If the universe's space-time is positively curved, like the surface of a sphere, parallel beams would come together.
如果宇宙的时空像球体表面一样正向弯曲，平行的光线就会交合在一起。
A two-dimensional model of such a universe would look like a sphere. It's impossible to have parallel geodesics (straight lines on a curved surface) — the two lines will cross at some point.
这样的2维宇宙模型就像是球体，不可能出现平行的测地线(测地线是曲面上的直线)——两直线必然在某点相交。
The parallel milling is adopted to curved surface NC machining. The row spacing has an effect on surface roughness of workpiece.
采用平行铣削对曲面进行数控加工时，行距对工件的表面粗糙度有一定的影响。
The parallel milling is adopted to curved surface NC machining. The row spacing has an effect on surface roughness of workpiece.
采用平行铣削对曲面进行数控加工时，行距对工件的表面粗糙度有一定的影响。
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