Strategic Reserves

President Bush recently announced that the strategic petroleum reserves would be breached to counter gasoline shortages in the wake of Hurricane Katrina. Did you know that government maintains strategic reserves of other materials as well? The strategic helium reserves are kept in Amarillo, TX in a natural formation called the Bush Dome. The He reserve was created in 1925, when the major strategic use was military dirigibles. Helium extraction is incidental to methane (natural gas) production. These days helium is used in magnetic resonance imaging to cool the coils in the magnets so they will superconduct and other cryogenic applications. The reserve contains about 30 billion scm (an scm is a cubic meter at standard conditions -- not a square cubic meter as one report states!)

Camille Minichino visited the chemistry department at Bryn Mawr this week. She is the author of the Periodic Table mystery series. In her second book, The Helium Murder, physicist Gloria Lamerino suspects Congresswoman Hurley has been murdered because of her position on the sale of helium in the reserves.

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Standard conditions for a gas are 298 K and 1 atmosphere of pressure.

Flying Objects

One of the major uses of helium is to keep superconducting magnets very cold. The coils must be kept at a chilly 450 degrees Fahrenheit below zero in order to achieve the strong magnet fields necessary for magnetic resonance imaging. MRI is a widely used medical imaging technique, partly because the radiation used is of much lower energy than that need for CT scans, for example. MRI is actually an application of a quantum mechanical phenomena called NMR (nuclear magnetic resonance). The energy states of the nuclei in a magnetic field can be changed by tickling them with very small amounts of energy (radio waves to be precise), and the changes in these states can be used to produce an image of living tissue. The stronger the magnet field, the more easily detected the energy changes are, hence the use of the strong field superconducting magnets.

So how strong are these magnets? They are on the order of 1 Tesla, thousands of times more powerful than your basic horseshoe magnet. If you're not careful with a superconducting magnet of this strength, it can suck up a lot of metal. See the photos here for some stunning examples.

Quantum jokes?

Q: Why won't Heisenberg's operators live in the suburbs?

A: They don't commute.

To really understand the joke, it's helpful to know the general form of the Heisenberg uncertainty principle. The Robertson-Schroedinger inequality



leads directly to the more general statement of the Heisenberg uncertainty principle. The piece in the little square brackets [A,B] on the right hand side is called the commutator of the operators A and B. When A and B don't commute, [A,B] is non-zero and you end up with uncertain simultaneous measurements.

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Commuting operators can be applied in any order and you get the same result.

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My 9 year-old says that if you have to explain a joke, it's not a joke. And by this definition, he says, this post is not a joke!