Circling around magnetic field lines. ... The ring current . Because positive ions and negative electrons drift in opposite directions (see drawing), that motion will create an electric current that circulates clockwise around the Earth when viewed from north. ... How then can the radiation belt and ring current arise? ... Electric fields are able to push trapped particles earthward, and unlike the purely magnetic motion described earlier, an electric field can also energize them. ...
... The gravity-gradient force on the Moon. 4b Craters of the Moon--why round, why middle higher. ... Intuitive concept of 2nd law--planet or satellite slows down when further away, relation to conservation of energy and analogy to motion of thrown stone. 12a Example of non-algebraic equation (Kepler's) . ... Principle of rocket motion. ... Design of house windows, taking advantage of the Sun's motion. 4a Poem by Vachel Lindsay. 4b The story of exploration of the Moon using space vehicles. ...
Jupiter is the largest of the nine planets, more than 10 times the diameter of Earth and more than 300 times its mass. ... The mean density of Earth is 5.245 times that of water. The pull of gravity on Jupiter at the top of the clouds at the equator is 2.4 times as great as gravity's pull at the surface of Earth at the equator. ... It is tipped about 11њ to Jupiter's axis of rotation, similar to Earth's, but it is also offset from the center of Jupiter by about 10,000 kilometers (6,200 miles). ...