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Light being bent by the sun - Einstein, gravity, relativity

  • 26-06-2012 10:42am
    #1
    doctoremma
    Registered Users, Registered Users 2 Posts: 1,870 ✭✭✭


    Hello again,

    Once again, I am confused by something I have read in a popular astronomy book. Can you help?

    In order to examine how gravity causes light to deflect, Einstein proposed observing the apparent position of the stars around the sun during a solar eclipse. Sure enough, the light from such stars was deflected to such an extent that his theories proved correct compared to those of Newton.

    If the light from such stars is deflected by the sun, how did he/we/others know the actual positions of the stars in order to measure the light deflection? If we maps stars by observing the light from them, why is it not always deflected?

    It seems obvious that the stars under observation had been mapped against eachother while in a position away from a massive gravitational pull. However, the book does not explicitly say this - possibly it's too freaking obvious - and just wanted to check I was on the right lines?


Comments

  • #2
    murphyme2010
    Registered Users, Registered Users 2 Posts: 230 ✭✭murphyme2010


    doctoremma wrote: »
    Hello again,

    Once again, I am confused by something I have read in a popular astronomy book. Can you help?

    In order to examine how gravity causes light to deflect, Einstein proposed observing the apparent position of the stars around the sun during a solar eclipse. Sure enough, the light from such stars was deflected to such an extent that his theories proved correct compared to those of Newton.

    If the light from such stars is deflected by the sun, how did he/we/others know the actual positions of the stars in order to measure the light deflection? If we maps stars by observing the light from them, why is it not always deflected?

    It seems obvious that the stars under observation had been mapped against eachother while in a position away from a massive gravitational pull. However, the book does not explicitly say this - possibly it's too freaking obvious - and just wanted to check I was on the right lines?

    You are on the right lines.

    The stars would be mapped in the ususal way at night and the positions established. The positions were then measured during the eclipse and the positions compared. The actual difference observed was quite small I believe but I don't know the exact number.

    Technically, I suppose the light from stars is always being deflected to some extent by other stars but the deflection is too small to make a difference.

    Michael.


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