Suppose you are on a spaceship of speed 0.8c and you flew horizontally above a circular stadium of radius 1km.what would be your calculated area of that stadium?

At rest: circle

A=πR²
Motion with v=0.8c
r=Rsqrt(1-β²)
=R(1-0.8²) =0.6R
Area of the ellipse
A₁=πRr=π0.6R² =0.6A