Browse Definitions :
Definition

Earth's mean orbital speed

Earth's mean orbital speed is the average speed at which the Earth revolves around the sun. This is defined in two different ways, based on the sidereal year and the tropical year.

The sidereal year is the time it takes for the Earth to revolve once around the sun with respect to the distant stars. This is approximately 365.2564 mean solar days, or 3.155815 x 107 seconds (s). The tropical year is the time it takes for the Earth to revolve once around the sun, as measured between two consecutive March equinoxes. This is about 365.2422 mean solar days, or 3.155693 x 107 s.

The circumference of the Earth's orbit is approximately 2 pi (6.283185) times the mean radius of its orbit. This radius is also known as the astronomical unit (AU), and is about 1.4959787 x 1011 meters (m). Therefore, the circumference is about 9.399511 x 1011 m. The Earth's mean orbital speed, in meters per second (m/s), is obtained by dividing this number by the length of the year in seconds. This can result in either of two figures.

Let vs be the Earth's mean orbital speed as defined based on the sidereal year. This speed is:

vs = (9.399511 x 1011) / (3.155815 x 107)
= 2.978473 x 104 m/s

Let vt be the Earth's mean orbital speed as defined based on the tropical year. This is:

vt = (9.399511 x 1011) / (3.155693 x 107)
= 2.978589 x 104 m/s

A rough, general figure for the Earth's mean orbital speed is 30 kilometers per second (km/s), or 18½ miles per second (mi/s).

Also see the Table of Physical Units and Constants.

This was last updated in September 2005
SearchCompliance
  • ISO 31000 Risk Management

    The ISO 31000 Risk Management framework is an international standard that provides businesses with guidelines and principles for ...

  • pure risk

    Pure risk refers to risks that are beyond human control and result in a loss or no loss with no possibility of financial gain.

  • risk reporting

    Risk reporting is a method of identifying risks tied to or potentially impacting an organization's business processes.

SearchSecurity
  • biometric payment

    Biometric payment is a point-of-sale (POS) technology that uses biometric authentication physical characteristics to identify the...

  • Melissa virus

    Melissa was a type of email virus that initially become an issue in early 1999.

  • Twofish

    Twofish is a symmetric-key block cipher with a block size of 128 bits and variable-length key of size 128, 192 or 256 bits.

SearchHealthIT
SearchDisasterRecovery
  • What is risk mitigation?

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

  • fault-tolerant

    Fault-tolerant technology is a capability of a computer system, electronic system or network to deliver uninterrupted service, ...

  • synchronous replication

    Synchronous replication is the process of copying data over a storage area network, local area network or wide area network so ...

SearchStorage
  • hard disk drive (HDD)

    A computer hard disk drive (HDD) is a non-volatile data storage device.

  • Remote Direct Memory Access (RDMA)

    Remote Direct Memory Access (RDMA) is a technology that enables two networked computers to exchange data in main memory without ...

  • storage (computer storage)

    Data storage is the collective methods and technologies that capture and retain digital information on electromagnetic, optical ...

Close