The 3rd installment of the what if series. Add your "What If" scenarios here, and the producers of NOVA scienceNOW might have Neil act out the answers.

To see more "what if" please go to our Cosmic Perspective page on our website. http://www.pbs.org/wgbh/nova/sciencenow/

Watch NOVA scienceNOW on Super Science Tuesdays on PBS (please check local listings).