No idea what you're saying here.
Again, not sure what you're saying here
-Jeff
Or tying yourself in knots because you are stuck with a poor design?
It may be that he's doing it this way on purpose--showing you the icky approach first so that you'll appreciate the more OO approach when he has you do it again that way. If so, then I would call that acceptable. If he's actually teaching this as the right way to store and manipulate data though, then I'd take anything he teaches with a grain of salt.
It can be done using parallel arrays. When you're sorting, you have to make sure that every change you make to one array gets made to all of them. So if you swap planets[2] with planets[3], then you also have to swap diameters[2] with diameters[3] and lengths[2] with lengths[3].
Not lazy; parallel arrays require much more work than a proper object‑oriented solution. You have to follow all your parallel arrays; if you sort array1, you have to duplicate all changes exactly in array2, array3, etc. That is error‑prone, and there is a risk of your missing out a change somewhere. Sorting a Planet[] array means you sort one array, and all the data for each Planet object stay together in that object.