The idea that Earth is a magnet is far from new. It was first proposed in 1600 by a British physician named William Gilbert. Knowing it acts like a magnet is one thing. Knowing why it acts like a magnet is more difficult. In fact, finding out why is a fairly recent discovery. To find out why required new technology. It was the seismograph that made it possible to learn why the Earth acted like a magnet. Seismograph are used to study earthquakes. By studying earthquake waves they were able to learn about Earths interior. They discovered that Earth has an inner and outer core. The outer core consists of liquid metals, mainly iron and nickel. Scientists think that Earths magnetic field is generated here. It is caused by the motion of this liquid metal. The liquid metal moves as Earth spins on its axis.

Question: "Why was William Gilbert unable to explain prove theory that the Earth acts like a magnet in 1600?"

Answer: "There was no appropriate technology"

Response: yes

The digestive system is the body system that digests food. It digest food in two ways, mechanically and chemically. Both help in the process of turning food into nutrients. The digestive system also eliminates solid food waste. The major organs of the digestive system include the mouth, esophagus, stomach, and small and large in- testines. These organs all work together to help you gain energy from the food you eat. Digestion starts in the mouth. When food is swallowed, it travels through the esophagus to the stomach. In the stomach, digestion continues and a small amount of absorption of nutrients takes place. Most chemical digestion and nearly all absorption of nutrients take place in the small intestine. This organ consists of three parts: duodenum, jejunum, and ileum. The large intestine is the last stop in the digestive system. This is where water is absorbed. The food not digested is released as waste.

Question: "What are the three parts of the small intestine?"

Answer: "The duodenum, the jejunum, the ileum"

Response: yes

Mechanical energy is a combination of the energy of motion or position. This type of energy describes objects that are moving or could move. A moving ball can have energy from motion. An arrow can also have the energy of motion. Both are types of mechanical energy. Can you think of some other examples? Where does the energy of motion come from? It comes from the energy created by position. This energy is stored energy. This means it is not moving yet, but it has the potential to move. How can you store energy? The arrow gains energy from the drawn bow. As the arrow is released, the bow releases its stored energy and puts the arrow into motion. Can you think of some other ways to store energy using position?

Question: "What does stored energy have the potential to do?"

Answer: "It has potential to gain energy"

Response: no

Right after the Pentagon was hit, NEADS learned of another possible hijacked aircraft. It was an aircraft that in fact had not been hijacked at all. After the second World Trade Center crash, Boston Center managers recognized that both aircraft were transcontinental 767 jetliners that had departed Logan Airport. Remembering the "we have some planes" remark, Boston Center guessed that Delta 1989 might also be hijacked. Boston Center called NEADS at 9:41 and identified Delta 1989, a 767 jet that had left Logan Airport for Las Vegas, as a possible hijack. NEADS warned the FAA's Cleveland Center to watch Delta 1989. The Command Center and FAA headquarters watched it too. During the course of the morning, there were multiple erroneous reports of hijacked aircraft. The report of American 11 heading south was the first; Delta 1989 was the second. NEADS never lost track of Delta 1989, and even ordered fighter aircraft from Ohio and Michigan to intercept it. The flight never turned off its transponder. NEADS soon learned that the aircraft was not hijacked, and tracked Delta 1989 as it reversed course over Toledo, headed east, and landed in Cleveland. But another aircraft was heading toward Washington, an aircraft about which NORAD had heard nothing: United 93. United Airlines Flight 93 FAA Awareness. At 9:27, after having been in the air for 45 minutes, United 93 acknowledged a transmission from the Cleveland Center controller. This was the last normal contact the FAA had with the flight. Less than a minute later, the Cleveland controller and the pilots of aircraft in the vicinity heard "a radio transmission of unintelligible sounds of possible screaming or a struggle from an unknown origin." The controller responded, seconds later: "Somebody call Cleveland?"This was followed by a second radio transmission, with sounds of screaming.

Question: "Which buildings that were hit by aircraft?"

Answer: "World Trade Center"

Response:
yes