Ellipsoid from Circular Cross Sections

The ellipsoid above is made from circles slipped together. (The perspective of the photo makes them look like ellipses, but they are circles.) This model folds flat.

Steps

1. Cut out the circles from card stock.
   
2. Cut a very narrow slot along the lines. You should try to remove a narrow strip of material. If you don't, it will be harder to put the model together, the cross sections might warp and the model won't flex easily.
   
3. Slip the circles together starting from the inside working out. Viewed from above, the circles make the grid shown. Use this grid to determine the placement of each circle.
   

Notes

• This model illustrates the circular cross sections of this ellipsoid.
  

References

• (Cundy and Rollett 1961, 173-5) (Hilbert 1952, 18-9)(Peterson 1999)