Gravity it ain't...   Astrologers have a hard time explaining what really is making astrology "work". Most claim it is gravity, based on the old analogy of the Moon causing the tides: If the Moon can cause the waters on Earth to move, then why not the water in our bodies? After all, we consist of about 70% water, so it follows that the Moon has a similar effect on us. So should the rest of the planets, the logic goes.   How much of a pull is this anyway? It is fairly easy to calculate the exact force any planet exerts on us. We only need to know Newton's law of Gravity that states: If the first object has a mass of m1, and the second object has a mass m2, and there is a distance r between them (between their centers of mass, that is), the magnitude of the gravitational force is given by:   where:   We need the distance and mass of two objects to find the gravitational pull between them.           Object Mass(kg) Mercury 330.200.000.000.000.000.000.000 Venus 4.869.000.000.000.000.000.000.000 Moon 73.500.000.000.000.000.000.000 Mars 641.900.000.000.000.000.000.000 Jupiter 1.898.600.000.000.000.000.000.000.000 Saturn 568.500.000.000.000.000.000.000.000 Uranus 86.830.000.000.000.000.000.000.000 Neptune 102.430.000.000.000.000.000.000.000 Pluto 12.500.000.000.000.000.000.000 Person 100 Car 1.000   Distance from Earth (you)       Object Distance(m) Mercury 91.700.000.000 Venus 41.400.000.000 Moon 385.000.000 Mars 78.300.000.000 Jupiter 628.700.000.000 Saturn 1.277.400.000.000 Uranus 2.720.000.000.000 Neptune 4.347.000.000.000 Pluto 5.763.900.000.000 Person 1 Car 1   Using the equation, a person is influenced this much by:       Gravitational pull from: Newton(N) Mercury 0.000000261917328 Venus 0.00001894806763 Moon 0.003307438017 Mars 0.0000006983444492 Jupiter 0.00003203851586 Saturn 0.000002323819969 Uranus 0.00000007828126352 Neptune 0.00000003615544625 Pluto 0.000000000002509591137 Person 0.000000667 Car 0.00000667   As we can see, the pull from the planets is very weak. In fact, most of the pull comes from objects very close to us. Your car pulls at you 10 times more than Mars does. But you wouldn't include your car in your horoscope, would you?   Conclusion   If astrology "works" at all - and nothing points in that direction - it sure isn't because of gravity.   The water in human bodies shows no sign of tidal behaviour. This is because tides are caused by the change in gravity over distance. The Earth's diameter is big, and the gravity from the Moon changes across the Earth's diameter. But people are tiny compared to the distance to the Moon. The change in gravity from the Moon of our head and our feet is incredibly small, so there are no appreciable tides across a human being.   But if you are afraid of upcoming bad astrological effects, just stand on your head and reverse the effect! And if you are worried about the Moon pulling at you, just remember that people on the other side of Earth are pulled in the opposite direction!