Science fiction has become reality. You can also have a stand-in! 丨 Expo Daily

Spring Festival travel rush encounters snowstorm! High-speed rail slows down and stops running.

Why can the green train still move forward in the snow?

A rainy and snowy weather hit the southeast region, causing many high-speed trains to be delayed or even suspended, but anxiously waiting netizens also saw the "green trains" running all the way in the snow. Why are the seemingly more advanced high-speed trains not as good as the "old predecessor" green trains?

On February 4, the Wuhan Railway Bureau released an announcement on its Weibo account, explaining the reasons for large-scale delays in high-speed trains due to freezing, rainy and snowy weather. The reasons mainly include three points: poor conductivity due to ice covering the contact network, inflexible conversion of iced switches, and trains running at reduced speeds due to snow accumulation on the line.

Among them, contact network icing has the greatest impact on high-speed rail operation.

Unlike traditional trains, the power source of high-speed rail is not traditional diesel, but electricity. This electricity comes from the high-voltage wires above the high-speed rail carriages. The network composed of these high-voltage wires is called "contact network" or "overhead contact network".

High-speed trains can draw electricity from high-voltage lines through a structure called a pantograph. The pantograph draws high-voltage electricity into the car, and after voltage reduction, it is used to drive the high-speed train. However, if ice appears on the wires, the contact between the bow head and the wires will be affected. In addition, ice on the wires may also make the wires heavier and shake more violently. This also affects the power supply of high-speed trains. In order to obtain current as stably as possible, high-speed trains can only reduce their running speed. In serious cases, they can only stop temporarily and wait.

The green-skinned train will of course be affected by ice on the switches and snow on the lines, but because it travels at a relatively slow speed and the railway workers work overnight to repair it, these problems have little impact on the operation of the green-skinned train.

In addition, green-skinned trains have different types of power sources. Some green-skinned trains are purely electric like high-speed trains, some are powered by internal combustion engines, and some are powered by steam engines. Therefore, the "contact network icing", which has the most serious impact on high-speed trains, has almost no impact on the latter two types of "green-skinned trains", which is why there are scenes where high-speed trains are parked on the roadside waiting while green-skinned trains whiz by.

Image source: News screenshot

Science fiction enters reality,

You can also have a Stand!

In the movie "Avatar", the protagonist can control a stand-in to act on the alien planet while sleeping in a sleeping chamber. This kind of stand-in technology may not be far away from us.

Last week, Stefano Dafarra's research team from the Italian Institute of Technology released their latest upgraded iCub3 stand-in robot system, which made us feel the shock of future technology. iCub3 is a robot that replaces a real person. The operator can remotely control the iCub3 robot within a range of 300 kilometers without leaving home.

The robot carries a VR camera that can transmit real-time scenes to the operator's VR glasses, so that the operator can see the robot's perspective. In addition, iCub3 also carries mechanical sensors, texture sensors, etc. These sensors transmit the received signals to the equipment worn by the operator, allowing the operator to experience the real physical world such as weight, collision, texture, etc.

The newly upgraded iCub3 robot has specially added a facial expression function, which can read the operator's facial expressions and make corresponding expressions on the robot's face, making it more like a "human".

The researchers took the robot out of the laboratory and tested it in the real world, examining a range of new capabilities of iCub3, including large-scale activities such as running and jumping, as well as flexible hand movements such as picking up stones and playing chess, all of which the stand-in robot was able to successfully complete.

At the same time, the system upgrade makes the stand-in robot easier to operate. The current version of the robot does not require professional operation, and ordinary people can use it smoothly after learning. And the application scenarios are extremely rich, such as dangerous work (underwater, desert and other dangerous areas), Mars exploration, telemedicine, etc.

iCub robot walks, turns on switches, looks at screens, turns on electric drills, picks up bottles, and touches rocks (Image source: science.org)

Glass impersonating crystal? Two tips to help you avoid being fooled

Glass is not valuable and its appearance is very similar to that of transparent crystal, so some unscrupulous vendors sell glass as crystal! In fact, glass has many unique physical properties, and these properties can make it show its true form.

Compared with crystal, glass is significantly less hard. In mineralogy, there is a scale that reflects the relative hardness of different minerals, called the Mohs hardness scale. The Mohs hardness of crystal is 7, while the Mohs hardness of glass is only about 5.5. We can use this difference in properties to distinguish the two.

Since relatively hard minerals can scratch relatively hard minerals, the way to distinguish them is to find a substance with a hardness between crystal and glass to scratch the two, and then you can tell which is glass and which is crystal. The small steel knife is the substance that can make glass appear, and its Mohs hardness is between 5.5-6.

Scratching with a small steel knife will leave obvious scratches on the glass, while crystal, agate and chalcedony will not leave any marks. However, the merchants are definitely unwilling to use this method. At this time, we can use a low-power magnifying glass to observe.

When we observe, there will be many round or oval bubbles inside the glass, which is inevitable during the firing process. Although there are some inclusions in crystal, they are still clearly different from the bubbles in glass. In addition, crystal also has double refraction, but glass does not.

How did ancient humans weave ropes?

In Chinese mythology, there is a legend that Leizu taught people how to raise silkworms and make silk. It can be seen that weaving natural fibers into ropes was one of the most important skills of primitive humans. So, how did humans learn to weave ropes?

The difference between rope and other tools is that making rope requires tools. Therefore, the key to deciphering how ancient humans made ropes lies in finding the tools they used to make ropes.

A complete ivory implement was revealed from fragments of mammoth tusks found during excavation and sediment screening at Hohle Fels Cave in southwestern Germany in 2015. Radiocarbon dating of the cave’s ancient Aurignacian culture from Eurasia puts the artifacts at 35,000 to 40,000 years old.

Because this prop was very exquisite and carefully carved, with four small round holes at almost equal distances and carved grooves, scientists at the time believed that it was a sacrificial item.

Conard from the University of Tübingen in Germany and Rots from the University of Liege in Belgium saw this collection in the archives when they were free. But they doubted the so-called sacrificial offering.

High-power microscopes and chemical analysis showed that this cultural relic was stained with a lot of plant residues, and the direction of the microscopic wear on it was highly consistent. It can be inferred that a lot of plants must have been pulled from one side of these small holes to the other.

What kind of activity would have such a scene? The two suddenly had an idea: braiding ropes!

They soon figured out how to use the tool: thin plant fibers were threaded through the holes, with one person holding each fiber. Another person held the tool tightly while another twisted the bundle of fibers leaving the holes into a single rope.

So, the scientists made a replica of each using wood, animal bones, warthog tusks and bronze (all materials commonly used by ancient humans), and then tried to weave ropes using five different plant fibers and cattle tendons.

It was found that a team of four or five people could produce a five-meter-long strong, flexible rope in 10 minutes. The team found that cattail leaves worked particularly well as a rope material.

The findings don't answer all the outstanding questions about ancient rope production, but they are the first to document artifacts that were likely used to make rope and show how they worked.

The related results were published in the journal Science Advances on January 31, 2024.

The content is compiled from China Science Popularization Expo Weibo, Science Popularization, Science Academy, and Earth Magazine

This article was first published in China Science Expo (kepubolan)

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