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I`m wondering if the gravitational pull from earth that should be constant around the planet, will get amplified by a celestial body like the moon orbiting the earth?

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  • $\begingroup$ Yes it will, and that's the cause of tides. $\endgroup$ – pela Jul 13 '18 at 13:32
  • $\begingroup$ Cool @pela. So if we look at our solar system as a hole with regards to its density where the outer rim is the Helios sphere we can say that out whole solar system combined has a mas and density and therefore has a gravitational pull outwards?it this correct? $\endgroup$ – JanErik Jul 13 '18 at 13:37
  • $\begingroup$ No, that's not the case. First of all, the Sun contain by far the most of the mass of the Solar System, so unless you're close to the surface of a massive body (like a planet or asteroid), gravity will be dominated by the Sun and hence directed inward. Second, even if you ignore the Sun, planets, and other massive bodies and only regard the combined effect of "small" bodies (atoms, dust grains, small rocks, …), the density decreases as you move away from the center, so gravity is again inward. Third, even if you ignore the density gradient and assume a constant density throughout the… $\endgroup$ – pela Jul 13 '18 at 14:31
  • $\begingroup$ …heliosphere, at any point there would be more mass in the direction of the center than away from, so again gravity points toward the center. $\endgroup$ – pela Jul 13 '18 at 14:33
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    $\begingroup$ @pela I think superposition is a better word for that than amplification. $\endgroup$ – peterh Jul 13 '18 at 14:49
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Gravity itself cannot be amplified but the forces are additive. The earth is held in orbit by the Sun's gravity but earth is also affected by the moon's gravity. Depending on their position the moon's gravity could be aligned with Sun's gravity, increasing the gravitational pull. Or the moon could reduce the effect of suns gravity if on opposite side of the earth relative to the sun.

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  • $\begingroup$ thank you for the answer. So the Milkiway for example can not act as a whole gravitational force and attract smaller galaxys?What i mean is that is only the center of the galaxy / the black hole that would exert a gravitational force on the other galaxy , so if a galaxy is very big it will not have more gravitational pull then a small galaxy? $\endgroup$ – JanErik Jul 13 '18 at 22:29
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    $\begingroup$ Yes the Miley Way can act as a single body for large distances. Sine the forces are additive the total gravitational attraction is that due to all bodies in the Milkey wWay. Some confusion may be due to the word amplified. I read the question to mean can the gravitational attraction of a body be amplified. That answer is no. But 2 bodies of equal mass will have twice the attraction of one of the bodies alone. That is not amplified really, its just the effect of the forces being additive. $\endgroup$ – jmh Jul 13 '18 at 23:36

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