8 scientific cold knowledge you don't know, knowledge sharing, interesting and useful

8 scientific cold knowledge you don't know, knowledge sharing, interesting and useful
1. The pencil does not contain lead, why is it called a pencil?

It turns out that before modern pencil was invented, people used lead blocks for marking, which is also origin of pencil's name. Before 1564, people accidentally discovered graphite, which is main raw material for modern pencils. This substance has a high degree of color rendering and marks left are much darker than before. The name is also transferred.

2. Are fish thirsty even if they live in water?

In fact, freshwater and marine fish are different from each other. Freshwater fish have a higher concentration of salts in their blood than in surrounding water, and if they drink water, they are at risk of blood thinning. In order to maintain balance of salt and water in body, freshwater fish will not actively drink water. The blood of marine fish has a lower concentration of salts than surrounding water, so they are constantly at risk of dehydration, so they need to constantly drink water actively.

3. Why is Napoleon fish so prized?

The Napoleon fish is named for its high, raised forehead, reminiscent of Napoleon's hat, but it is expensive due to lack of production. The way this fish food is processed is also unique. Of course, price of this sashimi is also high, and you can't eat it without half a month's salary.

4. Why do some extinct species often reappear?

In fact, so-called extinction of species does not mean that they have completely disappeared from face of earth, but because professionals judge that they have disappeared, and basis for judgment is mainly based on conclusions drawn from relatively long-term observations. once. In other words, when professionals determine that a species is extinct, this means that this species has not been found for a long time. But environment of earth itself is also relatively complex. Man cannot penetrate into every corner, and there will always be places that we cannot discover. That is why we sometimes find individual extinct species reappearing on earth.

5. How is a total solar eclipse formed?

A solar eclipse is also called a solar eclipse. The moon moves between sun and earth. When all three are in a straight line, Moon blocks light from Sun to Earth, and figure behind Moon falls to Earth. A phenomenon that occurs. This phenomenon is seen by people standing on ground, in same way as sun gradually disappears, so people called it a solar eclipse.

6. Why is it said that a woman is stupid for three years after pregnancy?

Actually, just because we often talk about being pregnant for three years, it doesn't mean that women will actually become stupid, but that women's estrogen will change during pregnancy. Although these changes will not affect intelligence, but will affect thinking ability and memory of pregnant women, which will slow down reaction of pregnant women to surrounding objects. In addition, during period of raising a child, I often wake up in middle of the night and sleep poorly, rest poorly, which leads to a bad mental state, which leads to this situation. So, ladies and gentlemen, please rest.

7. How much electricity does China Tianyan use per second?

The China Sky Eye consumes 0.83 kWh of electricity per second to explore universe, and when running 24 hours a day, it needs 71,712 kWh of electricity. While power consumption is amazing, it is negligible compared to value it creates. At present, China Sky Eye has detected 102 pulsar signals that can be traced to 13.7 billion light years, and in future, China Sky Eye will undoubtedly generate more astronomical data and data, and it is no longer just an astronomical device. , more This is a symbol of national strength.

8. How does a pencil lead get stuck in wood?

The raw material for pen stem is mainly composed of graphite and clay. Firstly, they need to be mixed with water, and then put into a pressing, shaping and heating machine to make it into a long strip, and then cut it into pencil lead. Then cut logs into boards of a suitable size, and finally cut a groove for rod in center of template, put pen rod in middle and glue it with glue.

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