![]() ![]() Patla wanted to see if the magnetic interactions in two different atoms, even though they are assembled from different numbers of protons, electrons, and neutrons, would behave the same way over time and space. The concept they tested is similar to Galileo’s apocryphal experiment, in which he dropped two objects of different mass off the Leaning Tower of Pisa and found that they fell at the same acceleration. They also wanted to know if the magnetic interaction occurred in the same way for different atoms-so they used two different types of clocks, one that contained hydrogen atoms, and another that contained cesium, which is more than 100 times heavier. “Most of it is automated, but someone watches it all the time, and someone carries a beeper.” Patla’s team can account for every single source of environmental effects they can think of, such as Earth’s gravity. “If the temperature changes more than 0.5 degrees, they’ll get alarms to go fix it,” says Patla. NIST employees take rotating shifts to coddle the clocks properly. The clocks stay in a temperature and humidity-controlled room, and its atoms are kept in a vacuum-sealed chamber. Patla’s lab chose to study this obscure-sounding phenomenon because they could observe it in the clock with high precision. But what if the laws of physics do change over time and in different locations, and we’re just too galumphing to perceive it? ![]() We assume that baking soda and vinegar will make a frothy mess because it always has. We assume that an airplane will fly because it always does. But how do we actually know that the laws of physics aren’t changing, ever so slightly, from day to day? It’s a hidden logical assumption that underpins all science, ever. Throw a ball today, and it lands in the same way it did yesterday. The laws of physics apply in the same way today as they did 4.5 billion years ago when the moon formed, or in 2000 when you were listening to Creed. It’s one of the basic ideas in Einstein’s theory of general relativity, a set of rules that correctly describes how the planets orbit the sun and how neutron stars collide to produce gravitational waves. The ticking of the clocks, Patla says, actually illustrates one of the most fundamental principles in the laws of physics: that no time or place in the universe is special. In a paper published in Nature Physics on Monday, Patla’s team reveal a profound result from an exceedingly monotonous experiment. And they’ve kept watching for some 450 million seconds*-over 14 years.īut their patience paid off. Patla’s team, based at the National Institute of Standards and Technology in Boulder, Colorado, began monitoring the clocks on November 11, 1999. It’s like a physicist’s version of watching paint dry. Bijunath Patla’s experiment sounds like a real bore: Gather 12 of the most accurate clocks around the world, and watch them tick. ![]()
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