Timeline by Michael Crichton is a book about a group of archeological students who get the chance to not only study the past but experience it first hand. Edward Johnston, a professor of history that is leading a group of graduate students on an archeological dig on a medieval site in France. ITC, the company that sponsors the archeological site, summons him to the states to meet with them. He soon finds out that the company has developing a form of time travel secretly. Insisting on trying it out, he is sent back to the very site that he has been working on- six hundred years ago. After abandoning his machine the Professor becomes trapped in medieval France.
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While the professor is gone, the students find a startling document that disturbs them all. Only two words- help me on it. The document is in the professor's handwriting. Unable to explain it, the students contact ITC in hope of a reasonable explanation. They were told only to get four of their best archeologists together to come to ITC headquarters and that everything would be explained to them later.
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On the plane an ITC employee explains to the students that the professor has traveled back in time to medieval France and is trapped there. Their job is to travel back in time, rescue him and bring him back. .
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According to ITC time travel is based on quantum technology and the quantum theory. Physicist Max Planck concluded from his experiments energy wasn't a continuous wave, but composed of individual units. He called this energy, quanta. This was the beginning of quantum physics. Soon after, physicists realized that not only light, but all matter in the universe were made of particles. These particles are called quanta. The quantum theory explains how the particles behave. The theory is proven over and over. Basically it is the correct mathematical description of the universe.
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The technology ITC developed is based on the theory that there are an infinite number of universes existing side by side.