Each time I take a plane and get ready for a long-hour flight, the same thought goes through my mind: why can’t planes be faster? Everything else is speeding up: smartphones, the Internet, the speed of life in general! So why can’t we get a superfast passenger plane?

Speed has always interested engineers and pilots. At least at first, they were pretty good at getting these metal birds to fly faster and faster. As long ago as 1945, a German test pilot reached a speed of 610 mph (miles per hour). But then, something happened, and the speed stopped growing. In fact, it’s slowing down! Any guesses why? Because unlike riding a bike down the hill, there’s no surface of the road trying to push the front wheel this or that way. No, it’s all air! Besides air, there’s this thing called aerodynamics. That’s a word for the movement of air around a certain thing. If you’ve put your hand out of the car window, then you know how much force (力) air can have. When the car moves fast, the air will hit your hand so hard that you may have trouble pulling it back.

Faster doesn’t mean better. A plane isn’t always in the air—you also have to consider take-off and landing. Those two situations can be quite dangerous at high speeds. Taking the speed down a bit is also more comfortable for passengers since the ride is less noisy.

Another reason is about engines (引擎) and fuel (燃料). The faster the plane is flying, the more the engines have to work. If the engines are always working fully, they won’t last long and need to be repaired more often. Also, they burn more fuel, which makes ticket prices higher and fewer people will choose the plane trip.

After all these years of experience, plane engineers have found the best speed of flight: 560 mph. That’s because safety always comes first. One day, the best scientific minds will come up with something to make planes faster, comfortable and affordable!

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It’s a common belief that fish can’t remember anything for longer than seven seconds. It may seem sad to think that every moment in their lives would be like seeing the world for the first time. But don’t be so quick to feel sorry for them. A new study has found that fish have much better memories than we used to think.

In the study, researchers from Mac Ewan University in Canada trained a kind of fish called African cichlids to go to a certain area of their tank to get food. They took the fish out and then waited for 12 days before putting them back in the tank again. They found that after such a long break the fish still went to the same place where they first got food.

In fact, scientists had been thinking for a long time that African cichlids might have a good memory. But there was no clear evidence until the latest findings.

Just as a good memory can make our lives easier, it also plays an important part when a fish is trying to survive in the wild. “If fish are able to remember that a certain area contains (容纳) safe food, they will be able to go back to that area without putting their lives in danger,” lead researcher Trevor Hamilton told Live Science.

So next time you are watching your pet fish from outside the tank, perhaps you should feel close to them——they may remember who you are.

The 24th Winter Olympic Games were just hosted in Beijing, but the city was no stranger to competitive (竞争性的) sports on snow and ice.

Actually competitive winter sports were already popular in China a thousand years ago in the form of bingxi (playing on ice). Bingxi began in the Song Dynasty and became really popular during the Qing Dynasty. Emperor Qianlong hosted bingxi nearly every year. He had the first one in 1742, almost two hundred years before the first Winter Olympic Games.

Events of bingxi were recorded by many ancient palace painters. A bingxi painting just shows scenes of bingxi during the Qing Dynasty.

In bingxi,three types of ice skating are performed. The first one is the speed race which is similar to modern speed skating. Participant(参赛者)race to the emperor’s ice bed, the emperor is seated inside his ice bed. Whoever reaches the emperor first wins first prize. The second is finger skating. Jumps, spins (旋转), kick and try to score goals. If the “tool”for scoring goals is changed from legs to sticks, it is similar to today’s ice hockey(冰球).

The love of winter sports has never diminished in China. Since Beijing hosted the 2022 Winter Olympic Games, more and more people have taken part to winter sports.