It is well known for the Good Housekeeping Seal, popularly known as the Good Housekeeping Seal of Approval.. The magazine was founded May 2, 1885 by Clark W. Bryan in Holyoke, Massachusetts. The magazine achieved a circulation of 300,000 by 1911, at which time it was bought by the Hearst Corporation.
Gravity, Forces, magnetism. Jupiter's moons stay in orbit because gravity pulls them towards Jupiter. it mainly happens like a game of tug of war. Two forces are included, one pulls the moons towards Jupiter, the other one pulls them towards space.
Ganymede, Europa and Io are all in orbital resonance with Jupiter. Io completes exactly four orbits and Europa completes exactly two orbits in the same time it takes Ganymede to complete one orbit around Jupiter. During the course of their orbits, the three moons line up like in the picture seen to the left.