Why Earth is Closest to Sun in Dead of Winter

Space.com ^ | January 2, 2007 | Mary Lou Whitehorne

[SunkenCiv]

Earth's orbit is not a perfect circle. It is elliptical, or slightly oval-shaped. This means there is one point in the orbit where Earth is closest to the Sun, and another where Earth is farthest from the Sun. The closest point occurs in early January, and the far point happens in early July (July 7, 2007). If this is the mechanism that causes seasons, it makes some sense for the Southern Hemisphere. But, as an explanation for the Northern Hemisphere, it fails miserably.

In fact, Earth's elliptical orbit has nothing to do with seasons. The reason for seasons was explained in last month's column, and it has to do with the tilt of Earth's axis. But our non-circular orbit does have an observable effect. It produces, in concert with our tilted axis, the analemma...

Earth reaches perihelion on January 3, 2007 (Figure C). The Earth-Sun distance will be 147,093,602 km. Aphelion, the greatest distance from the Sun, occurs on July 7, 2007, when the Earth-Sun distance will be 152,097,053 km.

The difference between the two is 5,003,451 km, (3.3 percent), and not enough to cause the seasons. Even though, at this time of year, we're as close to the Sun as we can get, for the Northern Hemisphere, it will always be winter.

---

TOPICS: Astronomy; Science
KEYWORDS: analemma; aphelion; astronomy; axialtilt; ellipse; elliptical; flatearthmorons; globalwarminghoax; marylouwhitehorne; orbit; perihelion; science; seasons; winterwhathemisphere

[SaveFerris]

Oh dang, you beat me

Good job 👍👍👍

I was going to post similar
but was too busy with the
crybaby Liberal Judge

[Sirius Lee]

The difference between the two is 5,003,451 km, (3.3 percent), and not enough to cause the seasons.

Yeah, but lets bring the Milankovitch Cycle into the mix and talk about ice ages.

[Ignatz]

I’ve long maintained that anyone who believes the “man-made climate change” hoax has never toasted a marshmallow over a campfire.

Facts the author(s) might have included:

Neither the speed of the Earth’s rotation on it’s axis nor the speed of it’s orbit around the Sun are constant.

Also, the Earth “wobbles” a bit as it spins.

[Buttons12]

This is simple. The thing I struggle with is how we only see one side of the moon.

[DoodleBob]

The Campfire would like to have a word with you.

[HYPOCRACY]

Hawaii is a beach on a mountain top. Just saying...

[lefty-lie-spy]

This reads like it was written for 6 year olds. I hate it when these science journalists dumb everything down to the point that it’s only words and no actual science.

[Tell It Right]

Thanks for posting.

The analemma plays into the optimum angle for solar panels. People with ground mounted solar panels often have a hinge they can pivot (maybe twice per year) to point closer to straight up during the summer. Then during the winter lower the angle to point the panels closer to the horizon. The idea is that the solar panels work best when the sunlight hits the panel at 90 degrees.

[trebb]

I learned this in 7th grade science class.

[Paal Gulli]

A circle is a special case of ellipse but all orbits (in a 2-body system) are (non-circular) ellipses because gravitational forces are not distributed evenly throughout the universe, and over time even tiny differences in gravity will cause orbits to gain eccentricity.

We might hang a satellite in orbit in a perfectly circular orbit but even if the earth and that satellite were the only objects in the universe, the surface of the earth is not cue-ball smooth, and those irregularities cause differences in gravitational pull, which, over time, would cause the orbit to become eccentric. So in every case, eccentricity is inevitable.

You could use thrusters to keep it (sort of) circular but you'd have to burn fuel to do it, and refuelling satellites is an expensive proposition, so they tend to let grabity have its way.

Pluto's orbit is so eccentric, it sometimes is closer to the sun than Nepture is.

[SunkenCiv]

I went to school with some of the Lemma kids, big family. Ana was in my graduating class.

[norwaypinesavage]

I can explain a couple of those.
1. Air pressure... Gravity holds the air from flying off into space. If it didn’t, we wouldn’t have any air to breathe. The air pressure on earth is about 15 pounds per square inch. This means that every square inch of earth has about 15 pounds of air above it, if you totaled the weight of the air molecules all the way out until there aren’t any more. The higher you go, the less air there is above you to create that pressure. When you pressurize air it gets hot. All the energy it takes to make the pressure is turned to heat in the air. When you release that pressure, it cools by the came amount. That’s why air compressors need cooling fins. That means, the higher you go the colder it gets since the pressure is lower. It’s called the “lapse rate”. Look that up if you want more information about this.

2....Meteors and spacecraft get hot only because they’re coming in at an extremely high speed, thousands of miles per hour. When they hit molecules of air, they accelerate that molecule to nearly the speed they are travelling. Much of he energy of the collision (mass times velocity squared) in that molecule is turned into heat in the impacted item. At the very low speeds of cooling fans, the energy of the collision is negligible, and much of the cooling effect is either evaporation of sweat on a person’s skin, or also the cooler temperature of the blowing air.

I hope that helps for these two.
2.

[SunkenCiv]

😁

[SunkenCiv]

Yup, that’s the Chandler Wobble. There’s a keyword for that, but I’m not going to post the list, the Analemma keyword (sorted) is what got nuked in message 4.

[SunkenCiv]

🌜 Wait a sec... there's more than one side to the Moon?!? 🌛

There's at least a few discussions of this on FR, and good links offsite, but a couple of offsite links is what got nuked in post #3.

Bodies in prograde motion participate in the tidal transfer momentum, whereby the rotational motion is slowly lost and pushes the other object (parent or satellite) away into ever-higher orbit. The Earth is 100 times more massive than the Moon, and (assuming the Moon used to rotate all the time while in orbit) the Moon eventually ran out of rotational momentum. Obviously it still turns on its axis per se, otherwise it would not show the same face all the time.

[SunkenCiv]

You probably had to walk three miles to school through pouring rain and deep snow, too.

[SunkenCiv]

The Milankovitch Cycle has not been borne out by further study or data. It would make a great name for a biker shop though.

[SunkenCiv]

Thx.

[SunkenCiv]

Thanks.

[SunkenCiv]

Whoops, “tidal transfer OF momentum” not “tidal transfer momentum”.