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Day length variation on planet earth
Posted: Thu May 26, 2011 11:42 pm
by Eternity
Hi
Is it possible that a day on planet earth was once 25 hours and will be 22 hours (in 6 billion years for example)? Or vice versa (25 hours in 1.5 billion years)? Are there any realistic causes that could change day length drastically?
Thanks for answering!
Re: Day length variation on planet earth
Posted: Fri May 27, 2011 12:45 am
by rstevenson
The day length was less in the past, perhaps as little as 6 hours when the Earth was formed. The day was about 22 hours long about 620 mya. Tidal acceleration is causing this gradual change in the day length.
More info here.
Rob
Re: Day length variation on planet earth
Posted: Fri May 27, 2011 12:48 am
by bystander
The rotation of the Earth is slowing and the days are getting longer, though we won't notice the difference within our lifetimes.
http://en.wikipedia.org/wiki/Tidal_acceleration
lol, Rob beat me to it.
Re: Day length variation on planet earth
Posted: Fri May 27, 2011 1:16 am
by neufer
Eternity wrote:Hi
Is it possible that a day on planet earth was once 25 hours and will be 22 hours (in 6 billion years for example)?
Or vice versa (25 hours in 1.5 billion years)? Are there any realistic causes that could change day length drastically?
http://asterisk.apod.com/viewtopic.php? ... 78#p141878
http://en.wikipedia.org/wiki/2011_TC5%8Dhoku_earthquake_and_tsunami wrote:
<<The 2011 TÅhoku earthquake shifted the Earth's axis by 25 cm. This deviation led to a number of small planetary changes, including the length of a day and the tilt of the Earth. The speed of the Earth's rotation increased, shortening the day by 1.8 microseconds due to the redistribution of Earth's mass. The axial shift was caused by the redistribution of mass on the Earth's surface, which changed the planet's moment of inertia. Because of conservation of angular momentum, such changes of inertia result in small changes to the Earth's rate of rotation. These are expected changes for an earthquake of this magnitude.>>