The earth is a sphere

Firstly, to avoid any nitpicking from Con, I am arguing that the earth is an oblate spheroid, as the earth is not exactly spherical. I will provide a variety of proofs that this is correct. 1. Observation from space Countless photographs from satellites show the earth is spherical (1). These photos come from many independent sources and have not been shown to be fake, so they are in all likelihood real photographs. Also, there is no conceivable reason why anyone would want to convince the world that the earth was spherical if it actually wasn't. 2. Circumnavigation It is possible to circumnavigate the earth (go around it in a great circle), but if the earth wasn't spherical then ships would reach the edge of the earth. Because ships don't reach the edge of the earth, this is strong evidence that the earth is edgeless. 3. Gravity If the earth was not spherical, then there would not be a uniform gravitational strength wherever you are in the world. The fact is that anywhere you go on earth (disregarding changes in altitude) the gravitational strength is the same. Since gravity is a non-contact force following the inverse square law, the constant gravitational strength means that all points on the earth's surface are equidistant from the earth's centre of gravity. Geometrically, the only shape where all points on its surface are equidistant to its centre is a sphere. Therefore, the earth must be a sphere. 4. Gyroscopes When one spins a gyroscope in a particular plane, it will remain spinning in that plain regardless of the movement of the gyroscope stand. However, if one spins a gyroscope and observes its movement over 24 hours, it appears to move. The only explanation for this behavior is that the earth itself is rotating around an axis, which further suggest that the earth is a spinning sphere. (3) 5. Dipping distances When one sails out of sight of a lighthouse, it is not the visibility that eventually hides it from view, it is the observation that it dips below the horizon. But if the earth was flat, then the horizon would not obscure anything. So long as there were no obstructions between two things, they could be seen. But this is not the case. Even in perfect visibility, eventually a lighthouse becomes obscured by the horizon. Since this would not happen on a flat earth, the earth must have a rounded surface. Because this phenomenon is present at all points around the earth, the earth must have a round surface everywhere. If something has a constant round surface, then it must be shaped spherically. 6. Stars Some stars are visible in the Northern Hemisphere but not the Southern Hemisphere (and vice versa) (2). If the earth was flat then all stars would be visible irrespective of the latitude of the observer. Since this is not the case, the earth must be round. 7. Photographs from airplane windows show that the earth's surface is round. (4) 8. Planets are formed by a centre of gravity in a cloud of rock and gas that draws more and more matter onto it. This manner of growth means that planets can only be spherical; the way planets form does not permit planets of any other shape to exist. Since the earth is a planet, it can therefore only be spherical. (5) (1) http://news.nationalgeographic.com... (2) http://www.skymaps.com... (3) http://blog.modernmechanix.com... (4) http://davejoh.com... (5) http://coolcosmos.ipac.caltech.edu...-