Getting back to why the axis exists, it's mainly the result of the rough-and-tumble environment of the early solar system. Scientists believe that the sun and the eight planets formed by chunks of rock and debris that self-accumulated through gravity. In other words, objects collided and clumped together, which increased their gravitational pull, which in turn drew more objects in, which made the object even more gravitationally powerful, and so on until the solar system looks like a sun and eight fairly neat planets with not much stray junk flying around.
Of course, occasionally these forming objects happen to attract something that's big enough to knock it off-kilter. That's what probably happened to the earth, after it was already large enough to start rotating.
Actually, Wilson says it probably took several substantial impacts to whack the earth into the position it's in today. Incidentally, back in the "old days," the earth used to rotate a lot faster—once every 6 to 10 hours at the start of the solar system—and the moon's gravity has played a big role in slowing us down to It's a good thing too, because a 6-hour day would certainly lead to an awfully hectic work week.
Now try and answer these questions:. The Nine Planets , created by astronomer Bill Arnett, has this feature on the earth and its general characteristics. See the Tool. But this tilt changes. During a cycle that averages about 40, years, the tilt of the axis varies between Because this tilt changes, the seasons as we know them can become exaggerated.
It's the cool summers that are thought to allow snow and ice to last from year-to-year in high latitudes, eventually building up into massive ice sheets. There are positive feedbacks in the climate system as well, because an Earth covered with more snow reflects more of the sun's energy into space, causing additional cooling.
As the orbit gets more eccentric oval the difference between the distance from the Sun to the Earth at perihelion closest approach and aphelion furthest away becomes greater and greater. Gravity data from the Grace satellite, launched in , had been used to link glacial melting to movements of the pole in and , both following increases in ice losses. The research, published in the journal Geophysical Research Letters , showed glacial losses accounted for most of the shift, but it is likely that the pumping up of groundwater also contributed to the movements.
Groundwater is stored under land but, once pumped up for drinking or agriculture, most eventually flows to sea, redistributing its weight around the world. So today we tilt at But what would happen if we tilted even more? What if Earth spun sideways on its axis? Well, it wouldn't take long before utter chaos ensued.
One of the most important consequences of Earth's axial tilt is the seasons. Seasons happen because the tilt points different parts of the planet toward the sun at different times of the year. But the tilt also means that different parts of the globe receive different amounts of sunlight during each season.
And that's where a more extreme tilt starts to cause problems. Right now, during the summer in the Northern Hemisphere, places far north, like Utqiagvik, Alaska, receive 24 hours of sunlight for 82 days straight. Because Earth is tilted far enough on its axis that as the planet rotates, Utqiagvik never leaves direct sunlight. On the other hand, the contiguous US receives a max of 17 hours a day, because after that it rotates out of daytime sunlight and into night.
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