Antarctic Craters Reveal Asteroid Strike

dhuff writes "Scientists using satellites have mapped huge craters under the Antarctic ice sheet caused by an asteroid as big as the one believed to have wiped out the dinosaurs 65m years ago."

Comments

Re:Curious

[Ralph Wiggam]

"Does the magnetic field being reversed actually affect anything important?"

It doesn't matter what direction the field points, what matters is that there is a magnetic field around the Earth. During the time it takes for the field to flip, the field becomes very weak. That causes two problems. Some animals use the magnetic field for navigation. More importantly, the field is a shield protecting us from cosmic high energy particles. According to a story in the NY Times (covered on /.), Earth's magnetic field has weakened 10-15% since we started measuring 150 years ago. Maybe our grandkids will have to wear lead undies.

-B

Re:Parent is ignorant or trolling? Hard to tell.

[Aardpig]

Magnetism has nothing to do with the direction in which water flows in a drain. That would be the rotation of the planet.

And for all reasonable-sized drains (such as the ones you have at the bottom of your bathtub), the Earth's rotation has a completely-negligible effect on the outflow. The notion that the Coriolis force causes water to drain in opposite directions, in the Northern and Southern hemispheres, is a fallacy.

To see why this is so, consider the so-called Rossby radius of deformation , defined as the ratio between wave speed and rotation frequency. This quantity is the length scale at which the Coriolis force begins to have an appreciable effect on disturbances in a fluid in a rotating system. Plugging in the appropriate values for water waves in a bathtub on the rotating Earth, you find a Rossby radius of around 20km. This is four orders of magnitude larger than the scale of the bathtub, indicating that the influence of the Coriolis force on draining water will be almost non-existant.