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.


In the past 10 years or so, I’ve become more and more of a skeptic. Especially in the last 5 or so years, the American public has become increasingly susceptible to scaremongering and inflated fears about health issues, doomsday nonsense, and other junk science that has no basis in reality. The myth about cell phone radiation causing brain cancer is one example of this. The flat truth is that there had been no proven link between cell phone use and brain cancer. In fact, according to Christopher Wanjek’s column on LiveScience there has been no significant increase in brain cancer that correlates in any way with the increase of cell phone usage. We all know how much cell phone usage has risen in the last 2 decades… if they cause brain cancer, why the hell hasn’t there been a corresponding increase in the disease? Because there’s no connection. That being said, this article on NewScientist is one of many covering research into the effects of cell phone radiation on the brain, and in fact it does affect brain tissue, and there have been some hints that extremely prolonged exposure could cause some degree of tissue damage, but tissue damage is not the same thing as brain cancer. Furthermore, another recent study actually showed that cell phone radiation reversed the effects of Alzheimer’s disease in mice! (And if you look at the bottom of that article, you’ll see that the study wasn’t funded by any cell phone companies…) We might even soon be seeing cell phone radiation used as a treatment for the disease. So, the jury may still be out on whether it causes tissue damage or has therapeutic effects on memory, but with as many studies as have been done on the link between the radiation and brain cancer, it’s pretty obvious that cell phones don’t cause brain cancer. Unfortunately some companies have tried to capitalize on the scaremongering by marketing products that are supposed to “protect” you brain from the radiation. These don’t work, and several have been shut down by the FTC.

Now that I’m off my skeptic soapbox, something actually interesting:

Biologists have discovered a species of sea slug that is the first know organism to be able to produce chlorophyll. This creature actually has aspects of both plants and animals, and thus sounds like something straight out of a sci-fi movie. But it’s real. Scientists have determined that it somehow “borrowed” the plant genes that allow chlorophyll production from the algae that it consumes. Exactly how it did that in it’s evolutionary path is still a mystery. It still can’t produce the actual chloroplasts (the cells that are responsible for the conversion of sunlight into energy) without consuming algae, but it apparently can produce chlorophyll entirely on its own.

And just for kicks: How the main LOST characters would each make a peanut butter & jelly sandwich. (Via Yewknee’d)