Perhaps the weirdest prediction of relativity is that rotating masses twist space around them. This effect is known as frame dragging, and it is most dramatic around black holes. But even the Earth’s rotation twists space ever so slightly. In 2011 a spacecraft known as Gravity Probe B successfully observed this effect due to the Earth. The frame dragging effect of Earth is so small that it’s astounding we can perceive it at all. To observe these effects, the team had to create quartz spheres so precise that their surface varied no more than 40 atoms from a mathematically perfect sphere. They were then covered with a thin layer of niobium so they could be suspended within an electric field. Their rotation created a small magnetic field, which was measured by superconducting quantum interference devices. Of course all of this is packed into a probe and shot into space for an 18 month mission. Over the duration of the experiment, the rotation of the spheres had to be measured with milliarcsecond precision. Despite the challenges, Gravity Probe B confirmed the Earth’s gravitational curvature of space to within 1% of predictions, and confirmed frame dragging to within 19%. When it comes to physics, there sure are some strange theories — and even stranger phenomena — out there. The notion that particles don’t have fixed, intrinsic properties that are simultaneously measurable can only be described as weird, and the fact that you can add as much energy as you want to a particle but it will never accelerate to beyond a particular speed is certainly counterintuitive. Yet one theory has them all beat. For ninety-nine years, now, General Relativity has made a whole host of unique predictions, ranging from time slowing down in a gravitational field to the bending of starlight to the decay of pulsar orbits, that have been observationally confirmed each and every time. Its the strangest theory we know to be true, and were on the brink of testing (and possibly confirming) its predictions to even better precision!
Posted on: Tue, 30 Sep 2014 16:06:59 +0000
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