Each time I see a balloon , my mind flies back to a memory when I was a six-year-old girl . It was a rainy Sunday and my father had recently died . I asked my mum if my dad had gone to heaven . “ Yes , honey . Of course , ” she said . “ Can we write him a letter ? ”

    She paused , the longest pause of my short life , and answered , “ Yes . ” My heart jumped . “ Can the mailman go there ? ” I asked .

    “ No , but I have an idea . ” Mum drove to a party store and returned with a red balloon . I asked her what it was for . “ Just wait , honey . You'll see . ” Mum told me to write my letter . Eagerly , I got my favorite pen , and poured out my six-year-old heart in the form of blue ink . I wrote about my day , what I learned at school , how Mum was doing , and even about what happened in a story I had read . For a few minutes it was as if Dad were still alive . I gave the letter to Mum . She read it over , and a smile crossed her face . She made a hole in the corner of the letter to tie it to the balloon . We went outside and she gave me the balloon . It was still raining . “ Okay , on the count of three , let it go . One , two , three . ” The balloon , carrying my letter , flew upwards against the rain . We watched until it was swallowed by the mass of clouds . Later I realized , like the balloon , that Dad had never let his sickness get him down . He was strong . No matter what he suffered , he'd keep on , fly up , and finally go beyond this cold world and his sick body . He rose into sky and became something beautiful . I watched until the balloon disappeared into the grey and white and I prayed that his strength was passed on . I prayed to be a balloon .

    How the Grand Canyon (大峡谷) was created remains one of the geology's greatest mysteries. Some evidence suggests that the process was a gradual one in which the Colorado River (which runs through the canyon) slowly cut deeper and deeper into the ground over millions of years. But volcanic rock samples taken from the canyon now suggest that the canyon was down-cut instead.

    Down-cutting is when a flood of water rushes over a landscape (地形) with enough force to cut deeply into the ground and leaves behind a canyon. Such a flood is usually released when a natural or man-made dam (堤坝) bursts.

    Robert Webb, a research geologist, says natural dams seem to have formed and broken across the Colorado River several times during the last million years. The dams were built when lava(熔岩) from the eruptions of nearby volcanoes flowed into the river. The lava hardened into hard rocks and blocked the river, causing it to back up and form a lake. Each time the lake grew so huge that it broke the rock dam, releasing a flash flood that furthered the down-cutting process and deepened the canyon.

    Down-cutting is not just an earthly event. Satellite photos sent back from Mars suggest that the process has happened there, too, say many other researchers.

    The photos, taken by the Mars Global Surveyor, indicate that an enormous lake existed on Mars 3.5 billion years ago. The lake spilled into a large nearby hole. One edge of the hole broke, releasing a flash flood that quickly carved out a grand canyon.

    The existence of down-cutting on Mars is just one more piece of evidence that the cold, dry planet was once warm and wet.

    The morning had been a disaster. My tooth was aching, and I'd been in an argument with a friend. Her words still hurt: “The trouble with you is that you won't put yourself in my place. Can't you see things from my point of view?” I shook my head stubbornly-and felt the ache in my tooth. I'd thought I could hold out till my dentist came back from holiday, but the pain was really unbearable. I started calling the dentists in the phone book, but no one could see me immediately. Finally, at about lunchtime, I got lucky.

    “If you come by right now,” the receptionist said, “the dentist will fit you in.”

    I took my purse and keys and rushed to my car. But suddenly I began to doubt about the dentist. What kind of dentist would be so eager to treat someone at such short notice? Why wasn't he as busy as the others?

    In the dentist's office, I sat down and looked around. I saw nothing but the bare walls and I became even more worried. The assistant noticed my nervousness and placed her warm hand over my ice-cold one.

    When I told her my fears, she laughed and said, “Don't worry. The dentist is very good.”

    “How long do I have to wait for him?” I asked impatiently.

    “Come on, he is coming. Just lie down and relax. And enjoy the artwork,” the assistant said.

    “The artwork?” I was puzzled.

    The chair went back. Suddenly I smiled. There was a beautiful picture, right where I could enjoy it: on the ceiling. How considerate the dentist was! At that moment, I began to understand what my friend meant by her words.

    What a relief!

    Growing up, I wanted to be just like my mom. She was kind. People always seemed to feel comfortable in her presence. For years, she was a volunteer in our community. I loved going to the local nursing home with her where she taught a ceramic(陶艺)class.

    On one summer day, Mama told me to get changed and meet her at the car. I had planned to spend the day at the lake with friends. Why did she have to ruin everything? I imagined the cool lake water. Irritated, I climbed into the car and slammed the door shut. We sat in silence. I was too upset to make conversation.

    “Tasha, would you like to know where we are going?” Mama asked calmly.

    “No,” I said.

    “We are going to volunteer at a children's shelter today. I have been there before and I think it would benefit you.” she explained.

    When we reached the shelter, Mama rang the doorbell. Moments later, we were greeted by a woman. She led us to the front room where all of the children were playing. I noticed a baby whose body was scarred with iron marks. I was told it was because she wouldn't stop crying. The majority of the children had noticeable physical scars. Others hid their emotional wounds.

    As I took in my surroundings, I felt a gentle tug on my shirt. I looked down to see a little girl looking up at me. “Hi! You want to play dolls with me?” she asked. I looked over at Mama for reinforcement. She smiled and nodded. I turned back and said, “Sure.” Her tiny hand reached up and held mine, as if to comfort me.

    My mom taught me a valuable lesson that summer. I returned to the shelter with her several times. During those visits, some of the children shared their troubled pasts with me and I learned to be grateful for what I had. Today as I convey these values to my own child, I reflect back to that experience. It was a time that I will never forget.

    A night at the movies is always a good idea. But when you leave the theater and realize you just dropped $45 on a ticket and some snacks, you'll wish you had been patient enough to wait until the movie came out on Netflix. The average movie ticket price in the United States in 2000 was $5.39; now, a ticket is over $9.

    The main reason that movie tickets have gotten so expensive is because of inflation(通货膨胀). It was actually more expensive to go to the movies in the 70s than it is now. A ticket in 1978 cost $2.34. If you plug that into an inflation calculator, the same ticket would cost you $9.46 today. According to the National Association of Theater Owners, the average cost for a ticket today is $9.11.

    Another reason you need to dip into your life savings to see a movie on the big screen is that theaters are competing with streaming services that produce their own films, such as Netflix, Hulu, and Amazon. And let's be honest, sitting at home on your couch or in your bed is more comfortable than sitting in a cold theater.

    Because of streaming technology, movie theaters have to do something to bring in customers. Attractions­including alcohol, reclining seats(躺椅), surround sound, and 3-D movies are all examples of that. And those upgrades come at a price, leading to more expensive tickets.

    "There's all that extra cost, and it's really important for theater owners and companies to make that experience as enjoyable as possible," Patrick Corcoran, vice president of the National Association of Theatre Owners told Marketplace. "Because you're offering a superb experience­audience expectations are for the latest and greatest technology. Audiences are willing to pay more for a particular experience."

Every four or five years, vast quantities of warm water build up along the west coast of South America. This phenomenon, El Nino, creates storms that cause destructive floods. The result is costly.

Modern farmers come to terms with El Nino. They use money saved in good years to rebuild in bad ones. But history suggests it need not be like that. In a paper published recently, Ari Caramanica, an archaeologist at University of the Pacific, in Lima, shows how it used to be done. And the answer seems to be, "better".

Dr Caramanica and her colleagues have been studying the Pampa de Mocan, a coastal desert plain in northern Peru. Pampa de Mocan is not suitable for farming. Its soil contains little organic matter and the annual rainfall in non-Nino years is usually less than two centimeters. Today's farmers therefore depend on canals to carry water from local rivers to their fields.

It had been assumed that ancient farmers had a similar arrangement — and so they did. But Dr Caramanica also found eight canals that could carry water far beyond the range of modern farms. She thinks that they were intended to guide the floodwaters arriving during Nino years. Around a quarter of the ancient agricultural infrastructure of this area seems to have been built only for managing Nino-generated floodwaters.

Evidence from pollen supports this theory, revealing that Pampa de Mocan produced lots of crops in some years, while remaining nearly barren in others. The team also uncovered two cisterns in the area serviced by the extended canals. These, probably, were used to store extra flood-water.

These findings suggest that, rather than resisting El Nino, early farmers in Pampa de Mocan were ready to make use of it when it arrived. Modern farmers might do well to learn from them.