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Earth

Earth’s tilt toward the sun > Seasons

Patterns of the Sun

Archaeoastronomy Database

6 December 2019

Patterns of the Sun

Video Archaeoastronomy Database 6 December 2019

This is a description of some of the broad patterns of the sun

that can be observed in the sky from the earth so the focus

is a geocentric description specifically to help understand

applications to archaeoastronomy.

The Archaeoastronomy Database

facilitates the gathering of crowd-sourced data

relating to archaeoastronomy.

YouTube

https://www.youtube.com/watch?v=mS9dTN0IEK8

Why Do We Have Different Seasons?

California Academy of Sciences 2015

Why Do We Have Different Seasons?

Video California Academy of Sciences 29 August 2015

Did you know that the Sun’s light shines differently on Earth

at different times of the year?

In this visualization watch as the Earth orbits the Sun, rotating,

like a slightly tilted, spinning top.

This rotation changes the angle

at which sunlight hits the surface of our planet,

creating the different seasons we experience here on Earth.

Can you see how sunlight at different times of the year

changes the productivity of life on land and in our oceans?

YouTube

https://www.youtube.com/watch?v=WgHmqv_-UbQ

Seasons

Earth Rocks! 10 February 2015

Seasons

Video Earth Rocks! 10 February 2015

Review of the causes and impacts of Earth's seasons

on daily light cycles and heat input.

Designed for an introductory oceanography course.

YouTube

https://www.youtube.com/watch?v=tX3Y5bzNDiU

Earth's Rotation & Revolution:

Crash Course Kids 8.1 29 April 2015

Earth's Rotation & Revolution: Crash Course Kids 8.1

Video Crash Course Kids 29 April 2015

YouTube

https://www.youtube.com/watch?v=l64YwNl1wr0

Earth's Tilt 1: The Reason for the Seasons

14 November 2012

Earth's Tilt 1: The Reason for the Seasons

Video MITK12Videos 14 November 2012

YouTube

https://www.youtube.com/watch?v=Pgq0LThW7QA

Earth's axis USA

https://www.nytimes.com/2023/06/28/
climate/groundwater-earth-spin-axis.html

average position of our planet’s rotational axis,

the imaginary rod around which it turns USA

https://www.nytimes.com/2023/06/28/
climate/groundwater-earth-spin-axis.html

Earth's spin USA

https://www.nytimes.com/2023/06/28/
climate/groundwater-earth-spin-axis.html

The Earth's axis > The seasons USA

https://www.nytimes.com/2017/12/20/
science/winter-solstice-december-21.html

http://www.npr.org/sections/thetwo-way/2016/03/
20/471185302/happy-spring-a-roundup-of-stories-for-the-vernal-equinox

https://www.npr.org/sections/13.7/2015/12/22/
460655319/do-you-really-know-why-earth-has-a-solstice

https://www.youtube.com/watch?v=l64YwNl1wr0 - 29 April 2015

solstices and equinoxes explained

https://www.youtube.com/watch?v=To-oFiyd6Dc

https://www.npr.org/sections/13.7/2015/12/22/
460655319/do-you-really-know-why-earth-has-a-solstice

equinoxes USA

Both equinoxes and solstices

only happen twice a year

— the first days of fall and spring are equinoxes,

while the first days of summer and winter

are solstices.

https://www.npr.org/2022/09/22/
1124443543/first-day-fall-autumn-equinox

equinox USA

What is an equinox?

On the day of an equinox,

the Earth is tilting neither toward

or away from the sun,

and therefore receives almost

an equal amount of daylight and darkness,

according to the National Weather Service.

At places along the equator,

the sun is directly overhead

at about noon on these days.

Day and night appear to be equal

due to the bending of the sun's rays,

which makes the sun appear

above the horizon

when it is actually below it.

During an equinox,

days are slightly longer

in places with higher latitudes.

At the equator, daylight may last

for about 12 hours and seven minutes.

But at a place with 60 degrees of latitude,

such as the North Pole,

a day is about 12 hours and 16 minutes.

https://www.npr.org/2022/09/22/
1124443543/first-day-fall-autumn-equinox

solstice USA

What is a solstice?

On the day of a solstice,

the Earth is at its maximum tilt,

23.5 degrees,

either toward or away from the sun.

During a summer solstice,

the sun is directly above the Tropic of Cancer

in the Northern Hemisphere

and is tilting toward the sun,

causing the longest day of the year.

It is winter in the Southern Hemisphere,

where the Earth is tilting away

from the sun.

Likewise, a winter solstice happens

in the Northern Hemisphere

when the hemisphere is tilting awa

from the sun, making it the day

with the least amount of sunlight.

The sun is above the Tropic of Capricorn

in the southern hemisphere,

making it summer there.

https://www.npr.org/2022/09/22/
1124443543/first-day-fall-autumn-equinox

tilt USA

https://www.npr.org/2022/09/22/
1124443543/first-day-fall-autumn-equinox

Earth’s tilt toward the sun

On the summer solstice this Saturday,

the Northern Hemisphere

will dip toward the sun

and bathe in direct sunlight

for longer than any other day of the year.

That will cause the sun to rise early,

climb high into the sky

— sweeping far above city skylines

or mountain peaks —

and set late into the evening.

The solstice occurs

because Earth does not spin upright

but leans 23.5 degrees on a tilted axis.

Such a slouch, or obliquity,

has long caused astronomers

to wonder whether Earth’s tilt

— which you could argue is in a sweet spot

between more extreme obliquities —

helped create

the conditions necessary for life.

https://www.nytimes.com/article/
summer-solstice-meaning-sunset.html - June 20, 2020

- updated June 20, 2021

tilt

https://www.youtube.com/watch?v=Pgq0LThW7QA - 14 November 2012

tilted

https://www.youtube.com/watch?v=vDgUmTq4a2Q - 17 January 2010

on a tilted axis USA

https://www.nytimes.com/2017/12/20/
science/winter-solstice-december-21.html

Corpus of news articles

Space > Solar system > Planets > Earth

Earth’s tilt toward the sun

Seasons

Something Was Messing

With Earth’s Axis.

The Answer Has to Do With Us.

Scientists knew the planet’s centerline could move.

But it took a sharp turn sometime

around the start of the 2000s.

June 28, 2023
5:13 a.m. ET
NYT

For decades, scientists had been watching the average position of our planet’s rotational axis, the imaginary rod around which it turns, gently wander south, away from the geographic North Pole and toward Canada. Suddenly, though, it made a sharp turn and started heading east.

In time, researchers came to a startling realization about what had happened. Accelerated melting of the polar ice sheets and mountain glaciers had changed the way mass was distributed around the planet enough to influence its spin.

Now, some of the same scientists have identified another factor that’s had the same kind of effect: colossal quantities of water pumped out of the ground for crops and households.

“Wow,” Ki-Weon Seo, who led the research behind the latest discovery, recalled thinking when his calculations showed a strong link between groundwater extraction and the drifting of Earth’s axis. It was a “big surprise,” said Dr. Seo, a geophysicist at Seoul National University.

“Are we doomed?”

Water experts have long warned of the consequences of groundwater overuse, particularly as water from underground aquifers becomes an increasingly vital resource in drought-stressed areas like the American West. When water is pumped out of the ground but not replenished, the land can sink, damaging homes and infrastructure and also shrinking the amount of underground space that can hold water thereafter.

Between 1960 and 2000, worldwide groundwater depletion more than doubled, to about 75 trillion gallons a year, scientists estimate. Since then, satellites that measure variations in Earth’s gravity have revealed the staggering extent to which groundwater supplies have declined in particular regions, including India and the Central Valley of California.

“I’m not surprised that it would have an effect” on Earth’s spin, said Matthew Rodell, an earth scientist at NASA’s Goddard Space Flight Center. But “it’s impressive they were able to tease that out of the data,” Dr. Rodell said, referring to the authors of the new research, which was published this month in the journal Geophysical Research Letters. “And that the observations they have of the polar motion are precise enough to see that effect.”

Earth’s axis hasn’t been wandering enough to affect the seasons, which are determined by the planet’s tilt. But fine patterns and variations in the planet’s spin matter hugely to the satellite-based navigation systems that guide planes, missiles and map apps. This has helped motivate researchers to try to understand why the axis moves and where it might be headed next.

You can’t feel it, but our planet’s rotation is nowhere near as smooth as that of the globe on your desk.

As it moves through space, Earth wobbles like a poorly-thrown Frisbee. This is partly because it bulges at the Equator and partly because air masses are constantly whirling through the atmosphere and water is sloshing around in the oceans, pulling the planet ever-so-slightly this way and that.

And then, there’s that wandering axis.

One main cause is that Earth’s crust and mantle are springing back after being covered for millenniums by gigantic ice sheets, rebounding like a mattress unburdened of a sleeper. This has been steadily changing the balance of mass around the planet.

More recently, the balance has also been altered by factors more closely linked to human activity and the global climate. These include the melting of mountain glaciers and the Greenland and Antarctic ice sheets, changes in soil moisture, and our impounding of water behind dams.

Another big factor, according to the study by Dr. Seo and his colleagues, is groundwater depletion. In terms of the effect on Earth’s axis, pumping up water from underground was second in magnitude, between 1993 and 2010, only to the post-glacier adjustment of the planet’s crust, the study found.

Other forces might also be pulling Earth’s axis in its new direction but aren’t yet fully understood, said Clark R. Wilson, a geophysicist at the University of Texas at Austin and another author of the study. “It’s possible, for example, there’s something in Earth’s fluid core that’s going on, that’s contributing as well,” he said.

Even so, the latest discovery points to new possibilities for using information about Earth’s spin to study the climate, Dr. Wilson said.

Because scientists have collected highly precise data on the position of Earth’s axis during much of the 20th century, they might be able to use it to understand shifts in groundwater use that took place before the most modern and reliable data became available.

It is a possibility Dr. Seo says he has already begun to explore.