Spacecraft can be launched anytime to travel from one planet to another. Spacecraft are not affected by the sun. Motion relative to Earth is same as motion relative to the sun. Jets can fly in space. Spacecraft in orbit about Earth don't follow a sinusoidal path relative to the sun.
Black holes are big.
Light always travels in straight lines. Black holes exert a greater gravitational force on distant objects than the star from which it was formed. Observations made in a gravitational field are different that those made in a system undergoing constant acceleration. Things in space make sounds. If the Sun were to become a black hole, the Earth would get sucked into it.