(Why Wood and Nahle were correct and Pratt was in error.)
The famous experiment by Robert W. Wood, at John Hopkins University, with two carton boxes/greenhouses, in 1909, is being mentioned everywhere, and on many websites,* as simple experimental evidence proving the fallacy of the greenhouse gas effect theory (GHE).
According to the GHE theory, the small greenhouse with a glass cover had to reach a temperature of nearly 15°C higher than the other small greenhouse with a salt rock (halite) ceiling. This is because salt rock is a material which is “neutral” to infra-red, while glass can theoretically “trap” almost 80-85% of infra-red outgoing from the heated bottom of the greenhouse, and significantly increase the temperature, by “backradiating” the infrared (IR) waves.
Nothing of that took place, and both greenhouses showed almost the same temperatures inside, with a discrepancy of “scarcely one degree”. For years this experiment was sufficient to dispel giving any scientific ground to the greenhouse gas effect theory. But several decades later, many GHE advocates “forgot” this experiment.