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Editor's Blog

Jonathan Vos Post
September 28, 2010


Want to slow the aging of your brain? Wear shoes with flatter heels.

Physicists at NIST (National Institute of Standards and Technology) have measured a general relativity effect at a scale of 33 centimeters, or about 1 foot, proving, that you age faster when you stand a couple of steps higher on a staircase.  [“Pair of Aluminum Atomic Clocks Reveal Einstein's Relativity at a Personal Scale”]

This is exactly as predicted by Albert Einstein, but is not about aging more slowly by moving faster, as astronauts do, which is a result of the “Twin Paradox” of the Special Theory of Relativity.  If Alice and Betsy are twin sisters, and Alice orbits Earth at 17,000 miles per hour, she is technically aging slower in reference to the Earth than Betsy, who stays home, because she is moving at a high velocity, even though that speed is only 25.3498038 millionths of the speed of light.

NIST researchers were doing the most sensitive test of a very different effect, based on the General Theory of Relativity.

As Science Daily editors summarize: “Scientists have known for decades that time passes faster at higher elevations — a curious aspect of Einstein's theories of relativity that previously has been measured by comparing clocks on the earth's surface and a high-flying rocket.”

But NIST brought this down to less than the difference in height between an average adult and a professional basketball player, namely 33 centimeters, or about 1 foot.

NIST scientists used their enhanced version of an experimental atomic clock based on a single aluminum atom, which is now the world's most precise clock, more than twice as precise as the previous pacesetter based on a mercury atom.  [“Second 'Quantum Logic Clock' Based on Aluminum Ion Is Now World's Most Precise Clock”]



Described in the September 24, 2010 issue of Science, the difference in the aging rate of the brain over that 1 foot difference in altitude is orders of magnitude too small for humans to perceive directly — roughly 90 billionths of a second accumulated over a 79-year lifetime — but may provide practical applications in geophysics and other fields.

The NIST team experimentally measured both a twin paradox effect, with a speed of about 20 miles per hour, and also on Einstein’s prediction that when two clocks are subjected to unequal gravitational forces from different elevations above the surface of the Earth, the higher altitude clock — experiencing a smaller gravitational force — runs faster.

This is distinct from yet a third kind of relativity effect, due to the rotation of the Earth, the so-called frame dragging.  Stanford University student Keith Bechtol explains this in a paper titled “Gravity Probe B and the Search for the Lense-Thirring Effect”, “Gravity Probe B and the Search for the Lense-Thirring Effect”.

In late 1959 and early 1960, George Pugh and Leonard Schiff independently proposed satellite gyroscope experiments to detect the Lense-Thirring effect produced by the Earth's rotation.  According to concept of rotational inertia, the axis of a perfectly constructed gyroscope should always point in the same direction.  However, twisting of spacetime around a massive rotating body could effectively rotate the spin axis of a gyroscope.  The theorized frame-dragging effect around the Earth would be small — a deflection angle of only 42 milliarcseconds per year for a gyroscope in low orbit.

Science Fiction authors have explored the effect of an extreme deceleration in aging when one stays close to a much more powerful gravitational field, in a close orbit around a black hole.  For example, the Heechee, an alien race from the stories and novels of Frederik Pohl, did this.  Pohl, by the way, is a member of the American Association for the Advancement of Science.  He didn’t gain membership for research, but for his wonderful writing on subjects that excited the brains of scientists.  His book, Chasing Science, is, in his words, “about the pleasures of science as a spectator sport.  The pleasure of going to a laboratory and seeing what they're doing, listening to the scientists talking, going to the A.A.A.S. and listening to the scientists gossip, and visiting places where scientific things are happening, like volcanoes, earthquakes, geysers, all that.”

So think twice before wearing high heels, or standing on a ladder.  Do the math!

See Also

All About Space Travel, Time Travel, Quantum Tunneling & Zero-G Sex

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