Chilean Earthquake Shortened Earth's Day 374
ailnlv writes "Days on Earth just got shorter. The recent earthquake in Chile shifted the planet's axis by about 8 cm and shortened days by 1.26 microseconds 'The changes can be modeled, though they're difficult to detect physically given their small size. ... Some changes may be more obvious, and islands may have shifted. ... Santa Maria Island off the coast near Concepcion, Chile’s second-largest city, may have been raised 2 meters (6 feet) as a result of the latest quake ...'"
Did this affect climate (Score:2, Interesting)
GPS affected? (Score:5, Interesting)
Re:How often do such quakes occur? (Score:3, Interesting)
That's assuming every single one shortens the day. Do we know if they'll actually do that, or if there's more likely to be some kind of gaussian spread across positive and negative shifts?
Re:GPS affected? (Score:3, Interesting)
It's not about the speed of the bomb. It's about the speed of the sattelites which orbit Earth and which the bomb uses to guide itself.
A sattelite travelling in Geostationary orbit clocks 3.8km/s. In 1.26 microseconds it would travel about 5mm. If it, say, takes a month until the government calculates and issues the correcting commands, the offset would accumulate to 15cm.
If a guided missile is launched to fly into a window of an enemy-occupied building, the offset can be enough to make a difference between hitting the window and hitting the wall.
Re:Did this affect climate (Score:4, Interesting)
I actually liked the ACLU until I followed that link. Thanks a lot. Now I'm starting to wonder if they're any less crazy than the Ron Paul fanatics.
Re:Did this affect climate (Score:4, Interesting)
You say this to make fun of the global warming debate, but theoretically it's not completely impossible that underground nuclear testing has something to do with the specifics of any earthquakes since the 1950s or so. Earthquakes are undoubtedly chaotic, and a series of megaton explosions underground might have shaken things a little and helped them get where they're going faster (temporarily).
Mind you, I'm not claiming that's necessarily the case either (or even probably the case). Just that, much like a decent conspiracy theory, it's not entirely nonsense or outside the realm of possibility. (I'd guess that overall seismicity remains the same overall but chaotic effects will change the locations of, say, half the aftershocks next century.)
USGS FAQ here [usgs.gov].
Re:How often do such quakes occur? (Score:3, Interesting)
From wikipedia:
>> Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; in terms of energy, each whole number increase corresponds to an increase of about 31.6 times the amount of energy released.<<
This quake was 8.8 ram == 15.8 gigatons of TNT delivered
The one (the comet impact) that owned the dinosaurs was 13.0 ram or 100 teratons of TNT
And we really need one, very powerful in the right place at the right time to cause a polar swift. You know, after that you would start to see random Angels coming to Neo New York and Evas and stuff... no in all seriousness a polar swift will fuck us all big time.
http://en.wikipedia.org/wiki/Richter_magnitude_scale
Re:Not worth mentioning (Score:4, Interesting)
The earth is naturally slowing down at a rate that makes this sort of thing hardly worth mentioning.
Actually, the slowdown is only about 2ms/century, or about 0.054 microseconds/day. So a 1-microsecond jump in a day should be noticeable. This information is tracked. Here's the raw data from the Earth Rotation Service. [iers.org]
With GPS systems working down to 15cm, changes like this get noticed.
Re:Great! (Score:5, Interesting)
Wasn't there a famous quote to the effect that you could say the earth was the center of the universe, but it just makes calculations needlessly difficult?
Re:Nit-Picking Science (Score:4, Interesting)
Okay, if this is the case, explain the sudden three inch drop in shadow (I use the shadow on a tarp to determine seasonal change) which usually indicates a full month of time passing, and this happening within two days of the earthquake.
I learned how to read time and the season by the shadows while in prison. Pretty neat when you learn how to do it, but this totally throws the estimation off.
Re:Did this affect climate (Score:5, Interesting)
In Chaos Theory, a small change to the inputs can cause large changes to the results.
However the changes are just as likelly to go in one direction as they are to go in the opposite direction: the butterfly effect is just as likelly to result in a typhoon instead of clear weather as it is to result in clear weather instead of a typhoon.
Also, small changes to inputs can cause small changes to the outputs or even no changes at all (that's why it's called Chaos Theory) - plenty of butterflies flutter-about with out creating typhoons ;)
If indeed the system that underpins earthquakes is chaotic, underground nuclear tests are just as likelly to have brought forward quakes as they are to have delayed quakes as they are not not have had much effect at all - in fact, they're likelly to have done all of them.
Re:Did this affect climate (Score:3, Interesting)
Right, but it only takes a single pebble to start an avalanche.
Now, mind you, if a nuclear weapon ever did trigger an earthquake it would probably just be the trigger event, and the pressure would still have been there from the start. If anything, the nuclear weapon would cause the earthquake to happen sooner, thereby possibly reducing the severity of the eventual quake.
Wow, I just had a brilliant idea. California is worried about the Next Big Quake, and the solution to their problem is so simple - let's trigger whatever pressure is there now in a smaller quake.
Dust off and nuke the state from orbit. It's the only way to be sure.
Re:Great! (Score:1, Interesting)
I just said "the Earth moving around the Sun" to conform to modern standard. I could have said "the Sun moving around the Earth" but then it would have been "in the same direction of the Sun moving around the Earth" but anyway, the principle would still be valid. It always apply for any object shining on another one while one is rotating around the other, or more precisely, when they rotate together around their center of mass.
Time to listen how the The Day The Universe Changed Episode 1 - The Way We Are starts:
"Let me tell you a joke: Somebody apparently once went up to the great philosopher Wittgenstein, and said “What a lot of morons people back in the Middle Ages must have been to have looked every morning at what is going on behind me now, the dawn, and to have thought that what were seeing was the Sun going round the Earth. Well, as every school kid knows, the Earth goes round the Sun and it doesn't take too many brains to understand that”.
To which Wittgenstein replied, “Yeah, but I wonder what it would have looked like if the Sun had been going round the Earth”. The point being, of course, it would have looked exactly the same.
You see what your knowledge tells you you are seeing. "
Re:Great! (Score:3, Interesting)
It has to do with second moments, rotational inertia, that sort of thing... all very complicated and I don’t remember much of it.
However, what I do remember is this. Basically, for any given mass and assuming that you can’t significantly change its density, it has the least possible rotational inertia if its mass is circularly distributed as close to the axis of rotation as possible*... e.g. a cylinder, sphere, disc, etc. So, a torus (donut) will have more rotational inertia than a disc of the same mass, and a sphere will have even less rotational inertia than the disc.
Since rotational momentum is the product of angular velocity and rotational inertia, and the momentum is conserved since there are no outside forces, if the rotational inertia increases, the speed must decrease to conserve energy. Conversely if the rotational inertia decreases, the speed increases.
Basically, the tl;dr version of that is, lumpy shapes spin more slowly than smooth round ones do. If an earthquake makes the earth generally more round, it speeds up the earth’s rotation; however if it lowers some parts while thrusting others upward it does the opposite: slows it down.
*The rotational inertia is actually dependent on the axis of rotation; a perfect sphere will have more rotational inertia than a long, cylindrical rod... but only if the rod is spinning on its longwise axis. In other words, a perfect sphere has the least rotational inertia in all possible axes of rotation, although not in any particular one. The rotational inertia is an integral of mass times its distance from the axis of rotation. A sphere minimizes this for all possible axes; a cylinder with infinite length and zero radius minimizes it for exactly one axis... in fact this hypothetical cylinder would have zero rotational inertia along that axis and its angular velocity would be infinite.
For us in Chile, the days just got longer (Score:3, Interesting)
For us in the disaster zone (I am in Temuco 100 miles south of the worst hit areas), it feels like 48 hour days. They likly will just get longer as this goes on.
if you want to help, visit http://www.allchile.net/ [allchile.net]