The Typo We’ve All Been Waiting For

posted by Stal on 2010.03.22, under Stal
22:

It’s an easy mistake to make.

Why It Doesn’t Matter Which Way You Orient Your D&D Dice

posted by Stal on 2010.02.16, under Stal
16:

There was some discussion on the physical properties of glass and whether it flows over time, similar to a liquid. From the Wikipedia article on the behavior of glass:

The observation that old windows are often thicker at the bottom than at the top is often offered as supporting evidence for the view that glass flows over a matter of centuries. It is then assumed that the glass was once uniform, but has flowed to its new shape, which is a property of liquid. In actuality, the reason for this is that when panes of glass were commonly made by glassblowers, the technique used was to spin molten glass so as to create a round, mostly flat and even plate (the crown glass process, described above). This plate was then cut to fit a window. The pieces were not, however, absolutely flat; the edges of the disk became thicker as the glass spun. When actually installed in a window frame, the glass would be placed thicker side down both for the sake of stability and to prevent water accumulating in the lead cames at the bottom of the window.

[...]

Several other points exemplify the misconception of the “cathedral glass” theory:

  • Writing in the American Journal of Physics, physicist Edgar D. Zanotto states “…the predicted relaxation time for GeO2 at room temperature is 1032 years. Hence, the relaxation period (characteristic flow time) of cathedral glasses would be even longer.” (1032 years is many times longer than the estimated age of the Universe.)
  • If medieval glass has flowed perceptibly, then ancient Roman and Egyptian objects should have flowed proportionately more — but this is not observed. Similarly, prehistoric obsidian blades should have lost their edge; this is not observed either (although obsidian may have a different viscosity from window glass).
  • If glass flows at a rate that allows changes to be seen with the naked eye after centuries, then the effect should be noticeable in antique telescopes. Any slight deformation in the antique telescopic lenses would lead to a dramatic decrease in optical performance, a phenomenon that is not observed.
  • There are many examples of centuries-old glass shelving which has not bent, even though it is under much higher stress from gravitational loads than vertical window glass.

Conclusion: to observe glass flowing at room temperature, you would have to wait for periods far beyond that of human existence.

Infrasound and Brown Notes

posted by Stal on 2009.09.24, under Stal
24:

Claims were previously made that there exist low-frequency sound wave weapons capable of causing people to involuntarily have bowel movements. After poking around the internet for a bit, it appears that there is no scientific evidence that this so-called “brown note” exists.

The brown note was tested on the television show MythBusters using twelve Meyer Sound 700-HP subwoofers—a model and quantity that has been employed for major rock concerts…The experimenters on the show tried a series of frequencies between 5 and 10 Hz at a level of 120–153 decibels of sound pressure, but they were unsuccessful in producing the rumored effects. The test subjects all reported some physical anxiety and shortness of breath, even a small amount of nausea, but this was dismissed by the participants, noting that sound at that frequency and intensity moves air rapidly in and out of one’s lungs.

However, infrasound (sound waves below 20 Hz) does cause a sense of fear, disorientation and anxiety in humans. Since the sound waves are below the human threshold for hearing perception but are subconsciously detected, they can make people feel that supernatural events are taking place. One such case:

Research by Vic Tandy, a lecturer at Coventry University, suggested that the frequency 19 Hz was responsible for many ghost sightings. He was working late one night alone in a supposedly haunted laboratory at Warwick, when he felt very anxious and could detect a grey blob out of the corner of his eye. When he turned to face it, there was nothing.

The following day, he was working on his fencing foil, with the handle held in a vice. Although there was nothing touching it, the blade started to vibrate wildly. Further investigation led him to discover that the extraction fan was emitting a frequency of 18.98 Hz, very close to the resonant frequency of the eye (given as 18 Hz in NASA Technical Report 19770013810). This was why he saw a ghostly figure — it was an optical illusion caused by his eyeballs resonating. The room was exactly half a wavelength in length, and the desk was in the centre, thus causing a standing wave which was detected by the foil.

Cadbury Egg Rube Goldberg Machine

posted by Stal on 2009.04.17, under Stal
17:

In the event that you have a lot of leftover Easter candy

[ via Atlantic Food ]

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