# Attosecond

SI unit of time

An attosecond (as) is a very short period of time. It is equal to one quintillionth of a second (or 0.000000000000000001 seconds). It can also be written as 10−18 seconds. Because it can be hard to think about how short this period of time is, on this page is a list of descriptions of periods of time longer than 1 attosecond, but shorter than one femtosecond (which is 10−15 seconds). This should help when thinking about periods of time that have different orders of magnitude.

Here is a list of time spans shorter than 1 attosecond:

• 10−21 seconds = 1 zeptosecond
• 10−24 seconds = 1 yoctosecond
• 10−27 seconds = 1 xonosecond
• 10−30 seconds = 1 vecosecond
• 10−33 seconds = 1 mecosecond
• 10−36 seconds = 1 duecosecond
• 10−39 seconds = 1 trecosecond
• 10−42 seconds = 1 tetrecosecond
• 10−45 seconds = 1 pentecosecond
• 10−48 seconds = 1 hexecosecond
• 1 attosecond: It takes 1 attosecond for light to travel the length of three hydrogen atoms.
• 1 attosecond: It takes 1 attosecond for an atomic nucleus to react when another particle hits it.
• 150 attoseconds: It takes 150 attoseconds for an electron to circle the nucleus of an atom.
• 320 attoseconds: It takes about 300 attoseconds for an electron to jump from one atom to another.