The universal speed limit of any kind of wave—whether electromagnetic or gravitational travelling through a vacuum(真空)has been known since Albert Einstein developed his theory of special relativity in 1905. But the maximum speed of sound moving through a solid or a liquid has just been calculated for the first time. It is about 36 kilometre per second, more than 8, 000 times lower than the speed of light in a vacuum.
To make this calculation, Kostya Trachenko at Queen Mary University of London and his colleagues started with two well-known physical constants:the ratio(比率)of proton mass(质子质量)to electron mass, and the fine structure constant, which characteristics the strength of interactions between charged particles(粒子).
Trachenko says we have a pretty good idea of these values, because if they were changed even a bit, the universe wouldn't look at all like it does. "If you change these constants by a few percent, then the proton might not be stable anymore, and you might not even have the processes in stars resulting in the combination of heavy elements, so there would be no carbon, no life, "he says.
Sound is a wave that spreads by making neighbouring particles interact with one another, so its speed depends on the density of a material and how the atoms within it are bound together. Atoms can only move so quickly, and the speed of sound is limited by that movement.
"The common wisdom was that diamond has the highest speed of sound, because it is the hardest material, but we didn't know whether there was a theoretical fundamental limit to it, "says Trachenko. The theoretical bound is about twice the speed of sound in a diamond.
The speed of sound is also dependent on the mass of the atoms in the material, so there searchers predicted that solid metallic hydrogen—a material that theoretically exists at the centre of giant planets, but for which laboratory evidence has been hotly questioned—should have the highest speed of sound. They calculated that it should be close to the theoretical limit. They also looked at experimental data for 133 materials and found that none of them broke the limit.
NY Giants game-by-game predictions for the 2023 NFL season
Week 1:vs Cowboys
Sunday, Sept. 10, 8:20 p. m.
At some point, the Giants are going to have to break through and prove they can play atthe level of Dallas and Philadelphia in the NFC East. Dak Prescott has had their number for awhile now, too. But let's just say Big Blue rides the momentum(势头)of being at home in the opener
Prediction:Win
Week 2:at Cardinals
Sunday, Sept. 17, 8:05 p. m.
It's unlikely that Kyler Murray is on the field to face the Giants this early in his ACL recovery. That's a positive for the defense, and I can see the Cardinals being out manned(数量优势的) here as Daniel Jones tests this defense being put together by new head coach Jonathan Gannon.
Prediction:Win
Week 3:at 49ers
Thursday, Sept. 21, 8:15 p. m.
This is a tough spot, even if the Giants stay out west and practice in Phoenix in order to cut down on the short-week travel to California for this one. The 49ers are loaded defensively and Christian Mc Caffrey is going to test the Giants' rebuilt run defense, putting pressure on the revamped(改进过的)middle featuring Bobby Okereke. It's uncertain which quarterback will be available for San Francisco, and it could be Sam Darnold.
Prediction:Loss
Week 4:vs Seahawks
Monday, Oct. 2, 8:20 p. m.
The Giants return home to Met Life for"Monday Night Football"against Geno Smith and his team the Seahawks, who beat Big Blue in their building last year. Let's say for argument's sake that the Giants return the favor.
Prediction:Win
Surely one of the world's most attractive rivers as well as being its longest, the mighty Nile River runs constantly ever northwards 6, 650 kilometre(4, 132 miles)from its or iginsin Africa to its mouth on the Uat-Ur, the Egyptian word for the Mediterranean Sea. Along its passage, it gave life to the ancient Egyptians, nourishing(滋养)them with its annual deep layers of rich black earth providing the basis for the agriculture, which supported the flowering of their culture.
Seneca, the Roman philosopher and statesman, described the Nile as a"remarkable sight" and an amazing wonder. The surviving records indicate this is an opinion widely shared by ancient writers who visited Egypt's"mother of all men".
The river gains its name from the Greek"Neilos", meaning valley, although the ancient Egyptians called their river Ar, or"black"after its rich earth. However, the story of the Nile River doesn't begin in the expansive delta(三角洲)of marshes(沼泽)and lakes of its Mediterranean exit, but in two distinct sources, the Blue Nile, which falls down from the Abyssinian highlands and the White Nile, which springs from equatorial Africa.
The Nile's broad fan-shaped Delta is flat and green. At its farthest reaches, Alexander the Great built Alexandria, a busy port city and home to the Library of Alexandria and the famed Pharos Lighthouse, one of the Seven Wonders of the Ancient World. Beyond the expanse of the Nile Delta lies the Mediterranean and Europe. At the far end of the Nile, sat Aswan, the gateway city to Egypt, a small, hot, garrison town for Egypt's armies as they hotly contested the territory with Nubia over the centuries.
Having an off day when you feel stressed or sad is totally normal. We've put together some different things you can try to help turn your mood around and get feeling like
yourself again,
Take a few minutes to breathe deeply. The simple action of taking full, deep breaths can help you start to feel better. Deep breathing increases oxygen supply throughout the body. Deep breathing also helps activate(激活)your parasympathetic nervous system, which produces a calming effect.
Start keeping diaries. It is a way to cognitively(认知上地)deal with the circumstances behind how you are feeling. In fact, studies have shown that writing offers benefits of emotional well-being, including relief of emotional distress. Besides, adjourning has been shown to benefit the immune system.
Emotional tears signal the body to let out endorphins or"feel-good"hormones to promote a feeling of calm and well-being. Not only does crying allow your body to let out stress hormones, but at the end of a good cry, the body assumes a calmer state with a lower heart and breathing rate.
Rely on your support system. Studies have shown the benefits of having a close support system of family and friends to whom you can turn. Social support leads to a sense of belonging and security rather than loneliness while dealing with emotional pain.
A. Take a break to laugh.
B. Go ahead and cry if you need to.
C. Take some time for yourself and treat yourself.
D. It's also been linked to an increased sense of self-worth.
E. Writing down your feelings provides a great benefit.
F. This can help to relax muscles and reduce your blood pressure.
G. The good news is that there are things you can do for yourself to start feeling better.
The need for speed is so deeply rooted in modern society that we often forget to press pause and think about the things that get(good)with time:antiques, aged wine, long-term relationships and expertise over the years.
Peking Opera is a slow process too. An often-repeated saying goes as follows:Three minutes on stage, 10 yearsstage. It's meant as a nod to its demanding nature and are minder of its high standards that ensure that any performance(do)the way the forefathers wanted it.
Peking Opera is(demand)because of the extensive list of skills it requires. A performer is an actor, singer, dancer, acrobat, mime and martial artist all rolled into one. They're also expected(apply)delicate make-up, put on heavy costumes and, (depend)on their character, perform on stage in 15 cm platform shoes.
There is so much to take indisciples(学徒)usually start their career as young children, spending years conditioning their bodies and minds for the stage.
So what chance doestheatre beginner with little patience and zero flexibility like me stand against Peking Opera?Do I haveit takes to put on a successful show?There's only one way to find out:I'm rolling up my sleeves and training under the(guide)of senior stage masters in the field.
At 28 years old, I lost my job as a full-time magazine editor. I'd always dreamed of becoming a self-employed writer, but I1 doing it at 35 or even 40 years old, 2 I had a more solid financial footing.
Despite the fear I felt at 3 this dream before I was ready, it was my best, most practical 4 at the time. With my husband's encouragement, I took a leap of faith, 5 my fear and jumped.
I've been working for myself full-time for two years. Not only am I happier thanks to a(n) 6 schedule and the freedom to take on the projects I want, but I'm earning much more than I did as a7 editor.
When it comes to big dreams, many of us plan out every last detail so that we feel8 for success. But often, this over-planning prevents us from ever taking action. No matter how much planning we do, we'll never feel 100% ready.
When Jennifer Qiao got9 , she struggled to find a modern version of a cheongsam, a traditional Chinese wedding dress, and an idea was10 . Neither she nor Vivian Chan, her co-founder, had experience in entrepreneurship(创业). They didn't even know if there was a11 for their products in the U. S. But they decided to just start small and test out their idea 12 . They never truly felt ready to start a(n)13 , let alone make custom wedding dresses. However, through hard work, trial and error, they've14 their team to a successful company.
Never let over-planning get in the15 of you taking action.
Today I am going to share my experience that is related to the quote that I just read. I tall started when the drawing competition was taking place. I really wanted to win it and get the trophy(奖杯)of the best artist, so I started working really hard on my weak points in drawing and I started to plan on how I could win the trophy. I spent so many hours working on it that the time flew really fast and I didn't even notice that finally the day came. I was so excited but nervous at the same time. I just hoped my plans worked to make me good enough to win the trophy and the competition.
I went to the hall where we had to draw in and I saw my best friend, so I waved to her and she waved back. When the drawing competition started I drew what I needed to draw in the given time and the funny thing was that I didn't even face any problems. Everything went in place and I was feeling very confident that I would finally get the trophy of the best artist.
Then came the day when they announced the winner. I was so confident to get the prize that I didn't even bother to hear who was getting it because I knew I would be the one to get it. Then I heard my friend's name being called and this shocked me so much. How could she get it and not me?I congratulated her and went home, making sure nobody saw how sad I was. I was happy for my friend but I was very disappointed at the same time, so I did something that I usually do when I am sad or disappointed—read a book. The first book I saw was the book of moral stories.
注意：
1. 续写词数应为150左右；
2. 请按如下格式在答题卡的相应位置作答。
Depending on your job, you may have the chance to make a kid's day while at work. Or even better, you may have memories of an adult going the extra mile just to make you smile. For a group of construction workers, the opportunity popped up in the form of a toy truck. Excited to see some building work being done in the area, a small boy paid a visit with his tiny truck as if to join the action. What happened next is something that the little one will surely value forever.
The heart-warming moment was shot in a video that has since gone viral. Wanting to be a part of it all and hoping to see the big excavator(挖掘机)at work, the kid placed his wheeled toy under the big metal machine. The machine operator, moved by it all, was grateful and filled the toy truck with earth. With careful precision, as if it were a crucial part of the construction work being done, he made the little boy's dreams come true. While it's hard to find the location or the time from the video alone, the excitement of the kid as the machine slowly fills the mini dump truck is universally lovely. Even the other construction workers stop for a while to witness the cute scene. All the while, the kid's mom holds him firmly to keep everyone safe until the toy truck is full and the machine is still.
While anyone can appreciate the sweetness of a group of adults taking a few minutes to put a smile on a child's face, the video has had all kinds of positive responses. For some, it brought back memories of seeing construction work and big machines when they were little and being blown away. For others, it allowed them to enjoy the unexpected delicacy of the great machine. If there's one thing we all can agree on, it's that the boy wasn't the only one who benefited from this tiny action. As one editor wrote, "I used to work in the field. I can tell you it made everyone's day. "
The Paleozoological Museum of China, one of the largest natural museums in Asia, was opened in Baoding, North China's Hebei Province, in January, (serve) as a crucial component in the broader effort to relocate non-capital functions outside Beijing.
This newly (establish) museum, covering around 80, 000 square meters with a total construction area of around 73, 000 square meters, is thought of a national-level theme museum in the field of natural sciences.
The museum, themed around nature, life and humanity, provides a series of systematic (presentation) on paleontology and evolutionary biology. It tells the stories of natural history, and (set) to promote the natural concept that "humans and nature are a community of life".
The exhibits, numbering around 6,000 items, (primary) come from the Chinese Academy of Sciences' Institute of Vertebrate Paleontology and Paleoanthropology. Among the displayed items (be) rare treasures, including one of the world's few well-preserved pterosaur (翼龙) eggs, the world's (early) known jawed fish species, as well as the longest and largest individual horse skull.
"The Paleozoological Museum of China will become one of landmark buildings in Baoding, is just in need of a cultural salon like this to showcase its cultural feature," noted Gao Tianwei, project manager of the museum.
