Tuesday, June 20, 2023

4062 - MOON - and Earth's rotation?

 

-    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?

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-    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.

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-    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.

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-   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.

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-   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.

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-    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.

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-    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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-    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.

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-   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.

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-     “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.

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-   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.

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-   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.

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-    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.

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-   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.

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-    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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--------------------- ---  Tuesday, June 20, 2023  ---------------------------------

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