Suppose that we have Galois covering $$X\longrightarrow P^{1}_{\mathbb{Q}}$$ defined over the rationals which is cyclic, in the sense that the Galois group associated to the covering is a cyclic group. 
Then $X$ can not be $P^{1}_\mathbb{Q}$. I read this result somewhere. Is this result true? I tried this over the complex numbers and I found that over complex numbers it is true:

$P^{1}_{\mathbb{C}} \longrightarrow P^{1}_{\mathbb{C}}$ defined by $z$ going to $z^{n}$.