Hey I just had a few questions:
Why is Jet lag worse when an individual travels east?
I hope this isn't too late, but I think my teacher explained it because of the reason that the body has a natural tendency for the sleep-wake cycle to be extended to a 25 hour long period rather than a 24 hours long period. (Jacaranda Textbook, pg397 Box 9.1). Therefore, since travelling east 'shortens' the day (since time will 'jump' forward'), it runs counter to our natural tendency for the biological clock to extend the day. Whereas, travelling west 'lengthens' the day (since time will 'jump' backwards' - giving more daylight) and therefore runs with our biological clock's tendency to extend the day.
To clarify the 'jump' forward or backward: imagine you are travelling to Singapore. There is normally a three hour difference, with Australia being 3 hours ahead of Singapore, i.e. 12pm in Melbourne is 9am in Singapore. When you get on the plane to go to Singapore, you are travelling west. If you depart Melbourne at Noon, you will arrive Singapore at 8pm (Melbourne time). However, in Singapore, this is only 5pm (local time), meaning that your day has been 'extended'.
On the other hand, if you are travelling from Singapore to Melbourne, leaving at noon and arriving at 8pm (Singapore time), the local time in Melbourne will be 11pm. Therefore, your day has been 'shortened'.
Hope this clarified things.