Description: 我們周圍的空氣每立方釐米含有大約 1000億億個分子。理想的真空應該是不含任何分子的區域。但實際上，如果一個區域內粒子比通常情況下少得多，我們就可以稱之為真空。“高真空 ”每立方釐米的粒子數只有通常的百萬分之一，而 “超高真空”每立方釐米的粒子數不到 10 億。外太空的大部分區域甚至比這還要空。平均而言，宇宙中普通物質粒子的密度不到每立方米一個。那些被天文學家認為密度相對較高的物質，如巨大的分子氣體雲，仍然比我們在地球上所能產生的任何真空更“空”。

Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher
The translation of this term and its definition is still awaiting approval

This is an automated transliteration of the simplified Chinese translation of this term

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