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Jet lag
The world is divided into 24 time zones. The Greenwich meridian in London is the base. The time changes by one hour for every 15 degrees travelled in either direction from the Greenwich meridian.
Jet lag happens when you cross over a number of time zones and disrupt the body’s normal 'circadian' rhythms or 'biological clock'.
Your internal body clock controls when you are sleepy and when you are alert, as well as hunger, digestion, bowel habits, urine production, body temperature, secretion of hormones and blood pressure. This biological clock is normally synchronised with your local time so that you feel hungry in the morning and sleepy in the evening.
When you travel across time zones, the body needs time to adjust.
