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Chile Earthquake May Have Shortened Days on Earth
March 2, 2010 5:16 PM   Subscribe


 
This morning, when I read the headline "Chile Earthquake May Have Shortened Days on Earth," I was just starting to drink my caffeine. I was so sleepy that I parsed it as "shortened our days on Earth," as in the number of days we all have left. Naturally I caught up with myself and realized what it meant by the time the article loaded, but not before I wondered if there might not be an excuse to get off work in it.
posted by Countess Elena at 5:22 PM on March 2, 2010 [2 favorites]


I waited all day yesterday to see if someone would post this. By the time I decided to post it, I was too tired and went to bad.

Glad to see someone else was paying attention.
posted by Malice at 5:24 PM on March 2, 2010


"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."

...wait, what? Whose summer? This makes no sense.
posted by oulipian at 5:24 PM on March 2, 2010 [4 favorites]


I was just starting to drink my caffeine. I was so sleepy that I parsed it as "shortened our days on Earth," as in the number of days we all have left.

I read it right now, perfectly awake, not misreading, and that's still the way I interpreted the sentence.
posted by Solon and Thanks at 5:25 PM on March 2, 2010


wait, what?...This makes no sense.

eponysterical!
posted by OmieWise at 5:27 PM on March 2, 2010


I waited all day yesterday to see if someone would post this. By the time I decided to post it, I was too tired and went to bad.

How could you be tired, with a full 1.26 fewer microseconds of work done that day?
posted by DU at 5:32 PM on March 2, 2010 [3 favorites]


Wait, 1.26 milliseconds. A 1000-fold increase in spare time!
posted by DU at 5:33 PM on March 2, 2010


Obligatory xkcd link.

So, who can explain how an earthquake shortens the day? Is the earth actually spinning faster? IIRC the earth is slowing down for the most part, but I didn't know about this phenomenon.

If I had to make a guess I'd say that oscillations have no net effect, but apparently I'm wrong?

Reading the original article leads me to believe the earth is now spinning faster because more of the mass is closer to the center. Does this mean erosion also speeds up the earth?
posted by poe at 5:35 PM on March 2, 2010


Well, that's 1.26 milliseconds I'll never get back.
posted by gman at 5:35 PM on March 2, 2010


bed* Apparently, I'm still tired.

And indeed, DU, I'm feeling refreshed already!
posted by Malice at 5:37 PM on March 2, 2010


...wait, what? Whose summer? This makes no sense.
posted by oulipian at 5:24 PM on March 2 [+] [!]


Yeah, not a good word choice. Perhaps they're talking about orbital perihelion vs. aphelion. The apparent or solar day is a little bit longer at perihelion than at aphelion because our orbital motion is faster, which subtracts a bit more from the sun's apparent motion across the sky. IIRC, perihelion corresponds to Northern winter, so presumably that's what they mean.
posted by George_Spiggott at 5:46 PM on March 2, 2010 [1 favorite]


How could you be tired, with a full 1.26 fewer milliseconds of work done that day?

Because I had to get out of bed 1.26 milliseconds earlier!
posted by L.P. Hatecraft at 5:46 PM on March 2, 2010


poe: It's conservation of angular momentum. The earthquake shifted the distribution of the Earth's mass, which changed its moment of inertia. Since angular momentum is conserved, the planet's angular velocity increased, and the Earth is now spinning marginally faster. This demonstration shows an example of how changing the moment of inertia changes rotation speed, if you're curious. And yes, erosion could theoretically change Earth's rotation slightly.
posted by Upton O'Good at 5:49 PM on March 2, 2010 [1 favorite]


Well, that's just great! I got shit to do!
posted by dirigibleman at 6:06 PM on March 2, 2010


This sucks! I've got stuff to do!
posted by Mister_A at 6:07 PM on March 2, 2010


Gaaahhhhh! 1.26 msec late again.
posted by Mister_A at 6:14 PM on March 2, 2010 [21 favorites]


Strange.

If the 'axis of figure' is not the same as the axis of rotation and has no fixed relationship to it, I don't see how you'd measure it experimentally except by arduous and prolonged collection and analysis of the data from those satellites that measure the Earth's gravitational field.

Has there even been enough time for that?

Because the earth sped up, we can say the principle of minimum potential energy favored the occurrence of the Chilean quake without reference to the plate tectonics of it.
posted by jamjam at 7:20 PM on March 2, 2010


Ok, everyone go outside, take a deep breath, and blow eastward!! BLOW DAMMIT! I WANT THOSE MILLISECONDS BACK!
posted by Salvor Hardin at 7:32 PM on March 2, 2010 [2 favorites]


Yeah, but as they grudgingly admitted in one article, clouds moving around do this all the time.

Running east does this too, as does moving to a tropical country if you're not already in one.
posted by dunkadunc at 7:56 PM on March 2, 2010


I wouldn't worry about it, because the next big earthquake will probably undo this change.

What goes around comes around.
posted by bwg at 8:10 PM on March 2, 2010


Are we closer or further in regards to the north/south axis?
posted by scottymac at 8:23 PM on March 2, 2010


So this is going to offset global warming right
posted by danb at 9:18 PM on March 2, 2010


Wait, 1.26 milliseconds. A 1000-fold increase in spare time!

The original story from space.com says microseconds, which sounds a lot more plausible. If it were milliseconds, the average radius of the entire planet would have to have dropped by about two inches, according to my back-of-the-envelope calculations.
posted by teraflop at 9:25 PM on March 2, 2010


"Perhaps more impressive is how much the quake shifted Earth's axis," NASA officials said in a Monday update.

Formerly neutral, Earth's axis has now shifted to become an axis... of evil.

We must commence bombing the Earth's core.
posted by problemspace at 10:10 PM on March 2, 2010


Is this going to affect my paycheck?
posted by IvoShandor at 10:29 PM on March 2, 2010


My watch doesn't have milliseconds on it. Am I exempt?
posted by TwelveTwo at 12:48 AM on March 3, 2010


The computer model used by Gross and his colleagues to determine the effects of the Chile earthquake effect also found that it should have moved Earth’s figure axis by about 3 inches (8 cm or 27 milliarcseconds).

Drat, now my next few days are going to be dominated by attempts to use “milliarcseconds” in regular conversation…
posted by DreamerFi at 12:55 AM on March 3, 2010 [1 favorite]


Wait, if the Earth is spinning faster, wouldn't that mean that our days are getting shorter, but we'd have more of them?
posted by iamkimiam at 2:15 AM on March 3, 2010


Nah, it just means a few more leap seconds here and there over the next decade or so.
posted by Rhomboid at 2:29 AM on March 3, 2010


There just ain't enough milliseconds in the day, I tell ya.
posted by flapjax at midnite at 5:08 AM on March 3, 2010


I heard the scientist who started this story on NPR, and he was saying microseconds not milliseconds. This is confirmed by New Scientist.
He calculated it solely from the mass of the land that moved, and how much it decreased in altitude. As he said, this spins up the Earth's rotation in the same way a spinning figure skater rotates faster when they pull their arms closer to their body.
I'd say that only linking to a story that's off by three orders of magnitude makes this single link FPP worthless.
posted by w0mbat at 7:50 AM on March 3, 2010


This will help to offset the fact that the Chinese Three Gorges Dam lengthened days by 0.06 microseconds.
posted by quin at 8:43 AM on March 3, 2010 [1 favorite]


I had an argument with one of the less well informed members of my class today, who came in exclaiming about how days were shorter after the earthquake, to which I replied "Bollocks!", then when I got the actual figure of 1.26 microseconds or thereabouts, I had to go through the entire top to bottom calculations (with a lot of explaining what scientific notation was) to demonstrate to her how ridiculously insignificant the difference was.

I need to get out more.
posted by Biru at 9:15 AM on March 3, 2010


Milliarcseconds ain't what they used to be
posted by illy at 6:56 AM on March 4, 2010


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