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  • Imagine Alice has an idea,

  • and she wants to share it.

  • There are so many ways to share an idea.

  • She could draw a picture,

  • make an engraving, write a song,

  • send a telegraph,

  • or an email.

  • But how are these things different?

  • And more importantly,

  • why are they the same?

  • This story is about the fundamental particle

  • of all forms of communication.

  • It begins with a special skill

  • you likely take for granted --

  • language.

  • All language allows you to take a thought --

  • or mental object --

  • and break it down in a series of conceptual chunks.

  • These chunks are externalized

  • using a series of signals -- or 'symbols.'

  • Humans express themselves

  • using a variation in sound and physical action --

  • as do chirping birds --

  • and dancing bees --

  • and man-made machines,

  • exchanging a dancing stream of eletrical vibrations.

  • Even our bodies are built according to instructions

  • stored inside microscopic books -- known as 'DNA.'

  • All are different forms of one thing -- 'information.'

  • In simplest terms,

  • information is what allows one mind to influence another.

  • It`s based on the idea of communication as selection.

  • Information -- no matter the form --

  • can be measured using a fundamental unit --

  • in the same way we can measure

  • the mass of different objects -- using a standard measure --

  • such as kilograms or pounds.

  • This allows us to precisely measure and compare

  • the weight of, say, rocks, water, or wheat --

  • using a scale.

  • Information, too, can be measured and compared

  • using a measurement called 'entropy.'

  • Think of it as an information scale.

  • We intuitively know that a single page

  • from some unknown book

  • has less information than the entire book.

  • We can describe exactly how much

  • using a unit called the 'bit' --

  • a measure of surprise.

  • So, no matter how Alice wants to communicate

  • a specific message --

  • hieroglyphics, music, computer code --

  • each would contain the same number of bits,

  • though in different densities.

  • And a bit is linked to a very simple idea --

  • the answer to a yes-or-no question.

  • Think of it as the 'language of coins.'

  • So how is information actually measured?

  • Does information have a speed limit?

  • A maximum density?

  • Information theory holds the exciting answer to these questions.

  • It`s an idea over 3000 years in the making.

  • But before we can understand this,

  • we must step back --

  • and explore, perhaps, the most powerful invention

  • in human history --

  • the alphabet.

  • And for this, we return to the cave.

Imagine Alice has an idea,

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B1 information measure measured language idea alice

What is Information Theory? (Language of Coins: 1/16)

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    劉老 posted on 2013/08/12
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