We've talked about snails（蜗牛）and their slow move.But much of the time snails don't move at all.They're in their shells（壳）—sleeping.

    Hot sun will dry out a snail's body.So at the least sign of hot sun,a snail draws its body into its shell and closes the opening with a thin cover.Then it goes to sleep.A snail will die in a heavy rain.So whenever it rains,it goes inside its shell house and goes to sleep.A snail can sleep for as long as it needs to.It can take a short sleep.Or it can sleep for days at a time.And it spends all the winter months in its shell,asleep.

    the shell.When hungry,the snail looks for food.It can't see very well.Its eyes,at the ends of the top feelers（触角）are very weak.But its sense of smell is very strong.It helps the snail to the new greens.Then the snail's little mouth goes to work.

    A snail's mouth is no longer than the point of a pin（针）.Yet it has 256,000 teeth!The teeth are so small that you can't see them.But they do their work.If you put a snail in a hard paper box,it will eat its way out.And if a snail wears out its teeth,it will grow new ones.

    Mostly,a snail looks for food at night.But on cloudy days it eats in the day time.It cats all day long.A snail can go on eating for hours and never feel full.

    We know that many animals do not stay in one place. Birds, fish and other animals move from one place to another at a certain time. They move for different reasons: most of them move to find food more easily, but others move to get away from places that are too crowded.

    When cold weather comes, many birds move to warmer places to find food. Some fishes give birth in warm water and move to cold water to feed. The most famous migration(迁移) is probably the migration of the fish, which is called “salmon”. This fish is born in fresh water but it travels many miles to salt water. There it spends its life. When it is old, it returns to its birthplace in fresh water. Then it gives birth and dies there. In northern Europe, there is a kind of mouse. They leave their mountain homes when they become too crowded. They move down to the low land. Sometimes they move all the way to the seaside, and many of them are killed when they fall into the sea.

    Recently, scientists have studied the migration of a kind of lobster(龙虾). Every year, when the season of bad weather arrives, the lobster get into a long line and start to walk across the floor of the ocean. Nobody knows why they do this, and nobody knows where they go.

    So, sometimes we know why humans and animals move from one place to another, but at other times we don't. Maybe living things just like travel.

Learning, Fast and Deep

    Over the past five years researchers in artificial intelligence have become the rock stars of the technology world. A branch of AI known as deep learning, which uses neural(神经的) networks to scan through large volumes of data looking for patterns, has proven so useful that skilled practitioners can command high six-figure salaries to build software for Amazon, Apple, Facebook and Google.

    The standard route into these jobs has been a PhD in computer science from one of America's top universities. Earning one takes years and requires a personality suited to academia, which is rare among more normal folk.

    That is changing.

    Last month fast.ai, a non-profit education organization based in San Francisco, kicked off the third year of its course in deep learning. Since its foundation it has attracted more than 100, 000 students around the globe from India to Nigeria. The course and others like it, come with a simple idea: there is no need to spend years obtaining a PhD in order to practise deep learning. Creating software that learns can be taught as a craft, not as a high intellectual pursuit to be undertaken only in an ivory tower. Fast. ai's course can be completed in just seven weeks.

    To make it accessible to anyone who wants to learn how to build AI software is the aim of Jeremy Howard, who founded fast.ai with Rachel Thomas, a mathematician. He says school mathematics is sufficient. "No. Greek. Letters," Mr. Howard intones, pounding the table with his fist for punctuation.

    Some experts worry that this will serve only to create a flood of unreliable AI systems which will be useless at best and dangerous at worst. In the earliest days of the Internet, only a select few nerds, namely computer holies with specific skills, could build applications. Not many people used them. Then the invention of the World Wide Web led to an explosion of web pages, both good and bad. But it was only by opening up to all that the Internet gave birth to online shopping, instant global communications and search. If Mr. Howard and others have their way, making the development of AI software easier will bring forth a new crop of fruit of a different kind.

    A new "paparazzi-proof" scarf has got heatedly welcomed since launched. A new "paparazzi-proof" scarf could be a game-changer for celebrities who prefer to shy away from the stage light. The ISHU scarf is the creation of Dutch-born fashion entrepreneur Saif Siddiqui and is designed to "give people their right to privacy back". A host of celebrities including Cameron Diaz, singer Joe Jonas, Bayern Munich footballer Jerome Boateng and music producer Major Lazer have worn the ISHU after it was spotted at London Fashion Week last year.

    It works by reflecting the light back into a camera, effectively becoming "invisibility clothes" for celebrities who don't want their photos taken. Anyone wearing the scarf is protected from mobile flash photograph, with the fashion accessory's fabric(附件结构)effectively blocking out any unwanted pictures, although it doesn't stop no-flash photographs from being taken.

    The 28-year-old Siddiqui was inspired while visiting family in Amsterdam in 2009 when his friends attempted to take a photo of him using an iPhone in front of some bikes. "He noticed that the bike's reflector carried the flash of his mobile camera in a way that confused the faces of his friends in the picture." the ISHU website explains. "He immediately realized that if developed into the right product, this feature would be an ideal solution for his friends and is now available to the public who want to keep their private moments in public private. "Saif put together a team of experts who dug into the science of light and reflection, and how to blend technology with fashion."

    He told Decoded Magazine: "The ISHU scarf effectively allows an individual to control what pictures and videos are taken of him." There are no more unwanted pictures and videos on Snapchat, Instagram, or Facebook! Everyone carries a phone with them nowadays that has an amazing camera. So, it all made sense to me." More ISHU products are set to launch in August, with mobile phone cases set to launch in the next few weeks. The ISHU is currently sold out but you can pre-order it online for￡289.