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Thread: 2 cents worth of questions

  1. #1 2 cents worth of questions 
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    =P hello everyone, sorry if im wrong in anything, for i just finished my O-levels education, so im not exectly very knowledgable... but i would be direct to the point...
    _______________________

    Question A:
    Being new and unsure into relativity, i was wondering if this is correct...
    ___________
    | Observer A | --> Moving at 1/4 c

    ___________
    | Observer B | --> Moving at 1/8 c

    Hence, Observer B will observe Observer A moving at 1/8 c
    Let V = 1/8 c

    Hence, for every 1 second observer B "experiances", Observer A will "experiance" (1 - V^2 / C^2)^(1/2) seconds

    T[a] = (1 - V^2 / C^2)^(1/2)
    T[a] = (1 - 1/8^2)^(1/2)
    T[a] = (1 - 1/64)^(1/2)
    T[a] = (63/64)^(1/2)
    T[a] ~ 0.9921567416 [10.sf]
    _______________________

    Question B:
    All i know is a black hole is a huge lump of mass, so huge that the gravity will suck in anything, and turn anything into "spegetti" while sucking them in, and is effected theoretically by Hawking radiation and hence "slowly, very slowly decaying"....

    BUT what is the black hole really made of, a super condensed mass of neutrons? protons?... ?_? electrons?... or something else.... ?_?


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  3. #2 Re: 2 cents worth of questions 
    Forum Radioactive Isotope mitchellmckain's Avatar
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    Quote Originally Posted by TheExile
    =P hello everyone, sorry if im wrong in anything, for i just finished my O-levels education, so im not exectly very knowledgable... but i would be direct to the point...
    _______________________

    Question A:
    Being new and unsure into relativity, i was wondering if this is correct...
    ___________
    | Observer A | --> Moving at 1/4 c

    ___________
    | Observer B | --> Moving at 1/8 c
    This is insufficiently described because motion is relative. In each case you must say what this motion is relative to. For example you get different results depending on which of these two you mean:

    Possibility 1: A is moving at 1/4 c relative to Observer C and B is moving at 1/8 c relative to Observer C

    Possibility 2: A moving 1/4 c relative to Observer C and B is moving 1/8 c relative to Observer A



    Quote Originally Posted by TheExile
    Hence, Observer B will observe Observer A moving at 1/8 c
    Let V = 1/8 c
    Only in the Case of Possibility 2, but in that case Observer C will observe B moving at velocity (.25c + .125c)/(1 + .25(.125)) = .37121212 c

    In the case of Possibility 1, B will observe A moving at (.25 c - .125 c)/(1 - .25(.125)) = .129032258 c



    Quote Originally Posted by TheExile
    Hence, for every 1 second observer B "experiances", Observer A will "experiance" (1 - V^2 / C^2)^(1/2) seconds

    T[a] = (1 - V^2 / C^2)^(1/2)
    T[a] = (1 - 1/8^2)^(1/2)
    T[a] = (1 - 1/64)^(1/2)
    T[a] = (63/64)^(1/2)
    T[a] ~ 0.9921567416 [10.sf]
    No it does not work like this. Your calculation is correct in the case of possibility 2, but what you are failing to understand is that time dilation is also relative and you cannot say who is "experiencing" more time than the other except in a relative manner. According to the way each observer is measuring space and time each will think that the other observers are experiencing less time than he is. B will also say that for every second he experiences A is only experiencing .991567416 seconds.




    Quote Originally Posted by TheExile
    Question B:
    All i know is a black hole is a huge lump of mass, so huge that the gravity will suck in anything, and turn anything into "spegetti" while sucking them in,

    BUT what is the black hole really made of, a super condensed mass of neutrons? protons?... ?_? electrons?... or something else.... ?_?
    It is NOT a huge lump of mass. All the mass is at the center point. A black hole is called a collapsar because gravity has exceed all the forces that keeps matter from colapsing in on itself. The size of a black hole is a measure of its gravitational effect ALONE. This is determined by it mass of course and is best represented by the distance from the center point at which light can no longer escape. This is called the Schwarzschild radius.

    The black hole does however keep all the fundamental properties of the mass which it has absorbed like angular momentum and electrical charge.



    Quote Originally Posted by TheExile
    and is effected theoretically by Hawking radiation and hence "slowly, very slowly decaying"....
    Well how fast it decays apparently depends on its size, for the smaller the black hole is, the faster it decays.


    See my physics of spaceflight simulator at http://www.relspace.astahost.com

    I now have a blog too: http://astahost.blogspot.com/
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  4. #3  
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    :-D thx for the help... lol let me amend my question then, sorry about the mistake i made

    Question A:
    Being new and unsure into relativity, i was wondering if this is correct...
    ___________
    | Observer A | --> Moving at 1/4 c relative to C
    ___________
    | Observer B | --> Moving at 1/8 c relative to C
    ___________
    | Observer C |

    Quote Originally Posted by mitchellmckain
    Quote Originally Posted by TheExile
    Hence, Observer B will observe Observer A moving at 1/8 c
    Let V = 1/8 c
    Only in the Case of Possibility 2, but in that case Observer C will observe B moving at velocity (.25c + .125c)/(1 + .25(.125)) = .37121212 c

    In the case of Possibility 1, B will observe A moving at (.25 c - .125 c)/(1 - .25(.125)) = .129032258 c
    I dun quite get the (Va - Vb)/(1- [Va].[Vb]) part =X maybe my reading aint that broad scope. So indirectly my answer is somewhat correct in this case? What im getting, is that B time is slowed down relative to C, hence A speed relative to C will be differant to A speed relative to B, and thats where this equation kicks in to caculate the correct speed relative to B. am i right?
    ___________
    | Observer A |
    ___________
    | Observer B | --> Moving at 1/8 c relative to A

    Quote Originally Posted by mitchellmckain
    Quote Originally Posted by TheExile
    Hence, for every 1 second observer B "experiances", Observer A will "experiance" (1 - V^2 / C^2)^(1/2) seconds

    T[a] = (1 - V^2 / C^2)^(1/2)
    T[a] = (1 - 1/8^2)^(1/2)
    T[a] = (1 - 1/64)^(1/2)
    T[a] = (63/64)^(1/2)
    T[a] ~ 0.9921567416 [10.sf]
    No it does not work like this. Your calculation is correct in the case of possibility 2, but what you are failing to understand is that time dilation is also relative and you cannot say who is "experiencing" more time than the other except in a relative manner. According to the way each observer is measuring space and time each will think that the other observers are experiencing less time than he is. B will also say that for every second he experiences A is only experiencing .991567416 seconds.
    So =X i need to replace V, with the updated V explained above??

    And hmm... i was thinking of somewhere along that lines too... that the time each observer observe is sorta relative [which is einstines whole point]... cause i found it =X wierd abit in this case.
    ___________
    | Observer A | --> Moving at -1/8 c relative to C
    ___________
    | Observer B | --> Moving at 1/8 c relative to C
    ___________
    | Observer C |

    Both Observer A and B are traveling at opposite directions.

    To observer C, "time" slowed down relative to C is both the same, so if both were to have a clock, and travel for Xmin and stop instantanously. Both clocks on A & B would be the same relative to C

    However if u view from either Observer A/B view, to them both A/B would have "time" slowed down relative to them, which would then be inconsistent to observer C observations, and even each other.

    (so lets say all 3 have perfectly good watchees. A/B claims each others clock should slow down more then themselves, while C claims that both slowed down to the same time, so which one of the three really happens if they all to meet?)

    oh yea thx for the summary of black holes, i was kina unsure what winki and other online stuff was saying here and there... @_@
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  5. #4  
    Forum Radioactive Isotope mitchellmckain's Avatar
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    Quote Originally Posted by TheExile
    :-D thx for the help... lol let me amend my question then, sorry about the mistake i made

    Question A:
    Being new and unsure into relativity, i was wondering if this is correct...
    ___________
    | Observer A | --> Moving at 1/4 c relative to C
    ___________
    | Observer B | --> Moving at 1/8 c relative to C
    ___________
    | Observer C |
    And what goes with this is

    | Observer B | --> Moving at .129032258 c relative to A



    Quote Originally Posted by TheExile
    What im getting, is that B time is slowed down relative to C, hence
    B time is slower than C time according to C, but C time is slower than B time according to B.



    Quote Originally Posted by TheExile
    A speed relative to C will be differant to A speed relative to B, and thats where this equation kicks in to caculate the correct speed relative to B. am i right?
    Correct.

    Quote Originally Posted by TheExile
    ___________
    | Observer A | --> Moving at 1/4 c relative to C
    ___________
    | Observer B | --> Moving at 1/8 c relative to A
    These go together with
    ___________
    | Observer B | --> Moving at .37121212 c relative to C



    Quote Originally Posted by TheExile
    ___________
    | Observer A | --> Moving at -1/8 c relative to C
    ___________
    | Observer B | --> Moving at 1/8 c relative to C
    ___________
    | Observer C |

    Both Observer A and B are traveling at opposite directions.
    And what goes with this is

    | Observer B | --> Moving at .470588235 c relative to A



    Quote Originally Posted by TheExile
    To observer C, "time" slowed down relative to C is both the same, so if both were to have a clock, and travel for Xmin and stop instantanously. Both clocks on A & B would be the same relative to C
    That is correct. But before slowing down, both A & B think that it is the time of C which is slowed down. What makes C correct in the end is the fact that A and B are doing the accelerating. If C accelerates to catch up with A, observer C will find out that A was correct and that it was C's time that was slower. The point here is that acceleration causes one to change how one must measure space and time.

    The key to really understanding all this, is the relativity of simultaneity. Events (for example, a star in the direction from C to where A is heading going nova and star in the direction from C to where B heading going nova) which C thinks are both happening at the same time, are not happening at the same time according to A and B (who each think the star in the direct they are going is the one that goes nova first)



    Quote Originally Posted by TheExile
    However if u view from either Observer A/B view, to them both A/B would have "time" slowed down relative to them, which would then be inconsistent to observer C observations, and even each other.

    (so lets say all 3 have perfectly good watchees. A/B claims each others clock should slow down more then themselves, while C claims that both slowed down to the same time, so which one of the three really happens if they all to meet?)
    Whoever does not accelerate will turn out to be correct. If they all accelerate then they will all have been wrong. AGAIN, the point here is that acceleration causes one to change how one must measure space and time. As a result of this, the assertion that nothing will appear to move faster than the speed of light relative to you ONLY applies while you are moving at a constant velocity. While you accelerate towards your destination, your destination can appear to zoom towards you MUCH faster than the speed of light.
    See my physics of spaceflight simulator at http://www.relspace.astahost.com

    I now have a blog too: http://astahost.blogspot.com/
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