1705505474
Jakarta –
A 24-hour day doesn’t just happen. The Earth must undergo several significant changes until a temporary equilibrium is finally achieved between the tidal forces of the Moon and the Sun.
When the Moon formed about 4.5 billion years ago, most likely as a result of a strong impact, the Moon was much closer to Earth than it is today and our planet was rotating much faster, so the length of a day was less than 10 hours.
Since then, the moon has been slowly moving outward, robbing the Earth of some of its angular momentum, causing the Earth’s rotation to slow. As we know, a day on Earth currently lasts 24 hours.
However, at the rate at which the Moon is moving away from us, measured at (3.78 cm) per year, based on experiments with laser reflectors left on the Moon by Apollo astronauts, our planet is likely to be moving at about 60 cm per year slow down the year. So what is slowing this decline?
Astronomers at the University of Toronto and the University of Bordeux, led by Hanbo Wu of Toronto, now have the answer. This is all related to the balance of torque created by heat waves in the Earth’s atmosphere and gravitational waves emanating from the Moon.
As we know, the Moon’s gravity pulls Earth’s oceans, causing high tides on the opposite side of the planet as the ocean ridge follows the Moon around our planet. The greater the mass of the tidal bulge in the ocean, the more the moon’s gravity pulls on it, coupled with the friction effect between the tides and the ocean floor. The end result is a slowing of the Earth’s rotation by about 1.7 milliseconds per century.
However, heat waves in Earth’s atmosphere can overcome this point effect if their resonance period around the planet is consistent with Earth’s rotation. The temperature of the atmosphere controls the speed of heat waves, and as the atmosphere warms, it swells, creating a different type of bulge.
“Sunlight also creates atmospheric waves with the same type of bulge,” said Norman Murray of the Canadian Institute for Theoretical Astrophysics at the University of Toronto, quoted by Space.com.
“The Sun’s gravity pulls on this atmospheric bulge, creating torque on Earth, but instead of slowing Earth’s rotation like the Moon does, it actually speeds it up,” he said.
For most of Earth’s history, the Moon’s tides were ten times stronger than thermal tides, so Earth’s rotation slowed.
However, based on global atmospheric circulation models and geological evidence from bands in sedimentary rocks associated with past spring and neap floods, this changed between 2.2 and 600 million years ago.
As the atmosphere warmed (evidenced by the lack of icing during this period), the heat waves became larger and faster until they reached a resonance frequency with the Earth’s rotation.
Resonance is a type of reinforcement. A common analogy is that a child is swinging. So if you give it a push at the right time and in accordance with the arc of the swing, it will swing faster and higher. Something similar happens with resonance in nature.
About 2.2 billion years ago, heat waves began to surround the Earth lasting almost 10 hours, while the day length on Earth was 19.5 hours. In other words, heat waves orbit the Earth twice with a resonance of 2:1 for every rotation of the Earth on its axis.
This resonance only amplifies the heat waves, causing the atmospheric bulge to grow larger and the Sun’s gravitational pull to become strong enough to match the Moon’s pull.
As a result, the slowing of the Earth’s rotation due to the Moon’s tides begins to be offset by the acceleration of thermal tides. Over a long period between 2.2 billion years and 600 million years ago, day length on Earth stopped slowing and remained at 19.5 hours.
Eventually the two tidal forces became unbalanced and over the last 600 million years the Earth’s rotation began to slow again. Currently, the duration of a day is 24 hours, while a heat wave takes 22.8 hours to circle the earth.
However, this situation has not been updated. Although recent measurements show that the Earth’s rotation is increasing slightly, in the long term the Earth may not return to a time when tidal forces balance each other out.
Conversely, climate change could cause heat waves to become increasingly out of sync with the planet’s rotation, increasing the influence of lunar waves in slowing the planet.
“As Earth’s temperature rises due to global warming, we also increase this resonance frequency and move our atmosphere further away from resonance,” Murray said.
“As a result, the Sun’s torque will decrease and the length of the day will increase faster than vice versa,” he concluded.
Watch the video “Scientists: Earth will spin faster in 2022.”
(rns/rns)
#day #hours #long #explanation