1. The word equinox
comes from two Latin words:
-
aequus,
meaning equal
-
nox,
meaning night
The
sun rising
at
the spring equinox at the equator.
Credit: Getty Images.
2. If you went to the equator on either of these days, you'd see
the sun straight overhead at noon.
This isn't its actual
position, however. It's below that point. This optical illusion
is due to the refraction or bending of the sun's rays as they
travel through the atmosphere.
The
Earth's axis.
Credit: Wikipedia.
3. An image illustrating the Earth's axis can be different,
depending on the illustrator.
While some prefer a
left-to-right tilt, others portray it right-to-left. Both are
accurate, depending on the positions of the Earth and the sun.
Comparison between the size of
Mars and the Earth.
Credit: NASA.
4. How did the Earth get tilted in the first place? It's thought
that an object the size of Mars crashed into it some
4.5 billion
years ago, while our planet was still young.
Credit: Wikipedia.
5. The Earth's axial tilt, also called its
obliquity, isn't a
static number.
The Earth wobbles on
its axis, as the result of earthquakes, but also different
gravitational forces acted upon it by the moon, the sun, and the
other planets in our solar system.
Therefore, Earth's
obliquity varies at times
between 22.1° and 24.5°.
Credit: Pintrest.
6. Other names for Earth's wobble include the
precession of the
equinoxes and the axial precession.
Hipparchus of Nicea (left) and Ptolemy.
The
School of Athens by: Rafael, 1509.
Credit: Wikipedia Commons.
7. In 130 BCE,
Hipparchus of Nicea discovered the Earth's axis
shifted slowly over time.
He came across this
by comparing astronomical observations separated by 100 years.
The
Heliophysics System Observatory (HSO).
Even though it has many parts,
it's considered one observatory.
Credit: NASA.
8. Although we've looked into this for a long time, we didn't
really get highly detailed data until we went into space. And
we're still learning.
Consider NASA's
Heliophysics System Observatory (HSO), which started in 2013 and
is wrapping up in 2022. The HSO includes
20 missions and 23
spacecraft.
It'll investigate
"space weather," how our star interacts with the Earth and other
planets as well.
A
modern-day druid ceremony
near Stonehenge during the vernal equinox.
Credit: Wikipedia Commons.
9. Cultures all over the world celebrate holidays and festivals
on
the equinoxes.
One of the most
notable is the Japanese celebration of
Higan, which takes places
on both equinoxes. During each Buddhist holiday, it's said that
the spirits of the dead pass into Nirvana. It lasts for six
days.
During that time, the
observant visit the graves of loved ones, clean and decorate
them and reflect on and share memories of them.
El
Castillo pyramid in Chichen Itza, Mexico.
Revelers come even today to see the "snake of sunlight"
making its way down the steps.
Credit: Getty Images.
10. In the
ancient Mayan culture, a ritual including human
sacrifice took place at the spring equinox. It happened at
El
Castillo, a pyramid located in Chichen Itza, Mexico.
The pyramid
has four staircases. The angle of each was
carefully calculated so that the "snake of sunlight" would
slither down the stairs at the dawning of each equinox, as the
sun rose into the sky.
