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# earthquakes can make days shorter

## best excuse for why I miss my deadlines :)

#### LifeinAsia

6:00 pm on Mar 2, 2010 (gmt 0)

#### Moderator from US

joined:Dec 10, 2005
posts:5847

[cnn.com...]

#### mack

6:14 pm on Mar 2, 2010 (gmt 0)

#### Moderator from GB

joined:June 15, 2001
posts:7844

I am realy going to miss that millionth of a seconds sleep each night. :)

Mack.

#### pageoneresults

6:28 pm on Mar 2, 2010 (gmt 0)

#### Senior Member from US

joined:Apr 27, 2001
posts: 12172

He determined that the quake should have moved the Earth's figure axis about 3 inches (8 centimeters). The figure axis is one around which the Earth's mass is balanced. That shift in axis is what may have shortened days.

3 inches, yikes! Isn't there something in the books about the axis reversing themselves? Ah yes, they refer to it as Polar Reversal. Scary stuff.

I watch too much NatGeo! ;)

#### grandpa

7:03 pm on Mar 2, 2010 (gmt 0)

#### Senior Member

joined:Sept 7, 2003
posts:1408

I'm curious as to where the tipping point might occur. At what point does the axis shift and then keep on going until it can find a place to settle down?

The same article (see above) also mentioned the Three Gorges reservoir in China. Filled, it will hold 10 trillion gallons of water, enough to take off another millisecond or two.

...millionth of a seconds sleep each night.

I need a nap. If this keeps up I may need 2.

#### KenB

7:08 pm on Mar 2, 2010 (gmt 0)

#### Senior Member

joined:Nov 24, 2003
posts:729

Grandpa, you slightly misread the article, the Three Gorges Reservoir will add to the length of our days, not subtract once it is full.

#### grandpa

7:11 pm on Mar 2, 2010 (gmt 0)

#### Senior Member

joined:Sept 7, 2003
posts:1408

In all seriousness, I wonder how this will affect systems that require critical timing. Some communications systems, weapons systems, and probably others all depend on timing that is usually controlled by an atomic clock. In the communications systems I used to maintain the timing was provided by a cesium beam clock, and all the clocks in the system had to be in sync. So where milliseconds don't really matter to most people, they are critical in some cases.

#### lawman

7:18 pm on Mar 2, 2010 (gmt 0)

#### Senior Member from US

joined:May 28, 2001
posts:3615

Over the course of a year, the length of a day normally changes gradually by one millisecond. It increases in the winter, when the Earth rotates more slowly, and decreases in the summer, Gross has said in the past.

[news.yahoo.com...]

Since winter happens only in one one hemisphere at a time, how does that work?

#### KenB

8:28 pm on Mar 2, 2010 (gmt 0)

#### Senior Member

joined:Nov 24, 2003
posts:729

@Grandpa,

This isn't the first time such things have happened. Every now and then those responsible for defining the accurate time will throw in a leap second or leap millisecond if it becomes necessary.

@Lawman,

This is because there is more landmass in the northern hemisphere and there are higher mountains in the northern hemisphere. Thus snow pack build up would be heavier during northern winters than southern winters.

#### kaled

8:29 pm on Mar 2, 2010 (gmt 0)

#### Senior Member

joined:Mar 2, 2003
posts:3710

I would hope that all navigational systems, etc. can cope without difficulty...

I believe the Earth's rotation is gradually getting slower anyway. For instance, I seem to recall that many millions of years ago a year was more than four hundred days long (because days were shorter). I always assumed this was due to the energy loss caused by Earth/Moon/Tide interaction but I've never seen this written down anywhere.

Incidentally, the "polar flip" refers only to the magnetic core and is not expected again for quite some time. When it does happen though, protection from solar radiation will weaken during the transition so things could get pretty nasty.

Kaled.