Thursday 8 December 2016

You Might Not Even Noticed But Your Days Are Getting Shorter


Our days are getting ever so slightly longer thanks to the slowing down of the Earth’s orbit.

The average day has increased by around 1.8 milliseconds every century over the last 27,000 years – according to new research.

But because of this painfully gradual change, it would take 6.7 million years for the average day to gain just one minute more.

The study, co-authored by retired Royal Greenwich Observatory astronomer Leslie Morrison, found that the 1.8ms increase was “significantly less” than the previous 2.3ms estimate.

“It’s a very slow process,” said Dr Morrison.

“These estimates are approximate, because the geophysical forces operating on the Earth’s rotation will not necessarily be constant over such a long period of time.

“Intervening Ice Ages etcetera will disrupt these simple extrapolations.”

The preious 2.3ms estimate was based on calculations of the Moon’s power to cause ocean tides and therefore influence its orbit.

But for the new study, the team of scientists used gravitational theories about the movement of the Earth around the sun, and the Moon around the Earth, to find out exact timings of eclipses.

They compared this to eclipse observations recorded by the ancient Babylonians, Chinese, Greeks, Arabs and medieval Europeans.

Factors affecting the globe’s rotation include the Moon’s wave braking effect, Earth’s altering shape due to shrinking polar ice caps since the last Ice Age, electro-magnetic interactions between the mantle and core, and changes in the main sea level.

The slowing of the Earth’s orbit is the reason timekeepers have to adjust high-precision clocks every few years to ensure they remain in sync.

Scientists earlier this year found the "closest ever" second Earth outside our solar system.



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