Why this night will be the longest ever The reason is that the rotation of the Earth is slowing over time. Every year, scientists estimate, the length of a day increases by about 15 to 25 millionths of a second. It may be a truly tiny amount (and it means that even in your entire lifetime, the length of a day will only expand by about two milliseconds), but it forces official timekeepers to add a leap second every few years. The main reason Earths rotation slowing down is the moon. Shortly after the formation of Earth, it was impacted by a planet-sized object. This enormous collision threw off the material that would eventually coalesce into the moon, and also sent Earth spinning quite rapidly. In the four-plus billion years since, that spinning has slowed down pretty significantly (with an Earth day going from about six hours to 24 hours as a result) because of the moons gravity. (This is all theory, of course...) vox/2014/12/21/7424371/winter-solstice
Posted on: Sun, 21 Dec 2014 15:55:10 +0000
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