Astrology, that unlikely and vague pseudoscience, makes much of the position of the planets at the moment of birth. The only known force a planet exerts on earth is gravitational.

(a) Calculate the gravitational force exerted on a 4.00 kg baby by a 90 kg father 0.200 m away at birth (assisting so he is close). N (b) Calculate the force on the baby due to Jupiter if it is at its closest to the earth, some 6.29 10¹¹ m away, showing it to be comparable to that of the father. The mass of Jupiter is about 1.90 10²⁷ kg. Other objects in the room and the hospital building also exert similar gravitational forces. (Of course, there could be an unknown force acting, but scientists first need to be convinced that there is even an effect, much less that an unknown force causes it.)

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