The reason is so-called dark matter, the hidden stuffthat makes up more than 80 per cent of the mass of the universe.

原因在于所谓的暗物质，这种隐藏的物质占了宇宙质量的80%以上。

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If the dark matter is made mostly of MACHOs, then it is likely that baryonic matter does make up most of the mass of the universe.

如果暗物质主要由大孩子组成，那么就有可能重子物质确实组成了我们宇宙的大部分物质。

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Our findings suggest that as much as 90 percent of the mass of the universe is not radiating at any wavelength with enough intensity to be detected on the Earth.

我们的研究结果表明占宇宙质量90%的物质不能发出可从地球上观测到的光。

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In fact, there's a property of gravitational fields anywhere, even in outer space, but there is some residual field between all the planets and all the stars in the universe, that the force on a body is proportional to the mass of the body.

实际上,这是任何地方的引力场都具备的属性,甚至是在外太空,在所有的行星和恒星之间,存在着某种剩余场,在这个场里作用在物体上的力,和物体的质量之间存在比例关系

耶鲁公开课 - 基础物理课程节选

Dark matter comprises slightly more than 80% of the mass of the universe.

FORBES: Mapping The Universe Through Collective Brainpower

Perhaps a more upbeat story is the news that in about two weeks, a scientific paper could provide the first evidence of dark matter -- the mysterious substance said to account for much of the mass of the universe.

ENGADGET: Alt-week 2.24.13: Mapping the brain, discovering dark matter and our inevitable, grizzly end

There also is a significant difference between what physicists believe should be the total amount of mass in the universe and what they have observed so far.

ENGADGET: AMS detects excess of positrons, could suggest existence of dark matter