Aviation, aerospace, astronautics... can you tell them apart? | Expo Daily

Aviation, aerospace, astronautics...can you tell them apart?

Although the words "aviation" and "aerospace" are often used together, a common misunderstanding should be clarified: aerospace is not exactly the same thing. They have clear boundaries in terms of technical fields and scope of application.

There is no unified view internationally on the exact boundary between aviation and aerospace, but in order to establish a relatively universal standard, the International Aeronautical Federation introduced the concept of the "Kármán Line".

The flight altitude of the passenger planes we usually take is between 6800-8000 meters, near the junction of the troposphere and the stratosphere. At the "Kármán Line" 100km above the ground, the atmosphere is too thin for the aircraft to fly normally. Therefore, the Kármán Line can be considered the dividing line between the atmosphere and space.

Qian Xuesen defined the scope of the three technical terms "aviation, aerospace, and astronautics" as follows: flight activities within the atmosphere are called "aviation"; flight activities outside the atmosphere and within the solar system are called "aerospace"; and activities flying out of the solar system and into the vast universe are called "astronautics."

In short, aviation refers specifically to the navigation of aircraft within the Earth's atmosphere, whether manned or not. Aerospace, on the other hand, refers to the navigation of spacecraft leaving the atmosphere and entering outer space, also known as space flight or space navigation.

As humans yearn for and explore wider space, our activities have expanded from land to ocean, from ocean to atmosphere, and finally through the atmosphere and into the universe. This process is a vivid reflection of humans constantly expanding the boundaries of their activities.

Image source: People's Daily

Henan Wind-Moving Stone:

The gears of fate have turned, but they have turned too far...

The wind-moving stone in the picture was discovered in Niu Dazhai, Jiyuan, Henan. It is amazing because it is located on the edge of a dangerous cliff and has an extremely narrow supporting surface. But what is more amazing than the stone itself is its ups and downs in fate. After it was discovered and exposed in December 2020, it immediately became a hot "Internet celebrity"; it became popular for less than 3 months, and in February 2021 it was pushed down by a busybody and has since ceased to exist.

The wind-moving stone, more academically known as the balancing stone, is actually a special type of balancing stone, which refers to a balancing stone that can shake - "when the wind comes, the stone moves slightly, and when the wind stops, the stone remains firm."

Sometimes, people can push the wind-blowing stone with their palms to make it shake without falling. To do this, several conditions need to be met. First, the base under the wind-blowing stone must be a hard rock. The wind cannot blow the boulder pressed on the soft soil. Second, the shape of the wind-blowing stone is close to an ellipsoid or a sphere, so the contact area between the wind-blowing stone and the base rock is very small. Third, the contact surface between the wind-blowing stone and the base is not flat, and there is often a small shallow depression in the shape of a plate bottom.

It is this inconspicuous little dimple that helps the Wind-Moving Stone to regain its balance in time when it is about to lose its balance due to a certain external force, making it look like a tumbler.

For a long time, there was no strict definition of balancing stone. Whenever a huge stone was supported by a small fulcrum and looked shaky but in a balanced state, people would call it a balancing stone.

Image source: National Geographic China

They say curiosity kills the cat, but will it kill the fish?

The exploratory behavior brought about by curiosity can significantly affect the survival probability of animals. For example, curious animals tend to explore and expand their habitats, but at the same time, they also face a greater risk of being discovered and hunted.

Recently, a study published in Science found that there are huge differences in the exploratory behavior of different cichlids in Lake Tanganyika, Africa, which may enable them to show diversity in morphology and habitat, inhabiting a variety of ecological niches and thus reducing competition with each other.

The researchers recorded the exploratory behavior of 702 cichlids from 57 species in Lake Tanganyika over a period of nine months in different areas of a large experimental pond. After analyzing the videos, they found that the differences in the exploratory behavior of these cichlids were closely related to their habitat and body size. For example, cichlid species that were larger and lived closer to the shore generally showed higher curiosity.

Next, they found a genetic variation in the cichlid genome that had a high correlation with the cichlid's exploratory behavior, and this genetic variation was located near the gene cacng5b. They also found that if the nitrogenous base at this position is thymine T, such cichlids have a higher curiosity, and if it is cytosine C, then they have a lower desire to explore. In addition, gene editing at this location can significantly change the cichlid's desire to explore, and can be combined with AI to predict the cichlid's exploratory behavior. This study shows that animal curiosity may play an important role in evolution.

One circle of tree rings equals one year?

Pattern! Don’t be fooled by the tree~

When we saw a tree trunk horizontally and expose a cross section, we will see that the surface is covered with concentric rings, which are annual rings. We usually think that we can count the number of rings to find out the age of the tree, and each ring represents one year. But annual rings can sometimes deceive us~

For example, if you count a hundred circles on a tree, it is actually only 98 years old, with two extra circles. What are the two extra circles? The tree is very sensitive. When it was growing in the summer, a cold front suddenly came. The tree thought it was winter, so it grew another circle, but it was actually fake.

Some trees were originally 1998 years old, but they were actually 1996 years old. Where did the other two years go? This is a lost growth ring. Some trees got sick that year and simply stopped growing - "You guys go ahead and grow, I won't grow anymore!"

To accurately determine the age, it is also necessary to use the professional "cross-dating" method of tree rings , that is, through cross-verification between a large number of tree ring samples living in similar habitats and having a common growth period, in order to determine the "missing rings" and "pseudo rings".

Don't underestimate its insignificant size.

If you get bitten, you may die...

As the weather warms up, red fire ants enter their active period. Red fire ants are bright red in color and are an alien invasive pest that poses a serious threat to agricultural and forestry production, human health, and the ecosystem in the areas they invade.

It is understood that Guangdong is the province with the largest occurrence area and the most serious damage caused by red fire ants. They are most active from March to May and from September to November each year.

Red fire ants and common ants belong to the family Formicidae. They like to build nests in farmland, woodland, lawns, green land, and even near lakes, fish ponds and other water areas. Although they are small and look very inconspicuous, if you accidentally disturb a red fire ant nest in the wild, you will face a large number of brave worker ants rushing out of the nest and quickly climbing onto your legs, arms and other parts.

When stung by red fire ants, the human body will feel a burning pain. Generally speaking, most people only feel pain and discomfort, while a few people will be severely allergic to the protein in the venom, and will have a fever, temporary blindness, vomiting, shock or even death.

If you are bitten by a red fire ant, don't take it lightly. If conditions permit, use soap or water to quickly clean the wound, and apply some allergy-relieving drugs such as steroids to reduce the pain and itching. However, if you have a fever or difficulty breathing, you must go to the hospital in time.

The content is compiled from China Science Expo Weibo, Beijing Science Center, People's Daily, Science Popularization China, China National Geographic, Gezhi Lundao Forum, and Global Science

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