1 Two new sections to 'Einstein's thought experiments' in Wikipedia

2 Two new sections to 'Einstein's thought experiments' in Wikipedia

I have studied the foundations and history of SR and GR, but not the foundations and history of quantum mechanics. I have long known, rather vaguely, that Einstein was an important contributor to the latter, without details, and had never heard of the "Bubble paradox". Your additions are well written and informative.

Tom Roberts

3 Two new sections to 'Einstein's thought experiments' in Wikipedia

4 Two new sections to 'Einstein's thought experiments' in Wikipedia

5 Two new sections to 'Einstein's thought experiments' in Wikipedia

Likewise. Interesting stuff, I appreciate the time you've devoted to it.

-- Jan

6 Two new sections to 'Einstein's thought experiments' in Wikipedia

Thanks likewise.

I find that there are quite a number of thought experiments "attributed to Einstein" for which I have found no documentation that he had actually originated them. It's sort of like all the famous Yogi Berra malapropisms that really were inventions of other people. :-)

My most important message is that Einstein was arguably the most important single contributor to the "old" quantum theory, and that even when wrong, when his intuitions failed him as to how quantum mechanics should work, his failed intuitions have pointed to phenomena that even today are transforming physics.

In the future, as my mastery of physics topics *gradually* increases, I hope to expand the article with more documented thought experiments...

7 Two new sections to 'Einstein's thought experiments' in Wikipedia

> >	Also "Reflection 4 - Thought experiments versus hypothesis"

You CLEARLY do not understand the Bubble Paradox. This is absolutely ***NOT*** a beta-emission versus electron capture thought experiment with neutrino involvement. *** SHEESH! ***

Talmudic analysis must be bolstered up by a wealth of accurate background knowledge and the use of good judgment.

You apparently have neither, and thus seem capable of nothing but "pilpul".

8 Two new sections to 'Einstein's thought experiments' in Wikipedia

9 Two new sections to 'Einstein's thought experiments' in Wikipedia

Dear PCH,

Please try to combine your comments in one message.

If this is not what you mean: p + e- -> n + nue + photon then clearly explain in the Wikipedia Bubble Paradox article what you mean. Of course, this can also a problem on my side.

Nicolaas Vroom

10 Two new sections to 'Einstein's thought experiments' in Wikipedia

This is absolutely and totally a problem on your side. You do not understand how X-rays are produced.

11 Two new sections to 'Einstein's thought experiments' in Wikipedia

Forget temporarily this Reflection. More important is here: Reflection 4 - Thought experiments versus hypothesis

>	You completely goof up your analysis. https://en.wikipedia.org/wiki/File:Train_and_Embankment_Thought_Experiment_And_Its_Inverse.gif

12 Two new sections to 'Einstein's thought experiments' in Wikipedia

You are very confused.

13 Two new sections to 'Einstein's thought experiments' in Wikipedia

Dear PCH

Thanks for your comments. What we are discussing here are thought experiments. Specific thought experiments performed by Albert Einstein. You are apparently an expert on this issue of X-rays. If that is the case you should write somewhere else in Wikipedia all that you know.

Still, it is my opinion that thought experiments are not, the way to perform science.

>	I presume a certain minimal level of science literacy among my readers. The article is not written for high school students but should be totally accessible to someone who has gone through an introductory college physics or college chemistry course.

This sentence: "(b) The atom emits a spherically radiating electromagnetic wave." is not clear. IMO that is the problem. Also this sentence: "Associated with each atom was a "virtual radiation field" that determined an electron's emission probability." is not clear. Again IMO that is the problem.

Nicolaas Vroom.

14 Two new sections to 'Einstein's thought experiments' in Wikipedia

15 Two new sections to 'Einstein's thought experiments' in Wikipedia

>

Dear PCH Thanks for your comments. What we are discussing here are thought experiments. Specific thought experiments performed by Albert Einstein. You are apparently an expert on this issue of X-rays. If that is the case you should write somewhere else in Wikipedia all that you know. Still, it is my opinion that thought experiments are not, the way to perform science.

They are not a means of performing science. They are a tool to help one logicalize the consequences of an assumed set of preconditions.

16 Two new sections to 'Einstein's thought experiments' in Wikipedia

>	Associated with each atom was a "virtual radiation field" that determined an electron's emission probability.

The above statement has *NOTHING* to do with the Bubble paradox. It has to do with the BKS proposal, which represented a desperate attempt by Bohr, Kramer and Slater to "explain away" Compton's experiment. Hardly anybody in 1924 took BKS seriously, although the prestige of the authors was such that nobody was going to say that Bohr, Kramer and Slater were crazy. It took EXPERIMENT to disprove BKS.

17 Two new sections to 'Einstein's thought experiments' in Wikipedia

In the original scenario M observes that light arrives simultaneously. Let me call this event t1. Light does not arrive simultaneously at M'. Let me call these events t2 and t3. t2 comes before t1 and t3 later as t1.

>	The basic facts do not change with a change in reference frame. My point is that you MUST include second order effects in the analysis.

When I include physical length contraction in the moving rod (l'=l*(1-v^2/C^2)) the two events t2 and t3 will merge together and become t4 As such the moving observer M' will observe the two flashes simultaneously. The observer M not. This because the sparks are not generated simultaneously M his frame (considered at rest).

>	You confused yourself when you tried to jump off with your "three observers" oral arguments, which you put together without carefully considering the physical setup.

There is already a problem when you have two trains and two observers. (you make this a symmetrical problem as you do) In principle, both can claim that they are at rest and both can claim that they observe the two flashes simultaneously. Only one can speak the truth. Only a real experiment can verify who speaks the truth.

As part of this discussion, you can also consider clocks. A clock at rest by M will tick faster as a clock by M' When no length contraction is considered the clock by M' will tick slower as M. When length contraction is considered the clock by M' will tick faster as without LC but still slower as M. Only real experiments can decide.

18 Two new sections to 'Einstein's thought experiments' in Wikipedia

19 Two new sections to 'Einstein's thought experiments' in Wikipedia

>

In Scientific American of 2 February 2020 there is a beautiful article about "The enigma of aerodynamic lift" The article describes two 'competing' theories to explain why airplanes can fly. For a review see: https://www.nicvroom.be/ScientificAm_February_2020_The_enigma_of_aerodynamic_lift.htm In that review, I try also to give my own explanation. I don't know if my explanation is better.

The problem isn't that we can't model aerodynamic lift. Detailed solution of the Navier-Stokes equations does an *extremely* good job of modeling lift.

The problem is translating the equations into words.

>

Simulations are also a sort of thought experiments. In order to simulate vissible length contraction I have written a VB program. To get an idea what it does please select: https://www.nicvroom.be/VB%20Train%20operation.htm We can consider two types of length contraction: Vissible and Physical. Vissible length contraction is like an illusion: You can see it but it is not real. In the simulation this is demonstrated as Length contraction when an object moves away from an observer and as Length expansion when an object approaches an observer. Vissible Length contraction involves the speed of light. Physical length contraction implies that the physical length of an object changes. Physical length contraction in the simulation is demonstrated by setting a parameter to ON. Physical length contraction requires a physical explanation. Physical length contraction does not involve the speed of light. The question is if physical length contraction has any thing to do with the concept of 'a rigid rod', as if when the train or a clock is considered 'rigid' there exists no physical length contraction. IMO physical length contraction can only be demonstrated by means of a real experiment and not by any thought experiment.

You STILL misunderstand the purpose of thought experiments after this has been explained to you MULTIPLE TIMES!!!!

20 Two new sections to 'Einstein's thought experiments' in Wikipedia

The writer of the Scientific American paper uses the Bernouilli's Theorem and Newton's Third Law to explain that there is no simple one-liner answer why an aircraft can fly. Regarding the Navier-Stokes equations he writes on page 42: Still, they do not by themselves give a physical, qualitative explanation of lift.

> >	IMO physical length contraction can only be demonstrated by means of a real experiment and not by any thought experiment.

>	You STILL misunderstand the purpose of thought experiments after this has been explained to you MULTIPLE TIMES!!!!

Then tell me in a couple of sentences what the purpose of thought experiments are and if there are limitations to its use.

IMO a thought experiment is a story which describes what can happen if you perform a certain experiment often based on certain assumptions. The problem is that in reality there is no certainty that this actual happens.

It is clear that if you perform the train experiment as described by Einstein that the observer considered at rest, at the platform will see the two flashes simultaneous. It is also clear that the observer at the train will not see the two flashes simultaneous.
However, it is also possible, when you consider the same experiment, that the observer on the train claims that he is at rest and observes the two flashes simultaneous and not the observer on the platform. Only a real experiment can settle this issue.

You can discuss, with a thought experiment, what will be observed if there is physical length contraction involved. To actual test, what is predicted, can only be decided by a real experiment. Only when this issue is solved, the problem if there is length contraction involved, as part of the behaviour of a moving clock, can be tackled.

IMO the use of thought experiments is limited

Nicolaas Vroom

21 Two new sections to 'Einstein's thought experiments' in Wikipedia

22 Two new sections to 'Einstein's thought experiments' in Wikipedia

23 Two new sections to 'Einstein's thought experiments' in Wikipedia

> >	IMO a thought experiment is a story which describes what can happen if you perform a certain experiment often based on certain assumptions. The problem is that in reality there is no certainty that this actual happens.

>

That last sentence is absolutely true. Thought experiments tell you nothing about how nature actually works. That is left to real experiments. This is why arguing for or against the validity of a theory using thought experiments is pointless. Their popularity on this group is based solely on their accessibility and low effort. What they DO provide is a clearer understanding of what the theory actually says, from a logical perspective if consequences derivable from premises. It�s telling that so many people get balled up and confused with thought experiments; that�s an indicator of how poorly those people really understand the theory.

I fully agree with you. The whole issue depends on how to perform science.
IMO the first step is a qualitative approach and the second step is quantitative.
During the qualitative approach, for example, you try to unravel the details of the reactions involved. You also try to change certain physical conditions to see how they influence the outcome.
In the quantitative approach, you try to stick numbers on the quantities involved and try to unravel the mathematical details of the reactions. When you have a certain type of mathematical equations which describe the processes considered you can also try to optimize the outcome. As a benefit, you can try to make the processes more stable.

Along this same line I liked the article in Scientific American around the question why do airplanes fly. I agree with the approach that the use of existing laws is tricky. The problem is that first of all that any existing law is a description of a physical process, that means you have to know for which types of processes the law applies, which in fact you have to indicate to the reader. This makes a clear explanation difficult.
The second reason is that it is much better to try to explain something bottom-up, from scratch. The starting point should be to explain all concepts used in detail, and why. When you do that the whole explanation becomes more logical and easier to accept.

Nicolaas Vroom

24 Two new sections to 'Einstein's thought experiments' in Wikipedia

25 Two new sections to 'Einstein's thought experiments' in Wikipedia

> >	I fully agree with you. The whole issue depends on how to perform science. IMO the first step is a qualitative approach and the second step is quantitative.

>

A lot of amateurs, especially the ones who post here, would love for this to be true. They desire this because the qualitative is easier and smacks of philosophy, which is something anyone can do. The game plan is then to ask for buy-in and endorsement of the qualitative proposal, and then hope someone else picks up the quantitative ball. Unfortunately this is not how physics really works. Nor should it. There is a key sanity check that is quantitative even before the conceptual framework progresses beyond idle speculation. If physics were easy, then people wouldn�t need a ton of training to do it.

Let me try to explain the qualitative step better. It is definite not easy. Consider the Schr�dingers cat thought experiment.
Is it important to use a cat in that experiment: No.
Is it important to use a poisson to kill the cat: No.
Is it important to use a glass container filled with poisson: No.
Is it important to do this whole experiment in isolation: No.
The only thing that is important is to have a radioactive element and to measure its decay time.
How do you do that (approximately): You take a piece of radioactive material, a Geiger counter and a stopwatch. Each experiment consists of starting both the Geiger counter and the stop watch. As soon as when there is a count you stop the stop watch. This you repeat 1000 times and you calculate the average decay time. You take a different piece of the same material and you repeat. You do this 1000 times for different siezed pieces. All of this belongs to the qualitative step. You can also call this data gathering.

It is the same as if you want to predict the position of the planets First you must collect the positions of all the objects considered. based on visible observations.

Step two in the Schr�dinger cat experiment is to define the mathematical equation which describes the average time between of the first radioactive decay as a function (material, amount, age i.e. degree of pollution?) This is the quantitative step.

The Schr�dinger type experiment now becomes: You measure the amount of material you have and using the equation you calculate the average (first) decay time. For example this is 30 seconds. Now you start the Geiger counter and the stop watch. In stead of waiting 30 seconds you stop the whole experiment after 15 seconds. Now before observing the actual state of the Geiger counter you inform the audience that the Geiger counter is in a superposition state of both count=0 and count=1. This is equivalent for the cat to be in a ss of both alive and dead. It is interesting to know what the audience thinks.

What I think is not important.

Nicolaas Vroom

26 Two new sections to 'Einstein's thought experiments' in Wikipedia

----snip----

>	Consider the Schr�dingers cat thought experiment.

----snip----

>	Now before observing the actual state of the Geiger counter you inform the audience that the Geiger counter is in a superposition state of both count=0 and count=1.

Which is false. Either it's zero or it's not. As soon as the event occurs, the counter becomes non-zero, perhaps taking a detectable amount of time to reach one.

>	This is equivalent for the cat to be in a ss of both alive and dead. It is interesting to know what the audience thinks.

And it's nonsense. The cat is either alive or dead. No ifs or buts.

27 Two new sections to 'Einstein's thought experiments' in Wikipedia

> >	This is equivalent for the cat to be in a state of both alive and dead. It is interesting to know what the audience thinks.

>	And it's nonsense. The cat is either alive or dead. No ifs or buts.

I agree with you. To demonstrate my point of view I removed all the extras. As such you get a picture of how misleading thought experiments can be.

Nicolaas Vroom.

28 Two new sections to 'Einstein's thought experiments' in Wikipedia

>	On Saturday, 8 February 2020 13:23:53 UTC+1, Ned Latham wrote:

>>	Nicolaas Vroom wrote:

>

>> >	This is equivalent for the cat to be in a state of both alive and dead. It is interesting to know what the audience thinks.

>>	And it's nonsense. The cat is either alive or dead. No ifs or buts.

>	I agree with you.To demonstrate my point of view I removed all the extras. As such you get a picture of how misleading thought experiments can be.

amazing how you guys can be so stupid. How can that cat be _either_ one or another, when you _don't know_?

29 Two new sections to 'Einstein's thought experiments' in Wikipedia

> > > >

This is equivalent for the cat to be in a state of both alive and dead. It is interesting to know what the audience thinks.

> > >

And it's nonsense. The cat is either alive or dead. No ifs or buts.

> >	I agree with you. To demonstrate my point of view I removed all the extras. As such you get a picture of how misleading thought experiments can be.

>	amazing how you guys can be so stupid.

You misspelt "well informed", Ward. Do you need help with that bottle?

>	How can that cat be _either_ one or another, when you _don't know_?

A little birdy told us. Little Tweety bird.

30 Two new sections to 'Einstein's thought experiments' in Wikipedia

Please don't call us stupid, there can be a simple misunderstanding.
What has the effect that we don't actually perform a measurement (i.e. perform an observation) has to do with the state of a process, i.e. the state of the cat or the state of a Geiger counter? The schr�dingers cat experiment is considered a thought experiment and IMO thought experiments are tricky.
Besides this experiment contains too many extra's. You don't need a cat. That is why I have removed all the extras. What is left is a radioactive element, a stopwatch and a Geiger counter. The first thing to investigate is what is the difference between an element and a radio active element? The only way to discover is by performing an experiment.
A geiger counter is used to measure radioactive decay. Each count is an indication of such decay. At the beginning of the experiment, you reset the counter and both reset and start the stop-watch.
Now you wait that the Geiger counter registers a count and you stop the stopwatch. That means the element tested is a radioactive element. Now you perform the same experiment 1000 times. Each time you only start and stop the stop-watch. When you do that the total time accumulates. suposse this time is 30*1000 seconds. When that is the case you know that the average between the start of the experiment and the release of a radioactive particle is 30 seconds. What this also means that in roughly 500 cases the radioactive release is less than 30 seconds and the same number that the radioactive release is more than 30 seconds. All of this is to collect data based on actual experiments.

Now comes the final experiment. This experiment is almost the same as the first experiment. In the beginning, you reset the counter and both reset and start the stop-watch. However, there one thing special after 30 seconds I remove the radioactive element (such that the Geiger counter will not count any longer) and I ask you (without you looking at the Geiger counter) what the state is of the Geiger counter.
Of course, you can claim that you don't know. But I think that is not the most accurate answer: IMO you should answer that there is 'exactly' a 50% change the counter is in a state of 0 or in state 1.

However, that is not what quantum mechanics teaches us: The Geiger counter is (before observing) in a superposition state of both a 0 and a 1.
I don't understand that.

Nicolaas Vroom.

31 Two new sections to 'Einstein's thought experiments' in Wikipedia

>> >	I agree with you. To demonstrate my point of view I removed all the extras. As such you get a picture of how misleading thought experiments can be.

>>	amazing how you guys can be so stupid. How can that cat be _either_ one or another, when you _don't know_?

>

Please don't call us stupid, there can be a simple misunderstanding. What has the effect that we don't actually perform a measurement (i.e. perform an observation) has to do with the state of a process, i.e. the state of the cat or the state of a Geiger counter? The schr�dingers cat experiment is considered a thought experiment and IMO thought experiments are tricky. Besides this experiment contains too many extra's. You don't need a cat. That is why I have removed all the extras. What is left is a radioactive element, a stopwatch and a Geiger counter. The first thing to investigate is what is the difference between an element and a radio active element? The only way to discover is by performing an experiment.

my bad entirely, I didn't know somebodey can be this sensitive to the absolute time. Take it as an advance, you'll never see "so stupid" in papers published in physics journals.

But I can see you are confused terribly by that experiment. It's not about the cat, obviously, but the transition of the QM behavioural to the Macro scale. And it has nothing to do with radioactivity, but the unpredictable decay alone. Better luck next time.