The Bit: A Yes or a No
Strip a message of all meaning and ask only this: how many yes-or-no questions does it take to pin it down? That count is its information, and its unit is the bit.
Fewer possibilities, less information
The amount of information in a message depends on how surprising it is before it arrives. “The sun rose” carries almost nothing. “It snowed in July” carries a lot. Surprise is just uncertainty resolved.
The currency of the field
Shannon’s insight was to separate information from meaning entirely. Meaning is for humans. Information is a measurable, countable thing — and it behaves like a physical quantity, with laws of its own.
Naming the unknown
Once you can count bits, you can measure uncertainty as a number. The bigger the set of possibilities, the more bits it takes to name one of them. That number has a name — and a formula — and it is the next chapter.