I have a Norway (Ithink) maple that is about four years old and about 15-20 ft. tall. I would like to move it about 50 feet. Can I? How

That's a pretty tall tree to be moving. The root system reaches out to the tips of the branches. To dig this up, you'd have to size the root ball to make it moveable and I don't know if that would take away too much of the roots.

I suppose any tree service in your area could advise you on the pros and cons of moving a tree of this size.

Would it not be easier to plant another one and wait the four years? :)