The issue here is that your pattern space needs to be translated and scaled so that the [0,1] range fits the object you’re applying it to. If your sphere has radius 1, and is centered at (0,0), then the pattern (by default) will be covering [-1, 1] (from -x to +x), which means the gradient will be doubled (running once from [-1,0] and again from [0,1]). If you scale the pattern space by 2 (so the gradient runs from [0,2]) and then translate it by -x (so it runs from [-1,1]), it should look more like what you’re expecting.
Hopefully that helps! If you’d like me to restate/clarify anything, let me know.