A longtimeago, beforetheinventionofelectriclighting, ourbodiesusedthismethodtoallowustostayawakewhenthesunwasoutandallowustofeeltiredandrestwhenthesunwentdown.
很久以前,在電燈發明之前,我們的身體用此方法讓我們日出時保持清醒,日落後感到疲勞、想休息。
However, nowadaysthere's artificiallightingeverywhere--inourrooms, andonourscreens, onourphones.