause and effect is pertinent.
Does determinism require the whole chain, just part of it, or just the immediate precedent ?

When I said that humanity has never known enough to determine everything, I wasn't thinking of (only) data and the idea that if we knew the state variables of every particle at some time we could calculate the evolution or future history of the universe.

I was thinking rather of our knowledge of the laws we would use to calculate this.

And my counter example from the cuurent time would be dark matter and dark energy, not quantum theory (though obviously qm is not discounted)

13 minutes ago, Eise said:

fixed

Isn't fixed another word for determined ?

9 minutes ago, Eise said:

No. I think you smuggle in another meaning of 'determined'. Like in 'Can you please determine the temperature?', meaning, 'Can you please measure the temperature?'

You could apply the same meaning of 'determined' to a real stochastic process. After a measurement is made, one could say that the value of an observable was determined. But still, the result was not determined, i.e. the result was not fixed by conditions immediately before.

If a process is determined or not does not depend on if it is in the past, present or future. The only thing is that when it is in the past, it will not change anymore.

There is more than one meaning to 'determined' ?

19 hours ago, Angelgarcia12 said:

 

I would like to ask you a question:

Are the following statements True and False:

1. Hydrophobic molecules clump together in water thanks to hydrophobic forces

2. In stereoisomerism, the different D or L configurations indicate the deviation of the polarized light by the molecules.

Someone could explain me why this statements are true or false.

Thank so much

My answer to the first one is not necessarily, but you need to tell us your answer and why you think that since this looks like homework to me.

Is 'free will' not a form of determinism ?

Once we have made our choice and enacted it the result is determined.

Chocolate or Vanilla ?

Once I walk away scoffing my chocolate ice cream the result was determined by my free will.

39 minutes ago, exchemist said:

I had always thought quantum theory knocked determinism on the head, a century ago.

Which is why Einstein found it so disturbing and unsatisfactory.

Yet there seem to still be some who promote it in threads here. Some of these threads have been have been very long and it is now even difficult to determine (pun intended)

what their position actually is.

There have been several threads recently where some dubious statements about the distinction between constant and invariant have been made.

I am therefore posting this thread to examine this issue by discussion.

I am kicking off with a question

An observer is watching the rear end of a train which is receeding a high speed , but not accelerating.

Hanging on the back of the train by a long coil spring is a lamp which is oscillating up and down.

What is the relativistic effect on the spring constant, ie what is the difference, if any, between the spring constant according to the train guard and the observer ?

With the recent debates about determinism v some other explanation of  everything is a belief in determinism unwise ?

I ask this because throughout the entire history of mankind there has never been a time when there was not something known that was unexplained.

Even the God-did-it squad can only say GDI, they cannot say why or how he did it so cannot in all honesty say it was or was not determined.

Likewise those philosophers and scientists who cleave towards the mechanistic 'clockwork universe' have to admit that they cannot definitely conclude that everything, because if their their best explanation is ' we believe there is an explanation, we just don't know what that is' this is not conclusive.

1 hour ago, martillo said:

That is what you say. You have to demonstrate that to the Physics' community.

Yes, I'm working in a particles' model that seems could explain the wave-like behavior of them but I'm well aware it is a huge task. You seem to still be at the state of "storm of ideas" and you can't be so sure your model will really work as you insist to say. You have to demonstrate that.

You are definitely moving forward.   +1

26 minutes ago, lidal said:

will see if 'invariance' vs 'constancy' makes any difference.

My freezer is kept at a constant temperature of -20^oC, but this is not invariant as I can turn the control knob up or down.

15 minutes ago, CarlD said:

You are trying to go down to a level which even the best physicists would have issues with

Since you clearly think you know better than anyone else and are not interested in what they have to say I wish you goodnight and pleasant dreams.

1 hour ago, studiot said:

Yes indeed knowing the difference between invariant and constant is vitally important.

Perhaps I should add related words 'steady' and 'uniform' to the list of oft misapplied words.

12 minutes ago, CarlD said:

I answered your question about waves as well as I could. Maybe you want to rephrase it if you were going elsewhere?

Do you mean  this ?

1 hour ago, CarlD said:

Waves are disturbances spreading out in the otherwise more or less flat geometry of something. In the case of photons, disturbances of spacetime, moving at the speed of light. 

Just what is a disturbance of spacetime ?

18 minutes ago, CarlD said:

Gravitational fields vary with the mass of objects. So I assume you call them time varying?

If you don't understand something ask don't guess.

Of course I don't call them time varyiing. Why would I ? Is there any evidence of gravitational field varying with time ?

A gravitational field is however a good example to make my point.

When viewed as a field (it can be viewed or described in other ways) the quantity of interest is called the gravitational potential. This potential has a definite, measurable value at every point in the gravitational field. It is an example of a potential field, with some special properties, one being that it is a conservative field.
Other fields may also be assigned to the region of space occupied by the gravitational field.
One such is the field of gravitational force acting on a material body. Another is an example of a direction field as force is a vector and as such has a direction at every point in the field.

So you see, fields can be pretty complicated things, and so far we have just opened the book at static fields.

The answer to my question 'what is waving' is the quantity of interest. This quantity may be a field quantity (ie part of a field) or it may not. It may be a material quantity such as water or it may be non material such as displacement or amplitude.

13 minutes ago, CarlD said:

I'm pretty sure my definitions are compatible not only on the level of language, but also on the level of physics, where people often imagine fields as an abstract thing, even though we know already since Maxwell that they are related to waves.

People used to imagine the atom as a plum pudding before Rutherford.

I asked you what was waving., but received no answer.

My question was not a joke but a subtle hint as to the proper definition of a Field.

A Field is a region of 1, 2, or 3 dimensional space where some quantity can be defined and assigned a definite value.

Most primary fields are static which means that these values do not vary.

If the values are functions of another parameter such as time they are called time (or whatever) varying fields.

24 minutes ago, Bufofrog said:

I believe you have been informed several time that the invariance of light has been tested.  I also believe you have been informed multiple times that the term is invariance not constancy.  You seem to be trying very hard to ignore all attempts to help you.

Yes indeed knowing the difference between invariant and constant is vitally important.  +1

10 minutes ago, CarlD said:

field has a special meaningWaves moving through an area. The waves have a form, thus they slightly increase distances for anything crossing them. Which gives us curvature of spacetime or gravity, and is responsible for more where frequencies are higher or other factors apply.

fields have a special meaning iIn a wider sense, any physical effect from such waves which works at distances (probably all). Like resonance creating magnetic properties/fields or spin creating electric properties/charges.

I thought you might be using unusual definitions for your words.

In both Mathematics and Physics the term  the term field has special meaning, (unfortunately different in each) but neither meaning is the same as yours, whcih is more like a rolling mist.

I also do not think your use of the term resonance is the usual one.

Just as a matter of interest what do you think is 'waving' when you speak of waves ?

It is very difficult to hold a sensible conversation when you are not both speaking the same language.

2 hours ago, CarlD said:

I'll try to come up with more.

what exactly do you imagine  field to be ?

49 minutes ago, Killtech said:

i don't see the value in using odd numbers for this particular example, so i rounded them for convenience.

2.611, 3.533 and 1.0067 are no odd numbers ?

Pity if instead you didn't post the speed of sound you employed and the fact that you changed my figure of 45 m/s to 50 m/s.

That would have saved me looking up the speed of sound on Google and accepting the first reasonable academic answer listed.

Of course resulting in pointless exchanges of posts.

You still haven't shown how your claim that this method of analysis (Which is classical ) supports a Lorentz transformation into any inertial frame I choose.

I choose to work in the ground frame (as you did) and tranform this into the wind frame (as Arago et al did) and I arrive at the fact that the time of transit is dependent on the wind speed, as otheres did.

If you think there is a Lorenz tranformation then it should work and give these figures for the transformation to the wind frame.

So what is x' = ?(x, t)

                  t'  = ?(x, t)

in your system ?

For interest here is Professor Beiser's alternative and simpler explanation as to why other waves are not a good analog (which was my point).

The behaviour of light waves is unique.

8 hours ago, Killtech said:

Now we have to translate everything into a different geometry first. the distance between the flag poles has to be measured first and more importantly sonic means only. So we measure how much time sound takes to go from one flag post to another and back. In calm weather that will take roughly 6 seconds. in windy conditions it's 2.61s in one direction and 3.53 in the other, so 6.04s in total - so it would seem that flags have moved away from each other.

This sound authoritative because it contains number.

But when I analyse those numbers I find disturbing discrepancies.

Firstly in calm weather the outward and return journey should be identical so exacly half of 'roughly 6'.

In fact the double journey takes 2000 / 346 or 5.780 seconds.

Now this double journey should cancel out any effect of medium motion so if I add up your to outward and return times I make 2.61 + 3.53  = 6.14, not 6.04 as you have.

Either way this is quite different from my value.

Furthermore adding my outward and return times 1000 / (346 + 45) + 1000 / (346 - 45)  =  2.55754 + 3.32226  =  5.88 seconds.  Comfortingly close to my undisturbed double journey value.

You seem to have forgotten my comment from Einstein.

8 hours ago, studiot said:

This is the key result implied but not explicitly stated (you have to think about it to find it)  in the first postulate in Einstein's theory of relativity.

I see I owe you an apology here:  it is actually the second postulate.

Quote

Einstein :  On the Electrodynamics of Moving Bodies

 

..And also introduces another postulate, which is only apparantly irreconcilable with the former, namely that light is always propagated in empty space with a definite velocity c, which is independent of the state of motion of the emitting body.

What he does not describe is the effect of motion of any transmission medium, which is different from other waves where this motion has to be taken into account.

This is the key difference with light (in empty space). It has no transmission medium.  So c will be invariant in all frames.  there is nothing to add to it.

An acoustic wave between A and B however, depends also on the motion of the transmission medium.

15 minutes ago, dan_boi said:

What field do you work in?

I retired a few years ago.

3 hours ago, Sensei said:

But his name was Lorentz..

What would I do without other members to correct my atrocious spellung ?

Thans +1

3 hours ago, Killtech said:

i gave you the task to apply Lorentz trafos to the raw equations and verify that it stays invariant. Lorentz trafos are merely coordinate trafos and there is no physics involved in applying them - its just pure and simple math.

you are using SI lengths and therefore a different geometry. The analogy works only if you construct the units of time and length in an analogue way via acoustic signals.

Now we have to translate everything into a different geometry first. the distance between the flag poles has to be measured first and more importantly sonic means only. So we measure how much time sound takes to go from one flag post to another and back. In calm weather that will take roughly 6 seconds. in windy conditions it's 2.61s in one direction and 3.53 in the other, so 6.04s in total - so it would seem that flags have moved away from each other.

However, we still measured time with an SI clock and have to account that a geodesic sonic clock tick rate will be slightly slowed down by the windy conditions. In fact, a geodesic clocks works quite the same setup as your flags setup and thus we can calculate that it is slowed by a factor of 1.0067. Appling that to the sonic distance, we yield that in fact the flag poles did not move away from each other in soncic-meters as well.

If we now also translate the SI seconds into acoustic seconds in either case, we yield that in both times it took the acoustic signal 6 sonic-seconds to go back and forth, independently of the wind. So in terms of sonic proper time, there effect of the wind is irrelevant. Tada, the magic of frame and location dependent units in relativity.

 

we can also reverse the situation and make a similar experiment with light. instead of the calm weather take put one flag experiment into the rest frame of the barycentric coordinates, and the other in a frame moving with a given speed relative to that. Now we are stubborn and instead of providing the results of the experiments in time in proper time of the specific frame, we do it as IAU would do and give the result in TDB coordinate time. We now realize that in that time reference it took light a different amount of time to get back and forth.

Wow.

And here am I thinks this is easy Physics.

It is easy to find the speed of sound in still air (ignoring temperature effects) as 346 m/s

So in the ground frame both source and observer are stationary as is the transmission medium.

So the time of flight is simply 1000/346 = 2.890 seconds.

In the case including the wind, the wind carries the sound pulse forward at an additional 45 m/s so this pulse reaches the observer at 1000 / (346 + 45) = 2.558 seconds.

Now a transformation is to another coordinate system and the only one that makes sense here to use is the coordinate system comoving with the wind.

Here we have that the observer appears to be approaching the source at 45m/s but the sound is moving at 346m/s in the frame of the wind.

So the sound will appear to travel the distance (already measured as 1000m in both systems) in 1000 / (346 +45) = 2.558 seconds.

How is that a Lorentz transformation from the ground frame to the wind frame ?

1 hour ago, Killtech said:

Oh, then i leave it open to you to prove how the linearized 2nd order PDE acoustic wave equations is mathematically not Lorentz invariant to the corresponding Lorentz group. 

You have to read Einsteins postulates more carefully and notice how there is  no postulate about what clocks and rods have to be used. In fact that is left entirely open and instead those are constructed right from the postulates themselves. The construction i quoted does exactly that and as one can see, it works quite the same when applied to another wave signal. The reason is that Einsteins first postulate can be safely assumed for any simple physical model of waves when there is no other physics (particularly no other wave equations with a different propagation speed) that serves as a reference. That is why Einstein postulates in fact work for a much wider range of various wave equations when they are treated in isolation from other physics and if you construct the clocks and rods implied by treating the wave signals as null geodesics of some wave-specific geometry.

Through the construction of proper clocks and rods, any wave equation becomes Lorentz-invariant even in general non-linear case. You can just always find a geometry which assures that.

OK  consider this experiment:

There is a flagpole 1000m from where I am standing with a sound pulse apparatus.

My assistant is standing by the flagpole with timing apparatus.

At the beginning of the experiment all is calm and still.

Then storm Ciaran arrives and there is a wind directly towards the flagpole at 45 m/s.

Calculate the time of transit of my sound pulse to my assistant in the cases of still air and of the storm wind and explain how this difference exhibits Lorenz invariance.

11 hours ago, Killtech said:

Since we restricted ourselves to acoustic physics only

Sound waves do not obey Lorenz transformations.

This is the key result implied but not explicitly stated (you have to think about it to find it)  in the first postulate in Einstein's theory of relativity.

1 hour ago, lidal said:

Since the time difference to be measured (t₂ - t₁ ) is extremely small, typically tens of pico seconds,  I propose taking many measurements and averaging to suppress all random errors.

Since you propose measuring a time difference of the order of 10-11 seconds, please explain the electronics of your 'start pulse', which must be several orders of magnitude smaller.

Please also evaluate the accuracy to which the synchronisation must be achieved.