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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."
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"Does the magnetic field being reversed actually affect anything important?"
/.), Earth's magnetic field has weakened 10-15% since we started measuring 150 years ago. Maybe our grandkids will have to wear lead undies.
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
-B
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.
Tubal-Cain smokes the white owl.
My understanding is that tidal waves are seismic events that travel along the seafloor. They raise the water level only a few feet, and are essentially invisible until they hit shore and start climbing. Since icebergs float, it's not clear how they would suppress a shockwave happening below and around them.
I'm not a specialist in this in any way at all. But maybe this is a good analogy:
Smooth out 2 big comforters on your bed. Kneel on the side of the bed, and sweep your arm under the comforters from one end to the other. It's fairly easy because you only have to displace the comforters right around your arm.
Now put a piece of cardboard as big as your bed between the two comforters. This simulates iceburgs. Now slide your arm through. It will be harder because your arm has to displace a larger amount of comforter as it moves along - the cardboard kind of spreads out the force/displacement that your arm is causing.
That's the only thing I can think of.