Marine current power the rotation of the earth. The sun acts as the primary driving force, causing winds and temperature differences. Because there are only small fluctuations in current speed and stream location with minimal changes in direction, ocean currents may be suitable locations for deploying energy extraction devices such as turbines. Other effects such as regional differences in temperature and salinity and the Coriolis effect due to the rotation of the earth are also major influences. The kinetic energy of marine currents can be converted in much the same way that a wind turbine extracts energy from the wind, using various types
The Currents of Space more amenable. When Trantor offers to buy out the entire planet for a very high price, the offer is readily accepted. Even though there is not yet a full Galactic Empire, Trantor controls the now largely-radioactive Earth. The idea of evacuating Earth is mentioned, but that is strongly rejected by Rik. He insists that it is the original planet of the human race, but that is not generally accepted. "Galaxy" reviewer Groff Conklin described the novel as "one of Asimov's lesser efforts, but still considerably above the average space opera". The magazine's Floyd C. Gale told readers "Don't miss" it