osram

The radius isn't an object affected by relativity. The radius is a line only in your imagination. The circle however is an object affected by relativity and will shrink when it's rotating (around a line perpendicular to the circle plane). When circumference is shrinking the radius will too... Which means it's still a circle, just a bit smaller.

http://mathworld.wolfram.com/PerpendicularBisector.html Well now I know what a perpendicular bisector means in swedish =). That was what I was trying to say in my post... Was confused when bloodhound didn't show the circles.

My english might be wrong but. A line from edge to edge. A circle with centre in one of the intersections (border-line) and another circle in the other intersection. A line between the intersections of the circles. That line shows the middle of the circle. Then just repeat but approx 90 degrees rotated to get the other middle line to create a cross. Not sure you understand and I think someone mentioned something like this. But as I said my english isn't too good.