Weather RADAR. R.A.D.A.R. is actually an acronym that stands for Radio Detection and Ranging. As Oklahomans, we think of only needing radar when there are storms, but it does more than just that. It's also quite useful for detecting sunsets and sunrises.
Check out the image above. For most people they see a "quiet radar," but the radar is anything but quiet. It's doing something that I would label as cool. You see the green line? That is the radar detecting the sunset.
The "spike" in the radar occurs when the sun shines directly into the beamwidth of the radar antenna. While most of the radiation of the sun shines as visible light, there are signs that some of the energy comes as microwave. Specifically the same wavelength that radar uses.
And the "spikes" can be seen all over the United States at varying times, depending on when the sun is setting.
Of course the sunset spike will not always be in the same location every single day. The sun sets in various locations throughout the year. During the winter, the sunset spike will occur in the southwest since the sun angle is lower, and during the summer, the sunset spike will occur in the northwest. Between those seasons, the sunset spike will gradually move north or south.
So the next time you hear the radar is "quiet" as the sun sets, know that you can prove that to be false!