We always hear of seeing a spinning object. Not rocket shape with flames coming out like space craft we use for propulsion.
What if they have found how to control magnetism, hence a spinning electro magnet space ship that they can switch the poles to attract and repel from any given larger object.
Like any two magnets, like poles repel and opposite pole attract with no known energy required.
Only need power to rotate their craft to be an electro magnet.
When we earthlings go into other space, are we not aliens?
