So I know it's in French but if you want to translate it, here it is: http://sciences.blog.lemonde.fr/2010/03/02/depuis-le-seisme-au-chili-les-jours-ont-raccourci/#xtor=RSS-32280322
In sum, the earthquake in Chile was so large it threw off the rotation of the Earth and shortened our days by 1.26 microseconds! The 2004 earthquake in Sumatra did the same thing, by 6.8 microseconds.
I wonder if our days were a lot longer millions and millions of years ago?
How much does a microsecond affect plant life?
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I saw the documentary "Oceans" today with my school -- go!! It's certainly a film with an agenda, but one that you'll at least agree with. (You can be sickened by Michael Moore, but when it comes to animals, I don't think anyone can argue.)
Some highlights: a baleen whale's tail emerging from the water (one of the most beautiful images I've ever seen, actually); a baby sea lion crying; a crab fighting a lobster and getting its arm ripped off.
[I didn't know this was a Disney production until I found this trailer! Kind of makes me like it less...]
From one of my students right before the film started, in French: "Rachelle, the movie is in French, will you be able to understand it?"
EDIT: the movie was created and directed by a French director and crew, but Disney "adapted" it for American audiences... gross.
8 comments:
The Earth's rotation slows by 5 x 10^-5 seconds per year, so yes, days were longer millions of years ago.
Also, when the ice caps increase in size, the Earth's rotation speeds up (think of a figure skater pulling her leg in), and when they melt it slows.
This last part is a guess (but so was the second paragraph until I looked through journals and discovered that it had already been published, cutting off what I thought would be an easy thesis to prove), but I imagine that as the continents have drifted towards and away from the poles, this has increased and decreased the speed of the Earth's rotation.
Part of the reason that the Earth is slowing is because it is becoming tidally locked with the sun, this has almost completely happened with the Earth's moon, which is why we only ever see one face.
You can imagine what land based life would be like if Earth were tidally locked; a ring that ran around where the scorched, sun facing half met the frozen, away-from the sun facing half.
Oh, and as far as plant life goes, most organisms that deal with the sun have internal circadian rhythms that rarely conform to an exact 24 hour day, but use light cues to more finely calibrate to the Earth's rotation.
The selective pressure to keep an exact rhythm in the absence of the sun is rather low, since if you need to synchronize with the sun, you generally can see the sun.
And yes, you will be able to understand the movie that is in French.
why don't you just finish up ya damn bio degree already
Can you explain the process of becoming 'tidally locked'? How does that happen? When you get closer to something's gravitational pull? And just for clarification sake, you're saying our moon is tidally locked to the earth right? So it doesn't spin at all- which is why we see the one side?
Also, because Earth is slowly becoming tidally locked to the sun, do they already know which side of the earth is favoring the sun and which side is facing away?
The idea behind tidal locking is that the gravity of the larger body squeezes the smaller body, so for instance our moon is squashed towards us, bulging at what we could call it's sides.
As these bulges swing away from the larger body, the larger body pulls on them more strongly, slowing the rotation of the smaller body. This continues until the body is tidally locked.
I'm not sure if they've determined which side of the Earth will end up facing the Sun, it could be too dicey considering seismic activity disrupting things.
If our stratified society was still in operation when it happened, it would be interesting to see the resulting symmetrical band of poor-rich-poor areas of habitation ringing the Earth, with the poor occupying the too hot and too cold areas, and the rich occupying the Goldilocks zone.
Also, the Moon does spin, it just spins at exactly the same rate as the Earth.
It helps to visualize this with your hands, have them face each other, then rotate one and keep the other one facing it, and you'll see that it does indeed rotate.
Ahh, got it. Thanks, Don!
Now, Rach, you have to translate all of this into French and then do a lesson plan on it.
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