Nasa / Space

Geek Trivia: 21 years cold

What planet in our solar system has the harshest winter, one that is measured in decades?

What planet in our solar system has the harshest relative winter, one that is measured in decades?

Take a bow, Uranus, as your winter lasts roughly 21 Earth years. But that's not the half of it, as Uranus has the most extreme seasonal variation of any local planet.

Uranus' axial tilt is roughly 82 degrees, more than triple Earth's 23.5-degree inclination. In fact, it's really close to the 90-degree inclination (obviously) that would have its poles aligned with the ecliptic plane of the solar system.

Put another way, it's like someone knocked over Uranus, so that either its Southern or Northern hemisphere points away from the sun for half of Uranus' orbit. The wintering hemisphere is shrouded in almost persistent night, whilst the summer hemisphere bakes in almost perpetual sunlight. Thus, for one-quarter of its 84-Earth-year orbit, one of Uranus' poles endures the most extreme relative winter in our solar system.

Regardless of the season, Uranus is cold, with an average surface temperature (or, in the case of a gas giant, temperature at the tropopause) of -357 degrees Fahrenheit (-216 degrees Celsius).

Neptune actually has seasons that last over 42 Earth years, and its average surface temperature is slightly (four degrees Celsius) colder than that of Uranus, but Neptune experiences almost no appreciable seasonal changes in temperature or weather. It's equally cold all the time. The same is generally true of Venus, Jupiter, and Saturn -- they simply don't experience any major seasonal variation.

(As for Pluto, astronomers have no idea; it's not necessarily a planet, but its distance precludes any knowledge of whether it experiences seasons.)

Mars and Mercury, on the other hand, almost defy seasonal description. Mars has the most eccentric orbit of the local planets, with its distance from the sun changing so radically during the Martian year that Mars' atmospheric pressure swings by 25 percent, continent-sized dust storms rage across the planet, and the polar ice caps expand and contract visibly like mini-ice ages -- only with dry ice. Mercury, meanwhile, has a day that lasts 1.5 Mercurial years, no axial tilt, and no atmosphere to create weather, let alone seasons. However, Mercury's night is 1000 degrees Fahrenheit colder than its day -- except at the poles, where the temperature never changes.

That's not just calendar-crushing variation on a late spring, it's some seasonally sensational Geek Trivia.

Quibble of the week

If you uncover a questionable fact or debatable aspect of this week's Geek Trivia, just post it in the discussion area of the article. Every week, yours truly will choose the best quibble from our assembled masses and discuss it in a future edition of Geek Trivia.

This week's quibble can be viewed here.

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About

Jay Garmon has a vast and terrifying knowledge of all things obscure, obtuse, and irrelevant. One day, he hopes to write science fiction, but for now he'll settle for something stranger -- amusing and abusing IT pros. Read his full profile. You can a...

15 comments
jlw2135
jlw2135

THE DATES HAVE BEEN HANDED DOWN THRU RECORDED HISTORY FIRST DAY OF SPRING IS HAS AND ALWAYS SHALL BE MARCH 21 JUST CHANGING THEM ON A CALENDAR DOESNT MAKE IT SO

elhudman
elhudman

The meteorological seasons are determined by temperature, and don't lag behind their "scheduled" arrivals, but occur prior to them, on the first of the month. Wikipedia describes it well in the section on "season": "So, in meteorology for the Northern hemisphere: spring begins on March 1, summer on June 1, autumn on September 1, and winter on December 1. Conversely, for the Southern hemisphere: summer begins on December 1, autumn on March 1, winter on June 1, and spring on September 1."

boomchuck1
boomchuck1

The tilt of the earth putting the northern hemisphere closer to the sun isn't the real cause for the warming of the seaasons. The tilt just makes it so the radiation from the sun has less atmosphere to battle through so it is more efficient at warming our hemisphere. The earth is closest to the sun in December. This surprises a lot of folks that think summer is when we are closer to the sun, but then they are forgetting about the folks in Australia.

barksbruisers
barksbruisers

"Uranus is tilted"--sounds like the punchline to a joke!

Larry,
Larry,

Hi Jay, Thanks for another great astronomy-related article. I agree with everything you said, but you failed to mention one significant factor which affects the length of our day. That factor is atmospheric refraction. Atmospheric refraction, caused by the varying densities of air within of our atmosphere (more dense down low and less dense up high), causes light from the Sun to be bent toward the Earth. This lensing effect allows us to see the Sun for a few minutes after it has actually passed below our horizon in the evening, and also before it has risen above our horizon in the morning. Happy vernal equinox! Larry

dolthead
dolthead

When you say Mercury has a day that lasts 1.5 Mercurial years, does this mean it goes around the sun 1.5 times before it rotates 360 degrees? Fascinating. So how long is a Mercurial month? :o]

raul62
raul62

Hi Jay, I enjoy your posts a lot. And the Quibbles as well. In your "21 years cold", you say: "In the Northern hemisphere, this heralds the official start of spring, whilst antipodeans in the Southern hemisphere get started with autumn." I found surprising the use of "antipodeans" as those who live in the other Earth's hemisphere. Technicaly talking, for geographers, "antipode" is the exact place in the diametrically opposite side of the Earth's globe. It's a point, and not a continent (despite of the very british "Antipodes" denomination for Australia and New Zealand), or the whole hemisphere. You'll find y nice and clear definition in Wikipedia: http://en.wikipedia.org/wiki/Antipodes In this article you'll find also a nice paradox: The true "antipodians" are really rare. As most of the Earth's surface is covered by water, the "dry" places in the Earth with a "dry" antipode are not so frequent at all. The term "antipodian" refers better to fishes than people... You can say it is a kind of broad or poetical meaning. I can accept it. After all, I like imaginative literature. Best regards, Ra?l

ttlanhil
ttlanhil

Here in Australia, the 'official' start of the seasons corresponds to the meteorological seasons. Autumn has been in effect for almost three weeks now; although you wouldn't know it from the temperature, we've had a heat wave here in S.A. I believe it was 15-16 days of temperatures above 35C (95F in the old reckoning), with most of those days closer to 40C (104F)

Larry,
Larry,

I believe there is a new surgical procedure which can correct that physical anomaly now. It's worth it too, as the procedure eliminates potty problems, messy bathroom floors, ridicule in the showers at the gym, etc. Great post, BarksBruisers! I really needed a good laugh today! :o) Larry

dolthead
dolthead

Not to mention those of us who live up against towering Rocky Mountains, so the sun doesn't shine til well after "sunrise" and sets long before "sunset".

Dr. Tarr
Dr. Tarr

Wait a minute, Mercury doesn't have a moon, and therefore no month.

j1shalack
j1shalack

Hi raul62: I think you meant "subtle" instead of "subtile". Best, John

raul62
raul62

You're right, John.

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