If you look at the spinning girl’s silhouette below, you will think it is spinning clockwise, probably. When you check her shadow below, momentarily the spinning direction changes in your mind, and now the girl is spinning counter-clockwise. It can be quite hard at the beginning to notice switch of the spinning direction, but eventually you’ll manage.

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It had occurred to me that perhaps with an insane amount of perseverance, it might be possible to build a whole computer that runs on marbles. My second marble machine was however much less based on logic – more on just making lots of noise.

But a few months ago, I had an idea as to how the divide by two mechanisms from my first marble machine could be cascaded together to actually function as a sort of adder or counter. Once I had that idea, I knew I had to try it at some point, and recently, I finally got around to building my marble binary adding machine.

The core of the invention is a modification of the divide by two flipflop to retain the marble that falls off the right side, and retain it until the flipflop is flipped to the left by the next marble. See small diagram above right. The retention of this extra marble allows the state of the marble accumulator to be dumped. The adder would just as well add without it, but the number would have to be read off by the angle of the rockers, rather than have the device dump the count out. Really, if such an adder were integrated into a hypothetical marble computer, reading out the result as a series of marbles would be an essential element.

• Link (via MAKE: Blog)
• There a few more amazing marble machines on the site here.

Related:

• The Computer/Domino Connection

The principle is a cylindrical building with a helical shape for the floor. The slope of the floor is 1.5% (it rises by 1.5 cm every meter), thus hardly noticeable. The height of each ’storey’ is 3 meters, so that when you walk 200 meters along the corridor, you have walked a full circle, but you end up one ’storey’ above or below your starting point. This results in a diameter of approximately 60 meters, therefore quite common for large skyscrapers. The corridor is on the outside, so that everybody has access to the fabulous views over the city. Offices are all on the inside. As the tower is hollow in the middle, and the inner diameter of the patio is still approximately 40 meters, this makes for a very nice light shaft with peaceful lighting conditions.

• Link (via reddit)

Tons of folks have been writing to me this morning about the BBC story about an idiot math teacher who claims to have solved the problem of dividing by zero. This is an absolutely infuriating story, which does an excellent job of demonstrating what total innumerate idiots reporters are.

What this guy has done is invent a new number, which he calls “nullity”. This number is not on the number line, can’t be compared to other numbers by less than or greater than, etc. In other words, he’s given a name to the basic mathematical concept of “undefined”, and proclaimed that this is somehow a solution to a deep and important problem.

• Link
• BBC report

• Video (via reddit)

My friend Cory and I were sitting around one day, as we often do, contemplating the mysteries of the universe, when one of us brought up the possibility of building digital logic using only dominoes. We did a web search, figuring that someone must have done something like that before, but guess what? Nary a page was to be found. Cory immediately made a trip the local toy store and bought a package of faux ivory dominoes, and we began work.

Here’s a single-bit adder:

• Link (via reddit)

• Link (via Digg)

GNU Make has no built-in arithmetic capability. In this article I present a collection of GNU Make macros that implement functions for addition, subtraction, multiplication, and division of integers. Functions are also provided for integer comparisons such as “greater than” and “not equal.” These macros are implemented entirely using GNU Make’s built-in string manipulation functions.

• Link (via reddit)

»Optical illusion« sounds pejorative, as if exposing a malfunction of the visual system. Rather, I view these phenomena as bringing out particular good adaptations of our visual system to standard viewing situations. These adaptations are »hard-wired« into our brains, and thus under some artificial manipulations can cause inappropriate interpretations of the visual scene. As Purkinje put it: »Illusions of the senses tell us the truth about perception« (cited by Teuber, 1960).

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OK at first I definitely thought this was going to be one of those stare in the center and turn your speakers up maze scare things. But turns out it’s actually legit and kinda cool. Stare in the center and after a minute look away. You will hallucinate!

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Here’s the story. First, when I was a grad student in philosophy at Indiana a long time ago, John Tienson gave us the example of:

Dogs dogs dog dog dogs

whose syntax is the same as:

Mice cats chase eat cheese.

We found the -s morpheme unaesthetic, so we came up with

Buffalo buffalo buffalo buffalo buffalo

• Link (via reddit)

It is called the McCollough Effect, and was originally described by Celeste McCollough in a paper in Science in 1965. It has been the focus of on-going investigation ever since.

The effect typically lasts for hours, or even overnight. The duration can be changed by the consumption of coffee and other psychoactive drugs. One paper found that it is stronger in extroverts than introverts, and might be a reliable test for extroversion.

The precise cause of the effect is unknown, and currently under investigation. It is not a simple case of fatigued neurons: there are neurotransmitters involved and appear to be responsible for the long-lasting nature of the effect.

• Link (via Digg)

• Link (via Digg)
• Also on YouTube here

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According to Huffman, the magnet works by moving very slightly, or with a noticeable oscillation, in response to EM fields. This stimulates the somatosensory receptors in the fingertip, the same nerves that are responsible for perceiving pressure, temperature and pain. Huffman and other recipients found they could locate electric stovetops and motors, and pick out live electrical cables. Appliance cords in the United States give off a 60-Hz field, a sensation with which Huffman has become intimately familiar. “It is a light, rapid buzz,” he says.

• Link (via Boing Boing)

• Link (via reddit)

Let’s suppose your child wants to take a martial arts class. Being a conscientious parent, you check out the local dojos and find two good places. Both are suitable and well equipped. Both practice fighting with contact – but there’s one major difference. One dojo insists on a full range of protective padding – hands, feet, chest protectors, shin guards – the whole works. The other takes a much lighter approach – hands and feet, and sometimes not even those.

To the conscientious parent, the first place is going to look much safer, right? But when you look at the injury rates of the two dojos, you notice something odd: They’re about the same. The kids covered in foam padding are getting just as many bruises, scrapes, and sprains as the kids wearing almost none. What could be going on here?

• Link

• Link (via Digg)

After two years of work, with a purpose-built steel machine wired up to high-speed cameras, microphones and electronic sensors, a team of Japanese researchers has finally proved that a hard-boiled egg can jump. All it takes, according to Yutaka Shimomura and colleagues of Keio University, is a good spin.

A spinning egg will spontaneously rise up from lying on its side to standing on its end. Shimomura, along with physicists at the University of Cambridge, had previously worked out why this is so, and predicted that the forces involved could also make an egg leap a tiny bit into the air.

I don’t know what possible use this could have but there you go.

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