- 4062 - MOON - and
Earth's rotation? In the prehistoric
past, Earth may have been stuck with 19-hour days for a billion years and the moon was to blame. Between 2 billion and 1 billion years ago, a
full day lasted five hours less than it does now because of how close the moon
lingered near Earth.
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4062 - MOON
- and Earth's rotation?
-
- Scientists
recently discovered an asteroid that tags along with Earth during its yearly
journey around the sun. Asteroid “2023
FW13” is a space rock considered a "quasi-moon" or
"quasi-satellite," meaning it orbits the sun in a similar time frame
as Earth does, but is only slightly influenced by our planet’s gravitational
pull.
-
- It is estimated to
be 50 feet in diameter, roughly equivalent to three large SUVs parked bumper to
bumper. During its orbit of the sun, 2023 FW13 also circles Earth, coming
within 9 million miles of our planet. For comparison, the moon has a diameter
of 2,159 miles and comes within 226,000 miles of Earth at the closest point of
its orbit.
-
- 2023 FW13 was first
observed in March by the Pan-STARRS observatory, which is located atop the
volcanic mountain Haleakalā in Hawaii. The asteroid's existence was then
confirmed by the Canada-France-Hawaii Telescope in Hawaii and two observatories
in Arizona before being officially listed on April 1 by the Minor Planet Center
at the International Astronomical Union, a network of scientists responsible
for designating new planets, moons and other objects in the solar system.
-
- Some estimates
suggest that 2023 FW13 has been Earth's cosmic neighbor since at least 100 B.C.
and that the space rock will continue to follow this orbital path until around
A.D. 3700.
-
- Despite hovering
relatively close to Earth, this quasi-satellite likely isn't on a collision
course with our planet. This is not Earth's only quasi-companion; a different
quasi-satellite known as “Kamo'oalewa” was discovered in 2016. The rock sticks
similarly close to our planet during its orbit around the sun, and a 2021 study
suggested that this asteroid could actually be a fragment of Earth's moon.
-
- In the prehistoric
past, Earth may have been stuck with 19-hour days for a billion years and the moon was to blame. Between 2 billion and 1 billion years ago, a
full day lasted five hours less than it does now because of how close the moon
lingered near Earth.
-
- Since then,
Earth's days have steadily become longer as the moon has distanced itself from
our planet, slowing Earth's rotation.
Over time, the moon has stolen Earth's rotational energy to boost it
into a higher orbit farther from Earth.
-
- However, in the
mid-Proterozoic era, the moon consistently hovered at a set distance from
Earth, stalling the day length at around 19 hours for 1 billion years before it
eventually started getting longer again . Scientists call this time period the
"boring billion" because of the relative stability of Earth's
tectonic activity, steady climate and slower biological evolution.
-
-
“Cyclostratigraphy” is a technique that focuses on the variation in
sedimentary deposits of rocks. Cyclostratigraphy helps researchers identify
"Milankovitch cycles" , or changes in Earth's orbit and rotation that
have affected the planet's climate.
-
- Analyzing a wealth
of cyclostratigraphy records on Milankovitch cycles allowed the researchers to
peer into the past and determine why the moon clung so tightly to Earth during
this time period. They found that the answer is likely related to the tides
that affect the planet's rotation.
-
- Gravitational pull
from the moon controls Earth's ocean tides, thus slowing the planet's rotation.
However, the sun also exerts a gravitational pull in the form of "solar
atmospheric tides" that occur when sunlight heats Earth's surface and
speeds up the planet's rotation.
-
- Currently, lunar
tides are about twice the strength of solar atmospheric tides, meaning they
have more influence on how quickly Earth spins. But during the "boring
billion," Earth was rotating faster, indicating that the gravitational
pull of the moon was weaker than it is now, according to the study. And so,
during that time, solar and lunar tides were more evenly matched.
-
- Because of this, if
in the past these two opposite forces were to have become equal to each other,
such a tidal resonance would have caused Earth's day length to stop changing
and to have remained constant for some time.
-
- This prolonged
period of 19-hour days coincides with a similar slowdown in the rise of oxygen
in the atmosphere during the mid-Proterozoic era, which may have contributed to the slowdown in
evolution of life on Earth during that time.
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-
June 20, 2023
MOON - and
Earth's rotation 4061
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------ “Jim Detrick” -----------
--------------------- --- Tuesday, June 20, 2023
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