Thanks for the winter solstice. Without it, you might not be here.

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Thanks for the winter solstice. Without it, you might not be here.

On December 21 or Thursday, the sun will embrace the horizon. For the rest of us in the northern hemisphere, it seems barely rose – there is almost no snow cover in the skyline of the city or the forest of evergreen trees peep over – before it was quickly.

For months, the arc of the sky has been falling, shrinking every day.

In New York City, for example, the sun will be in the sky for more than nine hours – six hours less than in June. The winter solstice marks the shortest day of the year, climbing into the sky before the sun reverses. (at the same time, Australia in the southern hemisphere is also the longest day of the year.)

This is a very good chance, as you can imagine if we turned on another planet, so what it’s like to be such a day may, on this planet, the sun will be dancing in the sky. You may want to thank us for the good that we have, or we may not be here to see them.

Since most planets are not upright or perpendicular to their orbits, this is the case.

For example, the earth is tilted 23.5 degrees on a tilted axis. This causes the earth’s North Pole to point to the north star for quite a long time, even if the earth moves around the sun for more than a year. This means that in the northern hemisphere will tilt to half in half a month of time, bathed in summer is a long and happy life in the sun, in brief the cold days of winter, half a month of the time it will be a little away from the sun. December 21 marks the day when the North Pole is most far from the sun.

But every planet appears at different angles.

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The axial tilt of Venus is so extreme that when the South Pole points to it, the earth is essentially flipped over. Credit NASA/JPL

For example, the axial tilt of Venus is so extreme (177 degrees) that the planet essentially flips over and points upwards. Perhaps counterintuitively, this means that its upside-down spin is almost untilted, and its hemisphere never explicitly points to the sun or away from the sun. Thus, the sun’s dance in the sky will remain relatively stable – only about six degrees in the course of Venus.

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In “Paradise Lost Book 10,” John Milton argues that god has made the sun revolve around our equator. He…

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With the planetary science institute astrobiologist David green aspen (David Grinspoon) said, if we on Venus evolution, it is likely we didn’t notice that at least something or season.

The same is true of imagined aliens living in the cold blue clouds of Uranus.

“Uranus is wild,” Dr. Greenspen said.

The axial tilt of 98 degrees causes the ice giants to rotate on the side. So even though one of the poles of the earth is slightly tilted toward the sun during the winter solstice, one of Uranus’s poles can point almost directly to the sun – just like a perfect bull’s eye. This means that a half-ball will bask in the sun all day and night, while the other half will experience a cold and dark winter without a glimpse of the sun throughout the season.

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In 1986, two images of Uranus, taken by NASA’s voyager 2, were taken. The pseudo-color image on the right shows how the poles of Uranus turn toward the sun and its axes tilt 98 degrees. Credit NASA/JPL

“It can’t be more extreme,” says Heidi Hammel, a planetary scientist at the planetary society.

This tilt on earth means that the arctic is not starting at 66 degrees north of the equator, but on the equator itself. Half of North America, Europe, Asia and Africa will spend the winter in constant darkness and summer. In Uranus, 84 earth years around the sun, these seasons continue for decades.

“If there is life on Uranus, and I don’t think there’s this creature, seasonal affective disorder is a lifetime thing,” Dr. Hamel said.

But the extreme season is Pluto.

When NASA’s new horizons of the space shuttle in 2015 reached dwarf planet, scientists have discovered a unique world, the world is full of surface features, looks like a drainage network, and even a frozen lake. But given the low pressure and cold surface temperatures of Pluto, liquids can’t flow through the surface – at least not today. The mission’s lead investigator, Alan stern, said: “it’s not going to happen in the current environment. So, channels and lakes are impossible. ”

Scientists now have an explanation: in the past season, Pluto has pushed the atmospheric pressure high enough to allow the flow of methane and nitrogen to flow and to swim on the surface.

The axial tilt of the change is the most important driving force for the change of the season. For four million years, Pluto moved back and forth between 102 and 126 degrees, causing the arctic to grow and shrink. Occasionally the season is formed and atmospheric pressure is high enough that liquid methane and nitrogen can flow.

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