One of my first memories as a child in the 1950s was a discussion I had with my brother in our tiny bedroom in the family house in Bethlehem, Pennsylvania.

    We had heard in school about a planet called Pluto. It was the farthest, coldest, and darkest thing a child could imagine. We guessed how long it would take to die if we stood on the surface of such a frozen place wearing only the clothes we had on. We tried to figure out how much colder Pluto was than Antarctica, or than the coldest day we had ever experienced in Pennsylvania.

    Pluto, which famously was downgraded from a “major planet” to a “dwarf planet”(矮星) in 2006, captured our imagination because it was a mystery that could complete our picture of what it was like at the most remote corners of our solar system

    Pluto's underdog discovery story is part of what makes it so attractive. Clyde Tombaugh was a Kansas farm boy who built telescopes out of spare auto parts, old farm equipment and self-ground lenses. As an assistant at Lowell Observatory in Flagstaff, Arizona, Tombaugh's task was to search millions of stars for a moving point of light, a planet that the observatory's founder thought existed beyond the orbit of Neptune. On February 18, 1930, Tombaugh found it. Pluto was the first planet discovered by an American, and represented a moment of light in the midst of the Great Depression's dark encroachment(入侵).

    Pluto is much more than something that is not a planet. It's a reminder that there are many worlds out there beyond our own and that the sky isn't the limit at all. We don't know what kinds of fantastic variations on a theme nature is capable of making until we get there to look.

    Put technology in the hands of someone like Elon Musk and it can send people into space, make a future of clean and renewable energy a reality, or build electric cars. Put in your hands, and it can help you achieve all sorts of things, from learning to code to learning a language.

    Educational apps are becoming increasingly popular as a supplement(补充), and sometimes as an alternative(替代物), to traditional education. Why? Well, for starters, it's extremely convenient to learn on a pocket-sized device that you already carry around with you at all times. The best apps are also highly interactive and adaptive, coaxing you in and getting you hooked on learning.

 But apps, just like textbooks and language lessons, are a medium through which a language can be studied. The way you use them will affect how successful you are. If you flick through a textbook and don't dare say a word in your language lessons, you'll make slow progress. The keen reader who repeats each exercise in the textbook and engages the teacher in the conversation will move ahead. So how do you ensure you get the most out of your app, and what should you consider before you install(安装) one?

    Before that, a very quick introduction: I developed the following five points from my experience as both a language teacher and learner, and from working in startups in the field of language. I spent six years teaching in Germany and Spain as well as developing a video learning startup. However, I first came to language learning late. I started learning Spanish at 22, and was able to use Spanish and German freely by about 28. I've been using language apps for the last few years, and participated in two successful one-week challenges to go from zero to hero in Italian and French. If you're interested, you can see the French challenge here.

    So, just before downloading an app, here's what you should think about…

    I remember meeting him one evening with his pushcart. I had managed to sell all my papers and was coming home in the snow. It was that strange hour in downtown New York when the workers were pouring homeward in the twilight. I marched among thousands of tired men and women whom the factory whistles had unyoked. They flowed in rivers through the clothing factory districts, then down along the avenues to the East Side.

    I met my father near Cooper Union. I recognized him, a hunched, frozen figure in an old overcoat standing by a banana cart. He looked so lonely, the tears came to my eyes. Then he saw me, and his face lit with his sad, beautiful smile-Charlie Chaplin's smile.

    "Arch, it's Mikey," he said. "So you have sold your papers! Come and eat a banana."

    He offered me one. I refused it. I felt it crucial that my father sell his bananas, not give them away. He thought I was shy, and coaxed and joked with me, and made me eat the banana. It smelled of wet straw and snow.

    "You haven't sold many bananas today, pop, "I said anxiously.

    He shrugged his shoulders.

    "What can I do No one seems to want them."

    It was true. The work crowds pushed home morosely（愁眉苦脸的）over the pavements. The rusty sky darkened over New York buildings, the tall street lamps were lit, innumerable trucks, street cars and elevated trains clattered by. Nobody and nothing in the great city stopped for my father's bananas.

    "I ought to yell," said my father dolefully. "I ought to make a big noise like other peddlers, but it makes my throat sore. Anyway, I'm ashamed of yelling, it makes me feel like a fool. "

    I had eaten one of his bananas. My sick conscience told me that I ought to pay for it somehow. I must remain here and help my father.

    "I'll yell for you, pop," I volunteered.

    "Arch, no," he said," go home; you have worked enough today. Just tell momma I'll be late. "

    But I yelled and yelled. My father, standing by, spoke occasional words of praise, and said I was a wonderful yeller. Nobody else paid attention. The workers drifted past us wearily, endlessly; a defeated army wrapped in dreams of home. Elevated trains crashed; the Cooper Union clock burned above us; the sky grew black, the wind poured, the slush burned through our shoes. There were thousands of strange, silent figures pouring over the sidewalks in snow. None of them stopped to buy bananas. I yelled and yelled, nobody listened.

    My father tried to stop me at last." Nu," he said smiling to console me," that was wonderful yelling, Mikey. But it's plain we are unlucky today! Let's go home."

    I was frantic, and almost in tears. I insisted on keeping up my desperate yells. But at last my father persuaded me to leave with him.

    When your dream is to become a footballer, nothing should get in your way—even if you have no feet.

    Gabriel Muniz, an 11-year-old Brazil kid, was born without feet. Although his family thought he would have serious difficulties living a normal life, he started walking before he was one year old. His mother would go after him, expecting him to keep falling, but he never fell. It took him a while to make the jump from walking to playing football, but he did make it. And, in fact, there's nothing he loves more than playing football. In his school, the skillful youngster (年轻人) is not only the best player in his school team but also the captain of his gym team.

    He knows that his disability means he'll never be able to play for a professional (专业的) football team. So Gabriel is hoping that football will one day become a Paralympics (残疾人奥运会的) sport. He proved to everyone there he could go head to head with any other boy. Watching him play is unbelievable. He's fast and he's got a big bag of tricks—he's very skilled and he does everything he can to copy his hero, Messi so much that he is invited to go to Spain to meet his hero Messi and show his talent in the Barcelona Football Club.

    His coach says he is proving the disability only exists (存在) inside our heads.

    Candace Payne's life changed forever in May 2017 when she posted a video of herself laughing crazily and wearing a mask. The video spread widely and "Mask Mom "became a household name.

    During the two years since that, Candace has published several books, starred in a TLC. web series and went on tour with Mandisa. She made appearances on late night talk shows, met J. J. Abrams and was able to fulfill a dream of taking her family to Disney World. It was a busy but joyful time.

    Her latest book is Consider It Joy. "I feel like people need a tool in their hands to actually get the joy they are fighting for, "Candace says, "The book can help you keep track of how much space and time you are devoting to things that aren't worth it in comparison to the joy that I know I could have."

    Getting joy is something that has always been important to Candace. "What the opportunity offered me was not a forced open door," Candace says, "Many people are trying desperately to push things open when they have to be obedient(顺从的) to the little things."

    Trusting herself has required being confident in saying no. She uses a simple tool to evaluate whether an opportunity is right to her. Candace says, "I have a balance beam (平衡木)where I'm asked to walk every single day as a mom, a wife, a speaker and an author. There are so many things I need to balance at a time. I have to realize what belongs there and what doesn't. The most important factor is joy."

    That's the heart behind the book Consider It Joy. "I really wanted to give people more than just advice about joy, Candace says, "I wanted to give them the ability to actually own it in their everyday life."