[Math] Vector field on $S^2$ with exactly one zero

differential-topologyvector-bundles

My homework problem is to construct a vector field on sphere (and torus, but I guess I will be able to extend the idea if I figure out it for sphere) with exactly one zero. I don't know how to approach this so I'm asking for any explanation.
(Btw, this problem is from problemsheet on index of a vector fields, but I doubt that index would help somehow)

Best Answer

Hint Puncturing the sphere $\Bbb S^2$ at a point, say, $N$, leaves the space $\Bbb S^2 - \{N\} \cong \Bbb R^2$; we can make this identification explicit, e.g., with stereographic projection from the point $N$. Now, $\Bbb R^2$ admits plenty of vector fields that vanish nowhere, and some of them can be used (via that identification) to construct a vector field on $\Bbb S^2$ that vanishes only at $N$.

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