Why did my muscles turn to jello on the Equator?

January 11, 2007 2:03 PM

Equatorial physics filter: Please help explain (or debunk) the following three experiment results conducted on the equator.

(My apologies for the very lengthy question)

On a recent trip to Ecuador and the Galapagos, my wife and I had the good fortune of taking a side trip to the equator line, where they conducted three experiments to "prove" our location. I address each in turn.

First, the Coriolis Effect. Now I'm well aware that this subject has been discussed previously here and here, and thoroughly debunked, but that doesn't leave me without some questions. The experiment was demonstrated as follows: A large tub of water was hung directly over the Equator line and drained. There was no noticeable spin whatsoever. The tub was then moved 5 feet north of the line, and the experiment repeated. This time it drained with a sprial in one direction (can't remember which way, to be honest). The tub was then taken 5 feet south of the line, and lo and behold, more spin, presumably in the opposite direction. Now when the tub was north and south the line, our guide threw some small bark chips in the water to demonstrate that the water span. I suspect that when she did so, she subtly span the water in one way or another causing it to spin in a particular direction, because as discussed previously, the Coriolis effect simply isn't significant enough to make such a difference. My question relates to the draining over the Equator itself. No spin at all. That's hard to fake I'd think, and I'm curious if anyone might be able to shed some light on whether it has to do with the tub being over the equator, or because of some other factor.

Experiment 2 was the class balancing an egg on the head of a nail experiment. I didn't and still don't buy into this one, if for nothing more than the fact that there was no control experiment. People were successful balancing the egg on the nail over the equator, but there was no experiment demonstrating that you couldn't do this off of the equator. I think that this experiment is total bunk, but I'm curious if anyone knows any physics behind this, and whether there's even any reason to believe at all that the equator has an effect on egg balancing (alternatively, has anyone ever balanced an egg on the head of a nail off of the equator?).

Experiment 3 is the real baffler and where I really need some help. (Please, fellow mefites, accept these observations as true and accurate. I acknowledge that I'd have a hard time believing them if I hadn't been there myself and experienced it.) This was a strength test. Our guide had a visitor clasp his hands and raise them high up in front of his head while he was standing about 5 feet north of the equator. She then attempted to pull down his arms (after instructing him to resist) and was unable to do so. They then repeated the experiment with him straddling the equator line. This time she was able to pull down his arms with relative ease. They then did another similar experiment. Five feet north of the line, the guide had the visitor form a circle with his thumb and forefinger and she attempted to pull the fingers apart (aftering instructing him to resist). She was unable to do so. Again, this was repeated with him straddling the line and this time she was able to easily pull his fingers apart.

Now I'm not stupid, and would have been totally convinced that the guy was a plant except for the fact that there is simply no way to fake the look on his face. That left only one possible explanation -- the guide was simply not trying as hard north of the line as she did on the line itself. Only one way to test this...I had my wife try to duplicate the experiment with me (everyone else started doing this as well). We walked north of the line and my wife was unable to pull my arms down or separate my fingers. We then went to the line and to my extremey astonishment, my arms just fell and my fingers just separated...offering up no resistence. There were about 10 other people there, and this held true without exception. I was (and remain) STUNNED and I simply cannot explain this. I've even thought that maybe some psychological factor could be involved (after the initial demonstration we expected it to be true, so we made it be true, or some such), but I really don't think so. Instead, I ask my fellow readers....Can anyone explain this mystery?

posted by saladpants to science & nature (25 comments total)

It's common to have people balancing eggs on the equinox and giving whacky explanations about the gravity of the sun. They did this to me in 2nd grade, and I bought it. Hey, I was 7.

The truth is, you can always balance an egg if you try. Because we're orbiting the sun, we're essentially in a "freefall" (that's how orbiting works), so there are no gravitational effects on earth that are caused by the sun. (Just like how astronauts in the space station are weightless while they orbit the earth, and sky divers are weightless while they're falling.)
posted by knave at 2:20 PM on January 11, 2007 [1 favorite has favorites]

Two explanations: it's either suggestion, which can be surprisingly powerful, or it's some difference in the way it was set up that you didn't notice. I think the former is more likely (think of that classic levitation trick).

If I wanted to rig things to end up the way you described I'd look for certain signs of a suggestible person for the first case, and once you've got that under your belt it'll be easier to get the more skeptical ones to fall in line.

It's not physics at any rate, and don't trust any physicist that thinks it is. Not enough of us have any clue about this sort of psychology, which is why Uri Geller gets away with so much.
posted by edd at 2:42 PM on January 11, 2007

You don't mention on the third one if you did a control by doing it backwards - starting on the equator and being able to pull the person, then moving off it and being unable. Without this, it would seem that muscle fatigue could be an explanation - have you tried it back home with a pretend equator?
posted by -harlequin- at 2:56 PM on January 11, 2007

I've seen an experiment similar to the third one used as evidence of ley lines - stand on a water ley and, just like the equator, your muscles will be mystically weakened. I'm all for believing it's psychological, because I'd really rather not believe in ley lines.
posted by Lebannen at 3:24 PM on January 11, 2007

Harlequin: We did control for the fatigue factor by repeating the experiment in quick succession. After the equator proved me to be a terrible weakling, we went back to the north side of the line and my wife was again unable to pull my arms down or separate my fingers.
posted by saladpants at 3:39 PM on January 11, 2007

What you were doing is called muscle testing which is used often in Applied Kinesiology for testing for allergies and similar things. I have seen it demonstrated using fairly trivial true/false questions and answers - the subject does not to actually need KNOW the answer for the test to work. It's not the result of muscle fatigue, as the muscle can immediately go from testing weak to testing strong.

Muscle test comparisons of congruent and incongruent self-referential statements on PubMed
posted by goshling at 4:06 PM on January 11, 2007

More research here
posted by goshling at 4:11 PM on January 11, 2007

Physics certainly doesn't tell us that the equator would have that effect.
posted by Shutter at 4:30 PM on January 11, 2007

If the tests had been conducted on the "equator line" and then five hundred miles north, not five feet north, I'd be more interested.

The earth is 12,000 kilometres around, roughly, so surely being on the equator (or whatever line someone painted on the ground and told you was the equator) and being a couple of metres away from the equator, a 0.016 per cent difference, shouldn't have mattered. The same phenomena should have been in effect.
posted by AmbroseChapel at 4:53 PM on January 11, 2007

Agreed Ambrose. That distances in question certainly shouldn't matter. The only time I'm convinced it did was on experiment 3, and I still can't explain that one.

Also, as for the accuracy of the line itself, of that I have little doubt. My personal GPS put it literally within a few meters (and GPS units are known to have some margin of error depending on which system is being used). This particular line was actually determined by the US Army about 10 years ago using specialized GPS equipment. Interestingly, the former line was about 200 meters away, and the old monument is still visible from the line.

See the line itself, and the old monument off in the distance.
posted by saladpants at 5:03 PM on January 11, 2007

John Diamond wrote a book called `Snake Oil' in which he discussed a clinical trial of kinesiology.

"This was what Professor Hyman, in John Diamond's hilarious description of a similar case, undertook. When, predictably, the alternative technique ignominiously flunked the double blind test, its practitioner delivered himself of the following immortal response: "You see? That is why we never do double-blind testing any more. It never works!"
posted by tomble at 6:52 PM on January 11, 2007

Also, keep in mind that the axis of rotation of the earth is not generally perpendicular to the plane of the earth's rotation about the sun. Which is to say that even if you were on the equator, any effects explained by being on a "direct line" with the sun, or some such symmetry, would be meaningless because even on the equator you're not moving in the plane with the sun except for a few moments every year (the equator's equinoxes).
posted by njgo at 6:58 PM on January 11, 2007

Did they do the same demonstrations at the old equator line, I wonder, and did they work?
posted by hattifattener at 7:09 PM on January 11, 2007 [1 favorite has favorites]

What is somewhat depressing is I tried googling this and got stories of other people who went there (try '"middle of the world" egg') and almost all others bought all three demonstrations wholesale - saying how wrong they had been about the Coriolis force etc. So thats not much help at all.

My guess is you are leaving out some vital piece of information which you may not even realize is vital. But there's no way the equator causes effects like any of these. The gravitational effects of being at the "bulge" of the Earth are small compared to features on the Earth's surface as this map demonstrates.

The only thing I can deduce is that the Equator seems to make most people lose their sense of healthy skepticism.
posted by vacapinta at 8:59 PM on January 11, 2007

Well I feel gypped. I have been there and all we did was take pictures. And good question hattifattener.
posted by vronsky at 9:30 PM on January 11, 2007

Did you try the strength test on the equator first, and then away from the equator? Maybe you can only maintain arm strength for one try of the experiment - on the second try, you're weaker and can't hold your arms up.

As vacapinta suggests, while the equator might be a nice line on a map, and it might show itself accurately on your GPS, it means very little in terms of the physical forces you would experience there. The Earth isn't a sphere. It's actually kind of potato shaped. There's nothing special about the geographic equator that makes the forces you're experiencing balance out, or anything like that. The only thing special about it is that the sun will be directly overhead at local noon on the equinox. But shit, the sun will be directly overhead at local noon on a solstice on the Tropic of Cancer or the Tropic of Capricorn. So what?
posted by Jimbob at 9:54 PM on January 11, 2007

I don't know about the first two, but the third thing sounds like some neat little magic trick. I'm pretty sure I've seen Derren Brown do something like that involving a boxer being able to lift a small woman one minute and not the next after he told the boxer he was "sapping his strength" - whether this was due to suggestion, with the boxer being suddenly convinced he could no longer do it and his body responding accordingly, or just a difference with posture affecting the force required to lift her, I'm not sure. You say that when you stood on the equator you "straddled" it, while away from it you "stood" - any difference in your stance between the two positions, the distance between the one with the hands clasped and the one trying to separate them? It would be harder to unclasp someone's hand from a greater distance. I agree with vacapinta; you're probably missing something vital in this trick that explains how it works, but you were likely misdirected by the guides' talk of the Coriolis effect etc - they've probably had a lot of practice at this "demonstration".

(I'm aware Derren's stuff doesn't contain a great deal of real psychology, but his use of misdirection and manipulation of cognitive biases might be applicable here.)
posted by terrynutkins at 1:43 AM on January 12, 2007

Just to note, I got those figures completely wrong.

The earth is 12,000Km in diameter. It's 40,000Km round. Plus I mixed up metres and kilometres.

Say it's twenty million metres pole to pole, moving two metres from the equator makes about 0.00001% difference to whatever forces are in effect.
posted by AmbroseChapel at 2:29 AM on January 12, 2007

The ideomotor effect causes many odd things to seem to happen, usually very convincingly.
posted by flabdablet at 2:34 AM on January 12, 2007

I've been the victim of such an experiment (your experiment 3) once as well. This was very far from the equator in the great white north of Canada. Basically it was a psychological workshop, where first I was complimented by the presenter and could resist their efforts. Then I was called lazy and of course they had no problem bringing my arms down. Ahhh.. the power of suggestion.

We didn't do the control experiment of doing this in reverse, so it is possible it was muscle fatigue as also pointed out.
posted by ThinkNut at 4:31 AM on January 12, 2007

Offtopic, but this would have given AmbroseChapel a better way of spotting his error: 'Historically, the metre was defined by the French Academy of Sciences as 1/10,000,000 of the distance from the equator to the north pole through Paris.' - from Wikipedia on the metre.

Must return to the first comment briefly: 'Because we're orbiting the sun, we're essentially in a "freefall" (that's how orbiting works), so there are no gravitational effects on earth that are caused by the sun.'

Not true, as the existence of spring tides makes clear. There are tidal forces from the sun that affect things on Earth. However, tidal forces are a result of the difference in gravitational pull at two locations - in the case of the sea it's the water on one side of the Earth and the water on the other. Of course, for an egg - one end of an egg is very close to the other, even for a very very big egg. So it won't be anything tidal that's keeping an egg upright :-)
posted by edd at 5:13 AM on January 12, 2007

As far as experiment 3 is concerned, I swear I remember something from my karate class where we did that exact same experiment, and the straddling vs. standing (stance) made a big difference in our ability to resist.
posted by nekton at 8:48 AM on January 12, 2007

seconding nekton. I had a similar experience in my class as a demonstration of the impact of stance.
posted by tylermoody at 12:20 PM on January 12, 2007

standing on uneven ground can cause weakness like you describe. If one side of the line was raised about an inch from the other the misalignment of your spine could explain this effect. I don't know but straddle stance might serve to heighten this effect.
posted by subtle_squid at 1:29 PM on January 12, 2007

Hmm...I don't think the stance was any different. I was just using the word "straddle" to incidate that I had one foot on each side of the line.

All of these are good theories. It seems the collective thought is that there is no physics explanation, but that its more likely the power of suggestion. No matter how you slice it it was pretty strange.
posted by saladpants at 5:01 PM on January 12, 2007