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So I’m thinking that some Fridays I’m gonna steal NPR’s “Science Friday” idea and write a post debunking some popular myths. Not gonna happen every Friday, but I’m gonna make a pointed effort to do it somewhat often.

Today we’ll tackle the myth about water spinning in opposite directions down the drain in the northern and southern hemispheres. This is simply not true at all. While large-scale weather systems do indeed follow this pattern due to a phenomenon called the Coriolis Effect, water going down a drain does not. Minute things such as imperfections in the angle at which a basin was installed, inconsistencies in the surface or shape of the basin, and any residual motion in the water itself are what determine the direction the water rotates when drained. Once the water begins to drain, the conservation of angular momentum takes over and any hint of rotational motion in the water, whether clockwise or counter-clockwise, gets amplified as it moves toward the drain, creating a vortex. This is the same law of physics that causes tornadoes and dust devils to behave the way they do. The classic explanation for this concept is the spinning ice skater. As he/she moves her limbs closer to their body the conservation of angular momentum forces their rotational speed to increase. They can then move their limbs further away and they will slow down again. So no, no matter what you’ve heard, water does NOT always drain counter-clockwise in the northern hemisphere and clockwise in the southern. That being said, experiments have been done that show the Coriolis Effect can be seen in draining water IF AND ONLY IF all other forces are completely removed. A large and absolutely perfect cylinder-shaped container with one very small hole exactly in the center was filled with water and allowed to sit untouched for 24 hours to allow any residual motion in the water to die out. The container was perfectly balanced with extreme precision. The plug in the hole was then carefully removed and the water did eventually start rotating counter-clockwise, and continued to do so when the experiment was repeated. BUT clearly this only happens in extremely controlled conditions. In your sink or toilet, a myriad of other forces are orders of magnitude stronger and completely overwhelm the minute effect of the Earth’s rotation. Snopes has a decent debunking of this myth as well.

Tornadoes are different. I was asked about this yesterday, in the wake of the massive tornado outbreak on Wednesday. The Coriolis Effect does influence the direction tornadoes spin, but in a more indirect way. There have, in fact, been clockwise (anticyclonic) tornadoes documented in many cases in the U.S. There have even been a few storms that dropped multiple tornadoes, both cyclonic and anticyclonic, at the SAME TIME. As I said earlier, the Coriolis Effect is what causes large-scale weather systems such as hurricanes, low pressure systems, and high pressure systems to rotate the way they do. Low pressure systems and hurricanes always rotate counter-clockwise in the northern hemisphere and clockwise in the southern. The opposite is true for high pressure (clear weather) systems. The storms which produces tornadoes are always associated with a large-scale low pressure system. The Coriolis Effect determines the rotation of that large-scale system, which in turn has an indirect influence on the structure of the supercell thunderstorms which spawn tornadoes. Tornadoes are far, far more common in the U.S. than anywhere else in the world, and because the warm moist air which “feeds” these storms at the surface is moving in from the southeast, and the cooler, drier air aloft is moving in from the northwest, that setup naturally lends itself to counter-clockwise rotation, hence most but not all tornadoes in the U.S. spin counter-clockwise. This illustration from NOAA’s National Severe Storms Laboratory shows the inner workings of a tornadic storm quite well:

The U.S. Department of Energy’s Office of Science Education has a website called NEWTON, with a forum of sorts called “ask a scientist.” This very question regarding the rotation of tornadoes was asked, and I found this particular response quite helpful:

At least the great majority of tornadoes rotate counterclockwise (as do all low-pressure systems) in the northern hemisphere, and clockwise in the southern hemisphere, for the reason (coriolis force) given by Eric Peterson in response #1. But occasionally, it would seem, northern hemisphere tornadoes do rotate clockwise: S. Flora’s book “Tornadoes of the United States” cites an 1890 article in the American Meteorological Journal. Its author, a J.P. Finley, states that, of 550 American tornadoes he studied, 29 were deemed to have rotated clockwise. I have not been able to find any “modern” study of this question. But I believe it could be true. The region of swirling air that contracts to become the tornado is not itself large enough in extent to have its rotation dictated by the coriolis force; rather, it “inherits” this tendency from the great masses of air whose movement sets the stage for the storms and any associated tornadoes. If the study cited is correct and representative, on occasion the direction of rotation is set by some other factor, perhaps the topography in the area where the tornado forms, for example.

So there you have it. I won’t have as much time every week to write up a post this in-depth, so don’t expect this every Friday, but I’ll do my best.

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Image via boston.com

Image via boston.com

Boston.com, website of the Boston Globe, has an interesting article on how to create hallucinogenic effects without taking drugs such as LSD. These are pretty interesting, and I want to try them. I’ll let you know how it goes…

I wonder why M.I.A. hasn’t told anyone what she named her baby… It’s probably hard to pronounce, but seriously, does it really need to be a secret? Hipster Runoff muses about what it might be.

Earth, Wind & Fire are teaming up with Chicago for a huge US summer tour. It’s RETRO, people!

Scientists have finally confirmed that reality, is in fact, real. Like, the world actually exists when someone is not observing it. Phew… I’ve always been worried that reality doesn’t really exist… Seriously though, even the scientist who headed this experiment called the results “preposterous.” Something about this whole thing is perplexing to me though… basically what they’re claiming is a paradox; that they observed something without actually observing it. We are, though, talking about quantum mechanics here. The quantum world is probably the hardest thing in science for our brains to comprehend. Trying to visualize or understand the quantum world from our large, worldly perspective is simply impossible, so me trying to wrap my feeble mind around this experiment is futile in the first place. No matter how hard to understand, this could be a major scientific breakthrough… as long as the results can be duplicated and further analyzed.Via Kottke.org.

Now for a bit of debunking. Everyone has heard the claim that water going down a drain spins opposite directions in opposite hemispheres, the same way that large cyclones and storm systems rotate clockwise in the southern hemisphere instead of counter-clockwise as in the nothern. It’s not true. The Coriolis Effect is responsible for the rotation of large-scale storm systems such as hurricanes, but it simply does not affect something so small as water going down a drain. It only applies to large masses over long distances. The only thing that determines how water spins down a drain is the surface of the basin and/or the direction the water was poured. Unfortunately everywhere along the equator one can find rigged demonstrations that do nothing more than suck money from gullible tourists and contribute to the spread of ignorance.

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