In the 2nd installment of the what if series What would the world be like without us? In this video, Neil takes you through a scenario. What do you wonder about? 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).