Monthly Archives: August 2012

I Know Your Face

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Pareidoloop

What happens if you write software that generates random polygons and the software then feeds the results through facial recognition software, looping thousands of times until the generated image more and more resembles a face? Phil McCarthy’s Pareidoloop. Above, my results from running it for a few hours. Spooky.

prosthetic knowledge shows an image resolving

This is a cautionary tale of science, that you shouldn’t make a priori assumptions about results. If you assume that a noisy signal is a face, then you’re going to see a face.

This is reminiscent of some pseudoscience from so-called ghost hunters recording voices, in something called EVP (Electric voice phenomena). You record a tape and then filter the noise, keeping anything that sounds like a voice. Which is what you get, for the same reason as seeing the faces.

A Different Pitch Experiment

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Challenging Batters and Physics Experts Alike

The conflict was this: A split-finger is usually gripped to reduce backspin on the ball because backspin prevents the ball from dropping. The typical Magnus effect on the ball will tilt it slightly in toward a hitter.

“But the particular pitch that was unusual broke away from a right-handed hitter,” Nathan said.

Stumped, Nathan sent the video to the physicist Rod Cross at the University of Sydney in Australia. Cross performed several tests — often using polystyrene balls for better movement — and came up with what he views as a plausible theory. He published his findings in an article in the American Journal of Physics in January.

I'm in my Prime

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Prime Number Patterns

For each natural number n, we draw a periodic curve starting from the origin, intersecting the x-axis at n and its multiples. The prime numbers are those that have been intersected by only two curves: the prime number itself and one.

A Man's Vacation Home is His Sandcastle

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How to construct the perfect sandcastle

Just a bit of water enables one to turn a pile of dry sand into a spectacular sandcastle. Too much water however will destabilize the material, as is seen in landslides. Here we investigated the stability of wet sand columns to account for the maximum height of sandcastles. We find that the columns become unstable to elastic buckling under their own weight. This allows to account for the maximum height of the sand column; it is found to increase as the 2/3 power of the base radius of the column. Measuring the elastic modulus of the wet sand, we find that the optimum strength is achieved at a very low liquid volume fraction of about 1%. Knowing the modulus we can quantitatively account for the measured sandcastle heights.

Snell's Window on the Olympics

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Olympic Swimmers

I did a bit on Snell’s Window last summer, and you can see that effect quite clearly in photos 1 and 8. If you look carefully at photo #6, you can see the edge of the window at the top of the shot. Below that there is the total internal reflection, which is quite obvious with the first two swimmers. Now imagine you’re a predatory fish, and your target is swimming away from you and approaches the surface — he would see another fish come into view — the reflection, and if the fish then breached the water it would disappear completely, except for any glimpses possible from the disruption of the surface.

Toys in the Office: DIY Edition

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I have an airzooka air cannon as part of my office armament, and it does an admirable job of shooting projectiles of air. However, one of my colleagues had expressed an interest in upping the ante, so we took it upon ourselves to make one using a 5-gallon bucket.

We followed the general path of the steps outlined in an instructable, though we substituted light-duty bungee cords for the elastic.

Cutting out the end of the bucket is a tad messy with all the plastic shavings. In cleaning up my clothes I employed a version of a trick we used in the navy when getting ready for an inspection — a few windings of tape on your hand, sticky-side out, does a good job at grabbing lint. Or plastic shavings.


Another deviation from the basic instructions was that since we used bungee cord, we drilled holes in the bucket for the anchor end, and zip-tied the other ends together, having removed the hooks. That also allowed us to use 3 lines.

The handle is temporarily an optics post. The bucket is just strong enough for it, so we need to add a second layer of something to shore that up and put both a proper handle on the body and a proper grip on the elastic. No metal, though, since a failure of some sort could be very bad news if this became a slingshot. We should be ready for our picnic next week.

The Google Oxbow Incident

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Angleton, Texas

Years ago when Google Earth first added the time-slider tool, which makes my entire blog possible, I realized that one of the best uses for this tool would be for tracking geomorphological change. I, and others like me, had found various changes like landslides and sinkholes, but the evidence pointed to an opportunity for more undiscovered geographical features. I theorized that the most elusive of these was the formation of an oxbow lake.
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I contacted my colleague and showed him my discovery. He agreed, this was without a doubt the formation of an oxbow lake on the Brazos River!