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Thread: Length Contraction

  1. #1 Length Contraction 
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    While searching the forum for similar threads (I could not find any) I found this: http://www.thescienceforum.com/viewtopic.php?p=2954 lol

    *I may not be able to respond quickly for the next week or two, so please bear with me.

    http://en.wikipedia.org/wiki/Length_contraction

    I found their article....precisely vague. This method of conveying knowledge unfortunately does not help much though. What I want to know is, how and why does it occur. How exactly I realize is very hard to answer, but more importantly to start off I would like to know why.


    Of all the wonders in the universe, none is likely more fascinating and complicated than human nature.

    "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."

    "Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"

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  3. #2  
    Forum Radioactive Isotope MagiMaster's Avatar
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    In a very real sense, it occurs because the speed of light is fixed. Seriously. If you start with the idea that the speed of light in a vacuum is a constant in all reference frames, time dilation and length contraction (which are two sides of the same coin) simply must be.

    That may not really be what you were asking, so here's another view. Imagine trying to measure something with a ruler and a camera as you pass it at near light speed. If you accept that c is a constant then you will note that the travel time of the light from the camera to the object and back is different on different ends of the ruler. So, in some ways, the objects haven't changed length, but since simultinaity can only be defined by light, in other ways, they really did change lengths.


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    I think I do not know certain properties of the universe necessary to understand this....

    From what I can tell, time dilation occurs so that you cannot see light travel slower in your direction as you travel faster. The other side of this would be light traveling in the opposite direction, in which case time dilation would be detrimental towards the cause of a constant c. When you see light traveling in the opposite direction, why does time dilation not cause it to appear the same velocity faster as the forward traveling light? Is this where length contraction comes in?

    I remember seeing a weird demonstration of length contraction a while ago where it showed the perspective of an object traveling through a city at near light speed. It appeared as if the surrounding buildings were bent around the object, as if the object formed a light bending pipe around itself. Essentially the near by buildings seamed even closer, and the far buildings appeared even more distant. Why would you see this?

    If length contraction were to occur to you, if you looked at your body, what would you see? What if you were in a space ship traveling at .99c, what would your surroundings look like? Is length contraction only a relative appearance to those viewing you from an outside perspective? as in, would you actually be flattened and therefore killed in the process?
    Of all the wonders in the universe, none is likely more fascinating and complicated than human nature.

    "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."

    "Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"

    -Einstein

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    Use your computing strength for science!
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  5. #4  
    Forum Radioactive Isotope MagiMaster's Avatar
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    In a spaceship moving at 0.99c, you'd look around and see nothing different inside the spaceship. The things outside would look distorted though.
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  6. #5  
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    Quote Originally Posted by Cold Fusion
    I think I do not know certain properties of the universe necessary to understand this....

    From what I can tell, time dilation occurs so that you cannot see light travel slower in your direction as you travel faster. The other side of this would be light traveling in the opposite direction, in which case time dilation would be detrimental towards the cause of a constant c. When you see light traveling in the opposite direction, why does time dilation not cause it to appear the same velocity faster as the forward traveling light? Is this where length contraction comes in?

    I remember seeing a weird demonstration of length contraction a while ago where it showed the perspective of an object traveling through a city at near light speed. It appeared as if the surrounding buildings were bent around the object, as if the object formed a light bending pipe around itself. Essentially the near by buildings seamed even closer, and the far buildings appeared even more distant. Why would you see this?

    If length contraction were to occur to you, if you looked at your body, what would you see? What if you were in a space ship traveling at .99c, what would your surroundings look like? Is length contraction only a relative appearance to those viewing you from an outside perspective? as in, would you actually be flattened and therefore killed in the process?
    You ought to read a good treatment of special relativity. Wolfgang Rindler's Introduction to Special Relativity is one.
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  7. #6  
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    There will always be arguments regarding relativistic effects of near light speed conceptual travel in the absence of a conclusive argument regarding the status of the "observor".

    The idea of contraction is a very "loose" idea. One should ask, "what type of contraction". For instance, is it a "folding" of the same relative length of space?

    I know of a theory, very precisely put, that states that any near light speed travel would have an amount of contraction that halves the resting length of that object by a "folding" mechanism.
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  8. #7  
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    One should ask, "what type of contraction".
    That is part of what I do not understand...whether it is literal contraction or if it uses a more complex mechanism.
    Of all the wonders in the universe, none is likely more fascinating and complicated than human nature.

    "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."

    "Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"

    -Einstein

    http://boinc.berkeley.edu/download.php

    Use your computing strength for science!
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  9. #8  
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    To maintain the objects original composition, the object undergoing length contraction would also have to move in the X axis or transverse direction like most objects do when you crush them. The compacted matter has to go somewhere...unless the objects become invisible from front to back as it goes faster. What exactly would a ship traveling at .99c look like? Frankly I have never seen an object compressed or decompressed that did not alter its form in another direction than the longitudinal axis.
    Of all the wonders in the universe, none is likely more fascinating and complicated than human nature.

    "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."

    "Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"

    -Einstein

    http://boinc.berkeley.edu/download.php

    Use your computing strength for science!
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  10. #9  
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    Being a consequence of definitions, these contractions are not a consequence of any underlying dynamical laws.
    -wikipedia

    I suppose this is the problem in my understanding...there is nothing meant to be understood. They just expect you to except it without any real explanation.
    Of all the wonders in the universe, none is likely more fascinating and complicated than human nature.

    "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."

    "Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"

    -Einstein

    http://boinc.berkeley.edu/download.php

    Use your computing strength for science!
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  11. #10  
    Forum Radioactive Isotope MagiMaster's Avatar
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    The object does not get crushed. It's no where near the same as compressing a can.

    A better way to understand how this works is to take a rubber sheet (say from a balloon), stretch it out and draw a ruler on it. Measure something with this ruler. The length contraction experienced by a fast moving object would be somewhat like stretching the balloon out. Measure the same thing with the stretched balloon and you'll see that it covers fewer tick marks, meaning it looks shorter from the balloon's perspective. The balloon is somewhat like space-time. Going fast stretches space-time out, not the object itself. Of course, that's just an analogy. Don't think that that's exactly how things work.
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  12. #11 length contraction 
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    SR is a theory of transformations of one observers measurements to those of another. It does not physically transform objects. It reconciles many different perceptions so they agree on the one event that actually occurred..
    The finite speed of light actually causes fast moving objects to appear longer while approaching and shorter while receding.
    The real physical effect from very high speeds is time dilation, which is verified by experiment.
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