1 . American cities are similar to other cities around the world: In every country, cities reflect the values of the culture. American cities are changing, just as American society is changing.

After World War Ⅱ, the population of most large American cities decreased; however, the population in many Sun Belt cities increased. Los Angeles and Houston are cities where population shifts(转移) to and from the city reflect the changing values of American society. In the late 1940s and early 1950s, city residents(居民) became richer. They had more children so they needed more space. They moved out of their apartments in the city to buy their own homes. They bought houses in the suburbs(郊区).

Now things are changing. The children of the people who left the cities in the 1950s are now adults. Many, unlike their parents, want to live in the cities. They continue to move to Sun Belt cities and older ones of the Northeast and Midwest. Many young professionals(专业人士，专门人才) are moving back into the city. They prefer the city to the suburbs because their jobs are there; or they just enjoy the excitement and possibilities that the city offers.

This population shift is bringing problems as well as benefits. A large number of poor people must leave their apartments in the city because the owners want to sell the buildings or make apartments for sale instead of for rent. In the 1950s, many poor people did not have enough money to move to the suburbs; now many of these same people do not have enough money to stay in the cities.

Only a few years ago, people thought that the older American cities were dying. Some city residents now see a bright, new future. Others see only problems and conflicts. One thing is sure: many dying cities are alive again.

4 . What if we had the power to control time, instead of moving from the past to the present to the future? What if we could jump and travel through time in a machine? What if we could go wherever and whenever we pleased?

The mysterious puzzle of time has kept people debating its nature for hundreds of years. Science fiction writers have turned it into imaginative stories. Some scientists have even attempted to explain it using math, trying to make the dream of time travel come true.

Albert Einstein said that time and space are one thing called “spacetime.” He said there are three dimensions in space: height, width and depth. A scientist named Hermann Minkowski added time as a fourth dimension.

Einstein introduced two ideas that have led to theories about the possibility of time travel. The first is relativity. The idea of relativity is that the force of gravity causes space to bend, which causes time to twist. The second idea focuses on special relativity. The idea is that a traveler moving super-fast through flat spacetime will enter the future. Einstein considered time “relative” because it is measured based on where we are on Earth or in space.

Stephen Hawking believes that a time machine will never be built. If it were possible, he thinks we would already know. If a time machine could be built, how come no one from the future has invaded us?

The first science fiction story with this theme is The Clock That Went Backward by Edward P. Mitchell, which was published in 1881. Since then, thousands of books, films and television shows have explored the idea of time travel, in which some tools such as phones, watches, photographs and old books take travelers backward and forward.

Will time travel ever happen? Who knows? Most important is to keep your eyes open and have a sense of wonder.

5 . You’ve probably heard that brick-and-mortar retail(实体零售) is in trouble. Even industry giants are closing hundreds of stores. Given retail’s gradual change from physical stores to mobile and e-commerce(电子商务), you may be wondering, “What will retail look like in the future?” Nobody knows. But here are a few things you can expect to see based on current technology.

Super-fast delivery is coming. Today, the normal practice is two-day delivery. But if you’ve been paying attention, you know that’s changing. In fact, up to 25% of consumers said that they would abandon their orders if one-day delivery wasn’t available. Of course, that’s just the beginning. Two-hour delivery is coming in the foreseeable future, and Amazon has already been trying 30-minute delivery.

Your kitchen will resupply itself. You won’t have to worry about running out of essentials like coffee, pet food or snacks because your containers will sense stocks(库存) and replace those items without you having to lift a finger. No more waking up to find your coffee store is empty or last-minute rush to the grocery store because you forget to buy pet food.

Know exactly what’s in stock and where to get it. Have you ever gone to a store hoping to buy something, only to learn that it was out of stock? A new feature from Google Home allows people to ask the Google Assistant to find in-stock products at the closest store. For example: “Google, where can I find the Nintendo Switch console?” The assistant will tell you how many stores have it right away and how close they are. Of course, it isn’t currently available for all stores in all locations, but you can already see the future when it has become standard.

Convenience, experience, and options-retail will take on a new look.

8 . Is there anybody out there? For centuries humans have wondered although the ways in which we have gone about this have varied. As we have gained a greater understanding of the universe, our searches have taken on more concrete(具体的) forms. Questions about aliens(外星人) have become a subject for science rather than science fiction.

Now new cooperation between the Very Large Array (VLA) observatory in New Mexico and the SETI Institute in California means that our curiosity about whether aliens exist can be closer than ever before to being satisfied. Data from the VLA’S 28 radio telescopes, used to scan a vast area of sky, will be fed through a special supercomputer that will search for distant signals.

How likely it is that a signal will be found, and what this might mean, are hard questions to answer. SETI’s existing projects have not discovered any signals from other planets so far. But recent discoveries in space and Earth sciences have provided some encouragement for those who are enthusiastic about the possibility, however remote, of detecting other civilizations.

Once it was thought that our solar system could be unique. Since the discovery of the first exoplanet (a planet beyond the solar system) in the 1990s, thousands more have been located. Around one in five stars is now thought to have a planet in their orbit(运行轨道) in a so-called “habitable(适合居住的) zone”—that is, at a distance from the star where the temperature means that life is theoretically possible.

Are Earth’s 7.5 billion humans, along with billions of other animals and plants they share their home with, on their own in the universe? If there is another life form somewhere, could it be as intelligent as humans? Or could it threaten them? I think all of these need further exploration. As explorations of Mars continue, and a new set of observations from the James Webb Space Telescope are set to begin, our interest in the possibility of alien life appears as much as before.

9 . Ian Mercer doesn’t set an alarm clock. The former Microsoft senior manager doesn’t check the weather, either. He doesn’t turn on lights, water the yard, or adjust the thermostat ( 恒温器 ). He doesn’t open the curtains, answer the phone, or call his children for dinner. There’s something unique about Ian’s home. He has programmed it to do all these things for him.

Ian doesn’t live in a typical home or have a typical lifestyle. He spent over a decade designing the systems that feature in his unique home. He bought a home automation software package and then improved it.

Now there are 79 sensors and monitors, and 48 light switches in his home. Lights turn on automatically in rooms with people in them. Even being out, Ian can also control his home remotely using voice commands or his phone in any location. That is only the beginning of what this home has been programmed to do.

It connects with online calendars, caller ID, online weather services, online address books, and email, among other things, to get Ian through his day. For example, if there is a meeting in Ian’s calendar, it will wake him up, open his bedroom curtains, start and set his shower to his desired temperature. It also informs Ian about traffic conditions.

There is plenty more this home has been programmed to do. It keeps him updated on his favourite sports teams and scores. It even monitors online activity to check that Ian’s children are doing their homework. The “dinner’s ready” command stops operation of their computers and TVs. This is easier than asking his children to shut them down.

Ian’s home is unique. Most homes are not this smart, but soon more homes will be technologically advanced.

10 . You’ve heard the predictions from some of the brightest minds about AI’s influence. Tesla and SpaceX’s chief Elon Musk worries that AI is far more dangerous than nuclear weapons. The late scientist Stephen Hawking warned that AI could serve as the “worst event in the history of our civilization” unless humanity is prepared for its possible risks.

But many experts, even those who are aware of such risks, have a more positive attitude, especially in health-care and possibly in education. That is one of the results from a new AI study released Monday by the Pew Research Centre.

Pew canvassed the opinions of 979 experts over the summer, a group that included famous technologists, developers, innovators, business and policy leaders. The interviewed experts, some of whom chose to remain anonymous, were asked to join in the discussion of a serious and important question: “By 2030, do you think it is most likely that advancing AI and related technology systems will improve human capacities and control them?”

Nearly two-thirds of experts predicted most of us will be mostly better off. But a third thought otherwise, and a majority of the experts expressed at least some concerns over the long-term impact of AI on the “essential elements of being human”. Among those concerns were data abuse, loss of jobs and loss of control brought by autonomous weapons and cybercrime. Above all, by taking data in and spitting answers out, those “black box” tools make decisions in digital systems. It is an erosion in our ability to think for ourselves.