Attosecond

An attosecond is 1×10−18 of a second (one quintillionth of a second). For context, an attosecond is to a second what a second is to about 31.71 billion years.
The word "attosecond" is formed by the prefix "atto" and the unit "second". "Atto-" was derived from the Danish word for eighteen ("atten"). Its symbol is as.
An attosecond is equal to 1000 zeptoseconds, or of a femtosecond. Because the next higher SI unit for time is the femtosecond (10−15 seconds), durations of 10−17 s and 10−16 s will typically be expressed as tens or hundreds of attoseconds:
Times which can be expressed in attoseconds: