NASA Scientist Thinks Chile Earthquake Shifted Earth's Axis

[Naffa]

Just bash a lazy persons head in with a cpu cooler that'll teach you how to take time to relax

Righty, brb.

 

[GreatAuk]

Curious, how does rotational momentum get affected by an earthquake? As far as I'm aware, nothing was ejected into space, and that's the extent to which my Physics knowledge goes.

edit:

http://en.wikipedia.org/wiki/Angular_momentum

Okay, lets say the earthquake brought more material to the earths surface. To conserve momentum, that material would have to be travelling slower (radians per second). But obviously it can't travel slower than the rest of the surface and so slows the motion of the crust?

Sound about right?

I presume what happened was the earthquake moved mass up overall (eg seawater replacing the denser rock lower down or something) so that it's like spinning round on a chair and then putting your legs out.... But really I have no idea

 

[mark66]

So all we need is a ship to travel fast as light backwards around the earth and everything will be right as rain.

 

[RDM]

I presume what happened was the earthquake moved mass up overall (eg seawater replacing the denser rock lower down or something) so that it's like spinning round on a chair and then putting your legs out.... But really I have no idea

Surely for the day to be shortened then the planet needs to have sped up rather than slowed down?

 

[Hamzter]

I can understand the length of day changing veeeery slightly, by changing the earths moment of inertia (think about a roundabout or similar, if you move your weight towards the centre, it spins faster). 6.8 milliseconds sounds like a massive change when something weighs as much as the earth though! To the maths!!!

Using conservation of momentum, I came up with this lovely equation:

dI = 2/5*mr^2*(1-(T-dt)/T) where dI = change of moment of inertia, m = mass of earth, r = radius of earth, T = length of day, and dt = change in length of day

Plugging in numbers that means for a 6.8microsecond change, earths momentum must change by 7.65x10^27 kg.m2. In order to get that change, you'd need to launch 6000 cubic km of water 100km into the air! Earthquakes are powerful but not THAT powerful

Edit: Doh! On my second attempt I get 5.47x10^21kg.m2 and only 0.004km3 (4 million tons). Must have forgotten to carry the one.

 

[Naffa]

Just bash a lazy persons head in with a cpu cooler that'll teach you how to take time to relax

Righty, brb.

Nope, I still have the urge to withdraw people's brains from their heads.

 

[Tefal]

How about you have a gander at the brain of someone who faints when they see brains?

Could do the trick!


If not at least you'll be well rested.

 

[Naffa]

I'm not interested in that ability.