Making Light of1 Sleep
All we have a clock located inside our brains. Similar to your bedside alarm clock， your internal clock2 runs on a 24-hour cycle. This cycle，called a circadian rhythm，helps control when
you wake，when you eat and when you sleep.
Somewhere around puberty，something happens in the timing of the biological clock. The
clock pushes forward，so adolescents and teenagers are unable to fall asleep as early as they used to. When your mother tells you it's time for bed，your body may be pushing you to stay up3 for several hours more. And the light coming from your computer screen or TV could be pushing you to stay up even later.
This shift4 is natural for teenagers. But staying up very late and sleeping late can get your body's clock out of sync with the cycle of light and dark5. It can also make it hard to get out of bed in the morning and may bring other problems，too. Teenagers are put in a kind of a gray cloud6 when they don't get enough sleep，says Mary Carskadon，a sleep researcher at Brown University in Providence，RI7 .It affects their mood and their ability to think and learn.
But just like your alarm clock，your internal clock can be reset. In fact，it automatically resets
itself every day. How? By using the light it gets through your eyes.
Scientists have known for a long time that the light of day and the dark of night play important roles in setting our internal clocks. For years，researchers thought that the signals that synchronize the body's clock8 were handled through the same pathways that we use to see.
But recent discoveries show that the human eye has two separate light-sensing systems. One system allows us to see. The second system tells our body whether it's day or night.
詞匯：
circadian/s3:'keidiən/ adj. 晝夜節(jié)奏的，生理節(jié)奏的
adolescent/ædəu'lesənt/ n.青少年;adj.青少年的
puberty/ 'pju:bəti/ n.發(fā)育;青春期
sync/siŋk/ n. (口語)同步;和諧，協(xié)調(diào)
synchronize/'siŋkrənaiz / V.(使)同時(shí)發(fā)生;(使)同步
注釋：
1.make light of ：輕視，不在乎。例如： We should not make light of their achievements.我們不應(yīng)當(dāng)?shù)凸浪麄兊某删汀?BR> 2. your internal clock ：指的是第一句中的a clock located inside our brains ，也即是第二段第一句中的the biological clock (生物鐘)。
3. stay up：不睡覺，熬夜
4. This shift：這種調(diào)整。指上文所描述的由于生理時(shí)間的變化青少年上床時(shí)間越來越晚的現(xiàn)
象。
5. get your body's clock out of sync with the cycle of light and dark ：打亂了你的生物鐘與晝夜時(shí)間循環(huán)之間的平衡
6. gray cloud ：提不起精神的狀態(tài)
7. Brown University in Providence， RI：位于美國羅得島州普羅維登斯的布朗大學(xué)。RI是Rhode
Island(羅得島)的首字母縮寫;Providence 是羅得島州的首府。布朗大學(xué)是美國一流大學(xué)，
創(chuàng)建于1764 年，是世界聞名的美國“常春藤聯(lián)盟”(還包括哈佛大學(xué)、耶魯大學(xué)、普林斯頓大學(xué)、布朗大學(xué)、哥倫比亞大學(xué)、賓夕法尼亞大學(xué)、達(dá)特茅斯大學(xué)和康奈爾大學(xué))中的一員。
8. the signals that synchronize the body's clock：平衡生物鐘的光信號(hào)