Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Interesting, but ends without a satisfactory explanation..

It was a good book, but the ending kind of slowed down and wasn't nearly as good as the first two thirds of it.. He ended up with this weird "chicken and egg" scenario that didn't quite wrap up his ideas in my opinion.His idea that man in the not too distant future could have developed a way to send massive machines back 4.6 billion years to take material from the young Earth, then build a moon from it in orbit, doesn't reconcile easily.If our moon, being the size it is and distance it is, was required for "life" to arise on Earth.. Then how did life come into being, and eventually allow humans to evolve, that would one day send machines back to build it? If the moon was required for life to happen, then there would be no man if there was no moon, since there would be no man to create the moon, since there was no moon?I know.. I'm still trying to wrap my head around it too. I am curious if the Moon might really be hollow though..