Our body clock, or natural body rhythm, influences our energy and alertness. Paying attention to it can help us choose the suitable time of the day when we best perform specific tasks.

    The reality, however, is that most of us organize the time around work demands, school deadlines, commuting or social events. Doing whatever the body feels like doing is a luxury in today's fast-paced modern society.

    But that doesn't mean it isn't worth trying. Obeying our body clock has significant health benefits. Disrupting our natural body rhythm, on the other hand, has been linked to problems such as depression, obesity, or headache, says Steve Key, a biology professor.

    When the body clock can synchronize (使…同步) the rhythms of its natural processes, it “gives us an advantage in daily life”, says Key.

    According to him, when it comes to cognitive (认知的) work, most adults perform best in the late morning. As our body temperature starts to rise just before awakening in the morning and continues to increase until midday, our memory, alertness and concentration gradually improve.

    However, he adds, our ability to concentrate typically starts to decrease soon thereafter. Most of us are more easily distracted (分心) between noon and 4 pm.

    Alertness also tends to fall after eating a meal and sleepiness tends to peak around 2 pm, making that a good time for a nap.

    Surprisingly, tiredness may increase our creative powers. For most adults, problems that require open-ended thinking are often best dealt with in the evening when they are tired, according to a study in the journal Thinking & Reasoning.

    When choosing a time of the day to exercise, paying attention to your body clock can improve results. Physical performance is usually best from about 3 to 6 pm, says Michael Smolensky, a professor of biomedical engineering.

    Of course, not everyone's body clock is the same, making it even harder to synchronize natural rhythms with daily plans.

HOLIDAY FUN AT THE POWERHOUSE

    Join in the holiday fun at the powerhouse this month linked to our new exhibition , Evolution & Revolution : Chinese dress 1700s to now . DON'T FORGET out other special event , the Club Med Circus School which is part of the Circus ! 150 years of circus in Australia exhibition experience !

◆ Chinese Folk Dancing : Colorful Chinese dance and musical performances by The Chinese Folk Dancing School of Sydney . Dances include : the Golden stick dance and the Chinese drum dance . A feature will be the Qin dynasty Emperor's court dance . Also included is a show of face painting for Beijing opera performances .

Sunday 29 June and Wednesday 2 July in the Turbine Hall , at 11:30 am & 1:30 pm.

◆ Australian Chinese Children's Arts Theatre : Well-known children's play experts from Shanghai lead this dynamic youth group . Performances include Chinese fairy tales and plays .

Thursday 3 to Sunday 6 July in the Turbine Hall , at 11:30 am & 1:30 pm .

◆ Chinese Youth League : A traditional performing arts group featuring performance highlights such as the Red scarf and Spring flower dances , and a musician playing Er Hu .

Sunday 6 to Tuesday 8 July in the Turbine Hall , 11:30 am to 1:30 pm .

◆ Kids Activity : Make a Paper Horse : Young children make a paper horse cut-out . ( The horse is a frequent theme in Chinese painting , indicating a kind of advancement . ) Suitable for ages 8-12 years .

Sunday 28 June to Tuesday 8 July in the Turbine Hall , 12:00 pm to 1:00 pm .

◆ Club Med Circus School : Learn circus skills , including the trapeze , trampolining and magic . Note only for children over 5 : There are 40 places available in each 1 hour session and these must be booked at the front desk , level 4 , on the day .

Tuesday 1 to Saturday 5 July at 11:30 am & 1:00 pm .

Enjoy unlimited free visits and many other benefits by becoming a family member of the Powerhouse . Our family memberships cover two adults and all children under the age of 16 years at the one address .

    Members receive Powerline , our monthly magazine , discounts in the shops and the restaurants , as well as free admission to the Museum . All this for as little as $50.00 a year ! Call (02)9217 0600 for more details .

    Genetic engineering, in its broadest definition, means to control a species so that a particular trait is increased in the population. A trait is how an organism (有机体) looks or acts or what it does. Having brown eyes is a trait. Flying in circles is a trait. Climbing trees is a trait.

    The earliest forms of genetic engineering occurred on farms. People selected seeds from plants that had more fruit production or tastier leaves than other plants of their types. Then they chose to save the seeds from the best of that group to sow the next year. So, year by year, the farmers produced better and better crops. This type of activity probably has been going on since mankind first settled in villages and began making a life for themselves in one location, about 12,000 years ago!

    The same sort of thing would have also happened with animals. For example, people chose to eat the animals that didn't have favorable traits and let the animals with the favorable traits reproduce. It was thousands of years before mankind figured out how plants and animals reproduce themselves. With this knowledge, people could pollinate (授粉) plants by hand or keep a pair of animals together in order to deliberately cause an increase in a favorable trait.

    It was only in the last 250 years that scientists began figuring out chromosomes (染色体) and genes and the role they play in the way one generation passes its traits on to the next. And it's only been in the last 30 years that scientists have been able to cut out specific genes from one organism and put them in another. It is this 30-year-old technology that is described by the narrow definition of genetic engineering. Mankind has long been able to have a deliberate impact on the world around him. He now possesses the tools to deliberately impact himself. Some people are afraid of what might be done with that power.

Below is a list of women who changed the world when they were young girls and teens.

Mary Shelley

English author Mary Shelley was just 18 years old when she wrote Frankenstein, which many credit as the origin of science fiction. Thus, Shelley has been called "the teenage girl who invented science fiction."

Alexandra Scott

Alexandra Scott was diagnosed with a form of cancer shortly before her first birthday. When she was just 4 years old, she set up her first lemonade stand in her front yard to raise money for childhood cancer research. Inspired by her story, people around the world set up their own lemonade stands to raise money for her cause. By the time she died in 2004, she had raised SI million. Her family continues her legacy (遗志) through Alex's Lemonade Stand Foundation.

Yuanyuan Tan

Chinese ballet dancer Yuanyuan Tan started representing her country in international competitions as a young teen. At 17, she became the youngest ever principal dancer at the San Francisco Ballet, as well as the first Chinese dancer to earn that title in a major Western company. She gives talks around the world, inspiring young dancers to follow their artistic dreams.

Bindi Irwin

Bindi Irwin carried on her father Steve Irwin's conservation legacy following his death in 2006. When she was 8 years old, she launched "Bindi the Jungle Girl" to encourage more kids to get interested in animals and wildlife conservation. She has continued to make TV appearances, published books and furthered her father's causes.

In San Francisco,a large group of sea lions move themselves out of the bay waters and hang out on PIER 39, which is a popular tourist destination. According to dock（码头） officials, this is the most sea lions seen in the region in 15 years.

"Over 1,000 sea lions have been counted this week," PIER 39 harbor master Sheil a Chandor told many different medias. "The increase in sea lions is usually a good sign of their strong population and healthy living environment," said Adam Ratner, Director of Conservation Engagement at the Marine Mammal（海洋哺乳动物） Center in Sausalito, California.

"California sea lions are sentinels（哨兵） of the ocean," Ratner said. Their population to some extent reflects the health of the ocean. Therefore, seeing a large number of California sea lions is clearly a good thing.

For nearly 35 years, the animals have been a star attraction for visitors. That autumn in 1989, PIER 39 had just been repaired, but the ships had not yet been moved back. At that moment, the sea lions' unexpected arrival not only attracted fans but also created enemies. According to a website, some dock residents and workers were scared away by the strong and very unpleasant smell and noise of their new neighbors, while others saw these animals as a bright spot after the destructive Loma Prieta earthquake.

The officials sought help from the Marine Mammal Center to find a way to deal with sea lions. Ratner said that the final decision is to let the sea lions stay and coexist with humans. "The fact proves that this is really a good thing," he said. "This is just a proof of how we can truly work together and think about how we can share our coasts with marine mammals and other wildlife in a way that benefits all the parties involved."