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Keep an eye out on Joshua Samani's blog. It's coming soon, and is sure to dazzle you with lots of brilliant information (from articles to stuff about teaching). You don't want to miss it!The effect of time dilation illustrated by the twin paradox is not just a theoretical phenomenon. Time dilation has been measured in the real world. Physicist Joseph C. Hafele and astronomer Richard E. Keating tested the effects of time dilation in 1971 by synchronizing atomic clocks, sending one clock on a plane ride around the world, and then comparing the passage of time measured by the traveling clock to the time measured by the clock on Earth. They found that the traveling clock registered less time than the Earth clock in precisely the amount predicted by special relativity.It also turns out that without taking the effects of time dilation into consideration, the global position systems (GPS) used by smartphones and other devices would not work properly. The basic reason for this is that the time registered by GPS satellites must be accurate to within nanoseconds, and at this level of precision, the minute effects of special relativity become significant for the GPS system to function.You might be wondering which branch of physics time dilation falls under. Time dilation and the twin paradox are phenomena predicted by special relativity which was essentially introduced in 1905 by theoretical physicist Albert Einstein in his now famous paper “On the Electrodynamics of Moving Bodies.” (but he wasn't the only person to have contributed to the development of special relativity) Special relativity is wonderfully strange and predicts all sorts of bizarre, un-intuitive phenomena besides time dilation. For example, it also predicts that objects that are moving seem as though the are shorter in the direction of their motion. This effect is called length contraction.Another effect it predicts is called the relativistic Doppler effect. This is precisely the “Doppler effect” described in the video. The Doppler effect has many interesting consequences. For example, it causes the frequency of light emitted by objects moving away from us to appear to decrease, and it causes the frequency of light from objects moving towards us to appear to increase. Since red light is on the low frequency end of the visible spectrum, and since blue light is on the high frequency end, physicists commonly say that light we observe from objects moving away from us is red-shifted, while light we from objects moving toward us is blue-shifted. In other words, objects moving away from us look redder, and objects moving toward us look bluer.Although we’ve only really described a few of the qualitative aspects of special relativity, it is actually a field that contains a lot of really interesting mathematics. For example, the measurements made by observers in different reference frames are related by something called the Lorentz transformation. The Lorentz transformation is a special kind of mathematical transformation called a linear transformation, and linear transformations are mathematical objects that are central to a field of pure mathematics called linear algebra.