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Australian Toilets Don't Flush Backwards Because of the Coriolis Effect

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Toilet image via Shutterstock

File under "News to Me": you know that old story about how northern hemisphere toilets flush counter-clockwise, and southern hemisphere toilets (and buckets, drains, and such) flush clockwise, due to the Coriolis effect? It's bogus! Today I learned that while the Coriolis effect is significant for hurricanes, it's not strong enough to make toilets flush in different directions at different points on the Earth. The real cause of "backwards"-flushing toilets is just that the water jets point in the opposite direction. Mind blown. (Mind blown even more because this was the inciting event on a Simpsons episode, and everybody knows cartoons are never wrong.)

Let's Talk Science

So there is indeed a Coriolis effect, and we see it on grand scales -- hurricanes in different hemispheres tend to rotate in different directions, because the underlying Earth is spinning, and the effect is exaggerated as you move farther from the equator. This Penn State science page by Professor of Meteorology Alistair B. Fraser explains:

On the scale of hurricanes and large mid-latitude storms, the Coriolis force causes the air to rotate around a low pressure center in a cyclonic direction. Indeed, the term cyclonic not only means that the fluid (air or water) rotates in the same direction as the underlying Earth, but also that the rotation of the fluid is due to the rotation of the Earth. Thus, the air flowing around a hurricane spins counter-clockwise in the northern hemisphere, and clockwise in the southern hemisphere (as does the Earth, itself). In both hemispheres, this rotation is deemed cyclonic. If the Earth did not rotate, the air would flow directly in towards the low pressure center, but on a spinning Earth, the Coriolis force causes that air to be deviated with the result that it travels around the low pressure center.

So it works on large scales. But on small scales (like in your toilet, sink, or bucket), the rotation of the Earth itself (at a decidedly pokey rate of one rotation per day) is much weaker than other forces -- like the force of water jets in a toilet, or the force of water hitting slopes in a sink.

The Pole to Pole Problem

In tracking down where this drain-direction myth originated and how it got so firmly lodged in the heads of people like me, many sources discuss the (otherwise awesome) Michael Palin documentary Pole to Pole, in which Palin visits the equator in Kenya and observes a tourist trap in which a man "demonstrates" (via fakery) the draining of water in different ways on the equator itself, and just north and south of it. Palin doesn't point out that it's fake. I remember seeing this documentary when it came out, and it may be where I picked up the notion -- it seems like such an appealing demonstration of science, such an "ah-ha!" moment that of course the rotation of the Earth should cause such changes in draining water! We're all tiny ants on a huge spinning globe! What wonders! Sadly, it's BS. Again, Fraser has a good write-up; here's a snippet:

[T]he faker must be forcing the rotation by other means, and by a sufficiently unobtrusive way that the busloads of tourists do not spot the means. Indeed, a colleague of mine, who witnessed the performance first hand and knew it was a cheat, was not able to spot how the fraud was perpetrated. (It is an interesting sidelight that when back on the bus, he informed his fellow tourists that they had just witnessed fakery --- the Earth did not cause the rotation they had just seen --- there was widespread disappointment. The tourists preferred the fantasy to the reality.)

Fraser proceeds to explain how you can fake it yourself.

The Plot Thickens

According to various sources, it is possible to demonstrate a Coriolis effect on water on a small scale, but only under extremely controlled circumstances -- involving predictably shaped water vessels, long periods of time of waiting for water to become as still as possible, carefully removing a stopper in the bottom of the vessel without adding spin, and other such crazy stuff. But in your typical toilet or sink, the Coriolis force is so small as to be undetectable relative to other forces. Even holding a bowl of water and turning around introduces sufficient spin to get things going in one direction or another.

A Fun Experiment

Go to your bathroom now and observe water going down the drain -- any drain you want. Depending on the efficiency of your plumbing, you may need to stop up the drain, fill the basin, then unplug it and wait. (It might also help to have something lightweight floating in there, to mark any motion -- a few bits of tissue may work, or a matchstick or two.) Observe whether the draining water forms a clockwise or counter-clockwise spiral. Go ahead, I'll wait. Now check all the other drains you can find. Do they match? In my (admittedly unscientific) testing just now, one sink drained clockwise, the other counter-clockwise, one didn't have an easily observable spin (it's small), and the toilet was also counter-clockwise, clearly due to the position of its water jets. Well. There you go: science in action.

(Via Steven Frank, via Snopes. Note that we covered this topic back in 2007 as well.)

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Google's AI Can Make Its Own AI Now
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Artificial intelligence is advanced enough to do some pretty complicated things: read lips, mimic sounds, analyze photographs of food, and even design beer. Unfortunately, even people who have plenty of coding knowledge might not know how to create the kind of algorithm that can perform these tasks. Google wants to bring the ability to harness artificial intelligence to more people, though, and according to WIRED, it's doing that by teaching machine-learning software to make more machine-learning software.

The project is called AutoML, and it's designed to come up with better machine-learning software than humans can. As algorithms become more important in scientific research, healthcare, and other fields outside the direct scope of robotics and math, the number of people who could benefit from using AI has outstripped the number of people who actually know how to set up a useful machine-learning program. Though computers can do a lot, according to Google, human experts are still needed to do things like preprocess the data, set parameters, and analyze the results. These are tasks that even developers may not have experience in.

The idea behind AutoML is that people who aren't hyper-specialists in the machine-learning field will be able to use AutoML to create their own machine-learning algorithms, without having to do as much legwork. It can also limit the amount of menial labor developers have to do, since the software can do the work of training the resulting neural networks, which often involves a lot of trial and error, as WIRED writes.

Aside from giving robots the ability to turn around and make new robots—somewhere, a novelist is plotting out a dystopian sci-fi story around that idea—it could make machine learning more accessible for people who don't work at Google, too. Companies and academic researchers are already trying to deploy AI to calculate calories based on food photos, find the best way to teach kids, and identify health risks in medical patients. Making it easier to create sophisticated machine-learning programs could lead to even more uses.

[h/t WIRED]

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Land Cover CCI, ESA
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European Space Agency Releases First High-Res Land Cover Map of Africa
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Land Cover CCI, ESA

This isn’t just any image of Africa. It represents the first of its kind: a high-resolution map of the different types of land cover that are found on the continent, released by The European Space Agency, as Travel + Leisure reports.

Land cover maps depict the different physical materials that cover the Earth, whether that material is vegetation, wetlands, concrete, or sand. They can be used to track the growth of cities, assess flooding, keep tabs on environmental issues like deforestation or desertification, and more.

The newly released land cover map of Africa shows the continent at an extremely detailed resolution. Each pixel represents just 65.6 feet (20 meters) on the ground. It’s designed to help researchers model the extent of climate change across Africa, study biodiversity and natural resources, and see how land use is changing, among other applications.

Developed as part of the Climate Change Initiative (CCI) Land Cover project, the space agency gathered a full year’s worth of data from its Sentinel-2A satellite to create the map. In total, the image is made from 90 terabytes of data—180,000 images—taken between December 2015 and December 2016.

The map is so large and detailed that the space agency created its own online viewer for it. You can dive further into the image here.

And keep watch: A better map might be close at hand. In March, the ESA launched the Sentinal-2B satellite, which it says will make a global map at a 32.8 feet-per-pixel (10 meters) resolution possible.

[h/t Travel + Leisure]


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