Ping-pong balls can’t be brought on high-speed trains? Is this true? | Expo Daily

Ping-pong balls can’t be brought on high-speed trains? Is this true?

Recently, a table tennis enthusiast was told by staff that he could not bring his table tennis balls on board when he went through security check.

As we all know, table tennis is our national sport, and it has a huge number of fans. But why can't we bring it on trains or high-speed trains?

There are two main materials for table tennis balls. One is "acetate" material, which is made of a new material called cellulose acetate. It has a melting point of over 200 degrees Celsius and can be transported by rail.

There is also a type of material called "celluloid". The ignition point of this type of ping-pong ball is very low. According to the "List of Prohibited, Restricted and Checked Items for Railway Passengers", celluloid is a flammable solid and is prohibited from being carried into the station or on the train.

Therefore, if you want to bring table tennis balls on a train, you can choose table tennis balls made of cellulose acetate to ensure that they comply with the relevant regulations for railway transportation.

Image source: China Railway Weibo

There are duck and goose feathers in down jackets, why are there no chicken feathers?

Although chickens are the earliest domesticated poultry and are numerous, their feathers are not the first choice for down jackets.

This starts with the filling of down jackets - down feathers. Different from the closely arranged normal feathers, down feathers have a sparse branching structure suitable for heat preservation. The number and density of down feathers vary from bird to bird due to their different living environments and habits.

In the natural environment, birds of the Anatidae family of the order Anseriformes, such as the spotted-billed duck and mallard of the genus Anatidae, the crested duck and red-headed duck of the genus Pochard, and the Chinese merganser and white merganser of the genus Merganser, etc. These ducks living in cold environments have high-density down feathers, which will become the preferred filling for down jackets.

In contrast, domestic chickens are land birds that need to dissipate heat quickly when running, so they have fewer down feathers, and their down feather stalks are prominent. Down jackets made from them may feel burry, affecting wearing comfort.

In addition, domestic ducks and geese are larger in size, so down extraction is more efficient. Therefore, although domestic chickens are commonly raised, down jackets prefer feathers from domestic ducks and geese, which have higher down content and better structure.

Image source: theycantalk.com

Why do eyes lose focus automatically when daydreaming?

If you think that your brain stops working unconsciously when you are daydreaming, you are wrong.

Neuroimaging studies have shown that when we are in a daze or resting state, our brain does not stop working. On the contrary, although external stimuli are ignored by the brain, information is still being transmitted between brain regions. This uninterrupted information transmission is called the brain's default mode network (DMN).

The DMN is a complex network of brain regions that are interconnected and exchange information to maintain our internal thinking activities, including but not limited to self-reflection, memory review, future imagination, and emotional processing. Surprisingly, it consumes 20 times more energy than our conscious response to other external stimuli.

When we are in a daze, the DMN is activated, and the brain's attention turns to internal thinking activities, and no longer actively directs the eyes to focus on specific targets. At this time, the eye muscles, especially the ciliary muscles, will naturally relax, and the lens will return to its default shape. This change makes the images of both eyes no longer focus on the retina, resulting in blurred vision.

Daydreaming is not only a common human behavior, it is also part of the healthy functioning of the brain. So the next time you involuntarily enter daydreaming mode, don't feel guilty about wasting time. Maybe your brain is getting a "deep workout."

Mini cats found at Hualong Cave site

Recently, the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences and others made important discoveries at the Hualong Cave site in Anhui.

The research team not only unearthed a 300,000-year-old ancient human "family", but also discovered the smallest cat fossil to date - the Koi cat. This fossil is extremely small, comparable to the smallest existing cats, the rusty-spotted cat and the black-footed cat, and can be held in one hand. The unique sedimentary environment of Hualong Cave has preserved the leopard cat fossils, filling the gap in the fossil species of the genus Leopard Cat.

Although no traces of human cutting have been found, making it impossible to determine whether Kopi lupus was food for ancient humans, its discovery provides valuable clues to the evolutionary history of leopard cats and supports the hypothesis that leopard cats, cats, and manuls are a monophyletic group in evolution.

The large number of animal fossils in Hualong Cave, including Koi's leopard cat, help us understand the living environment, food sources and threats faced by ancient humans, and provide important fossil evidence for exploring human evolution.

Animal fossils like Koi's leopard cat have been discovered in large numbers at the Hualong Cave site, which helps us understand the environment in which the Hualong Cave people lived, what animals they fed on, and what animals threatened them...providing good fossil evidence for understanding how humans evolved.

What is the parallel universe theory?

For more than a century, scientists have been trying to uncover the mystery of the universe and understand how this vast universe works. In the process, scientists have discovered some puzzling phenomena. One of the most eye-catching is the theory of parallel universes. So, does the parallel universe really exist? If it does, what impact does it have on humans?

The content is compiled from China Science Expo Weibo, Shanghai Natural History Museum, Institute of Physics, Chinese Academy of Sciences, Voice of Chinese Academy of Sciences, Science Popularization China

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