Large number

Large numbers are numbers that are significantly larger than those ordinarily used in everyday life, for instance in simple counting or in monetary transactions. The term typically refers to large positive integers, or more generally, large positive real numbers, but it may also be used in other contexts.

Very large numbers often occur in fields such as mathematics, cosmology, cryptography, and statistical mechanics. Sometimes people refer to numbers as being "astronomically large". However, it is easy to mathematically define numbers that are much larger even than those used in astronomy.

Scientific notation was created to handle the wide range of values that occur in scientific study. 1.0 × 10⁹, for example, means one billion, a 1 followed by nine zeros: 1 000 000 000, and 1.0 × 10⁻⁹ means one billionth, or 0.000 000 001. Writing 10⁹ instead of nine zeros saves readers the effort and hazard of counting a long series of zeros to see how large the number is.

Examples of large numbers describing everyday real-world objects are:

Other large numbers, as regards length and time, are found in astronomy and cosmology. For example, the current Big Bang model suggests that the Universe is 13.8 billion years (4.355 × 10¹⁷ seconds) old, and that the observable universe is 93 billion light years across (8.8 × 10²⁶ metres), and contains about 5 × 10²² stars, organized into around 125 billion (1.25 × 10¹¹) galaxies, according to Hubble Space Telescope observations. There are about 10⁸⁰ atoms in the observable universe, by rough estimation.

According to Don Page, physicist at the University of Alberta, Canada, the longest finite time that has so far been explicitly calculated by any physicist is

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