Theory 10/Sleep-wake cycle/Onset phase
Onset Is Pressure Against Clock
The claim
Sleep onset occurs when homeostatic pressure exceeds the circadian wake signal, so the same sleep debt can leave a person alert at one hour and asleep at another.
01Mechanism
Two processes oppose; sleep begins at their crossover.
02Prediction
Onset should track the crossover.
03Refutation
Onset tracking debt alone would remove the clock.