Does the Moon Bend Radio Waves?

Question: Regarding radio astronomy, are there any “edge effects” to the moon, meaning can or does the moon bend or diffract radio waves emanating from behind it?  Is it possible it bends it enough to create a focal point on the earth?  What frequencies might be the most feasible for studying this?  — David

Answer: Yes.  Think of radio wavelength “light” as having the same properties as optical light, but having a longer wavelength.  In fact, even though the original observations, made in 1919, of the general relativistic prediction that light would bend as it passes around the edge of the Moon were made at optical wavelengths, those early measurements were somewhat inaccurate.  The uncertainty of these first and subsequent optical measurements remained quite large until the 1960s, when measurements at radio wavelengths were made which confirmed Einstein’s theory of general relativity.  These observations are generally done at centimeter wavelengths, which are a good choice for the availability of high-sensitivity facilities, such as the Very Large Array.

Jeff Mangum