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Does relativity show a higher or lower figure or does the difference in working out mean you cannot compare the 2.

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- Thread starter John15
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- #1

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Does relativity show a higher or lower figure or does the difference in working out mean you cannot compare the 2.

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A.T.

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The only effect you can directly compare it the gravitational acceleration. Here is a thread about it:

Does relativity show a higher or lower figure or does the difference in working out mean you cannot compare the 2.

https://www.physicsforums.com/showthread.php?t=310397

But GR predicts other effects that also affect trajectories like time dilation and space distortion.

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- #4

A.T.

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Why do newtons equations not correctly describe the orbit of mercury.

We recently discussed what a good explanation is here:

https://www.physicsforums.com/showthread.php?t=545174

But the thread died.

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Newton's theory is pretty accurate already, the error is only about 1 part in 10

The perihelion shift applies to all non circular orbits but the effect is largest for Mercury because Mercury is closest to the Sun.

We can actually express equatorial orbits in common form both for GR and Newton's theory:

[tex]\Large {\frac {{d}^{2}u}{{d\varphi }^{2}}}=1/2\,\mbox {D} \left( f \right)

\left( u \right)

[/tex]

Where f(u) is:

[tex]\Large f \left( u \right) =2\,{\beta}^{2}u+2\,k-{u}^{2}

[/tex]

for Newton and

f(u) is:

[tex]\Large f \left( u \right) =2\,{\beta}^{2}u+2\,k-{u}^{2}+2\,{u}^{3}

[/tex]

for GR.

The only difference is an extra term (u is defined here as m/r).

For details see for instance "General Relativity" - Woodhouse, chapter 8.2

With a lot of hand waving we get an

[tex]\Large 6\,{\frac {Gm\pi}{r_{{0}}{c}^{2}}}

[/tex]

where r

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Out of interest if the distance in newton was taken from the shwartzchild radii rather than exact centers would it bring newton and einstein any closer, it would obviously slightly increase g in newton especially close to a large body like the sun.

Not sure if the +2u3 above causes an increase or decrease in GR.

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