只有在平坦的宇宙中,空间才符合标准的几何规律——三角形的内角和精确地等于180度,平行线永远不相交。
Only in a flat universe does space obey all the standard geometry-class rules-the angles of a triangle add up to exactly 180 degrees and parallel lines never meet.
如果宇宙是“平坦”的,光束就会永远保持平行。
If the universe is "flat", the beams will always remain parallel.
如果密度正好等于临界密度,宇宙则是平坦的,但很可能仍然是无限的。
If the density just equals the critical density, the universe is flat, but still presumably infinite.
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