There is no such thing (AFAIK). There is "intellectual property", but ideas can't be that - a particular implementation of an idea can be copyrighted or even patented.
Asking for $25 mln for an idea of adding sky is ridiculous in any case - even if he is right, can he prove that Google made so much money from that idea? Chances are very good that Google Earth is a loss leader anyway without any hope to be ever profitable, and even if it is then this Sky idea surely does not contribute that much.
In the UK such a lawsuit won't make it far.