The value `r` above is off by a factor of 10^9. It should be 0.5 AU or 7.48x10^10 meters: http://www.wolframalpha.com/input/?i=distance+between+Mars+and+Earth

The value `r` above is off by a factor of 10^9. It should be 0.5 AU or 7.48x10^10 meters: http://www.wolframalpha.com/input/?i=distance+between+Mars+and+Earth http://www.wolframalpha.com/input/?i=distance+between+Mars+a... The current gravitational force between Mars and Earth is 2.832x10^15 N: http://www.wolframalpha.com/input/?i=(gravitational+constant)+*+(mass+of+Earth)+*+(mass+of+Mars)+%2F+(distance+between+Earth+and+Mars)%5E2 http://www.wolframalpha.com/input/?i=(gravitational+constant... For comparison, the current gravitational force between the Sun and Earth is 3.614x10^22 N: https://www.wolframalpha.com/input/?i=(gravitational+constant)+*+(mass+of+Sun)+*+(mass+of+Earth)+%2F+(distance+between+Sun+and+Earth)%5E2 https://www.wolframalpha.com/input/?i=(gravitational+constan... P.S. My favorite Wolfram Alpha feature is being able to use natural language descriptions of various quantities!