11. There is also the concept of space curves of constant width, whose widths are defined by tangent planes . 12. These, for planes sufficiently close to the tangent plane , intersect the surface to make convex plane curves. 13. In turn the geodesic curvature determines how vectors in the tangent planes along the curve should rotate during parallel transport. 14. The North, East, Down ( NED ) coordinates allow this as an alternative to the ENU local tangent plane . 15. Conversely, given a curve on " S ", the tangent plane can be rolled along that curve. 16. Thus tangent planes along a curve can be identified using the intrinsic geometry, even when the surface itself is not parallelizable. 17. Hence " as straight as possible " can only mean " is a straight line " ( in the tangent plane ). 18. The tangent plane for the black hole is also now the tangent plane between the most upper point on the down quark. 19. The tangent plane for the black hole is also now the tangent plane between the most upper point on the down quark. 20. If a surface does not have a tangent plane at a point, it does not have a normal at that point either.
