![]() ![]() The National Geodetic Survey measures and monitors our ever-changing planet. Sometimes this change is periodic, as is the case with daily tides that affect both the ocean and the crust sometimes the change is slow and steady, as with the drift of tectonic plates or the rebound of the crust after a heavy sheet of ice has melted and sometimes the shape of the planet changes in violent, episodic ways during events such as earthquakes, volcanic eruptions, or meteor strikes. Slight variations in Earth’s gravity field cause permanent hills and valleys in the ocean’s surface of over 300 feet relative to an ellipsoid.Īdditionally, the shape of the Earth is always changing. Sea level itself is even irregularly shaped. Mountains rising almost 30,000 feet and ocean trenches diving over 36,000 feet (compared to sea level) further distort the shape of the Earth. This is due to the centrifugal force created by the earth’s constant rotation. ![]() Our planet is pudgier at the equator than at the poles by about 70,000 feet. However, even an ellipsoid does not adequately describe the Earth’s unique and ever-changing shape. There is no way to create such a magnetic field on a flat disk.While the Earth appears to be round when viewed from the vantage point of space, it is actually closer to an ellipsoid. Now the compass gives you a very specific direction, North-South, ending in two distinct points, which we call the magnetic poles. We can observe the field generated as it surrounds us and extends all the way into space, and you can follow the field lines (like you might have seen in school experiments with magnets) using a compass. So our planet has a magnetic field generated by the motion of liquid iron alloy at the center of our planet. ![]() The Detroit musicians became meme-worthy in 2010 for asking “F#cking magnets, how do they work?” and magnets, or the magnetic field of the Earth, is by far my number one way to deal with flat-Earthers. How could this happen if we were on a static disk? Well, it wouldn't. This is aptly called Foucault’s pendulum. As a pendulum swings, the plane of its oscillations rotate and the time it takes to do a full circle depends on its latitude. This method was first performed by French physicists Léon Foucault in 1851. And by using such an instrument you can demonstrate that the Earth is not only a sphere, but it's rotating too. ![]() If you make your little gravity detector a smidgen more sophisticated you can create a pendulum. ![]()
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