In your own words, explain why the direction along which the electromagnetic wave travels is not the same as the direction along which the changing magnetic field is applied.

Because in an em wave the electric and magnetic fields are both perpendicular to each other as well as to the direction of travel. There are other modes where this isn't true, but I have the feeling they aren't asking about these more complex cases here.

The wave your talking about from the sun or earth? The energy from the sun spreads out the waves, and from the earth it is a shield that protects from radiation. It is also due to negative and a positive field we have center.