What material is in the airship?

When I was young, I lived in Seoul, Korea. There was airship in Seoul which advertise the electronic company Samsung. I'm not sure airship is still exist in Seoul because I moved to countryside when I was 8 years old. Every time I saw the airship I thought how airship can fly through the sky. At then, I thought inside of airship, there would be magic material that helps airship can fly. Actually, in today's airship, usually there is helium. Why helium? In the periodic table, helium and hydrogen are two lightest element. Because of helium's lighter weight, airship can fly. When airship is first invented, inside of airship, there was a hydrogen instead of helium. Hydrogen is explosive when there is a fire. May 6, 1937 in New Jersey, airship called zeppelin exploded. This airship was last airship that was filled with hydrogen. After this disaster, most of the airship was filled with helium.

"The Hindenburg Disaster." Airships The Hindenburg and Other Zeppelins RSS. N.p., n.d. Web. 15 Jan. 2014.

"Hydrogen vs Helium in Rigid Airship Operations." Airships The Hindenburg and Other Zeppelins RSS. N.p., n.d. Web. 15 Jan. 2014.

Types of Cloud

Today I'm going to talk about types of cloud. Cloud is made by water molecules and there is lots of types of clouds. Scientists classify the cloud based on height of cloud. There is 3 kinds of cloud. First one is high-level clouds. They form above 20,000feet and usually because of cold weather, water molecules freezes and formed a cloud. Second type of cloud is mid-level cloud. Mid-level clouds form between 6,500 ft to 20,000 feet. Because of their low altitude, a lot of mid-level clouds become the rain. If weather is cold enough, they can be changed in ice crystals and make snows. Last type of cloud is low-level clouds. Low-level clouds lie below 6,500 feet and it is the primary reason of raining. Also, if weather is cold enough to freeze them, it can be ice crystals and make snow also.

"National Weather Service Weather Forecast Office." Cloud Classification. N.p., n.d. Web. 07 Jan. 2014.

"Cloud Types:common Cloud Classifications." Cloud Types:common Cloud Classifications. N.p., n.d. Web. 07 Jan. 2014.