Hi,
Dwayne loves going to Las Vegas. Even when he is inside the casinos, where there are no windows to give him light cues, he still feels sleepy by midnight, because his body still is influenced by circadian rhythms.
The correct answer is "Jet Lag".
Known to be a physiological state, Jet Lag is caused by the alterations towards the body's circadian rhythms which is caused by the rapid long-distance trans-meridian travels. People who experience flying on airplanes for the first time, commonly experience this condition.
This question will never be answered and accepted by everyone. It depends on what you believe and what you perceive life as.
hopes this helps,
Xeno