Fresnel help

Hi all, I’m doing the cliché earth scene in blender and came across something that I just cant figure out.
Fresnel (being used for transparency), is there any way to reverse the effects? I’ll explain. With fresnel it fades the middle area of a sphere leaving the edge solid. Brilliant. But is there a way to reverse it and keep the middle solid and have the fresnel fade to transparent?

I know this won’t help my earth animation, but it’d be good to know.