This conceptual question really got me thinking but I'm not sure how I would explain it: Your friend has been studying physics. She tells you that because of Newton's Third Law, she exerts a force on the Earth opposite to the force that it exerts on her. this worries her a lot because she thinks that total force from all of the six billion people on the Earth will eventually push it out of orbit. Is she right - could this happen? Explain your answer using physics principle. Many thanks.