Americans, especially the millennials（千禧一代）, are always glued（固着于）to their phones. A common day of the average university student in America starts off like this: an alarm clock wakes you up, which is quickly followed by checking social media such as Twitter and Facebook. Once in classes, you are again attracted by your buzzing phone and access to the Internet rather than pay attention to the lecturing professor. Then you have lunch with some friends, only to look up from your screen to realize that no one has said a word in five minutes and instead all are looking at their phones. Once the day ends, you can't help checking all forms of social media again before finally being able to shut your eyes only to repeat this vicious cycle the next day.

    Cyberbullying（网络霸凌）, a concept unknown before, is now in fashion. Many of the millennials are using the Internet to make jokes about others to points of extremes. The Internet gives cowards bravery; people feel like their actions and words have no bad results because they cannot see the ache it causes another.

    Millennials also think that whatever information shows up on their screens must be taken as truth, whether the material is reliable（可靠的）or not.

    Social media is not all bad, however. People are still able to use social media to connect with friends and family who live a great distance away. With a few clicks of a button, someone could make another person smile, or give words of hope and encouragement to a friend in need, or even help repair a broken relationship. Cyberspace is a vortex（漩涡）that is easy to get caught up in, but we must find a balance to keep both feet in reality while traveling across the online world.

    A black hole is created when a large star burns out. Like our sun, stars are unbelievably hot furnaces(熔炉) that burn their own matter as fuel. When most of the fuel is used up, the star begins to die.

    The death of a star is not a quiet event. First there is a huge explosion. As its outer layer is blasted off into space, the dying star shines as brightly as a billion suns.

    After the explosion, gravity pulls in what's left of the star. As the outside of the star sinks toward the center, the star gets smaller and smaller. The material the star is made of becomes tightly packed together. A star is so solid that a teaspoon of matter from it weighs billions of pounds.

    The more the star shrinks(收缩), the stronger the gravity inside it becomes. Soon the star is very tiny, and the gravity pulling it in is unbelievably strong. In fact, the gravity is so strong that it even pulls light into the star! Since all the light is pulled in, none can go out. The star becomes black when there is no light. Then a black hole is born!

    That's what we know about black holes. What we don't know is this: What happens inside a black hole after the star has been squeezed into a tiny ball? Does it keep getting smaller and smaller forever? Such a possibility is hard to imagine.

    But if the black hole doesn't keep shrinking, what happens to it? Some scientists think black holes are like doorways to another world. They say that as the star disappears from our universe, it goes into another universe. In other words a black hole in our universe could turn into a "white hole" in a different universe. As the black hole swallows(吞噬) light, the white hole shines brightly--somewhere else. But where? A different place, perhaps, or a different time--many years in the past or future.

    Could you travel through a black hole? Right now, no. Nothing we know of could go into a black hole without being crushed(挤压). So far the time being, black hole must remain a mystery.

Black holes are a mystery--but that hasn't stopped scientists from dreaming about them. One scientist suggested that in the future we might make use of the power of black holes. They would supply all of Earth's energy needs, with plenty to spare. Another scientist wondered if a black hole could some day be used to swallow earthly waste--a sort of huge waste disposal(处理) in the sky!

    Gardening is popular in many parts of the world. This outdoor activity gives us beautiful plants, pleasant smelling flowers and fresh fruits and vegetables. But it also does a lot of good to our health.

    Gardening connects people. When you are gardening, you are outdoors. So it is a perfect chance to meet and spend time with your neighbors. Most people love to talk about their hobbies, and gardeners are no different. They usually enjoy showing people what they are growing. And most enjoy sharing advice and stories about their gardens almost as much as sharing flowers and vegetables from their gardens.

    Gardening is a great activity for children. It gets them outdoors and off computers, televisions and cell phones. Gardening is also a great teacher. It can teach a child about where food comes from and healthy eating. It also helps them to understand that the natural resources (资源) are not inexhaustible and the importance of using them carefully.

    Then, when you garden, you must move around. All the different movements needed for gardening, like bending and lifting, work small muscles (肌肉) in the body. And you can easily get good exercise when you are digging holes or pulling grasses.

    In a study, researches looked at more than 2,800 people over the age of 60. They studied their lifestyle habits, activities and health over a 16-year period. They found that gardening could lower the risk of future dementia (痴呆) by 36%. Gardening requires people do many repeated actions, such as picking off dying flowers. These actions have a calming influence on the brain. The brain is still active but not in the same way when we use computers.

    You'll feel wonderful when what you grow in a garden looks, smells, feels and tastes good.

    I have two kids, a boy and a girl. I don't worry about my girl; I'm sure she'll be well trained in mixed martial arts. I worry about my son. I'm pretty sure he's going to be feminine (女性化的). Sorry to say that, but let's face it. No dad wants his son to go feminine.

    At the rate we're moving in a couple of years you won't be able to tell the difference between boys and girls. Sound extreme? Think about this. In every movie where advanced time-traveling beings come to our planet, there's one constant: You can't tell the male aliens from the female aliens!

    But that's the future. Kids today are soft and fat. People ask why. Is it junk food? No. Junk food has been around for fifty years. Is it video games? No. Video games have been around for thirty years. None of the kids playing them back in the day were terribly obese. We're all scratching our heads trying to figure out what we've introduced to society to ruin our kids. But it's not anything we've added that has ruined our kids. It's stuff we've gotten rid of.

    Take the gym rope for example. Remember that thing that stretched from the floor to the ceiling in your gym class that you could never climb? Most of the kids couldn't make it to the top. But that wasn't the point; the point was that you had to try while some middle-aged guy who couldn't make it up a flight of stairs shouted at you. We should have put our son on that rope, and given him a head start. But we didn't want to shame the boy, so we took it down.

    Taking down the rope would be a good idea if there were no ropes in life. But they're everywhere. You just can't see them. They're in every goal unrealized and expectation not met. The point everyone missed about the rope is you weren't supposed to make it to the top. It was there to create a fire that burned in the oversize belly of every kid.

    How fit are your teeth? Are you lazy about brushing them? Never fear: An inventor is on the case. An electric toothbrush senses how long and how well you brush and it lets you track your performance on your phone.

    The Kolibree toothbrush was exhibited at the International Consumer Electronics Show in Las Vegas this week. It senses how it is moved and can send the information to an Android phone or iPhone via a Bluetooth wireless connection.

    The toothbrush will be able to teach you to brush right (don't forget the insides of the teeth!) and make sure you're brushing long enough. “It's kind of like having a dentist actually watch your brushing on a day-to-day basis,” says Thomas Serval, the French inventor.

    The toothbrush will also be able to talk to other applications on your phone, so developers could, for example, create a game controlled by your toothbrush. You could score points for beating monsters among your teeth. “We try to make it smart and fun,” Serval says.

    Serval says he was inspired by his experience as a father. He would come home from work and ask his kids if they had brushed their teeth. They said “yes,” but Serval would find their toothbrush heads dry. He decided he needed a brush that really told him how well his children brushed.

    The company says the Kolibree will go on sale this summer, from $99 to $199, and the U.S. is the first target market.