PerihelionA few hours ago, at 22:49 UTC (5:49 pm EST/2:49 pm PST), the planet Earth was as close as
PerihelionA few hours ago, at 22:49 UTC (5:49 pm EST/2:49 pm PST), the planet Earth was as close as it will be to the sun for the next 365 days.As originally described in Kepler’s Laws of Motion, the Earth’s orbit around the sun is an ellipse. The sun sits at one focus of that orbit, meaning the planet Earth (like every other planet) moves closer to and farther from the sun every year. Perihelion is the point where the Earth is closest to the sun: aphelion, in July, is when the Earth is farthest from the sun.The timing of perihelion, close to the December Solstice and in the middle of southern hemisphere summer/northern hemisphere winter, is basically a coincidence. Although the planet is moving closer and farther from the sun, the change in energy due to this movement is much less than the change in heating associated with the seasons. The change in energy of the sun between perihelion and aphelion is the equivalent of just over 2°C; we’re warmer than we would be otherwise, but a difference of a couple degrees isn’t really noticeable. Even though we’re closer to the sun right now, it’s still cold in the northern hemisphere and warm in the southern hemisphere every January.In fact, the timing of perihelion/aphelion changes every few decades as Earth’s orbit is flexed by Jupiter’s gravity and other influences. In the year 1246, perihelion actually occurred on December 21, the winter solstice (ignoring the calendar changes since then). If the calendar is not rewritten, then in the year 6430, perihelion will migrate all the way to the March Equinox. This gradual change in the timing of perihelion/aphelion is one of the Earth’s orbital cycles that have a slight but measureable influence on the size of glaciers during ice ages.Coincidentally, today is also the Lunar Apogee, the time when the Moon is as far as it gets from the planet Earth. The Moon’s orbit around the Earth is also elliptical, so once every orbit it also gets closer and farther from the planet Earth. Today the Earth is at its closest point to the sun and the Moon is at its farthest point from the Earth. Both the sun and Moon influence tides, but the Moon is a stronger source of tides as it is closer, so generally today the planet should be seeing mostly weak tides.-JBBImage credit: Pandiyan V (close to Perihelion in 2005)https://flic.kr/p/aqUvLRead more:http://bit.ly/1OrtCABhttp://bit.ly/JAlgILhttp://bit.ly/1OrtFfvhttp://bit.ly/1ZGNaET -- source link
Tumblr Blog : the-earth-story.com
#perihelion#orbit#winter#january#kepler#planet#science#gravity#earth#apogee