China's Dams Are Slowing The Earth's Rotation

[Everybody Wang Chung]

China's Three Gorges Dam is by far the largest dam on earth. It is so massive that it has literally slowed the rotation of the earth, however slight:
https://www.msn.com/en-us/news/technolo ... r-AA1rMFza

The good news is that China is now building another even more massive dam, that will be about 3 times larger than the Three Gorges Dam, further slowing the rotation of the earth.
https://thehill.com/opinion/energy-envi ... tal-risks/

[Chap]

Earth's speed of rotation has been changing for millennia. Nothing to worry about here.

Earth's rotation

Earth's rotation or Earth's spin is the rotation of planet Earth around its own axis, as well as changes in the orientation of the rotation axis in space. Earth rotates eastward, in prograde motion. As viewed from the northern polar star Polaris, Earth turns counterclockwise.

The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where Earth's axis of rotation meets its surface. This point is distinct from Earth's north magnetic pole. The South Pole is the other point where Earth's axis of rotation intersects its surface, in Antarctica.

Earth rotates once in about 24 hours with respect to the Sun, but once every 23 hours, 56 minutes and 4 seconds with respect to other distant stars (see below). Earth's rotation is slowing slightly with time; thus, a day was shorter in the past. This is due to the tidal effects the Moon has on Earth's rotation. Atomic clocks show that the modern day is longer by about 1.7 milliseconds than a century ago,[1] slowly increasing the rate at which UTC is adjusted by leap seconds. Analysis of historical astronomical records shows a slowing trend; the length of a day increased by about 2.3 milliseconds per century since the 8th century BCE.[2]

Scientists reported that in 2020 Earth had started spinning faster, after consistently spinning slower than 86,400 seconds per day in the decades before. On June 29, 2022, Earth's spin was completed in 1.59 milliseconds under 24 hours, setting a new record.[3] Because of that trend, engineers worldwide are discussing a 'negative leap second' and other possible timekeeping measures.[4]

This increase in speed is thought to be due to various factors, including the complex motion of its molten core, oceans, and atmosphere, the effect of celestial bodies such as the Moon, and possibly climate change, which is causing the ice at Earth's poles to melt. The masses of ice account for the Earth's shape being that of an oblate spheroid, bulging around the equator. When these masses are reduced, the poles rebound from the loss of weight, and Earth becomes more spherical, which has the effect of bringing mass closer to its centre of gravity. Conservation of angular momentum dictates that a mass distributed more closely around its centre of gravity spins faster.[5]

[Physics Guy]

There is no threshold size of structure above which something suddenly starts affecting the spin of the Earth, and below which there is no effect at all. Spit to the east and you slow the Earth’s rotation by a tiny amount, until your spit hits the ground. Spit west and you speed us up, briefly, by a tiny amount.

The Earth has a mass of about six sextillion tonnes and a radius of about 6400 kilometers. It rotates 360 degrees every 24 hours. Insofar as you can compete with that, you affect it.

[Bret Ripley]

There is no threshold size of structure above which something suddenly starts affecting the spin of the Earth, and below which there is no effect at all. Spit to the east and you slow the Earth’s rotation by a tiny amount, until your spit hits the ground. Spit west and you speed us up, briefly, by a tiny amount.

The science is clear: if we can get everyone to spit in the same direction at the same time and prevent the spit from hitting the ground for 6 months, we can finally do away with daylight savings time.