3 . Can you imagine your doctor warning that taking a bath could be unhealthy? In the early 1800s , many doctors thought that tubs (浴缸) could carry diseases, so they advised against their use.    1    The White House did not even have a bathtub until 1851.

In the 19th century ,only one home out of six had a bathroom,    2     On Saturday nights children all lined up for their turns to wash in a wooden tub in the kitchen. Mothers had to boil the water on the fire and carry it over to fill the tub.    3    

When the first bathtubs were introduced ,even their makers weren't sure whether the new fashion would last. They advertised their products as water containers that “could be used as bathing tubs”.

    4    By then most middle-class families had indoor taps (龙头). At first most tubs were made of wood, but as the popularity of the product increased, so did the creativity of tub makers. Before porcelain tubs there were rubber ones like the plastic swimming pools kids use today.

    5    Instead they tell their patients about the advantages of frequent bathing. Maybe one of the best reasons why doctors encourage frequent trips to the tub is that bathed patients smell better!

4 . With the rapid development of intelligent systems and new-age transit networks,life in the big cities will likely be more efficient and comfortable.

After all,more than 60 percent of the world’s population is expected to live in cities by 2050 , according to a UN report. The answer to making these cities more livable for so many people lies in creating “smart” cities. These cities will use 5G networks and the “Internet of things”(IoT) to make everyday life safer and more convenient. Some cities are already using smart technology to improve the lives of residents.

But what exactly does a smart city do? In the United States cities of Boston and Baltimore, smart trash cans can sense how full they are and inform cleaning workers when they need to be emptied. In Amsterdam, the Netherlands, traffic flow and energy usage are monitored and adjusted according to real-time data gathered from sensors(传感器)around the city. And in Copenhagen, Denmark,a smart bike system allows riders to check on air quality and traffic condition as they ride.

Smart cities will be interactive ，allowing their residents to feel like they’ re truly shaping their environment,instead of merely existing in it.“One of the most important reasons to have a smart city is that we can actually communicate with our environment in a way that we never have in the past,”said Mrinalini Ingram,head of a telecom company.

Smart cities will also allow us to save resources. By using sensors and 5G networks to monitor the use of water，gas and electricity,city managers can figure out how to distribute and save these resources more efficiently. Emissions of carbon dioxide and other air pollutants can be more closely monitored in smart cities as well.

Of course,it will take time and money to turn our current cities into the smart cities of the future. But as we’ve already seen, more cities around the world are already adopting smart technology in smart ways. China, for instance,is making investments in big cities like Shanghai and Guangzhou to make them “smarter”. It won’t be long before even more cities start to develop their own smart infrastructure( 基础设施).

5 . When Stephen Mills spotted a dusty old safe (保险箱) in a museum in Canada, he thought he'd try to crack the code (破解密码),"just like in the movies". But when he began turning the dial, he wasn't expecting a Hollywood ending.

For years, anyone who visited the Vermillion Heritage Museum in Alberta would have passed by a large, black metal box. Staff knew it had come from the long—gone Brunswick hotel and was donated to the museum in the 1990s,but its code and contents remained a mystery for decades- until Mills unexpectedly cracked the code.

Mills,who lived in Fort McMurray, Alberta, was visiting the museum with his family last month over a holiday weekend. As they wandered around the exhibits with the museum guide, Tom Kibblewhite,they spotted the safe.

Kibblewhite told the family what he told all other guests: the 900kg black box with a silver dial had remained closed for generations. For years, the safe has confused volunteers at the museum. The manufacturer was unable to provide advice on how to open its thick door.

A locksmith (锁匠) once suggested that years of inactivity might have slowed down the gears, making it inoperable. But Mills, who is a“mechanically-minded person”, asked whether he could give it a try.“Kibblewhite kept saying no one had opened it and that it was a mystery what was inside,”Mills said.“I thought this would be a great thing to do for a laugh for the kids. Maybe they can find some interesting historical things in it—like a time capsule.”

After pressing his ear against the cool metal, he began spinning the dial. With numbers ranging from zero to 60,he turned clockwise (顺时针方向地) three times to 20，counter-clockwise two times to 40 ,and then clockwise one time to 60. He was astonished to hear a click.“I jumped up and told everyone I' m buying a lottery ticket (彩票),”he said.

6 . Unsolved Mysteries About the Planet Earth

◆Mystery 1: Where did all the water come from?

Water covers 70 percent of Earth’s surface and earns it the nickname “the blue planet”. And where did it come from? The most popular scientific theory states that the water came from several violent asteroids (小行星) filled with ice. Another suggests that the water actually has been around since Earth’s formation. However it happened, though, it’s certainly worked out well for Earth’s life forms.

◆Mystery 2 :What about all the oxygen?

Another thing is the planet’s oxygen. Tiny creatures released oxygen as a waste product, filling the atmosphere with it. After that, the level of oxygen in Earth’s atmosphere went wildly up and down until it finally calmed down around 540 million years ago. Since then, it’s remained at about the breathable level we experience today. But what caused it to be suddenly steady?

◆Mystery 3: What caused the Cambrian (寒武纪) Explosion?

The Cambrian Explosion refers to the explosion of complex life forms that occurred on Earth about 540 million years ago. Before then, life had consisted mostly of bacteria. But at the beginning of the Cambrian period, complex creatures began developing at a rate never seen before. Suddenly, life forms had brains, eyes, and bones. Most living creatures today can trace their blood back to the Cambrian period.

◆Mystery 4: Will we ever be able to predict earthquakes?

We still haven’t been able to come up with a way to accurately predict earthquakes. We can certainly try, but our current technology cannot predict them exactly. We know that earthquakes start when rocks crack underground and send earthquake waves toward the surface, but we haven’t figured out why that happens, or how to predict it.

7 . For me, concerts have always been one of the best ways to spend a few dollars. Concerts have been promoted through flyers or posters, which over the years have become more and more elaborate (精心制作的).

Since the time of Bill Graham,who supported public access to live music in San Francisco in the 1960s, concert posters have become an incredible way for young art enthusiasts to connect with the visual artists that create the imagery for the bands they love.

That’s exactly what happened to me. I started reading OMGPosters. command I discovered artists who were making gig posters and art prints from A to Z. They’d draw it, pull the screens, and sell the prints on their own websites, because the Internet continues to encourage artists to create and art lovers to collect their works.

I started collecting works by artists like Jermaine Rogers_? Mexican Chocolate Design, Dan Grzeca, Emek, J ay Ryan and Justin Santora. When you can purchase a limited edition piece of art for as low as $ 20,the world of art collecting opens up even to art enthusiasts who don’t have much money.

I have always taken a grass-roots approach to life and work, so it makes sense that I would be motivated by artists whose work wasn’t being shown in museums or appearing on advertising for major brands. Although some of those lines have blurred (变得模糊不清)over the last 10 years, bringing more and more related and accessible work into respected galleries in New York and Los Angeles and being able to buy art prints directly from the artists who made them are major developments in the world of art.

8 . War and love should never be mixed together, but when it does, some stories are made during its experience. Here are some books about love stories which are set in wartime.

War Bonds by Cindy Hval

The idea to write this book was suggested to the author by her husband. It’s a compilation (汇编) of love stories that took place during the war when men and women who made lifelong commitments without knowing what the future would bring. Each story shares a lesson to inspire every heart.

Eve of a Hundred Midnights by Bill Lascher

Bill Lascher had always wanted to be a reporter, and soon discovered his cousin had lived the life he dreamed of living. A month after his grandmother gifted him with his cousin’s typewriter used during World War II, he slowly uncovered the story told in this book.

Just as World War II broke out, Melville and Annalee Jacoby, both war reporters, were faced with a life-and-death decision. Having been married for just a month, the couple had to run for their lives to escape being caught by their enemy.

GI Brides : The Wartime Girls Who Crossed The Atlantic For Love by Duncan Barrett and Nuala Calvi

This book tells the stories from the women in England who married American soldiers. Each GI Bride has her own unique hopes and fears during a time of war when their ever happy dreams are redefined (重新定义) by war, cultural differences, countries, and an uncertain future.

World War II Love Stories by Larry King

Each love story in this book is unique in its own way, but they all share a common topic: love overcomes all. Each couple interviewed shares how they met,how they fell in love,the difficulties they faced and how their love grew stronger leading to marriages that lasted a lifetime.

9 . Instagram（图片分享社交应用程序）is about to take its biggest step toward removing likes from its platform. After months of testing an option to hide likes in select international markets, Instagram, which is owned by Facebook（FB）, has already been testing hiding likes in seven other countries, including Canada, Ireland and Australia. For years, likes have been central to how celebrities, brands, politicians and everyday users experience Instagram and Facebook. It's a way of measuring popularity and success. But in recent months, Instagram has been rethinking how likes contribute to making its platform more toxic. Now it's considering a change.

The total number of likes on posts — which appear as hearts on the app ——will disappear from Instagram's main feed, profile pages and permalink（永久链接）pages. The owner of the account can still see their own likes, but their followers won't know the count.

CNN Business previously spoke with users in countries with the test. The majority felt this move would improve well-being on the app. Instagram is the most detrimental（不利的，有害的）social networking app for young people's mental health, such as negatively impacting body image, according   to one study.

But other users and psychologists said hiding likes won't fix everything. The test doesn't address some of the key ways that activity on Instagram can impact the well-being of users, including bullying, feeling left out and thinking other people's lives are better than their own.

Renee Engeln, a psychology professor at Northwestern University, voiced his opinion that the biggest impact of Instagram is the content and the exposure to this constant stream of perfected images is what seems to hurt psychologically. Plus, users can still see their own likes ——and feel badly if their posts don't perform well.