There is a very obvious joke in this tweet, but there is also a much more subtle one. The obvious joke is about sex. You can figure that one out on your own.

The subtle joke has to do with the way physicists describe electromagnetic radiation. You know – light, radio waves, that sort of thing. Those are waves, and you can think of them moving through space at a constant speed (the speed of light). Being waves, they bounce up and down. Like a sports bra on a jogger.

The rate at which they bounce up and down (I’m not letting that image go), is called the frequency. Typically described in how many times per second they do it, for which we use the unit Hertz (Hz). A jogger bounces about once per second, so the frequency of that sports bra is 1Hz. AM radio waves, in contrast, bounce up and down thousands of times a second (ouch, that hertz), so we use KHz (K means kilo, which means 1000) to describe them.

Another way to describe the same wave is by how much distance it travels between each up/down cycle. This distance is called the wavelength. The typical stride length of a jogger is 30 inches, so the typical wavelength of our sports bra is 30″. Suppose you had two joggers going exactly the same speed. One has long legs and the other has short legs. Ms Long Legs is going to be bouncing a lot slower than Ms Short Legs.

If the overall speed is constant, as it is with our two joggers (and light and radio waves), a low frequency covers a big distance on each bounce. And a high frequency only covers a short distance on each bounce.

Low frequency -> large wavelength; High frequency -> small wavelength. Mathematicians call this opposite relationship “inversely proportional.” So wavelength is inversely proportional to frequency.

A really low frequency wave will take a long time to reach its next peak. But a high frequency wave will reach its next peak in a short time. The duration of that wavelength, at constant speed, is proportional to the wavelength. And it is therefore also inversely proportional to frequency.

Hence the paradox. Physics tells us that duration is inversely proportional to frequency. But our own experience in the bedroom yields the opposite result.

Further study is clearly warranted.

Homework: For the sake of science, try convincing your partner to increase your frequency and see whether duration also increases. It’s really a win/win. Happy bouncing.