A rare galaxy type, polar ring galaxies have a substantial population of stars, gas, and dust orbiting in rings nearly perpendicular to the plane of the galactic disk.

极环星系是种稀有的星系类型，它们有着几乎和银盘平面垂直，呈环形公转的大量的恒星、气体和星尘。

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Now, if it's perpendicular to the plane, then in that case, it's perpendicular to the blackboard.

如果它垂直于这个平面，在那个例子里，它垂直于黑板。

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Being perpendicular to the surface means that you are perpendicular to its tangent plane.

垂直于曲面也意味着垂直于它的切平面，垂直于曲面也意味着垂直于它的切平面。

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This is a special type of Earth model which traces its idealised "horizontal" surface - the plane on which, at any point, the pull of gravity is perpendicular to it.

BBC: Europe's Goce satellite probes Earth's gravity