Flat-Earthers claim that moonlight is cold and cools down objects exposed to it. It is merely a myth from the 19th-century flat-Earthers, reinforced by confirmation bias in various so-called “experiments” performed by today’s flat-Earthers.
Flat-Earthers experimented and insisted that moonlight has a cooling effect because they failed to control other factors affecting the experiment and maybe even deliberately introduced them to influence the results. They also did not account for measurement errors —the variation between several measurements— and cherry-picked the results that fit their desired outcome while ignoring the rest.
Flat-Earthers usually performed their experiments using thermometers. They measured only two spots. One that is exposed to moonlight, and the other isolated from the moonlight. A better way to do this experiment is to use FLIR cameras capable of scanning a large area for temperature differences.
Using a FLIR camera, we know that the shaded part of the ground has practically no temperature difference than the parts exposed to moonlight. While temperature differences can exist between parts of the scene, it does not correlate to the shade’s boundary formed by moonlight. And therefore, we can conclude that moonlight does not have a meaningful effect on the objects’ temperature.
We can also point our FLIR camera toward the moon. It will show us the moon has a higher temperature than the surrounding night sky. While FLIR cameras will not accurately measure the temperature of the lunar surface, the result is sufficient to demonstrate that moonlight has a small heating effect, not a cooling one like claimed by flat-Earthers.