Imagine the measured distance planet earth-moon, which is growing about 3.8 centimeters a year, is not equivalent to a theory that the moon is going away, but planet earth may just be shrinking in the same way (or maybe a combination of these two movements).
In fact, we know the expansion of the mid-atlantic ridge (about 14 cm per year). But do we know the change in the subduction zones of the continental drift as well? If subduction exceeds the expansion, we`ll have a shrinking planet. How about measuring the equator once in a while, or does this take place already?