The History of China : Ancient Seismograph

This is the world's first seismograph. It was invented by Zhang Heng and its name is Didong Yi. Today only replica of it remains.

First, I want to tell you about the principle of the seismograph. We have to fix the pen on the pendulum which hangs in the air. Then we should put the paper(rotating drum) under the pen. If the earthquake occurs, the pen doesn't move but rotating drum moves. So the pen can record a seismic wave.

Second, I want to talk about its principle. It was an urn-like instrument with a central pendulum. An earth tremor would cause the pendulum to loose balance and activate a set of levers inside. Then, one of the eight dragons which are placed in eight directions outside the urn would release a bronze ball in its mouth. The ball would fall into the mouth of a toad and give off a sound. So people can notice that the earthquake will happen soon.

Third, why did Zhang Heng invent this seismography? At that time, people believed earthquake as signs of heaven. So, person who expect the earthquake rightly, he can get immortal fame.

Sources : http://100.naver.com/100.nhn?docid=142932

http://www.china.org.cn/english/scitech/131762.htm

http://earthquake.usgs.gov/learn/glossary/?termID=167

Chainwriting : The Aliens are Starving

Once upon a time, aliens arrived on the earth to find something to eat. But the earth was very different from where they had lived. So they didn't know how to eat or what to eat. At that time, humans who was living in the earth didn't know about fire. Because of the cold weather, aliens went into the cave to hide and to find some food. In the cave, aliens met humans. Aliens and humans all fainted looking at each others. Then, they woke up few hours later. They started to talking about their problems. Aliens said that they couldn't distinguish what to eat, so they were starving. Humans said that they had a big trouble with wild animals. Humans were very weak, so they couldn't save themselves. Suddenly alien got a good idea. They sad, "Let's make an agreement about symbiotic relationship." Humans agreed with their opinion and their agreement was succeed finally. After agreement, they lived together.

3 Things About me

1. I have older brother who is older than me 4 years old.
2. I have two puppies which are very cute.
3. I like Harry Potter series more than Twilight series.