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Look ma, no magnets
June 28, 2013 6:46 AM   Subscribe


 
I was hoping that instead of just holding the beaker higher, he would try it from the second floor or something. Guess I'll have to try it myself, McMaster-Carr sells continuous lengths up to 1000 feet...
posted by 445supermag at 6:58 AM on June 28, 2013 [6 favorites]


Well, that was completely cool and unexpected.
posted by jacquilynne at 7:17 AM on June 28, 2013 [1 favorite]


I was certain the bearded dude was wearing a plaid kilt.
posted by I'm Doing the Dishes at 7:18 AM on June 28, 2013 [7 favorites]


What!! Come on, he's yanking your chain...
posted by Mooseli at 7:34 AM on June 28, 2013 [1 favorite]


I have actually seen this done with 5/16" proof chain in a 550' pail. The demo had the pail about 12-15 feet off the ground and the loop was impressive - like 3 feet out of the pail. And the loops and kinks could be started from the bottom and they would slowly travel up and down the length of chain. Mind-blowingly cool when you're a 13yo aspiring physicist. I seem to remember it was Steve Wolf who did the demo at my school maybe in 1990? (and Steve is a character worthy of his own FPP some day...)
posted by cyclotronboy at 7:44 AM on June 28, 2013 [1 favorite]


whooo, that was really cool! What a great thing to slo-mo!
posted by rebent at 7:46 AM on June 28, 2013 [1 favorite]


Drop it down a mine shaft and you'd have a SPACE ELEVATOR!!11!! amirite??
posted by weapons-grade pandemonium at 7:55 AM on June 28, 2013 [1 favorite]


Reminds me of this demo from freshman physics.
posted by crazy_yeti at 7:59 AM on June 28, 2013 [4 favorites]


Drop it down a mine shaft and you'd have a SPACE ELEVATOR!!11!! amirite??

Actually, you are a lot closer to amirite than you think you are. The idea is called a launch loop, or a Loftström Loop. And the essential core idea is the same, using the KE of a moving chain to lift something into orbit.

The big problem, besides just the sheer size of the thing, is the KE in the chain is huge, so controlling it is critical. Bad -- you're literally talking nuclear weapons levels of energy. Good -- you're spreading that energy over a very long distance (2000km or so) so the actual energy density, while still pretty respectable, is controllable. And you'd need to control it so that if there's a failure, you can land the loop and fix it, rather than have it shatter into a billion pieces all raining down.

Another use for this idea is that you could make intermittent power sources -- solar, wind, slow-fill hydro -- into primary plants, because the storage capacity for energy is enormous.* One of the biggest problems in power systems today is that there's basically no way to store power on a large scale. If you could store power and release when needed, rather than generate on demand, not only do intermittent power sources become vastly more useful, you can downsize the constant ones, since you can then store power at night, when the demand is very low, and release it during the day, when the demand exceeds your generation capacity.

There's legions of practical issues, but unlike the straight-up space elevator, the materials technology and control technology we have today could theoretically build a workable loop.



* Which should be obvious -- if you can lift many tons 80+km over the ground and given them orbital velocities, you are talking a huge amount of energy.
posted by eriko at 8:30 AM on June 28, 2013 [11 favorites]


I saw this video yesterday. I searched for the quick explanation and didn't find it. It's one thing to be amazed at a physics demonstration, another to understand what's going on. Understanding is a deeper and more valuable experience.

The extent of my formal physics education is limited. I would appreciate input by people who actually KNOW what's happening here. Here is what I ~think~ is occurring.

To be specific, it's not so much the siphon action that's amazing, but the gravity-defying loop above the rim of the beaker, right? What is the force that causes the loop to resist the force of gravity?

Since the chain makes a quick 180 degree turn, the turn itself is a curve. Since the individual beads have mass, and move in a curve about a center, a centrifugal force is created that tends to move the beads away from that center. And yes, I recognize that the term "centrifugal" is somewhat tricky.
posted by Tube at 8:41 AM on June 28, 2013


Since the chain makes a quick 180 degree turn, the turn itself is a curve.

I wonder if the theoretical shape of the curve is a parabola or catenary? (or something else)
posted by 445supermag at 10:33 AM on June 28, 2013


The effect could be magnified if the chain were tapered. Drop the heavy end first, and through conservation of momentum the light end would arc ever higher, and might break the sound barrier like a bull whip.
posted by weapons-grade pandemonium at 10:54 AM on June 28, 2013


My great aunt, who was over ninety, showed me this when I was 9 years old.
I thought it was the coolest thing I had ever seen. I ran into town and showed all the towns people.

They burnt her for being a witch.
posted by QueerAngel28 at 12:34 PM on June 28, 2013 [1 favorite]


Did he refer to that beaker as a "pot?" And, yeah, I was hoping he'd eventually drop it off of something like a 40 story (storey) building.
posted by InsertNiftyNameHere at 8:44 PM on June 28, 2013


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