For thousands of years comets have been a mystery to man. They travel across the sky very fast and have a bright “tail” of burning gas. The comet Tempel 1 has an orbit（轨道） far outside the orbit of the furthest planet in our solar system, Pluto. It has been there for 4.6 billion years, 133 million kilometers from Earth. Last week a little American spacecraft crashed into Tempel 1. The spacecraft had a camera and it took a photograph of the comet every minute before it finally crashed into its surface.

    The space mission to Tempel 1 cost $335 million and was called Deep Impact. The spacecraft was travelling at 37,000 kilometers per hour when it hit the comet and the crash completely destroyed the spacecraft. But before it hit the comet, the spacecraft took some amazing photographs. The last one was a close-up picture which the spacecraft took just 3 seconds before it crashed into the comet.

    “Right now we have lost one spacecraft,” said a delighted NASA engineer. Deep Impact was like a American Independence Day fireworks display. It took many years to plan and ended in an enormous explosion. 

    The spacecraft which crashed into the comet was made of copper and was the size of a washing machine. It was dropped from a mothership into the path of the comet and the mothership then photographed the cloud of ice, dust and organic chemicals that rose from the surface of the comet after the crash.

    The crash completely destroyed the spacecraft but nothing really happened to the comet: experts believe that the crash slowed the comet down by no more than 1/10,000 of a millimeter a second.The aim of the mission was to study for the first time the interior of a comet.

    The mothership was 480 km from the explosion and observed the crash and the explosion with instruments for 800 seconds. Seven satellites, including the Hubble space telescope, watched the moment of drama, and over the next day and night about 50 telescopes on Earth were watching the distant comet.

    Are you preparing for a big test? If so, you may want to go to play some basketball in between hitting the books. Doctors are starting to find more and more information that suggests a connection between exercise and brain development. Judy Cameron, a scientist at Oregon Health and Science University, studies brain development. According to her research, it seems that exercise can make blood vessels (血管), including those in the brain, stronger and more fully developed. Dr. Cameron is sure that this allows people who exercise to think better. As she says, “While we already know that exercise is good for the heart, exercise can actually cause physical changes in the brain.”

The effects of exercise on brain development can even be seen in babies. Babies who do activities that require a lot of movement show greater brain development than babies who are less physically active. Even a little movement can show big results. Margaret Barnes, a scientist, also believes in the importance of exercise. She thinks that many learning disabilities that children have in primary school or high school can result from a lack of movement as babies. Babies need movement that encourages and excites their five senses. They need to set up a connection between motion and memory. In this way, as they get older, children will begin to connect physical activity with higher learning,” says Margaret.

    Older people can develop their brains as well. Cornell University studied a group of seniors who have a short-term memory increase of up to 40 percent after exercising just three hours a week. The exercise does not have to be very difficult, but it does have to increase the heart rate. Also, just like the motion for babies, exercise for older people should not be too simple. Learning some new skills or actions, such as with yoga or tat- chi helps to open up memory paths in the brain that may not have been used for a long time. For most people, any type of physical activity that increases the heart rate is helpful. The main aim is to increase the brain's flow of blood. And your brain can benefit from as little as two to three hours of exercise a week.

Best Way to Save Money

    Although the best way to save money can vary from person to person, depending on age, family size and other characteristics, there are still some easy things that all shoppers can do to keep more money in their bank accounts.

    Avoid impulse (冲动的) purchases.

    When you shop, a best way to save money is to have a plan in mind to help you avoid impulse purchases. {#blank#}1{#/blank#} And you only carry the exact amount of cash that you will need for your planned purchase. Some shoppers agree to discuss any purchases over a certain dollar amount with their spouses (配偶) first.

    {#blank#}2{#/blank#}

    Sometimes the best way to save money in the long term is to spend a little more money right now. {#blank#}3{#/blank#} A high-quality pair of shoes will last longer than a bargain pair and prevent foot pain. Leaner (瘦的) cuts of meat and organic produce provide health benefits for your family.

    Buy secondhand.

    Check classified ads, thrift stores and garage sales for used clothing, toys, furniture, and much more available at a part of their original cost. {#blank#}4{#/blank#} And there members offer unwanted items for free to anyone willing to pick them up.

    Borrow instead of buy.

    If you're only going to use something once, try to borrow it instead of spending your money on it. Borrow a tool from your neighbor. {#blank#}5{#/blank#} Check out the resources at your local library. You'll also be reducing disorder in your home.

A. Make things by yourself.

B. Exchange books with a friend.

C. Know when to pay for quality.

D. Refuse to buy things you can't use.

E. For instance, you might leave your credit cards at home.

F. A good piece of furniture can stay in the family for decades.

G. For the most secondhand savings, check out groups like Freecycle.

Ways to say “Happy birthday to me”

    Tomorrow is my birthday, and I'm at an age when not everyone looks forward to cakes and presents.

    {#blank#}1{#/blank#} It always makes me feel excited to be alive and grateful for my life and my family. So I think even if your birthday is a regular old day at work or home, there are some easy ways to raise it to the special occasion.

    Give a gift to someone else.{#blank#}2{#/blank#} While everyone loves to open a birthday present, there is a lot of joy and goodness to be gained from being generous with others. Making a birthday donation (捐赠) to a charity that means something to you.{#blank#}3{#/blank#}

    Try something new. Today is new to us. Why not enjoy the newness of the moment? Dip your tones into some new waters, sign up for an adult education class, go for a new-to-you park or plan a new trip. {#blank#}4{#/blank#}

    {#blank#}5{#/blank#} Whether or not you have the opportunity to share a meal, outing or party with friends and family, please take time on your birthday to connect with people who are important to your life, if you use social media like phones, you are likely filled with well—wishes from loved ones. Use these as a. jumping off point to start new conversations and reconnect with people who lift your spirits and support in your journey towards being your best self.

A.I love my birthday, though.

B. It's better to give than to receive.

C. Connect with people who matter to you.

D. This year my birthday is on a Saturday.

E. Freshen up yourself with countless opportunities.

F. One choice is to donate a dollar amount to match your age.

G. Download an app to learn a new language is also a good choice.

    Antarctica(南极洲)'s melting ice, which has caused global sea levels to rise by at least 13.8 millimeters over the past 40 years, was thought to primarily come from the unstable West Antarctic Ice Sheet(WAIS). Now, scientists have found that the East Antarctic Ice Sheet (EAIS)—considered largely unaffected by climate change—may also be melting at an unexpectedly rapid speed.

    The WAIS, whose base is below sea level, has long been considered the most likely to break down. Besides gravity, a deep current of warm water slips beneath the sheet, melting it from below until it becomes a floating shelf at risk of breaking away. In contrast, extreme cold and a base mostly above sea level are thought to keep the EAIS relatively safe from warm waters.

    But as greenhouse gases warm much of the planet, driving stronger polar winds, some scientists think warm water carried by a circular current will start to invade East Antarctica's once unassailable ice. A cooperation of more than 60 scientists last year, published in Nature, estimated that the EAIS actually added about 5 billion tons of ice each year from 1992 to 2017.

    Eric Rignot of the University of California, Irvine, and colleagues combined 40 years of satellite imagery and climate modeling and found that overall Antarctica now sends six times more ice into the sea each year than it did in 1979, with the majority coming from West Antarctica. But East Antarctica was responsible for more than 30% of Antarctica's contribution to the 13.8-millimeter sea level rise over the past 40 years. “The more we look at this system the more we realize this is fragile,” Rignot says. “Once these glaciers become unstable there is no red button to press to stop it.”

    Rignot hopes the study brings greater attention to a part of Antarctica that has traditionally been understudied. Helen Fricker, a glaciologist (冰川学家) in California, agrees. “We need to monitor the entire Antarctica and we just can't do that without international cooperation.”

Many scientists today are convinced that life exists elsewhere in the universe—life probably much like that on our own planet. They reason in the following way.

    As far as astronomers can determine, the entire universe is built of the same matter. They have no reason to doubt that matter obeys the same laws in every part of the universe. Therefore, it is reasonable to guess that other stars, with their own planets, were born in the same way as our own solar system. What we know of life on earth suggests that life will arise wherever the proper conditions exist.

    Life requires the right amount and kind of atmosphere. This eliminates(除去) all those planets in the universe that are not about the same size and weight as the earth. A smaller planet would lose its atmosphere; a larger one would hold too much of it.

    Life also requires a steady supply of heat and light. This eliminates double stars, or stars that flare up suddenly. Only single stars that are steady sources of heat and light like our sun would qualify.

    Finally, life could evolve(进化) only if the planet is just the right distance from its sun. With a weaker sun than our own, the planet would have to be closer to it. With a stronger sun, it would have to be farther away.

    If we suppose that every star in the universe has a family of planets, then how many planets might support life? First, eliminate those stars that are not like our sun. Next eliminate most of their planets; they are either too far from or too close to their suns. Then eliminate all those planets which are not the same size and weight as the earth. Finally, remember that the proper conditions do not necessarily mean that life actually does exist on a planet. It may not have begun yet, or it may have already died out.

    This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist.