Author Topic: Why Witch Sabrina Looks Thinner While Riding On Her Broom.  (Read 12776 times)

Offline entropy

Re: Why Witch Sabrina Looks Thinner While Riding On Her Broo
« Reply #105 on: September 05, 2013, 02:23:19 PM »
Quote from: "josephpalazzo"
Quote from: "entropy"

I did pretty much follow the graph, but now I understand better the point you were making about what is being measured. I think the most fruitful thing for me to ask now based on this last response is to ask about the red, bolded part of your response above about the moving observer. In the hypothetical, how do you determine which observer is the moving observer?

In this case, it doesn't matter. The easiest is to take that you are at rest, and your counterpart is moving. Your counterpart can do the same: he can look at his frame at rest, and yours moving. Both of you will agree to the same answer: the velocity between you and him will be v. (Both of you will draw exactly the same graph)

In the case of the twin paradox, here you are measuring two events: departure and arrival. Say the spaceship twin is going to Andromeda. She only needs one clock to measure both events, hence the proper time - this is the time measured by a moving clock. The earth twin needs two clocks: one at departure, and the other at arrival on Andromeda - both clocks are at rest wrt to the earth twin. If you compare the two times you get:

T ' [sub:2k1ykqiw](proper)[/sub:2k1ykqiw] = T (1-v[sup:2k1ykqiw]2[/sup:2k1ykqiw]/c[sup:2k1ykqiw]2[/sup:2k1ykqiw])[sup:2k1ykqiw]1/2[/sup:2k1ykqiw]

Moving clocks slow down.

At the same time, she will measure a shortened distance. From her perspective, the distance between earth and andromeda is like a moving stick.

L' [sub:2k1ykqiw](moving)[/sub:2k1ykqiw] = L(1-v[sup:2k1ykqiw]2[/sup:2k1ykqiw]/c[sup:2k1ykqiw]2[/sup:2k1ykqiw])[sup:2k1ykqiw]1/2[/sup:2k1ykqiw].

So when she calculates her velocity, V = L'/T ' , she will get the same answer as her twin on earth will have found, V = L/T.

Okay, I'm seeing where I misconstrued what "proper time" means (thanks to a surprisingly not particularly good explanation at the Wolfram site). Even with getting that notion squared away, I still see implications that don't square with the notion that there is a contraction that is actual in an absolute sense - which is notion I have been trying to explore. But I don't think there is much value any more in trying to hash it out - at least it doesn't feel that way to me now and there probably hasn't been any value to you in the effort since several posts back. :)

Offline josephpalazzo

Re: Why Witch Sabrina Looks Thinner While Riding On Her Broo
« Reply #106 on: September 05, 2013, 02:44:53 PM »
Quote from: "entropy"
Quote from: "josephpalazzo"


In this case, it doesn't matter. The easiest is to take that you are at rest, and your counterpart is moving. Your counterpart can do the same: he can look at his frame at rest, and yours moving. Both of you will agree to the same answer: the velocity between you and him will be v. (Both of you will draw exactly the same graph)

In the case of the twin paradox, here you are measuring two events: departure and arrival. Say the spaceship twin is going to Andromeda. She only needs one clock to measure both events, hence the proper time - this is the time measured by a moving clock. The earth twin needs two clocks: one at departure, and the other at arrival on Andromeda - both clocks are at rest wrt to the earth twin. If you compare the two times you get:

T ' [sub:3vavdzff](proper)[/sub:3vavdzff] = T (1-v[sup:3vavdzff]2[/sup:3vavdzff]/c[sup:3vavdzff]2[/sup:3vavdzff])[sup:3vavdzff]1/2[/sup:3vavdzff]

Moving clocks slow down.

At the same time, she will measure a shortened distance. From her perspective, the distance between earth and andromeda is like a moving stick.

L' [sub:3vavdzff](moving)[/sub:3vavdzff] = L(1-v[sup:3vavdzff]2[/sup:3vavdzff]/c[sup:3vavdzff]2[/sup:3vavdzff])[sup:3vavdzff]1/2[/sup:3vavdzff].

So when she calculates her velocity, V = L'/T ' , she will get the same answer as her twin on earth will have found, V = L/T.

Okay, I'm seeing where I misconstrued what "proper time" means (thanks to a surprisingly not particularly good explanation at the Wolfram site). Even with getting that notion squared away, I still see implications that don't square with the notion that there is a contraction that is actual in an absolute sense - which is notion I have been trying to explore. But I don't think there is much value any more in trying to hash it out - at least it doesn't feel that way to me now and there probably hasn't been any value to you in the effort since several posts back. :)

Depends what you mean by "absolute". More importantly, are these effects real? We know that the half-life of cosmic muons is longer than a lab muon's half-life, with the correction exactly as predicted by SR. We know that E = Mc[sup:3vavdzff]2[/sup:3vavdzff]. I have a blog in which I derived that formula exactly how Einstein did it. ( See You are not allowed to view links. Register or Login). You see the factor (1 - v[sup:3vavdzff]2[/sup:3vavdzff]/c[sup:3vavdzff]2[/sup:3vavdzff]) [sup:3vavdzff]1/2[/sup:3vavdzff] appearing in the calculation, so it seems that these effects are real.

Offline entropy

Re: Why Witch Sabrina Looks Thinner While Riding On Her Broo
« Reply #107 on: September 05, 2013, 08:42:42 PM »
Quote from: "josephpalazzo"
Quote from: "entropy"

Okay, I'm seeing where I misconstrued what "proper time" means (thanks to a surprisingly not particularly good explanation at the Wolfram site). Even with getting that notion squared away, I still see implications that don't square with the notion that there is a contraction that is actual in an absolute sense - which is notion I have been trying to explore. But I don't think there is much value any more in trying to hash it out - at least it doesn't feel that way to me now and there probably hasn't been any value to you in the effort since several posts back. :)

Depends what you mean by "absolute". More importantly, are these effects real? We know that the half-life of cosmic muons is longer than a lab muon's half-life, with the correction exactly as predicted by SR. We know that E = Mc[sup:2rdtathu]2[/sup:2rdtathu]. I have a blog in which I derived that formula exactly how Einstein did it. ( See You are not allowed to view links. Register or Login). You see the factor (1 - v[sup:2rdtathu]2[/sup:2rdtathu]/c[sup:2rdtathu]2[/sup:2rdtathu]) [sup:2rdtathu]1/2[/sup:2rdtathu] appearing in the calculation, so it seems that these effects are real.

Yes, it does depend on what is meant by "absolute" - and what is meant by "real" and what is meant by "apparent" and "actual". The intuition that I tried to follow to see if it was right is that the fundamental disagreement that occurred earlier in this thread is essentially one of semantics - the meaning intended when people use those words in this context.

I'll use the Doppler experiment analogy (as I did in an earlier post to Solitary) to see if it correctly correlates to the point I'm wondering about with respect to contraction in the direction of movement. In Doppler's experiment (as I'm sure you are aware), if I understand it correctly, the observer standing on the side of the tracks with a train whistle blowing as the train approaches the observer at "high" speed will hear the sound that is produced as a higher pitch than an observer traveling on the train. Is the higher pitch real? Yes it is, but the lower pitch heard by the observer on the train is real, too. Some people might be disturbed by this because they want to think of it in terms of ontological absolutes - if the sound is a higher pitch then it can't also be a lower pitch. A response someone could make is that the sound "appears" to be a higher pitch to the observer outside the train and "appears" to be a lower pitch to observer on the train. What they would intend by that semantic formulation is that both are real but that they are experienced (appear) differently to the two different observers. But someone hearing "appears" used in this context might assume that that isn't the intent; instead that the intent of using "appears" is to express the opposite of "real" - as in an optical illusion can fool you because one line appears longer than another but they are "really" the same length. If that is right, then I wonder if something much like that is the heart of the the disagreement earlier in the thread.

Unless there is something crucial that is intrinsically different about the relativity of what the observers of the train whistle hear compared to the relativity of length in Special Relativity, then I still suspect that this semantic ambiguity is likely to be why the disagreement arose early in this thread. The issue I was trying to track down through most of the discussion with you was whether or not there is something intrinsically different about the relativity of Special Relativity theory and the relativity of the pitch of a sound due to the Doppler effect. I still can't tell about that, so I'm not sure if my initial intuition was right or not.

Offline josephpalazzo

Re: Why Witch Sabrina Looks Thinner While Riding On Her Broo
« Reply #108 on: September 06, 2013, 10:09:16 AM »
Quote from: "entropy"
Quote from: "josephpalazzo"
Quote from: "entropy"

Okay, I'm seeing where I misconstrued what "proper time" means (thanks to a surprisingly not particularly good explanation at the Wolfram site). Even with getting that notion squared away, I still see implications that don't square with the notion that there is a contraction that is actual in an absolute sense - which is notion I have been trying to explore. But I don't think there is much value any more in trying to hash it out - at least it doesn't feel that way to me now and there probably hasn't been any value to you in the effort since several posts back. :)

Depends what you mean by "absolute". More importantly, are these effects real? We know that the half-life of cosmic muons is longer than a lab muon's half-life, with the correction exactly as predicted by SR. We know that E = Mc[sup:1y92udvz]2[/sup:1y92udvz]. I have a blog in which I derived that formula exactly how Einstein did it. ( See You are not allowed to view links. Register or Login). You see the factor (1 - v[sup:1y92udvz]2[/sup:1y92udvz]/c[sup:1y92udvz]2[/sup:1y92udvz]) [sup:1y92udvz]1/2[/sup:1y92udvz] appearing in the calculation, so it seems that these effects are real.

Yes, it does depend on what is meant by "absolute" - and what is meant by "real" and what is meant by "apparent" and "actual". The intuition that I tried to follow to see if it was right is that the fundamental disagreement that occurred earlier in this thread is essentially one of semantics - the meaning intended when people use those words in this context.

I'll use the Doppler experiment analogy (as I did in an earlier post to Solitary) to see if it correctly correlates to the point I'm wondering about with respect to contraction in the direction of movement. In Doppler's experiment (as I'm sure you are aware), if I understand it correctly, the observer standing on the side of the tracks with a train whistle blowing as the train approaches the observer at "high" speed will hear the sound that is produced as a higher pitch than an observer traveling on the train. Is the higher pitch real? Yes it is, but the lower pitch heard by the observer on the train is real, too. Some people might be disturbed by this because they want to think of it in terms of ontological absolutes - if the sound is a higher pitch then it can't also be a lower pitch. A response someone could make is that the sound "appears" to be a higher pitch to the observer outside the train and "appears" to be a lower pitch to observer on the train. What they would intend by that semantic formulation is that both are real but that they are experienced (appear) differently to the two different observers. But someone hearing "appears" used in this context might assume that that isn't the intent; instead that the intent of using "appears" is to express the opposite of "real" - as in an optical illusion can fool you because one line appears longer than another but they are "really" the same length. If that is right, then I wonder if something much like that is the heart of the the disagreement earlier in the thread.

Unless there is something crucial that is intrinsically different about the relativity of what the observers of the train whistle hear compared to the relativity of length in Special Relativity, then I still suspect that this semantic ambiguity is likely to be why the disagreement arose early in this thread. The issue I was trying to track down through most of the discussion with you was whether or not there is something intrinsically different about the relativity of Special Relativity theory and the relativity of the pitch of a sound due to the Doppler effect. I still can't tell about that, so I'm not sure if my initial intuition was right or not.


The problem in the case of the Doppler effect is better understood if you put detectors instead of human ears. On the detector, you will find higher frequencies when the train is moving towards the detector, and lower when moving away.

Now if you want a philosophical discussion on what is "real", then you need to address this question to a philosopher, not a physicist.  Is what you hear "real"? Is what the detector show "real"? If a dog bites your buttend, is that "real"? :P

Concerning SR and the Doppler effect - even though they seem to be similar, they stem from different principles, and are dealt differently. Similarly, the shift in frequencies when light passes through gravity is also similar but stems from different principles in GR.

 

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