Browse Definitions :
Definition

second (s or sec)

The second (abbreviation, s or sec) is the Standard International ( SI ) unit of time. One second is the time that elapses during 9,192,631,770 (9.192631770 x 10 9 ) cycles of the radiation produced by the transition between two levels of the cesium 133 atom.

There are other expressions for the second. It is the time required for an electromagnetic field to propagate 299,792,458 meters (2.99792458 x 10 8 m) through a vacuum. This figure is sometimes rounded to 3.00 x 10 8 m, or 300,000 kilometers (3.00 x 10 5 km). One second is equal to 1/86,400 of a mean solar day. This is easy to derive from the fact that there are 60 seconds in a minute, 60 minutes in an hour, and 24 hours in a mean solar day. This definition is, however, subject to limited accuracy because of irregularities in the earth's orbit around the sun.

Engineers and scientists often use smaller units than the second by attaching power-of-10 prefix multiplier s. One millisecond is 10 -3 s; one microsecond is 10 -6 s; one nanosecond is 10 -9 s; one picosecond is 10 -12 s. During these spans of time, respectively, an EM field propagates through a vacuum over distances of approximately 300 kilometers, 300 meters, 300 millimeters, and 300 micrometers.

The second is sometimes specified as a unit of angular measure, especially in astronomy and global positioning. In these contexts, it is also known as an arc second or a second of arc, and is equal to exactly 1/3600 of an angular degree or 1/1,296,000 of a circle. Sixty arc seconds comprise an arc minute; 60 arc minutes comprise an angular degree. One arc second of latitude at the earth's surface corresponds to a north-south distance of only about 31 m.

Also see Standard International ( SI ) System of Units and prefix multiplier s.

This was last updated in March 2011

Continue Reading About second (s or sec)

SearchCompliance

  • compliance risk

    Compliance risk is an organization's potential exposure to legal penalties, financial forfeiture and material loss, resulting ...

  • information governance

    Information governance is a holistic approach to managing corporate information by implementing processes, roles, controls and ...

  • enterprise document management (EDM)

    Enterprise document management (EDM) is a strategy for overseeing an organization's paper and electronic documents so they can be...

SearchSecurity

  • IPsec (Internet Protocol Security)

    IPsec (Internet Protocol Security) is a suite of protocols and algorithms for securing data transmitted over the internet or any ...

  • principle of least privilege (POLP)

    The principle of least privilege (POLP) is a concept in computer security that limits users' access rights to only what are ...

  • biometric authentication

    Biometric authentication is a security process that relies on the unique biological characteristics of individuals to verify they...

SearchHealthIT

SearchDisasterRecovery

  • risk mitigation

    Risk mitigation is a strategy to prepare for and lessen the effects of threats faced by a business.

  • call tree

    A call tree is a layered hierarchical communication model that is used to notify specific individuals of an event and coordinate ...

  • Disaster Recovery as a Service (DRaaS)

    Disaster recovery as a service (DRaaS) is the replication and hosting of physical or virtual servers by a third party to provide ...

SearchStorage

  • cloud storage

    Cloud storage is a service model in which data is transmitted and stored on remote storage systems, where it is maintained, ...

  • cloud testing

    Cloud testing is the process of using the cloud computing resources of a third-party service provider to test software ...

  • storage virtualization

    Storage virtualization is the pooling of physical storage from multiple storage devices into what appears to be a single storage ...

Close