# Japan quake causes day to get a wee bit shorter

You won't notice it, but the day just got a tiny bit shorter because of Friday's giant earthquake off the coast of Japan.

NASA geophysicist Richard Gross calculated that Earth's rotation sped up by 1.6 microseconds. That's because of the shift in Earth's mass caused by the 8.9-magnitude . A microsecond is one-millionth of a second.

That change in rotation speed is slightly more than the one caused by last year's larger earthquake. But 2004's bigger Sumatra earthquake caused a 6.8-microsecond shortening of the day.

The Japan quake is the fifth strongest since 1900.

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Mar 12, 2011
An earthquake can also lengthen a day. In the long run the effects of quakes cancel each other out. The long term slowing of the earth due to tidal locking (with the moon) is still the dominant effect. NASA stated 2.3 milliseconds per century, though I've seen other sources at 1.4 ms.

Mar 12, 2011
So after about 500,000 years our day will be a second shorter?

Mar 12, 2011
If the tidal deceleration lengthened the day by 2 ms/day per century, a billion years would find the day about 5 1/2 hrs longer. I'd bet the effect of the moon was more pronounced earlier in earth's history because it was so much closer.
2*(10^-3)*(10^9/100)/60/60 = 5.556 hrs., implying that the day was really short 4 billion yrs. ago, assuming that the oceans were in place to contribute tidal friction.

Mar 12, 2011
If the tidal deceleration lengthened the day by 2 ms/day per century, a billion years would find the day about 5 1/2 hrs longer. I'd bet the effect of the moon was more pronounced earlier in earth's history because it was so much closer.
2*(10^-3)*(10^9/100)/60/60 = 5.556 hrs., implying that the day was really short 4 billion yrs. ago, assuming that the oceans were in place to contribute tidal friction.

Many creationists have done that calculation unsuccessfully in an attempt to show that billions of years ago the Earth would have been spinning so fast that animals would have been practically thrown around. Your number seems reasonable, good job.

Mar 12, 2011
"BBCs Hawksley implicitly suggests that man-made climate change also contributed to the Japanese earthquake."
http://www.sovere...?p=15770

Global warming did it.

Mar 12, 2011
From what I've read, when the earth first formed the day was 8 hours long, then the collision that formed the moon shortened that to 5 hours. But the moon was 200 times larger from the earth's perspective, and its gravitational pull supposedly cause the hot new crust of the earth to rise by about a mile when the moon was directly overhead. Of course this affect rapidly decreased as the moon grew in distance from the earth, at a gradually slower rate over because of the reduced tidal interactions at the gradually increasing distances.

At that rate, by the time anything started crawling on the earth, the earth was likely already past the 20 hour day mark.

Mar 12, 2011
"BBCs Hawksley implicitly suggests that man-made climate change also contributed to the Japanese earthquake."
http://www.sovere...?p=15770

Global warming did it.

Well that's a lie.

Mar 12, 2011
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Mar 13, 2011
how come no-one is blaming it on the particle accelerator?
Global warming is such a crock! But consider this, the weight of all that water coming inland could be enough to set the next tremor off.
Since Japan is dislocated from it's previous position what is now under pressure? (there were five in the bed and the little one said roll over....)

Mar 13, 2011
"BBCs Hawksley implicitly suggests that man-made climate change also contributed to the Japanese earthquake."
http://www.sovere...?p=15770

Global warming did it.

Well that's a lie.

Those are the people, AGWites, so many here support and defend.

Mar 13, 2011
I always rely on that extra millisecond of sleep! ;)

Mar 14, 2011
Well if global warming caused it, then it was Bush's fault.

Mar 14, 2011
Well that's a lie.

Those are the people, AGWites, so many here support and defend.
Again Mr. Swenson, reading skills are important.