The original trilogy largely revolves around a soldier named Commander Shepard, whose mission is to save the galaxy from a race of powerful mechanical beings known as the Reapers and their agents, including the first game’s antagonist Saren Arterius. The first game, released in 2007, sees Shepard investigating Saren, whom Shepard slowly comes to understand is operating under the guidance of Sovereign, a Reaper left behind in the Milky Way 50,000 years before, when the Reapers exterminated all sentient organic life determined to have met or exceeded a threshold of technological advancement in the galaxy as part of a recurrent cycle of genocide for an unknown purpose. Sovereign’s purpose is to trigger the imminent return of the Reaper fleet hibernating in extra-galactic dark space, restarting the process of extermination. The second game takes place two years later, and sees Shepard battling the Collectors, an alien race abducting entire human colonies in a scheme to aid the Reapers’ return to the Milky Way. The final game of Shepard’s trilogy centres on the war being waged against the Reapers. The fourth installment takes place in the Andromeda Galaxy and features a new cast of characters.
Some astronomers think that the two gas-giants do not sport solid surfaces secreted beneath their immense and heavy gaseous atmospheres, although others suggest that the jumbo-size duo do, indeed, harbor relatively small cores of rocky-icy stuff. The two other large inhabitants of the outer limits of our Sun's family are Uranus and Neptune, which are both classified as ice-giants, because they harbor large icy cores secreted deep down beneath their heavy, dense gaseous atmospheres which, though very massive, are not nearly as heavy as the gaseous envelopes possessed by Jupiter and Saturn. The GRAIL mission determined the internal structure of the Moon in great detail for nine months during 2012. Armed with this the new information, GRAIL astronomers were able to redefine the sizes of the largest impact basins on the lunar surface. A billion years ago, our Moon was closer to Earth than it is now. As a result, it appeared to be a much larger object in the sky. During that ancient era, if human beings had been around to witness such a sight, it would have been possible to see the entire Moon--not merely the one near side face that we see now. A billion years ago, it took our Moon only twenty days to orbit our planet, and Earth's own day was considerably shorter--only eighteen hours long. Stupendous, almost unimaginably enormous tides, that were more than a kilometer in height, would ebb and flow every few hours. However, things changed, as the lunar orbit around our primordial planet grew ever wider and wider. Annually, Earth's Moon moves about 1.6 inches farther out into space. Currently, the lunar rate of rotation, as well as the time it takes to circle our planet, are the same.