1 'Gedanken' vs 'fabricated'

NO! Gedankens are about understanding a THEORY, and how it applies to some specific situation, which is often rather artificial (e.g. moving at 0.9 c, instantaneous accelerations to such speeds, etc.).

Gedankens are just that -- THOUGHTS, and cannot possibly enlighten anybody about the world we inhabit. That takes real experiments.

>	[... more nonsense]

Tom Roberts

2 'Gedanken' vs 'fabricated'

Boy do YOU need to learn how to read! I said nothing at all like that.

Tom Roberts

3 'Gedanken' vs 'fabricated'

4 'Gedanken' vs 'fabricated'

IOW, "thought experiments" are not experiments at all; they are procedures for developing predictions based on the theory behind them.

----snip----

5 'Gedanken' vs 'fabricated'

Doesn't matter, that's what the word MEANS.

Tom Roberts

6 'Gedanken' vs 'fabricated'

Suppose two people make different predictions based on the outcome of the same thought experiment. How do you decide who is right? Maybe the theorie is wrong.

Nicolaas Vroom

7 'Gedanken' vs 'fabricated'

8 'Gedanken' vs 'fabricated'

Not is that the purpose of a gedanken, On the contrary, the theory is built on certain postulates and laws and its mathematics are assumed to be correct. Gedankens are used to test for possible inconsistencies of the theory. So at the end a good gedanken could probably falsify a theory or verify it but never proof it right. Examples of this are the so called "paradoxes".

>	Anyway you have to be very carefull when performing thought experiments. You can claim that you have a spaceship that travels at a speed of 0.9 c but how do you know that?

It is set as a condition of the thought experiment. These conditions are clearly artificial but, as said before, the purpose is to check what is the theory response.

>	You say it your self: "it is often rather artificial". That is tricky because what you have in your mind it should be physical possible. Suppose in my thought experiment I use a speed of 2c is that allowed?

If you are designing a gedanken for SR or GR, that condition is contrary to the theories postulates, that is that the speed of light in vacuum (the maximum speed of propagation of information) is always c.

>	What for example about the https://en.wikipedia.org/wiki/Bell's_spaceship_paradox? Also this is a thought experiment. Does the string break yes or no? The issue is length contraction. but can you solve that with a thought experiment? Nicolaas Vroom

Of course the string breaks, as hundreds of papers have demonstrated.

9 'Gedanken' vs 'fabricated'

>	What for example about the https://en.wikipedia.org/wiki/Bell's_spaceship_paradox? Also this is a thought experiment. Does the string break yes or no? The issue is length contraction.

No. It's actually very simple. Continuously stretching a string will eventually cause its internal molecular bonds to fail. Stretching a string means an increase in its proper length.

---Tim Shuba---

10 'Gedanken' vs 'fabricated'

Precisely. The whole thing is worthless if you can't test it.

>	Suppose two people make different predictions based on the outcome of the same thought experiment.

One or both of them got it wrong.

>	How do you decide who is right?

Or even whether either of them is?

>	Maybe the theorie is wrong.

No "thought experiment" will reveal that. Of course, it might inspire a definitive physical experiment.

11 'Gedanken' vs 'fabricated'

Since a thought experience is doing rigorous DEDUCTION from a set of given assumptions, then this cannot happen without one of those people having made a rather obvious error in deductive logic.

That's the purpose of a theory, to be able to come up with clear and unambiguous PREDICTIONS from a set of assumptions, which predictions can then be put to test in a REAL experiment. The thought experiment is the process by which those predictions are generated.

>	How do you decide who is right? Maybe the theorie is wrong. Nicolaas Vroom

12 'Gedanken' vs 'fabricated'

Well done, Slow Boy! You've paraphrased my response to the question quite nicely. Well, a little verbosely, but never mind that.

>	That's the purpose of a theory, to be able to come up with clear and unambiguous PREDICTIONS from a set of assumptions, which predictions can then be put to test in a REAL experiment. The thought experiment is the process by which those predictions are generated.

Oh, and again, well done! You've paraphrased what I said above... again, a tad verbosely, but all in all quite nicely.

That's very good work, Slow Boy; you might not be very good at thinking but you certainly are good at the copycat routine.

> >	How do you decide who is right? Maybe the theorie is wrong.

But you didn't do my response to that question... too hard for you?

13 'Gedanken' vs 'fabricated'

Using a thought experiment you can only predict a possible outcome of a thought experiment, which is different from a real experiment. The only way to test a theory (or better to falsify a theory) is by performing a real experiment.

>	So at the end a good gedanken could probably falsify a theory or verify it but never proof it right.

That is correct and that limits the applicapability.

> >	Anyway you have to be very carefull when performing thought experiments. You can claim that you have a spaceship that travels at a speed of 0.9 c but how do you know that?

>	It is set as a condition of the thought experiment. These conditions are clearly artificial but, as said before, the purpose is to check what is the theory response.

And has a limitted value.

> >	What for example about the https://en.wikipedia.org/wiki/Bell's_spaceship_paradox? Also this is a thought experiment. Does the string break yes or no? The issue is length contraction. but can you solve that with a thought experiment?

>	Of course the string breaks, as hundreds of papers have demonstrated.

These papers ansich say 'nothing'. Part of the problem is that the Bell's spaceship paradox is too complex.

Consider a much simpler experiment:
Consider two bullet trains, which each a length of 1 km which travel each on two parallel tracks. The trains are completely identical and are electrical controlled by at least one internal clock. But trains are started simultaneous side by side. The internal controls take care that each train follows the same program to increase its speed: 100 km/hour 200 km/hour 300 km/hour 1 km/sec 10 km/sec etc. Because both train follow exactly the same program the expectation is that both train will run side by side for the whole trip. Q: Is that realistic? IMO the answer is Yes.

Now perform the same experiment with the different initial condition that one train will start in front of the other such that the end of one train will be the nose of the other train. (they will still travel each on their own track) Again like in the first experiment both train will start simultaneous and follow the same program. The question in this case is: Will the distance between the back of the first train and the nose (front) of the second train increase or stay the same? When the distance increases this is equivalent as when the string breaks, which is equivalent which length contraction.

Anyway this experiment is much more complex than the experiment I previously proposed using two lightsignals to demonstrate length contraction. (or not)

The true question is can you really use any thought experiment to demonstrate that length contraction is real (i.e. is a physical effect) IMO the anser is: No.

Nicolaas Vroom

14 'Gedanken' vs 'fabricated'

>	Not is that the purpose of a gedanken, On the contrary, the theory is built on certain postulates and laws and its mathematics are assumed to be correct.

No. The purpose of gedanken is simple. After 20-30 copies of gedanken "how an observer confirms relativity in a train/boat/plane" an idiot like you start believing these confirmations are real.

15 'Gedanken' vs 'fabricated'

>	That's the purpose of a theory, to be able to come up with clear and unambiguous PREDICTIONS from a set of assumptions, which predictions can then be put to test in a REAL experiment. The thought experiment is the process by which those predictions are generated.

:)You're as naive as you are dumb.

16 'Gedanken' vs 'fabricated'

>	Using a thought experiment you can only predict a possible outcome of a thought experiment, which is different from a real experiment. The only way to test a theory (or better to falsify a theory) is by performing a real experiment.

Yeah. Take a real car, accelerate it to 0.9c and go through a barn... what will you see? Poor idiot.

17 'Gedanken' vs 'fabricated'

I agree.

> >	Suppose two people make different predictions based on the outcome of the same thought experiment.

>	One or both of them got it wrong.

I agree

> >	How do you decide who is right?

>	Or even whether either of them is?

I agree

> >	Maybe the theorie is wrong.

>	No "thought experiment" will reveal that. Of course, it might inspire a definitive physical experiment.

I agree.

IMO thought experiments can be helpfull, for example they can be used to discuss different experiments (and you can predict the outcomes) as an introduction for real experiments, but they cannot be used as a final tool to unravel the laws of nature.

You also have to be carefull for the theories and postulates used to predict the outcome. Maybe when you perform a real experiment to explain the outcome you don't need all these theories and postulates or the actual experiments are much more complicated (and you also need others) That's why I always propose to make the (thought) experiments as simple as possible.

A typical case is the Schrödingers Cat paradox. Do you really need a cat? Do you really need an observer? The most important thing is what happens inside the box and that is radio active decay of a particle (which has a certain half live).

When you want to study how clocks behave, the first step is qualitative behaviour and then quantitative behaviour. With qualitive behaviour I mean that the experiment should indicate/demonstrate that when 'you' want to go from A to B using two synchronised clocks at A, when they meet at B the clock readings can be different. Quantitative behaviour means how much. The result of the experiment should be to agree that it actual makes a difference how you go from A to B. Next comes to identify which particular parameters influence this behaviour and how do you explain that. It is easy possible that different reference frames have nothing to do with this and one is enough.

Nicolaas Vroom.

18 'Gedanken' vs 'fabricated'

>	IMO thought experiments can be helpfull, for example they can be used to discuss different experiments (and you can predict the outcomes) as an introduction for real experiments, but they cannot be used as a final tool to unravel the laws of nature.

Bullshit. The reality is much simpler - after hearing 100 or more times that an observer in a train see relativistic wonders you start believing they're real; that's what gedanken are for.

19 'Gedanken' vs 'fabricated'

You're wrong again Woz. A thought experiment is just that: a thought, nothing more.

>	The reality is much simpler - after hearing 100 or more times that an observer in a train see relativistic wonders you start believing they're real; that's what gedanken are for.

Belief is not reality, Woz, though the two sometimes intersect.

20 'Gedanken' vs 'fabricated'

21 'Gedanken' vs 'fabricated'

So are your "laws of nature".

> >	The reality is much simpler - after hearing 100 or more times that an observer in a train see relativistic wonders you start believing they're real; that's what gedanken are for.

>	Belief is not reality, Woz, though the two sometimes intersect.

Beliefs are a part of reality, poor idiot. And gedankens are a tool to shape them.

22 'Gedanken' vs 'fabricated'

*My* laws of nature? You're not confusing me with the Voices in your head, are you Woz?

> > >

The reality is much simpler - after hearing 100 or more times that an observer in a train see relativistic wonders you start believing they're real; that's what gedanken are for.

> >	Belief is not reality, Woz, though the two sometimes intersect.

>	Beliefs are a part of reality, poor idiot.

Only inasmuch as people *have* beliefs, Woz.

>	And gedankens are a tool to shape them.

Have you noticed how nicely "geddanken" rhymes with "wankin'"?