Colonization of the outer Solar System the Solar System's gas giant planets for exploration and possibly mining of helium-3, which could have a very high value per unit mass as a thermonuclear fuel. The Jovian system in general has particular disadvantages for colonization, including its severe radiation environment and its particularly deep gravity well. Its radiation would deliver about 3,600 rems per day to unshielded colonists on Io and about 540 rems per day to unshielded colonists on Europa. Exposure to about 75 rems over a few days is enough to cause radiation poisoning, and about 500 rems over a few days is fatal. Jupiter itself,
Social gravity a manner "analogous in all cases, by which the center of gravity in the solar system" held the planets in their orbits. In making this analogy, Pownall's notion of 'social gravity' drew upon earlier visions of social cohesion, particularly ideas of sociability in eighteenth-century Britain. These ideas, in turn, were often predicated upon Stoic notions of cosmopolitanism, expressed by the key term oikeiôsis, in order to stress the "moral" imperative for like-minded humans to forge bonds dedicated to the common good. Social gravity Social gravity was an application of Newtonian gravity to the system of commerce influence. For instance, in