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San Francisco, 3:15 PM
Sat Dec 5
18 posts in the last 24 hours
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07:45 AM
12/04/09
[www.huffingtonpost.com]
#tips #nasa #spaceporn #space
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My girl caught a glimpse of me while watching this... asked me if I was watching porn :P
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As a kid, I used to keep newspaper clips about the space program and at one point I wrote to NASA for pictures, which they sent me, for free. I also followed with great interest the descent of SkyLab in 1979.
That is to say, I'm a total sucker for space-related stuff.
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[en.wikipedia.org]
You know, it reminds me of Thunderbirds...
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Its hilarious in a Dirty Jobs kinda way!
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As for the mechanics of flying, it shouldn't make much of a difference whether it's in normal or micro gravity, except for the energy expenditure.
The net external force on the butterfly is proportional to gravity and to the difference between the butterfly's density and the density of air.
If the butterfly is neutrally buoyant (its density is equal to that of the surrounding air), then gravity doesn't play any significant role in either case because the butterfly's weight is cancelled by the upward Arquimedes' force and the net external force is zero.
If the butterfly is much more or much less dense than air, then gravity does make a difference. Under microgravity it should be easier (less energy expenditure) to fly than under normal gravity (more energy expenditure).
Also of interest would be to bring those space-born butterflies back to Earth and see how well they adapt (if at all) to an environment with stronger gravity.
12/04/09
Here's a recent article on the effects of microgravity on embryonic development:
Embryonic development—lost in space?
[www.rikenresearch.riken.jp]
Here's an excerpt (dealing with mice, not insects):
Microgravity led to an overall reduction in the rate of blastocyst formation after 96 hours of culture, and closer examination of these blastocysts revealed that the differentiation of embryonic cells into trophectoderm—the tissue that nourishes the embryo and ultimately contributes to placenta formation—was markedly impaired.
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There's a lot of confusion about this issue.
First, gravity isn't at all necessarily small up there. At an altitude between 278 km (173 mi) and 460 km (286 mi) above the surface of the Earth, the acceleration of gravity inside the space station is between 87% and 92% of Earth's surface gravity, not at all close to zero.
The reason why objects appear weightless inside the station (or any other container in orbit) is that *all* objects inside it are "falling" along with the station itself. As a result, their *relative* acceleration is very close to zero, though not *exactly* zero. Hence the name microgravity.
Thus, there is an effective acceleration of gravity inside the station. Call that eff_g. As I pointed out, the net force on any object in the station is proportional to (object's density - air density) times eff_g.
If the butterfly is neutrally buoyant then that difference is zero and gravity (micro or normal) has no effect whatsoever.
If the density difference is not zero, then the net force is proportional to eff_g. Since, yes, eff_g is very small, the net force is close to zero, but that does *not* mean that buoyancy has no meaning in microgravity. It does. It has the same meaning it has in normal gravity.
"A lead weight in a bubble of water in space isn't going to sink any more than a cork will float."
True if the effective gravity is *exactly* zero. If not exactly zero, the lead weight will sink and the cork will float, except that it may take a very long time to notice.
12/04/09
Perhaps the point I should have made was this:
The mechanics of flying are vastly different in "normal" gravity vs. "microgravity." Yes there is still gravity, but since the entire system is falling there is no discernible up/down direction caused by the force of gravity as we experience it on the ground.
Butterflies don't know how to fly without that definition of up/down (in fact the gizmodo version of this article states that they stopped flying all together because they were tumbling).
Now, a fish would have no problem adapting, because they don't really care about up/down once they adjust their ballast.
12/04/09
The *mechanics* of flying doesn't depend on the direction of gravity per se.
Provided that the speed of air flow on one side of the wing is different than on the other side, there will be "lift", in accordance with Bernouilli's principle.
Yes, gravity has a much smaller effect then, because the effective gravity is nearly zero, and a fixed direction for gravity might not even exist (say, if the station is rotating), but - again - the physics is the same as that under normal gravity.
If the butterfly can't fly because it depends on having a sense of up and down (which is not surprising, since it evolved in an environment where those are well-defined and fixed), that's a biological issue.
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Yes its important, and thats why we build wings with air foils, but its not everything (i.e. planes can fly upside-down with the right angle of attack).
I would say that the mechanics of flying DO require gravity, otherwise it would be swimming! But anyway, semantics. :)
12/04/09
I didn't know that butterfly wings do not behave as airfoils. If so, you're absolutely right that Bernouilli's principle isn't the primary mechanism at work there. I stand corrected.
Now, putting aside any biological biases, what would prevent a butterfly from pushing the air "under" its wings in any direction it wants, effectively flying? I agree, though, that this would be more like swimming, but the point is, if it can push air in any direction, then gravity surely must not be a requirement for this kind of "flying", no?
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Ok, how about a duel where you use your TI-89 and I use my still working HP-41CV (which my brother bought for me in 1982!) ?
En garde! :)
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I feel like this will be the basis for Lady Gaga's next video.
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