(We are bracing ourselves for a severe ice storm today in this region so I am reproducing a blog post from back in 2006, before I moved to this site, because I thought that readers might find it interesting. I have edited it slightly, because tinkering with my writing is something I cannot help. This question formed the basis of an article by Robert Rosenberg in the December 2005 issue of Physics Today, p. 50-55.)

As you can see from this video, this man was reminded that ice is really slippery.

But why is ice so slippery?
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All of us, even if do not suffer from depression ourselves, know people, often many people, who do suffer from it. It is telling that often, when we are informed that someone has depression, we ask whether it is ‘clinical depression’, a term that suggests that it is not some transient phenomenon caused by some immediate factor whose effects may decrease with time (like the death of a loved one), but is instead caused by something that is not just deep-rooted but also based in biology.
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Ever wondered how hedges can be shaped into perfect spheres? Via Andrea James, I came across this video of a company that makes trimmers that can create spherical hedges with specific diameters. The rousing Wagner accompaniment is not included.

When roosters crow at the break of dawn, their sound output is quite prodigious, reaching as much as 140dB levels at very close range. If you get that close, you can damage your eardrum in less than a second. But at even moderate distances, levels can reach 100 dB, close to the levels of a chainsaw. So the question arises as to why roosters do not become deaf from their own sound output. Christie Wilcox writes that scientists intrigued by this question have investigated and found the reason.
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One of the things that any teacher soon realizes is that students come into your class with all manner of theoretical structures in their minds, even if they have never formally studied that topic or even consciously thought about it. People create these structures in order to successfully navigate the world and as long as it works to answer their immediate problems, the fact that it is wildly off from what the scientific community believes is not a hindrance to their adoption.
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I have not quite understood what the benefits are of wireless car entry and ignition. You still have to carry the key with you to enable the system to work, so the only advantage seems to be that you do not have to take it out of your pocket, which seems like a very minor benefit. However, I had a female friend who said she really liked it because she uses a handbag and finding and fishing a key out of it is not as simple as with a trouser pocket.
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The New York Times has an interview with two former US navy pilots who reported seeing a UFO in 2004. It appears that there was a secret multimillion dollar Pentagon program to investigate such sightings and keep a record of them. The program ended in 2012 but monitoring still goes on. The interview article describes in some detail how the two navy pilots pursued the object and its strange behavior, and there is a brief video of the object.
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I love optical illusions and this one in Iceland (that I came across thanks to Richard Kaufman) seems to suggest a pedestrian crossing that is floating on air. But it is not just for fun. Such trompe l’oeil (“fools the eye”) illusions claim to have the benefit of causing drivers, puzzled by what they see ahead of them, to slow down when approaching them, increasing the safety of street crossers.

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