Last month I was lucky enough to have a chance to make a trip into space with my friend Li Yanping, an astronomer. We visited the moon in our spaceship!

    Before we left, Li Yanping explained to me that the force of gravity would change three times on our journey and that the first change would be the most powerful. Then we were off. As the rocket rose into the air, we were pushed back into our seats because we were trying to escape the pull of the earth's gravity. It was so hard that we could not say anything to each other. Gradually the weight lessened and I was able to talk to him. "Why is the spaceship not falling back to the earth? On the earth if I fall from a tree I will fall to the ground." I asked. "We are too far from the earth now to feel its pull, " he explained, "so we feel as if there is no gravity at all. When we get closer to the moon, we shall feel its gravity pulling us, but it will not be as strong a pull as the earth's. " I cheered up immediately and floated weightlessly around in our spaceship cabin watching the earth become smaller and the moon larger.

    When we got there, I wanted to explore immediately. "Come on," I said. "If you are right, my mass will be less than on the earth because the moon is smaller and I will be able to move more freely. I might even grow taller if I stay here long enough. I shall certainly weigh less!" I laughed and climbed down the steps from the spaceship. But when I tried to step forward, I found I was carried twice as far as on the earth and fell over. "Oh dear," I cried, "walking does need a bit of practice now that gravity has changed." After a while I got the hang of it and we began to enjoy ourselves.

    From the modern London Eye to the historic Tower of London, below are London's most visited tourist attractions. Many of London's top attractions are free, making them affordable places to learn about some culture. Whether you prefer history or modern art, you'll find it at one of these must-visit spots.

British Museum

    The world-famous British Museum exhibits the works of man from prehistoric to modern times, from around the world. The most interesting and exciting parts include the Rosetta Stone, the Parthenon sculptures (雕塑) and the mummies in the Ancient Egypt collection. Some exhibitions require tickets.

National Gallery

    The greatest and most beautiful building of Trafalgar Square, London's National Gallery is a vast space filled with Western European paintings from the 13th to the 19th centuries. In this impressive art gallery you can find works by masters such as Van Gogh, da Vinci, Botticelli, Constable, Renoir, Titian and Stubbs. Some exhibitions require tickets.

Tate Modern

    Sitting on the banks of the Thames is the Tate Modern, Britain's national museum of modern and contemporary (当代的) art. Its unique shape is due to it being a power station before. The gallery's restaurants offer wonderful views across the city. Some exhibitions require tickets.

Coca-Cola London Eye

    The Coca-Cola London Eye is a major feature of London's skyline. It has some of London's best views from its 32 capsules, each weighing 10 tonnes and holding up to 25 people. Climb aboard for a breathtaking experience, with an unforgettable view of more than 55 of London's most famous landmarks — all in just 30 minutes!

Madame Tussauds

    At Madame Tussauds, you'll come face-to-face with some of the world's most famous faces. From Shakespeare to Lady Gaga you'll meet influential figures from show business, sport, politics and even royalty. Strike a pose with Usain Bolt, get close to One Direction or receive a once-in-a-lifetime audience with Her Majesty the Queen.

    When one tried to unify gravity with quantum mechanics (量子力学), one had to introduce the idea of 'imaginary' time. If one can go forward in imaginary time, one ought to be able to turn round and go backward. This means that there can be no important difference between the forward and backward directions of imaginary time. Yet there is a big difference between the forward and backward directions of 'real time' in ordinary life. Imagine a cup of water falling off a table and breaking into pieces on the floor. If you take a film of this, you can easily tell whether it is being run forward or backward. You can tell that the film is being run backward because this kind of behavior is never observed in ordinary life.

    The explanation that is usually given as to why we don't see broken cups gathering themselves together off the floor and jumping back onto the table is that it is forbidden by the second law of thermodynamics (热力学). This says that in any closed system disorder, or entropy (熵), always increases with time. In other words, it is a form of Murphy's law: things always tend to go wrong! An intact cup on the table is a state of high order, but a broken cup on the floor is a disordered state. One can go readily from the cup on the table in the past to the broken cup on the floor in the future, but not the other way round.

    The increase of disorder or entropy with time is one example of what is called an arrow of time, something that tells the past from the future, giving a direction to time. There are at least three different arrows of time. First, there is the thermodynamic arrow of time, the direction of time in which disorder or entropy increases. Then, there is the psychological arrow of time. This is the direction in which we feel time passes, the direction in which we remember the past but not the future. Finally, there is the cosmological arrow of time. This is the direction of time in which the universe is expanding rather than contracting.

    A story posted by The New York Post Monday tells the tale of Katrina Holte, a Hillsboro woman who quit her job to cosplay a 1950s housewife.

    Let me start by expressing admiration to Holte for using her 2019 freedoms to follow her 1950s dreams. Everyone should be so lucky as to get to decide what they wear and how they spend their time. That's the future our foremothers fought for.

    But as much fun as I am sure she is having living a vintage (复古的) life, which literally includes watching shows like "I Love Lucy" and listening to vinyl recordings (刻录碟片), I think it's important to remember that being a 1950s housewife was actually totally awful, and something our grandmothers and mothers fought against.

    For example, once I called my grandma and asked her for her recipe for Cloud Biscuits, these delicious biscuits she used to make that we would cover with butter and homemade raspberry jam on Thanksgiving.

    "Why would you want that?" she said. "Go to the store. Go to the freezer section. Buy some pre-made biscuits and put them in the oven."

    She straight-up refused to give me the recipe, because it was hard and took a long time to make. In her mind, it was a waste of time.

    Getting off the phone, it occurred to me that spending every day of your life serving a husband and five children wasn't fun at all. And then there are the grandchildren who eventually come along demanding Cloud Biscuits, a whole new expanded set of people to feed.

    She was basically a slave to those hungry mouths, cooking scratch meals three times a day.

    When she wasn't trapped in the kitchen, she had to keep the house clean, make sure she looked good enough to be socially acceptable, and make sure her kids and husband looked good enough to be socially acceptable. And she had no days off.

    I know my grandma loves her kids and her grandkids, her husband and the life she led, but man, it must have been a lot of thankless, mindless labor.

    No wonder everyone went all-in on processed foods when they came around. Imagine the nice break something like a microwave dinner would give a woman working, unpaid, for her family every single day?

    I also had another grandma. She was a scholar who helped found the Center for the Study of Women in Society at University of Oregon. She was a pioneering second-wave feminist who wrote books, gave lectures and traveled the world.

    But, she did all of that after divorcing my grandpa, when most of her kids were out of the house. Back then, in the 1950s and the 1960s, there was no illusion about women "having it all". How could that even possibly happen? If you were taking care of a family, waiting on your husband, you had no time to follow your dreams, unless you made that your dream.

    A lot of women took that approach. We call it Stockholm Syndrome now.

    And of course, these women I am talking about are upper-middle-class white women. Romanticizing the 1950s is especially disgusting when you think about how women of color and poor women were treated back then, and the lack of education and choices available to them.

    Because the women in this country demanded something approaching equality, Holte has the chance to live out her fantasy. Not every woman in America is so lucky.

    We still don't have pay equality and in many states, we still don't have autonomy over our own bodies. Poor women and women of color still lack the opportunities of their wealthy and white peers.

    And while it's getting better, women are still expected to be responsible for the emotional labor of running a household and raising the children.

    But at least we can get jobs. At least we don't have to sew our own clothes, wear a full face of makeup every day and spend hours making Cloud Biscuits some ungrateful kid will wolf down, barely remembering to say thank you.

Emily, a 14-year-old teenager, walked through her town one afternoon. Her eyes were drawn to the sight of people without homes on street corners, trembling（颤抖） against the chill. It was a scene that stirred something deep within her—a desire to make a difference, no matter how small.

Emily decided to turn her love of baking into a force for good. She whipped（搅打） cream, mixed flour, and baked cookies and cakes in her family kitchen. With the support of her friends and family, she set up a colorful stall in her bustling neighborhood, offering her homemade treats to passersby in exchange for donations.

The response was overwhelming. People were not only touched by Emily's handmade cookies but also inspired by her spirit. Before long, donations were pouring in. In just a few short weeks, Emily had raised over $1,000—a symbol of one's kindness to ignite a community's generosity.

But Emily's heart was set on doing even more. Inspired by the success of her bake sale, she came up with the idea of organizing a charity run. A community-wide event that would bring people together in support of a common cause. She reached out to local businesses and called for volunteers to help her realize the project. On the day of the charity run, participants ran under the clear, open sky, and the running campaign raised over $5,000 for the local homeless shelter.

For Emily, the true reward lay not in the dollars raised or the miles run but in the knowledge that she had touched the hearts of her community and shown that even the smallest act of kindness can make a difference to the world.

As the world struggles to deal with the climate crisis, some companies are working to remove polluting carbon dioxide (CO₂) from the air. {#blank#}1{#/blank#}, but two US companies have recently made important progress.

Scientists say large amounts of CO₂ must be removed from the atmosphere and stored. {#blank#}2{#/blank#}. But there's so much CO₂ in the atmosphere that just planting trees and protecting forests won't solve the problem. In addition, when plants and trees die, the carbon they've stored gets released again.

That means humans need to come up with ways of removing carbon from the air and storing it. This is called Direct Air Capture (DAC). The science of removing carbon from the air is challenging, and it's still pretty new. Most DAC processes require a large amount of energy, {#blank#}3{#/blank#}.

A company called Heirloom has just opened the first DAC plant in the United States. The company heats up the limestone (石灰岩)to separate out the CO₂, which is then locked away in concrete (混凝土). The process is extremely expensive. {#blank#}4{#/blank#}. That's a tiny amount compared to how much carbon needs to be removed from the atmosphere, but the company says it hopes to remove a billion tons per year by 2035.

{#blank#}5{#/blank#}. Some people worry that it will take too long for DAC technology to become powerful enough to make a difference. Others worry that focusing on removing carbon could take attention away from more important climate actions, like switching from fossil fuel s to renewable energy. But experts say the decision isn't to do one or the other. The world needs to end fossil fuel use and pull carbon out of the air.

A. It's a huge and challenging goal

B. Plants and trees can do this naturally

C. Everyone is not excited about carbon removal

D. The new plant can remove 1,000 tons of CO₂ year

E. Graphyte is another US company working on DAC

F. and CO₂ is just a small part of the gasses that make up air

G. so one puzzle for these companies is how to remove carbon without creating more pollution