Newton's universal law of gravitation

In summary: This is not true! If we assume that the motion is radial, theng=\frac{-e^\lambda \dot{r}\dot{{\dot{r}}}}{(e^{\nu}c^2-e^{\lambda}{\dot{r}}^2)^{1/2}},where a dot over r refers to the derivative wrt time.
  • #1
Orion1
973
3

Derivation of Newton's law of universal gravitation...

Non-relativistic Schwarzschild metric:
[tex]c^2 {d \tau}^{2} = e^{\nu} c^2 dt^2 - e^{\lambda} dr^2 - r^2 d\theta^2 - r^2 \sin^2 \theta d\phi^2[/tex]

metric identity:
[tex]g_{00} = e^{\nu} c^2 = \frac{ds^2}{dt^2}[/tex]

Non-relativistic Einstein tensor:
[tex]G_{11} = \frac{- r \nu' + e^{\lambda} - 1}{r^2} = 0[/tex]

Einstein tensor metric differential:
[tex]\nu' = \frac{e^{\lambda} - 1}{r} = \frac{d}{ds}[/tex]

Non-relativistic metric identity:
[tex]e^{\nu} = \frac{1}{2} \left(1 - \frac{r_s}{r} \right)[/tex]

metric identity:
[tex]e^{\lambda} - 1 = \frac{r_s}{r - r_s}[/tex]

Gravitational acceleration:
[tex]g = - \frac{d s^2}{dt^2} \cdot \frac{d}{ds} = - \frac{d^2 s}{dt^2} = - g_{00} \nu' = - \frac{c^2 e^{\nu} (e^{\lambda} - 1)}{r} = - \frac{c^2}{2r} \left(1 - \frac{r_s}{r} \right) \left(\frac{r_s}{r - r_s} \right) = - \frac{c^2 r_s}{2 r^2} = - \frac{G M_1}{r^2}[/tex]

Newton's second law and universal law of gravitation:
[tex]F_g = M_2 g = - M_2 g_{00} \nu' = - \frac{G M_1 M_2}{r^2}[/tex]

Are these equations correct?

Reference:
http://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation"
 
Last edited by a moderator:
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  • #2
Orion1 said:

Derivation of Newton's law of universal gravitation...

Non-relativistic Newton-Schwarzschild metric:
[tex]c^2 {d \tau}^{2} = \frac{1}{2} \left(1 - \frac{r_s}{r} \right) c^2 dt^2 - \frac{dr^2}{1 - \frac{r_s}{r}} - r^2 d\theta^2 - r^2 \sin^2 \theta d\phi^2[/tex]

metric identity:
[tex]g_{00} = e^{\nu} c^2[/tex]

Non-relativistic Einstein tensor:
[tex]G_{11} = \frac{- r \nu' + e^{\lambda} - 1}{r^2} = 0[/tex]

Einstein tensor metric differential:
[tex]\nu' = \frac{e^{\lambda} - 1}{r}[/tex]

metric identity:
[tex]e^{\nu} = \frac{1}{2} \left(1 - \frac{r_s}{r} \right)[/tex]

metric identity:
[tex]e^{\lambda} - 1 = \frac{r_s}{r - r_s}[/tex]

Gravitational acceleration:
[tex]g = - \frac{d^2 s}{dt^2} = - g_{00} \nu' = - \frac{c^2 e^{\nu} (e^{\lambda} - 1)}{2r} = - \frac{c^2}{2r} \left(1 - \frac{r_s}{r} \right) \left(\frac{r_s}{r - r_s} \right) = - \frac{c^2 r_s}{2 r^2} = - \frac{G M_1}{r^2}[/tex]

Newton's second law and universal law of gravitation:
[tex]F_g = M_2 g = - M_2 g_{00} \nu' = - \frac{G M_1 M_2}{r^2}[/tex]

Are these equations correct?

Reference:
http://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation"

How did you get [tex]g = - \frac{d^2 s}{dt^2} = - g_{00} {\nu}'[/tex]?

AB
 
Last edited by a moderator:
  • #3

Altabeh said:
How did you get [tex]g = - \frac{d^2s}{dt^2} = - g_{00} \nu'[/tex]?

metric identity:
[tex]g_{00} = e^{\nu} c^2 = \frac{ds^2}{dt^2}[/tex]

Einstein tensor metric differential:
[tex]\nu' = \frac{e^{\lambda} - 1}{r} = \frac{d}{ds}[/tex]

Gravitational acceleration:
[tex]g = - \frac{d s^2}{dt^2} \cdot \frac{d}{ds} = - \frac{d^2 s}{dt^2}[/tex]
 
Last edited:
  • #4
Orion1 said:



metric identity:
[tex]g_{00} = e^{\nu} c^2 = \frac{ds^2}{dt^2}[/tex]

Einstein tensor metric differential:
[tex]\nu' = \frac{e^{\lambda} - 1}{r} = \frac{d}{ds}[/tex]

Gravitational acceleration:
[tex]g = - \frac{d s^2}{dt^2} \cdot \frac{d}{ds} = - \frac{d^2 s}{dt^2}[/tex]

This is not true! If we assume that the motion is radial, then

[tex]g=\frac{-e^\lambda \dot{r}\dot{{\dot{r}}}}{(e^{\nu}c^2-e^{\lambda}{\dot{r}}^2)^{1/2}}[/tex],

where a dot over r refers to the derivative wrt time.

AB
 
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Related to Newton's universal law of gravitation

What is Newton's universal law of gravitation?

Newton's universal law of gravitation states that every object in the universe attracts every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

What is the formula for Newton's universal law of gravitation?

The formula for Newton's universal law of gravitation is F = G * (m1 * m2 / r^2), where F is the force of attraction, G is the gravitational constant, m1 and m2 are the masses of the two objects, and r is the distance between them.

What is the significance of Newton's universal law of gravitation?

Newton's universal law of gravitation is significant because it explains the force that governs the motion of celestial bodies in the universe. It also helps us understand the behavior of objects on Earth, such as why objects fall towards the ground and why the moon orbits around the Earth.

Is Newton's universal law of gravitation always accurate?

No, Newton's universal law of gravitation is not always accurate. It is an approximation that works well for objects with small masses and at relatively short distances. At very high speeds or in extreme gravitational fields, Einstein's theory of general relativity must be used.

What is the difference between Newton's law of gravitation and Kepler's laws of planetary motion?

Newton's law of gravitation explains the force of attraction between any two objects in the universe, while Kepler's laws of planetary motion describe the motion of planets around the sun. Newton's law of gravitation is a more general law that can be applied to all objects, while Kepler's laws are specifically for the motion of planets in our solar system.

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