I remember my mother as a strong woman. She came to America when she was 12—old enough to remember her language, she achieved scores and grades high enough to be admitted to Duke University. With a degree in computer science, she finally became the manager of a company in New York. My mother could give fluent speeches, say “wolves” correctly.

    It was my mother who always stressed the importance of language. From the time I was born, I was read to. I would fall asleep to the sounds of my parents' voices, whether it was my dad's softly accented, or my mother's clear English. The flow of language was unbroken, and whether in Chinese or English, the stream of communication flowed through our house.

    One October morning in sixth grade, after my mother had left to catch the train to the city, I left the house for the bus stop. I was surprised when I saw our car, the door hanging open. As I drew closer, I saw my mother lying on the ground.

    In the hospital, it was hard to believe that the lady who lay before me was my mom. My mother could not remember my name. As the leaves changed colors, it became clear that the stroke had created a wall between my mothers mind and mouth: her mind was not any less dear, but the words she spoke were not what she meant.

    The battle my mother faced taught me the importance of language. Without it, identity does not exist; relationships cannot be formed; stories cannot be told; directions cannot be given, and knowing anything about anyone is impossible. Without language, communication cannot take place. Without language, one cannot express the beauty of a sunset or the kindness of a stranger. The world would pass us by in silence.

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    Ever wonder how much a cloud weighs? What about a hurricane? A meteorologist（气象学家） has done some estimates and the results might surprise you.

    Let's start with a very simple white puffy cloud—a cumulus cloud(积云). How much does the water in a cumulus cloud weigh? Peggy LeMone, senior scientist at the National Center for Atmospheric Research in Boulder, Colorado, did the numbers. “The water in the little cloud weighs about 550 tons,” she calculates. “Or if you want to convert it to something that might be a little more meaningful...think of elephants.” Assume（假设） an elephant weighs about six tons, she says, that would mean the water inside a typical cumulus cloud would weigh about one hundred elephants.

    The thought of a hundred elephants' worth of water floating in the sky begs another question—what keeps it up there?

    “First of all, the water isn't in elephant-sized particles(微粒); it's in tiny tiny tiny particles,” explains LeMone. And those particles float on the warmer air that's rising below. But still, the concept of so much water floating in the sky was surprising even to a meteorologist like LeMone. “I had no idea how much a cloud would weigh, actually, when I started the calculations（计算）,” she says.

    So how many elephant units of water are inside a big storm cloud—10 times bigger all the way around than the “puffy” cumulus cloud? Again, LeMone did the numbers: About 200,000 elephants.

    Now, come to the calculations for a hurricane about the size of Missouri and the figures get really massive. “What we're doing is weighing the water in one cubic meter theoretically pulled from a cloud and then multiplying by the number of meters in a whole hurricane,” she explains.

    The result? Forty million elephants. That means the water in one hurricane weighs more than all the elephants on the planet. Perhaps even more than all the elephants that have ever lived on the planet.

    “Why do birds sing?” I asked a group of children. “To attract metes(配偶)!” answered a boy. A 4-year-old girl added shyly, “birds sing because they are happy, and they want to make us happy, too.” I think both answers are probably true in a way. If birds sing happily, it shows all is well in the forest: no predators (捕食者) are present, and the birds can feed, sing and do other bird things. The sound of a relaxed robin(知更鸟) singing is easy to understand because it makes us feel this way too—it's a sound that lifts our own hearts when we hear it.

    What happens when a predator comes into their areas? The nearby birds quickly give an alarm call, a short sound that warns, “Danger is coming!” On hearing the sound, the other birds stop singing and fly for cover, the deer lift their heads and stop moving and the rabbits run into the bushes. Suddenly, the forest becomes silent.

    When humans walk through the woods in a hurry or while talking with a friend, we don't see much wildlife. We may think that there aren't many animals living there, but more likely, they know we are coming and hide minutes before our arrival. But if we learn to avoid setting off alarms, we can see many more wild animals without frightening them. To practice, find a place in a park and sit quietly for an hour. Take note as the birds begin to relax and sing again. When I do this, I am always surprised at the wonderful thing animals will do when humans simply stay still long enough.

    Auctions (拍卖行) are everywhere. Here are just a few standouts and some of the areas they specialize in. All have brick-and-mortar (实体的) sales rooms in addition to online buying.

    Leslie Hindman Auctioneers

    Headquarters (总部): Chicago

    Founded: 1982

    Best bets: contemporary art, jewelry

    The founder, Leslie Hindman, has been on an expansion kick from her Chicago base and now runs eight offices across the country. Ms. Hindman said that plenty of items sell at her house for around $500. As in the auction world generally, jewelry and contemporary art receive lots of attention from bidders (出价者), and in 2017 a diamond ring sold for $97,000.

    Swann Auction Galleries

    Headquarters: New York

    Founded: 1941

    Best bets: books, works on paper, African-American art

    Founded as a rare-book auctioneers, Swann still holds dozens of such sales a year. The president, Nicholas D. Lowry, noted that Swann was the first auction house to sell old photographs, in 1952. The house has also had a department of African-American art for 12 years.

    Stair Galleries

    Headquarters : Hudson, N. Y.

    Founded: 2001

    Best bets: English and Continental furniture and paintings, modern and contemporary art

    Colin Stair, the founder and president, comes from a long line of antiques dealers. Stair is frequented by dealers and bargain hunters, and it's a place to find interesting things like a Gorge I carved walnut wing armchair, coming up as part of a sale on April 28 and 29.

    Heritage Auctions

    Headquarters : Dallas

    Founded: 1983

    Best bets: coins, sports memorabilia, movie posters

    With roots in coin auctions Heritage has grown quite large. But their bread and butter are items that the company president, Greg Rohan, calls "the kinds of things that everyone has." "People aren't buying what we're selling for decoration or for resale," he added. "They're buying things they absolutely love."

    City trees grow faster and die younger than trees in rural forestry, a new study finds. Over their lifetimes, then, urban trees will likely absorb less CO₂ from the air than forest trees.

    As we all know, the earth would be freezing or burning hot without CO₂. However, CO₂ is a greenhouse gas, meaning it traps energy from the sun as/heat. That makes temperatures near the ground rise. Human activities, especially the widespread burning-of fossil(化石)fuels, have been sending extra greenhouse gases into the air. This has led to a rise in average temperatures across the globe.

    Studies had shown forests readily absorb CO₂, but there hadn't been much data on whether city trees grow, die and absorb CO₂ at the same rate as forest trees do. So some researchers decided to find out.

    To figure out how quickly trees were growing, researchers tracked their diameters (the width of their trunks) between 2005 and 2014. A tree's diameter increases as it grows, just as a person's waist size increases as they gain weight. About half the weight of a tree is carbon, research has shown. Most of the rest is water. Over the nine years' tracking, the researchers found city trees absorbed four times as much carbon from the air as forest trees. However, they were twice as likely to die. So over the lifetime of each type of tree, forest trees actually absorbed more CO₂.

    City trees grew faster because they had less competition for light from their neighbors. In a forest，trees tend to grow close together，shading their neighbors. Street trees also benefit from higher levels of nitrogen (氮)in rainwater. Nitrogen helps plants grow. Waste gases from gas-burning cars also contain nitrogen, thus enriching city air with nitrogen. Later, rainwater may wash much of it to the ground. Some street trees may also have better access to water than trees in the country because the underground water pipes can leak.

Napa Valley is home to some of California's most beautiful hiking trails. Whether you're a seasoned hiker or a beginner, these trails are perfect for a day trip.

Robert Louis Stevenson State Park

Named after the famous author who spent his honeymoon in the area, it offers some of the most scenic hiking trails in Napa Valley. The park features over 5 miles of hiking trails, catering to hikers of all skill levels. You can even see the San Francisco Bay on a clear day.

Skyline Wilderness Park

It is a popular hiking destination in Napa Valley, featuring over 25 miles of hiking trails that offer magnificent views of the valley. On a clear day, you can even see the Golden Gate Bridge. The park is also home to a variety of wildlife, including deer, coyotes and mountain lions.

Westwood Hills Park

It is a hidden gem in Napa Valley. The park boasts over 4 miles of hiking trails, ranging from easy to difficult, making them ideal for a day trip. A wide range of wildlife, including deer and wild turkeys, also lives in this area.

Bothe-Napa Valley State Park

The park is located in the heart of the beautiful Napa Valley wine country and has over 10 miles of trails. It is a paradise for outdoor enthusiasts. It offers easy access to swimming areas and picnic spots. And if you can't get enough of the outdoor activities here, there is a camping site that can be booked for overnight stays.