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Metrorail(地铁）

    Each passenger needs a farecard to enter and go out .Up to two children under age five may travel free with a paying customer.

    Farecard machines are in every station .Bring small bills because there are no change machines in the stations and farecard machines only provide up to $5 in change.

    Get one ticket of unlimited Metrorall rides with a One Day Pass .Buy it from a farecard machine in Metro stations .Use it after 9:30 a,m. until closing on weekdays , and all day on weekends and holidays .

Hours of service

Open: 5a.m. Mon.-Fri.            7a.m. Sat.-Sun.

Close: midnight Sun.-Thurs.       3a.m.  Fri.-Sat. nights

Last train times vary .To avoid missing the last train, please check the last train times posted in stations.

Metrobus

When paying with exact charge , the fare is $1.35.When paying with a SmarTrip card , the fare is $ 1.25.

Fares for senior/disabled customers

Senior citizens 65 and older and disabled customers may ride for half the regular fare. On Metrorail and Metrobus , use a senior/disabled farecard or SmarTrip card .For more information about buying senior /disabled farecard , SmarTrip cards and passes , please visit MetroOpensDoors .com or call 202-637-7000and 202-637-8000.

Senior citizens and disabled customers can get free guide on how to use proper Metrobus and Metrorall services by calling 202-962-1100.

Travel tips

·Avoid riding during weekday rush periods –before 9:30 a.m. and between 4and 6p.m.

·If you lose something on a bus or train or in a station, please call Lost &Found at 202-962-1195,

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    “A good book might clarify something you knew little about, transform your world view, or move you in ways you didn't think possible. The Soul of an Octopus(章鱼)delivers on all three, ”the magazine New Scientist commented.

    After writing about birds, pigs and tigers, US naturalist Sy Montgomery decided to choose these many-footed animals as the subject of her latest book, The Soul of an Octopus: a surprising exploration into the wonder of consciousness.

    “Here is animal with poisonous liquid like a snake，a beak(喙)like a parrot，and ink like an old-fashioned pen. It can weigh as much as a man and extend as long as a car, yet it can pour its baggy; boneless body through an opening the size of all orange. It can change color and shape. It has a tongue covered with teeth. It can taste with its skin.” Montgomery explained to the National Geographic on why octopuses inspired her.

    What Montgomery is able to show in The Soul of an Octopus is that octopuses are creatures who exhibit personality, intelligence and emotion, despite having nervous systems completely different from our own. She uses different experiments to show that they possess consciousness as well as individual personalities. For example, based on her research, she finds out that Octavia, an octopus caught in the wild, is friendly and good at multi-tasking. And Kali, another octopus，who has been living at the New England Aquarium, is playful and loves exploring.

    Montgomery is a good storyteller. Through her study of, and communication with, these extraordinary creatures she shares what she learns from both science and her experiences. Her skillful writing presents facts together with personal description, which makes the book very informative but easy to read.

Life in the Clear

    Transparent animals let light pass through their bodies the same way light passes through a window. These animals typically live between the surface of the ocean and a depth of about 3,300 feet — as far as most light can reach. Most of them are extremely delicate and can be damaged by a simple touch. Sonke Johnsen, a scientist in biology, says, "These animals live through their life alone. They never touch anything unless they're eating it, or unless something is eating them."

    And they are as clear as glass. How does an animal become see­through? It's trickier than you might think.

    The objects around you are visible because they interact with light.  Light typically travels in a straight line. But some materials slow and scatter (散射) light, bouncing it away from its original path. Others absorb light, stopping it dead in its tracks.  Both scattering and absorption make an object look different from other objects around it, so you can see it easily.

    But a transparent object doesn't absorb or scatter light, at least not very much. Light can pass through it without bending or stopping. That means a transparent object doesn't look very different from the surrounding air or water. You don't see it — you see the things behind it.

    To become transparent, an animal needs to keep its body from absorbing or scattering light. Living materials can stop light because they contain pigments (色素) that absorb specific colors of light. But a transparent animal doesn't have pigments, so its tissues won't absorb light. According to Johnsen, avoiding absorption is actually easy. The real challenge is preventing light from scattering.

    Animals are built of many different materials — skin, fat, and more — and light moves through each at a different speed. Every time light moves into a material with a new speed, it bends and scatters. Transparent animals use different tricks to fight scattering. Some animals are simply very small or extremely flat.  Without much tissue to scatter light, it is easier to be see­through. Others build a large, clear mass of non­living jelly­lie (果冻状的) material and spread themselves over it.

    Larger transparent animals have the biggest challenge, because they have to make all the different tissues in their bodies slow down light exactly as much as water does. They need to look uniform. But how they're doing it is still unknown. One thing is clear for these larger animals, staying transparent is an active process.  When they die, they turn a non­transparent milky white.

    Sharpshooters refer to those who are skilled at firing a gun and accurately hitting what they are aiming at. However, some fish are also called amazing sharpshooters. People wonder how they hit their targets without using tools? By spitting! The fish shoot so accurately that they rarely miss their target.

    These amazing fish are archerfish (印度射水鱼).There are several different types of archerfish living in Southeast Asia. They spit at their dinner to catch it. To catch dinner, a fish first sets itself in a certain place, for example just below the surface of the water. It puts the tip of its mouth so it barely breaks through the water. Then, the fish waits for an unsuspecting insect to land on a leaf or branch hanging over the water.

    When an unsuspecting, or unknowing insect lands, the fish attacks. The fish squeezes its gill (腮)covers very rapidly, which forces water into the fish's mouth. In the roof of its mouth the fish has a groove (槽）. The fish forms the small groove and its tongue into a narrow tube by pressing its tongue up against its groove. The water forced into the fish's mouth is forcefully pushed out of the fish's mouth through the tube. Archerfish have been known to send a stream up to 5 meters (16 feet). However, archerfish can only shoot insects up to 1-2 meters (3-6 feet) away due to their limited accuracy.

    When the unsuspecting insect is hit with a sudden stream of water, it is knocked into or falls into the water. Once in the water, the insect becomes dinner. Archerfish learn how to spit when they are young. They get more accurate with practice. Adult archerfish rarely miss.

    Within a meter, archerfish will often spring out of the water and grab an insect in their mouths.

    Experts say there are about 6, 500 languages spoken throughout the world. But the United Nations estimates that about half of these languages are in danger of disappearing.

    One non-profit organization seeking to save world languages is a New York-based group called Wikitongues. Officials from Wikitongues say the organization has a simple goal: to provide the tools and support that people need to save their languages.

    Udell is the co-founder of Wikitongues. He said when a language disappears, many other things can go away as well. For example, parts of a community's culture, knowledge and identity can also be lost. Because of this. Udell believes the process of bringing languages back must be done by community members themselves, “from the ground up,” he said.

    “There is no way an outside organization can save someone's language for them.”

    Wikitongues was launched in 2016 as an open internet collection of world languages. The self-described “community” is operated by volunteers from around the world. The collection is in the form of language videos that people add to the Wikitongues website.

    There are currently more than 400 languages and dialects represented on Wikitongues' YouTube channel. Udell says more than 1,500 people from 70 different countries have added videos to the system.

    “We have people from India who record dozens of languages, which is beyond their own.” he said.

    One of Wikitongues'volunteers is Kolokwe, who lives in Namibia. His native language is Subiya, however, he does not get the chance to speak his native language every day. Like many other educated people from his area, he speaks a lot of English and Afrikaans.

    Kolokwe is hoping his involvement with Wikitongues call help keep Subiya and other African languages from going extinct. He wants the world to know about his language. But his goal goes beyond just sharing his language with others through video. He is also working to create a dictionary and language teaching materials that can be used in schools.

    In the space of just two years, the app Douyin, created by Beijing-based company ByteDance, has gathered more than half a billion users—around 40%of them outside China—who share short videos of themselves lip-syncing (假唱), cooking, dancing or just being silly. What sets ByteDance apart is its success in the social media category, which is controlled by Facebook, Twitter and Snap—all Western companies.

    ByteDance calls itself an artificial intelligence company. It uses machine learning and algorithms (算法) to figure out what people like most and give them more of what they want to see. On Douyin, people can edit and beautify 15-second videos before posting them online. The app has even made a phrase to describe people glued to their customized feeds: "shua Douyin" or "scrolling through Douyin". Last year, the company released TikTok, the overseas version of Douyin. ByteDance's growing video empire has made it the world's fifth biggest app maker. ByteDance says TikTok and Douyin together have more than 500 million monthly active users.

    Investors like ByteDance because its hundreds of millions of users attract a lot of advertising money. The video apps are lucrative because they attract a lot of users in their teens and 20s, who are more generous with the money. ByteDance also makes money through income sharing deals. People on TikTok, for example, can buy digital coins to give to other people on the app—like throwing money in a performer's tip jar. ByteDance takes a cut of those earnings.

    ByteDance's founder and CEO is Zhang Yiming, a 35-year-old former Microsoft employee. People who have worked with Zhang describe him as someone who thinks deeply about technology and spends much of his free time writing code.

    Like Facebook and Twitter, ByteDance is also battling fake news and inappropriate content. ByteDance promises to add thousands more employees to review content on Douyin.