You know what I haven’t talked about much lately? My own research! Well, today is a great day for it, because a paper I wrote with my student Ray Abney just came out in Physical Review A, titled “Nonradiating orbital motions.” It’s actually invisibility-related, and I thought I would say just a few words (and pictures) of what it’s all about!
So, one of the earliest physical phenomena studied that can be connected to invisibility is known today as a nonradiating source. The oxymoronic name refers to a source of electromagnetic radiation (or more generally other types of waves) that, in fact, does not produce any radiation at all.
This is counterintuitive because the mathematical formulas that describe electricity, magnetism and light, called Maxwell’s equations after their discoverer, predict that an oscillating electrical current will produce electromagnetic waves. All of our wireless communications technology is based on that principle; when you see a radio antenna, such as the mast radiator pictured below, you are looking at a metal structure that has an oscillating electrical current driven through it to produce radio waves.
Your cell phones produce a signal in a similar manner; they have an antenna for broadcasting and receiving. Apple infamously ran into trouble with the iPhone 4 when they changed the antenna design and put it around the edge of the case, causing dropped calls when people held the phone “wrong!”
If charges are accelerated more strongly, they can produce higher-energy electromagnetic waves such as X-rays. The Advanced Photon Source at Argonne National Laboratory takes advantage of this and sends electrons around an 1,100 meter ring at nearly the speed of light; the circular path of the electrons causes them to constantly shed X-rays that can be used for basic and applied research.
So it is widely known and assumed that accelerated electric charges produce electromagnetic radiation of some form. But this is not always the case!
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Skulls in the Stars 