In the PBS science program Cosmos: A Personal Voyage, Episode 9: "The Lives of the Stars", astronomer and television personality Carl Sagan estimated that writing a googolplex in standard form (i.e., "10,000,000,000...") would be physically impossible, since doing so would require more space than the known universe provides.
An average book of 60 cubic inches can be printed with 5×105 zeroes (5 characters per word, 10 words per line, 25 lines per page, 400 pages), or 8.3×103 zeros per cubic inch. The observable (i.e. past light cone) universe contains 6×1083 cubic inches (4/3 × π × (14×109 light years in inches)3). This math implies that if the universe is stuffed with paper printed with 0s, it could contain only 5.3×1087 zeros—far short of a googol of zeros.
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