
I know that without the closed disk, a sphere with the a diameter deformation retracts onto the wedge sum of a circle and a sphere. But I can't figure out how to deform the disk to a suitable space....
Could anyone help me?

I know that without the closed disk, a sphere with the a diameter deformation retracts onto the wedge sum of a circle and a sphere. But I can't figure out how to deform the disk to a suitable space....
Could anyone help me?
An idea: "squeeze" the disk to the point $\;(0,0,0)\;$ , so that you get two tangent spheres joined at this point and with a "stick" (the line $\;\{(0,0,z)\;:\;-1\le z\le 1\}\;$) as common diameter through their tangency point...