Measuring changes in Earth's rotation

[Astronuc]

I read an article about the earth's rotation slowing due to redistribution of mass (probably mostly water).

The headline indicated that Earth's rotation could slow to a rate of 25 hours per day, which seems rather large. This follows a publication announcing, Researchers improve measurement of the earth's rotation
TUM makes first daily current measurements of changes in the earth's rotation

https://www.tum.de/en/news-and-even...easurements-of-changes-in-the-earths-rotation

As far as I can tell (i.e., I am not aware), TUM and Geodetic Observatory Wettzell have not suggested the length of an earth day (rotational period) is increasing to 25 hours. It would be an interesting exercise in geophysics to determine the mass distribution (and change in diameter) required to slow the earth's rotation from 24 hours to 25 hours.

 

[Baluncore]

It would be an interesting exercise in geophysics to determine the mass distribution (and change in diameter) required to slow the earth's rotation from 24 yours to 25 hours.

Coral reefs provide daily growth bands, and annual spawning cycles, that make it possible to measure the number of days per year, all the way back to the Cambrian.

The expanding Earth model of S. Warren Carey explained the reduction in the number of days per year since the Cambrian as being due to the changes in density distribution and radius of the Earth. (If I remember correctly, back in the Cambrian there were about 450 days per year).

Deuser (1970), assuming constant earth mass, constant angular momentum,
and rotation rates 150 m.y. ago of 380 and 395 days per year (based on Well's
coral growth-line estimate), deduced equatorial radii between 6250 and 5990
km according to earth ellipticity assumed; these radii correspond to maximum
increases of the equator of 804 and 2437 km respectively.

One problem with quantising the reduction over hundreds-of-millions-of-years, in the rate of Earth rotation, is in separating out the loss of energy due to lunar tides.

The volume of ice at the poles causes Earth rotation rate changes over thousands of years.

By observing the meridian transit of a star, we can observe daily to monthly changes in Earth rotation rate, I believe due to redistribution of the atmosphere.