They shot strongy on the causeway. He’s dead.
Monthly Archives: August 2009
Those Who Can, Do. Those Who Can't, Explain.
Usain Bolt: The Science of Running Really Fast
Even without knowing the times, you can see that this is a special run. The first few seconds are fairly average, and as expected the acceleration trails off after around 40m, but then he just keeps going. Bolt covers 60-80m faster than 40-60m, somehow increasing his acceleration, and takes 80-100m at the same speed, with no significant deceleration.
Nonmoving Motion
Sculptures in Motion by Peter Jansen
Peter Jansen must have watched the slow motion parts in The Matrix thousands of times. A student of physics and philosophy, the Dutch artist captures sequences of human movements within a single frame of space and time.
Energy: It's Nothing to Snicker At
Of Car Crashes and Snickers Bars
Pop quiz, hotshot. Using the caloric energy content of a candy bar (e.g. Snickers, at 250 food calories), what is the kinetic energy of a two-ton behemoth SUV traveling at about 70 mph? A first-order approximation is fine — no need to worry about more than one significant digit.
Got it? Think of your number and then proceed to the analysis.
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Colliding Smoke Rings
The Dawn of the Squeaky-Voice Era
It’s time to celebrate Helium, that noble gas, once again. Aug. 18, 1868: Helium Discovered During Total Solar Eclipse
French astronomer Pierre Jules César Janssen camped out in Guntoor, India, to watch as the moon passed in front of the sun and revealed the solar prominences. Like other sun-gazers that morning, Janssen discovered that the prominences were mostly made of super-hot hydrogen gas. But he also noticed something extra: Using a special prism instrument called a spectroscope, he determined that the line of yellow light everyone had assumed to be sodium didn’t match up to the wavelength of any known element.
We did this last year, too.
TIME on Time
Why Can’t My Clocks Keep Time Accurately?
A short article, directed mostly at the problem of synchronization, as applied to everyday life: your electronic devices display different times. Why? Because you always have to synchronize your clocks, no matter how good they are. The question remains, how often do you need to do this?
From the article:
Most computers carry an on-board clock powered by a separate battery. As the battery drains over time, the computer’s timekeeping becomes less accurate.
This is true, but the clocks aren’t super-accurate to begin with. The battery draining isn’t the whole problem.
That's not a Gun. This is a Gun.
Modern MechaniX: Secrets of the Mystery Gun that Shelled Paris (Jun, 1930)
A scan/reprint of an article describing the “Paris Gun” used during WWI, firing from 75 miles away. (The text appears to have been scanned/OCR-ed, from some of the typos in it)
Now that the rest of the story can be told, consider the guns themselves: There was a barrel 120 feet in length, approximately twice as long as the biggest guns built to that time—so long, in fact, that the end had to be supported in the air to keep it from bending down and being shot off by its own shell. In fact, that very thing happened to the first of the guns tested at the German proving ground, for the barrel bent a full inch under its own weight.
Next they fired a shell 75 to 80 miles or more, over a total trajectory ranging from 90 to nearly 100 miles.
To do that the shell was shot 24 miles above the earth, higher than any man-made thing, save possibly a small sounding balloon, had ever penetrated. At that extreme height the shell traveled through what was almost a vacuum, at a temperature of far more than 100 degrees below zero.The shell, traveling at an average speed of 30 miles a minute—or sixty times as fast as the usual legal rate for automobiles — took three minutes to complete its aerial flight of 90 miles. It remained away from the earth so long, in fact, that the old world revolved on in space while the projectile was away, so the gunners had to aim a half mile east of the target in order that the target might be there when the shell arrived to hit it.
Ice to See You
NY Times: For Winter Games in Vancouver, Ice Isn’t So Easy
“You can’t just go out there and make ice,” said Hans Wuthrich, in charge of the surface at the newly built curling arena, where the final step is a delicate spritz of scientifically configured water droplets strong enough to alter the course of 44 pounds of sliding granite.
The five ice specialists, each with deep Canadian ties, have extensive experience from previous Olympics. On behalf of ice, they helped design new locales and the upgrades to existing ones. They toured Vancouver’s water-treatment plants to study their product’s key ingredient. They ponder every ice-dooming possibility.
Mars was Once a Fine Restaurant
It had plenty of atmosphere.
Starts With a Bang: A Meteorite on Mars
This makes Block Island the largest meteorite we’ve ever found on another planet, which is impressive in its own right. But what we learn from this is even more impressive. You see, Mars’ atmosphere, the way it is right now, isn’t thick enough to allow meteorites this large to land:
The atmosphere is so thin that a meteorite this big would have hit the Martian surface at too great a speed, and would have broken apart from the impact.
Sometimes the “how do we know this” explanations immediately become very complicated. This, I think, is not one of those times.