Browse Definitions :
Definition

astronomical unit (AU)

An astronomical unit (AU) is the mean distance between the center of the Earth and the center of the sun. The actual distance varies depending on the time of year, because the Earth's orbit around the sun is not a perfect circle. The mean, or average, separation is approximately 1.4959787 x 10 11 meters, which is 1.4959787 x 10 8 kilometers or 9.2955807 x 10 7 miles.

Distances within the solar system are commonly measured in AU. Mercury, the innermost planet, orbits at a mean distance of about 0.4 AU from the sun, while Neptune, one of the most distant planets known, has an average orbital radius of about 30 AU. Interstellar and intergalactic distances are expressed in light-years or parsec s.

Interestingly, the Earth is closest to the Sun during the month of January, and farthest during July. The variation is about ±1 percent of the mean distance. Seasonal weather results from the tilt of the Earth's axis, and is not significantly affected by the distance of the planet from the sun.

Also see the Table of Physical Units and Constants.

This was last updated in January 2011
Networking
  • network traffic

    Network traffic is the amount of data that moves across a network during any given time.

  • dynamic and static

    In general, dynamic means 'energetic, capable of action and/or change, or forceful,' while static means 'stationary or fixed.'

  • MAC address (media access control address)

    A MAC address (media access control address) is a 12-digit hexadecimal number assigned to each device connected to the network.

Security
  • Evil Corp

    Evil Corp is an international cybercrime network that uses malicious software to steal money from victims' bank accounts and to ...

  • Trojan horse

    In computing, a Trojan horse is a program downloaded and installed on a computer that appears harmless, but is, in fact, ...

  • quantum key distribution (QKD)

    Quantum key distribution (QKD) is a secure communication method for exchanging encryption keys only known between shared parties.

CIO
  • green IT (green information technology)

    Green IT (green information technology) is the practice of creating and using environmentally sustainable computing.

  • benchmark

    A benchmark is a standard or point of reference people can use to measure something else.

  • spatial computing

    Spatial computing broadly characterizes the processes and tools used to capture, process and interact with 3D data.

HRSoftware
  • talent acquisition

    Talent acquisition is the strategic process employers use to analyze their long-term talent needs in the context of business ...

  • employee retention

    Employee retention is the organizational goal of keeping productive and talented workers and reducing turnover by fostering a ...

  • hybrid work model

    A hybrid work model is a workforce structure that includes employees who work remotely and those who work on site, in a company's...

Customer Experience
  • BOPIS (buy online, pick up in-store)

    BOPIS (buy online, pick up in-store) is a business model that allows consumers to shop and place orders online and then pick up ...

  • real-time analytics

    Real-time analytics is the use of data and related resources for analysis as soon as it enters the system.

  • database marketing

    Database marketing is a systematic approach to the gathering, consolidation and processing of consumer data.

Close