<P> Additionally, some large - scale events, such as the 2004 Indian Ocean earthquake, have caused the length of a day to shorten by 3 microseconds by affecting the Earth's moment of inertia . Post-glacial rebound, ongoing since the last Ice age, is also changing the distribution of the Earth's mass thus affecting the moment of inertia of the Earth and, by the conservation of angular momentum, the Earth's rotation period . </P> <P> The primary monitoring of the Earth's rotation is performed with very - long - baseline interferometry coordinated with the Global Positioning System, satellite laser ranging, and other satellite techniques . This provides an absolute reference for the determination of universal time, precession, and nutation . </P> <P> There are recorded observations of solar and lunar eclipses by Babylonian and Chinese astronomers beginning in the 8th century BCE, as well as from the medieval Islamic world and elsewhere . These observations can be used to determine changes in the Earth's rotation over the last 27 centuries, since the length of the day is a critical parameter in the calculation of the place and time of eclipses . A change in day length of milliseconds per century shows up as a change of hours and thousands of kilometers in eclipse observations . The ancient data is consistent with a shorter day, meaning the Earth was turning faster throughout the past . </P> <P> The Earth's original rotation was a vestige of the original angular momentum of the cloud of dust, rocks, and gas that coalesced to form the Solar System . This primordial cloud was composed of hydrogen and helium produced in the Big Bang, as well as heavier elements ejected by supernovas . As this interstellar dust is heterogeneous, any asymmetry during gravitational accretion resulted in the angular momentum of the eventual planet . </P>

Write any 5 points about effects of earth rotation