It's time again for Friday Fodder, and this week features stories about the physics of Mylar balloons, the physics of finance, a forgotten dwarf engineer, and a long-running (80+ years) experiment to demonstrate that pitch (tar) is a fluid even if it seems like a solid.

Sad Balloon Physics. Is there anything sadder than the sight of a half-deflated Mylar balloon slumping dispiritedly towards the floor? On the heels of a couple of recent family birthday bashes, Big Daddy Chad over at Uncertain Principles faced just such a sight, and decided to accentuate the positive by finding the physics. In Part I, he tackled not just why the balloon floats -- elementary buoyancy -- but why it floats at that particular height, which turns out to be a bit more interesting. Then, after a short-term fix wore off, he followed up a few days later with Part II, exploring an ingenious method for determining how quickly the helium inside leaked through the Mylar of the balloon. Household physics in action, people!

How Many Magnets Does It Take to Light a Bulb? Tom Swanson of Swans on Tea explores what happens when you drop a magnet first through a coil of wire, then through a copper tube (well, actually a tube of aluminum foil), with an eye towards determining how much energy he could extract from the dropped magnet. His conclusion: "[T]he magnet lost about 0.1 Joules of kinetic energy in the foil, in less than 0.38 seconds, or an average power of just over a quarter of a Watt, in that worst-case scenario. The best-case is 50% higher. And this is using aluminum — copper will give is a better result." Stay tuned for the next installment, whereby Tom tries to harness that tiny bit of energy to a standard light bulb.

They Do It With Mirrors. Rhett Allain of Dot Physics answers a burning question: Why do mirrors reverse left and right, but they don’t reverse up and down? The answer: "Mirrors don’t reverse left and right and they don’t reverse up and down." Being Rhett, he can't just leave it at that; he shows exactly why this is so, with the help of an Obi-Wan action figure.

Why Dark Matter Probably Exists. There are numerous physics experiments underway right now intent on detecting the elusive dark matter -- unseen stuff that physicists think makes up around 23% of all the stuff in our universe (normal everyday matter only accounts for a measly 4%). But dark matter isn't necessarily the only theoretical game in town; there are a couple of alternatives being bandied about to account for observational data without invoking dark matter. Why is dark matter the favored candidate, you may well wonder. Ethan Siegel of Starts With a Bang lays it all out for you here.

The Wizard of Schenectady. Smithsonian shines a much-deserved spotlight on the unjustly forgotten Carl Steinmetz, a German-born scientist who counted Einstein, Edison and Tesla among his acquaintances. He was a dwarf, suffering from an abnormal curvature of the upper spine, but his mind was among the best of his era, leading to major breakthroughs in both direct and alternating current power generation. My favorite part was the story of how he helped Henry Ford's engineers solve their problems with a generator in the River Rouge plant in Dearborn, Michigan:

"Steinmetz listened to the generator and scribbled computations on the notepad for two straight days and nights. On the second night, he asked for a ladder, climbed up the generator and made a chalk mark on its side. Then he told Ford’s skeptical engineers to remove a plate at the mark and replace sixteen windings from the field coil. They did, and the generator performed to perfection."

Then he presented Ford with a bill for \$10,000. Ford, in turn, asked for an itemized bill, balking a bit at the high price tag. Steinmetz obliged, itemized \$1 for making the chalk mark on the generator, and \$9,999 for "knowing where to make mark." Needless to say, Ford paid the bill.

An-Ti-Ci-Pa-Tion: Waiting for The Ten-Year Drip. Via io9 comes news that a major milestone is approaching next year for one of the longest-running experiments. Back in the late 1920s, Professor Thomas Parnell, of the University of Queensland in Brisbane, wished to show his students that pitch (paving tar) was a fluid not only on very hot days or just after being poured, but all the time. So he set up an apparatus to demonstrate this: the ultimate slow drip.

Parnell started his demonstration in 1927 by melting down some pitch, making sure it was evenly mixed, and then pouring it into a funnel. The funnel was sealed at the bottom, to prevent the pitch from flowing right through. It wasn't until 1930 that the seal was removed. Parnell wanted to be sure that the pitch was completely cooled before the experiment could be started.

The tip of the funnel was opened and students waited for the first drip. They then graduated, and a new batch of students waited for the drip. They graduated, and the next batch of students saw the first drip of pitch, which came in 1938. The next one came in 1947. The next in 1954. Drips came about once every decade, except the seventies when two drops fell, one in 1970 and once in 1979 (it was a rockin' time). The nineties, on the other hand, were dropless.

The next drip should happen sometime in 2012, and there's a Webcam set up in the lab to capture the moment (you'll need Windows Media Player to watch, so Mac users might be out of luck -- I know, right?).

Of Bosons, Bosuns and Bosoms. Over at the Guardian, John Buttoerworth explains the difference between bosons and fermions in particle physics with his characteristic wry wit. "The difference between them is just spin. But in this context, spin is a quantum number of angular momentum. It is a bit like the particle is spinning, but that is really just an analogy, since point-like fundamental particles could not spin, and anyway fermions have a spin such that in a classical analogy they would have to go round twice to get back where they started. Quantum mechanics is full of semi-misleading analogies like this."

Modeling Financial Markets. Scientific American's David Biello offers a fascinating Q&A with statistical physicist H. Eugene Stanley, who argues against using standard Gaussian bell curves as a model, and in favor of the more L-shaped power law approach, "in which the frequency of one event varies as a power of some attribute of that event." Can mathematical modeling beat the market? Stanley says no. But it can be helpful in reducing risk.

Hot Underwater Recoil Action. Finally, via Laughing Squid, we stumbled across this nifty video by Smarter Every Day exploring what happens when you fire handguns underwater. Among other things, the aquarium breaks, but there's some cool-looking shock waves and fluid dynamics at work, too. I feel smarter already.