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In some cases, the order of magnitude may be implied (usually 1), like a "second" or "year". In other cases, the quantity name implies the base unit, like "century". In most cases, the base unit is seconds or years. Prefixes are not usually used with a base unit of years. Therefore, it is said "a million years" instead of "a megayear".
The year, defined in the Gregorian calendar as 365.2425 days has to be adjusted with leap days and leap seconds. Consequently, these units are now all defined for scientific purposes as multiples of seconds. Units of time based on orders of magnitude of the second include the nanosecond and the millisecond.
The relative accuracy of such a time standard is currently on the order of 10 −15 [13] (corresponding to 1 second in approximately 30 million years). The smallest time step considered theoretically observable is called the Planck time , which is approximately 5.391×10 −44 seconds – many orders of magnitude below the resolution of current ...
A femtosecond is a unit of time in the International System of Units (SI) equal to 10 −15 or 1 ⁄ 1 000 000 000 000 000 of a second; that is, one quadrillionth, or one millionth of one billionth, of a second. [1] A femtosecond is to a second, as a second is to approximately 31.69 million years.
A leap year occurs every fourth year during which a leap day is intercalated into the month of February. The name "Leap Day" is applied to the added day. In astronomy, the Julian year is a unit of time defined as 365.25 days, each of exactly 86 400 seconds (SI base unit), totaling exactly 31,557,600 seconds in the Julian astronomical year. [3] [4]
Scientific notation always has a single nonzero digit to the left of the point: not 60.22 × 10 22, but 6.022 × 10 23. Engineering notation is similar, but with the exponent adjusted to a multiple of three: 602.2 × 10 21. Avoid mixing scientific and engineering notations: A 2.23 × 10 2 m 2 region covered by 234.0 × 10 6 grains of sand.
In scientific notation, it is written as 10 7. ... 31,622,400 = standard number of seconds in a leap year (omitting leap seconds) 31,640,625 = 5625 2 = 75 4;
An attosecond (abbreviated as as) is a unit of time in the International System of Units (SI) equal to 10 −18 or 1 ⁄ 1 000 000 000 000 000 000 (one quintillionth) of a second. [1] An attosecond is to a second, as a second is to approximately 31.69 billion years. [2]