Mercury (planet) diagram on the right illustrates the effects of the eccentricity, showing Mercury's orbit overlaid with a circular orbit having the same semi-major axis. Mercury's higher velocity when it is near perihelion is clear from the greater distance it covers in each 5-day interval. In the diagram the varying distance of Mercury to the Sun is represented by the size of the planet, which is inversely proportional to Mercury's distance from the Sun. This varying distance to the Sun leads to Mercury's surface being flexed by tidal bulges raised by the Sun that are about 17 times stronger than the Moon's
Return to the Lost Planet on the development of this genre in Israel. The plot follows on precisely from "The Lost Planet". A previous expedition to Hesikos, the wandering 'lost planet' which is now within a few days flight of Earth, has crash-landed, and Dr Lachlan McKinnon (its organiser), Professor Hermanoff and American engineer Spike Stranahan are marooned. McKinnon's colleagues must build and launch a spaceship from their Scottish base to travel to Hesikos, but to construct the ship they must obtain the expert assistance of Dr Andrieff, a scientist and engineer, who risks exile from his Eastern European country by so doing. The crew,