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In cosmology, a Hubble volume, or Hubble sphere, is a spherical region of the Universe surrounding an observer beyond which objects recede from that observer at a rate greater than the speed of light due to the expansion of the Universe. The Hubble volume is approximately 1031 cubic light years. The proper radius of a Hubble sphere (known as the Hubble radius or the Hubble length) is , where is the speed of light and is the Hubble constant. The surface of a Hubble sphere is called the ''microphysical horizon'', the ''Hubble surface'', or the ''Hubble limit''. More generally, the term "Hubble volume" can be applied to any region of space with a volume of order . However, the term is also frequently (but mistakenly) used as a synonym for the observable universe; the latter is larger than the Hubble volume.〔For a discussion of why objects that are outside the Earth's Hubble sphere can be seen from Earth, see 〕〔For an example of mistaken usage, see 〕 ==Relationship to age of the universe== The Hubble length is 14 billion light years in the standard cosmological model, somewhat larger than times the age of the universe, 13.8 billion years. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hubble volume」の詳細全文を読む スポンサード リンク
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