The beatles are highly respected as musicians because they

They pioneered their own genre of music and their oeuvre has some seriously contrasting extremes, with 'Please Please Me' at one extreme and 'I Am The Walrus' at the other. Not only that, but they managed to produce bestselling hits for a decade. And after their career together, they managed to create successful solo careers, especially McCartney and Lennon.

This is all you, but i can give you some topics that you could try. if it rained when you want to do something outdoors, it 'limits' that human activity. maybe you want to do an experiment that goes throughout the whole year and you have to have above freezing the entire year. this 'limits' your activity. i thought of those just off of the top of my head. something that gets to me that might be getting to you is you are thinking too hard about what to do. think simply, and if it is too simple, then bump it up just a little bit.

Answer( solar wind );