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Thread: A little bit of a dig at relativity

  1. #1 A little bit of a dig at relativity 
    Forum Professor leohopkins's Avatar
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    Okay......

    I dont like it when I hear someone saying that if they are standing near to one clock and the clock strikes midday then someone else x distance away (further out) than the other observer then because both observers witness the event at different times means that it happens at different times....

    .....I do see this quite a lot and it annoys me a little because this is not true. Lets say someone is standing next to a star 4 light years away from earth and it goes supernova; the person next to it witnesses the event. Then 4 years later someone on earth witnesses the event. That doesnt mean the event has just happened....We as intelligent beings KNOW that light has a finite speed therefore we KNOW that the event didnt "just happen" but happened 4 years ago !


    The hand of time rested on the half-hour mark, and all along that old front line of the English there came a whistling and a crying. The men of the first wave climbed up the parapets, in tumult, darkness, and the presence of death, and having done with all pleasant things, advanced across No Man's Land to begin the Battle of the Somme. - Poet John Masefield.

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  3. #2 Re: A little bit of a dig at relativity 
    . DrRocket's Avatar
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    Quote Originally Posted by leohopkins
    Okay......

    I dont like it when I hear someone saying that if they are standing near to one clock and the clock strikes midday then someone else x distance away (further out) than the other observer then because both observers witness the event at different times means that it happens at different times....

    .....I do see this quite a lot and it annoys me a little because this is not true. Lets say someone is standing next to a star 4 light years away from earth and it goes supernova; the person next to it witnesses the event. Then 4 years later someone on earth witnesses the event. That doesnt mean the event has just happened....We as intelligent beings KNOW that light has a finite speed therefore we KNOW that the event didnt "just happen" but happened 4 years ago !
    In general, in special relativity, differences in time and space are the result of measurements made by obsevers in relative motion to one another, not simply displaced in space.

    I really does not matter whether you like it or not. Your likes and dislikes are quite irrelevant. Experimental evidence supports special relativity. It does not support your desires.


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  4. #3 Re: A little bit of a dig at relativity 
    Moderator Moderator Dishmaster's Avatar
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    Quote Originally Posted by leohopkins
    Okay......

    I dont like it when I hear someone saying that if they are standing near to one clock and the clock strikes midday then someone else x distance away (further out) than the other observer then because both observers witness the event at different times means that it happens at different times....

    .....I do see this quite a lot and it annoys me a little because this is not true. Lets say someone is standing next to a star 4 light years away from earth and it goes supernova; the person next to it witnesses the event. Then 4 years later someone on earth witnesses the event. That doesnt mean the event has just happened....We as intelligent beings KNOW that light has a finite speed therefore we KNOW that the event didnt "just happen" but happened 4 years ago !
    You obviously have no idea what you are talking about. What you describe of course has nothing to do with special relativity. Everything depends on the relative state of movement of the observers. Read the relativity primer! It is there for a purpose.
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  5. #4 Re: A little bit of a dig at relativity 
    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by leohopkins
    Okay......

    I dont like it when I hear someone saying that if they are standing near to one clock and the clock strikes midday then someone else x distance away (further out) than the other observer then because both observers witness the event at different times means that it happens at different times....

    .....I do see this quite a lot and it annoys me a little because this is not true. Lets say someone is standing next to a star 4 light years away from earth and it goes supernova; the person next to it witnesses the event. Then 4 years later someone on earth witnesses the event. That doesnt mean the event has just happened....We as intelligent beings KNOW that light has a finite speed therefore we KNOW that the event didnt "just happen" but happened 4 years ago !
    You are misrepresenting what Relativity says. With Relativity, in your example, the observer on Earth would conclude that the event happened 4 yrs ago by his clock.

    What Relativity says is that if you have two observers moving relative to each other, they will disagree as when a distant event happened. This is after they both have accounted for their distance from the object and the time it took the light to reach them.

    Consider the following animation:



    Two observers, one on a railroad car and one on the embankment, both see two flashes of light (the expanding circles). The flashes originate at points an equal distance from the embankment observer. They are timed so the flash reaches the embankment observer just as the railroad car observer passes them. Thus they both see the flash at the same time.

    This animation shows events according to the embankment observer.

    The following animation shows the same events according to the railroad car observer. He still sees both flashes at the same time, But he was not halfway between the origins of the flashes when either originated. And since the light from both flashes travel at the same speed relative to him, in order for them to meet at the same time as he passes the embankment observer. One flash has to occur before the other.

    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  6. #5 Re: A little bit of a dig at relativity 
    Forum Professor leohopkins's Avatar
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    Quote Originally Posted by Janus
    Quote Originally Posted by leohopkins
    Okay......

    I dont like it when I hear someone saying that if they are standing near to one clock and the clock strikes midday then someone else x distance away (further out) than the other observer then because both observers witness the event at different times means that it happens at different times....

    .....I do see this quite a lot and it annoys me a little because this is not true. Lets say someone is standing next to a star 4 light years away from earth and it goes supernova; the person next to it witnesses the event. Then 4 years later someone on earth witnesses the event. That doesnt mean the event has just happened....We as intelligent beings KNOW that light has a finite speed therefore we KNOW that the event didnt "just happen" but happened 4 years ago !
    You are misrepresenting what Relativity says. With Relativity, in your example, the observer on Earth would conclude that the event happened 4 yrs ago by his clock.

    What Relativity says is that if you have two observers moving relative to each other, they will disagree as when a distant event happened. This is after they both have accounted for their distance from the object and the time it took the light to reach them.

    Consider the following animation:



    Two observers, one on a railroad car and one on the embankment, both see two flashes of light (the expanding circles). The flashes originate at points an equal distance from the embankment observer. They are timed so the flash reaches the embankment observer just as the railroad car observer passes them. Thus they both see the flash at the same time.

    This animation shows events according to the embankment observer.

    The following animation shows the same events according to the railroad car observer. He still sees both flashes at the same time, But he was not halfway between the origins of the flashes when either originated. And since the light from both flashes travel at the same speed relative to him, in order for them to meet at the same time as he passes the embankment observer. One flash has to occur before the other.

    Hi Janus, Thanks for your reply.

    Regards;
    Leo
    The hand of time rested on the half-hour mark, and all along that old front line of the English there came a whistling and a crying. The men of the first wave climbed up the parapets, in tumult, darkness, and the presence of death, and having done with all pleasant things, advanced across No Man's Land to begin the Battle of the Somme. - Poet John Masefield.

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  7. #6 Re: A little bit of a dig at relativity 
    Forum Bachelors Degree Waveman28's Avatar
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    Quote Originally Posted by leohopkins
    Okay......

    I dont like it when I hear someone saying that if they are standing near to one clock and the clock strikes midday then someone else x distance away (further out) than the other observer then because both observers witness the event at different times means that it happens at different times....

    .....I do see this quite a lot and it annoys me a little because this is not true. Lets say someone is standing next to a star 4 light years away from earth and it goes supernova; the person next to it witnesses the event. Then 4 years later someone on earth witnesses the event. That doesnt mean the event has just happened....We as intelligent beings KNOW that light has a finite speed therefore we KNOW that the event didnt "just happen" but happened 4 years ago !
    Leo, you have my full support, you are correct. Janus and Dishmaster, I think he is tying this example in with special relativity regarding the relativity of simultaneity. He is saying that even though different observers may record different times of when an event happened, there is an underlying fact of when this event actually happened, regardless of who the bloody hell observed it.
    "Doubt is the origin of Wisdom" - Rene Descartes
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  8. #7  
    Administrator KALSTER's Avatar
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    He is saying that even though different observers may record different times of when an event happened, there is an underlying fact of when this event actually happened, regardless of who the bloody hell observed it.
    That would require an invariant reference frame though, no? Something like, an aether? Fail.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
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  9. #8 Re: A little bit of a dig at relativity 
    Universal Mind John Galt's Avatar
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    Quote Originally Posted by Waveman28
    Leo, you have my full support, you are correct.
    Leo, having the full support of Waveman in matters of relativity is like having Gary Glitter support your application to be a kindergarten teacher.
    Quote Originally Posted by Waveman28
    He is saying that even though different observers may record different times of when an event happened, there is an underlying fact of when this event actually happened, regardless of who the bloody hell observed it.
    Yes, that is what he is saying. It just happens that he is wrong to say it. (Regardless of when he actually said it.)
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