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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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Prof Van der Hoeven said: "The extraordinary thing about this meteor strike is that it appeared to do so little damage. Unlike the dinosaur strike there is no telltale layer of dust that demonstrates the history of the event. It may have damaged things and wiped out species but there is no sign of it."
One thing that did happen at exactly the same time was the reversing of the Earth's magnetic field. There is no other explanation as to why this took place and Prof Van der Hoeven believes it was caused by the impact.
Does this mean we're safe a a few more years
"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
If we lose our magnetic field, and start having much more solar wind hit the earth, the concern isn't so much for cancer as it is for our electronics. Solar storms will have a much bigger effect on our electrical system (electronics and primarly power distribution). The solar wind, during slight solar storms, could knock out our power, etc if we don't do something to shield it.
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.
WHAT MAKES THE WATER ROTATE WHEN IT GOES DOWN THE DRAIN?
Conservation of angular momentum. As the distance between a given fluid element and the drain gets smaller, the angular velocity of the element must increase, to ensure that angular momentum is conserved.
Is this simple enough for you now?
Tubal-Cain smokes the white owl.
We also don't know how long the reversals take to complete, and that's the worrisome aspect. If it happens fairly quickly, there wouldn't be too much of a problem. But if it takes thousands of years, mankind would be in serious trouble, maybe even to the point of extinction. Why? Because that field is all that protects us from the ionizing radiation from the sun. We might have to become cave dwellers again just to survive as a species, and that's no joke!
The world is my oyster. That's why it's always in a stew.
The timing of this event was 780,000 years ago. The timing of a period with a small population from which Homo Sapiens comes is estimated to be between 100,000 to 200,000 years ago. Genetic evidence from mitochondria suggest that we all had the same direct female ancestor about 150,000 years ago. There is evidence that she was somewhere in Africa. There is evidence that the direct male ancestor was substantially more recent than that, the reason for the discrepancy is not known.
The above is from this encyclopedia article. A sanity check of the figures shows that the meteor had nothing to do with the evolutionary event that you're talking about.
The idea that humans went through a period of restricted population should not surprise. The theory of Punctuated Equilibrium suggests that most species arise from a period of rapid evolution in a small isolated population. Most such "experiments" end quietly. But sometimes the new breed cannot interbreed with the original, and successfully outcompetes it. In the latter case, the new species spreads.
Therefore we should expect homo sapiens to have gone through such a period.
not true. we have thousands of years of data preserved in pottery, which aligns its metals when heated in kilns..we use that data to make a map of the field. We also have millions of years of data collected from hardened lava flow in hawaii.. so we have plenty of data.
pm
** "It's not my job to stand between the people talking to me, and the ones listening to me." -- Pego the Jerk
There is of course that nasty geological record at the Atlantic rift showing a periodic reversal of the magnetic alignment in newly formed rock going back millions and millions of years.
That of course doesn't count because humans didn't record it, right?
I just found out there's no such thing as the real world. It's just a lie you've got to rise above. - John Mayer
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.
You can't kill everything and everybody unless ~100% lived near the coast AND the water rises faster than people can run including those at the limit of the sea level rise! As for hot spots, like Yellowstone, Google the term "flood basalts" and you will get an idea of what has gone on in the past. See http://volcano.und.nodak.edu/vwdocs/volc_images/no rth_america/yellowstone.html for example. Notice the mention that the calderas get younger toward the east. This ties in with plate tectonics due to ocean floor spreading at the mid-atlintic ridge. If you want to put some models together to test the possiblity of "The Flood" and the likelihood and nature of future catastrophes, understanding plate tectonics is vital. It's bigger than evolution is. Predictions and observations, that is what makes for a good theory.
The only Diluvian stories that make some sense at all are those who interpret the Bbiel less than literally. such as a local inundation.
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