Monthly Archives: November 2010

What Quantum Mechanics is (and isn't) Good For

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What Is Quantum Mechanics Good for?

Max Born said that by manipulating this wave function that Schrödinger developed, you could tell the probability of finding the electron at any point in space and time. From that, it turns out that the electron can only have certain discrete energies inside an atom. This had been discovered experimentally; this is the source of the famous line spectrum that atoms exhibit and that accounts for why neon lights are red whereas sodium streetlights have a yellow tinge. It has to do with the line spectra of their respective elements.

But to have an actual understanding of where these discrete energies come from—that electrons and atoms can only have certain energies and no other—is one of the most amazing things about quantum mechanics. It’s as though you are driving a car on a racetrack and you are only allowed to go in multiples of 10 miles per hour. When you take that and you bring many atoms together, all of those energies broaden out into a band of possible energies.

I like the point about how in basic discovery, nobody is thinking about applications down the line — Schrödinger didn’t have the diode laser in mind when he was developing the theory

If you went to Schrödinger in 1926 and said, “Nice equation, Erwin. What’s it good for?” He’s not going to say, “Well, if you want to store music in a compact digital format…”

via

Life in Free Fall

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Life aboard the International Space Station

The space station has a permanent crew of six, so the arrival of new faces is a cause for celebration. That said, even the most welcome visitors can cause havoc if they are inexperienced. There is a subtle art to moving around without crashing into anything – or, more annoyingly, others – knocking computers, equipment and other objects off the walls to which they are attached with Velcro pads. One serving shuttle pilot confessed to leaving a wake of laptops and other vital belongings behind him the first time he tried to fly from one room to another. “When you first turn up, you are like a bull in a china shop,” he said. “I had no idea where to put any of it back.”

In time, people hone the skill and can fly down the length of the station, straight as an arrow, without touching anything, except with their fingertips. People sit in mid air, tapping away at a computer, with only a toe hooked under a wall strap to anchor themselves. Then, with a flick of the hand, they’ll float up to another computer and carry on typing there. Getting from one place to another is all the more difficult because up and down (and so left and right) have no absolute meaning. The ability to form a mental map of the space station – and then rotate it in 3D to suit your perspective – is a priceless skill for an astronaut.

Why so Blue?

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Causes of Color

Why use a black body radiator as a standard, when no such thing exists?

It turns out that black body radiation provides us with a set of very precise working equations that relate the temperature of an object to the light it emits. Working from the ideal and using Planck”s law, we can predict the energy distribution across the spectrum for a given temperature. The total emitted power is calculated using the Stefan-Boltzmann law. The wavelength of the peak emission, and hence the color that dominates for this temperature, is provided by Wien’s displacement law. Knowing the ideal case allows us to predict or calculate actual values by correcting for the imperfections of actual hot objects.

h/t to ewmon

Get Back To Me Later

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‘Sleeping on a problem’ may be the best way to solve it

A research has suggested that the best way to solve a complicated problem is to distract yourself for a few minutes with something else or sleep on it overnight.

However, as with most summaries of psychological studies I read, the actual experiment described seems somewhat limited, and the conclusion is an extrapolation from specific to general, without clearly showing that other factors have been eliminated. But that may just be a limitation of the reporting.