NASA Details Earthquake Effects on the Earth

Cuyamaca writes " NASA scientists, using data from the Indonesian earthquake calculated it affected Earth's rotation, decreased the length of day, slightly changed the planet's shape, and shifted the North Pole by centimeters. The earthquake that created the huge tsunami also changed the Earth's rotation." You now have 2.68 fewer microseconds each day to do whatever it is you do.

Comments

You might be wondering

[PhysicsGenius]

how something that happens on Earth can affect the rotation time. It's all about angular momentum.

Angular momentum is conserved and is calculated by L = Iw where I is the rotational inertia, w is the angular velocity and L is the constant product. So if I goes up (and I will show in a minute how that happens), w must go down. I, the rotational inertia, is calculated different ways for different geometries. A long stick held by the end has a larger I than the same stick held by the center, for instance. Another example is a sphere, like the Earth, rotating on an axis. If it suddenly puts out a long arm, that's going to increase its rotation inertia considerably, decreasing its angular velocity. Lifting up a whole region by a few inches could easily do that.