A Fifth Force (image) National Science Foundation Caption The long-range spin-spin interaction (blue wavy lines) in which the spin-sensitive detector on Earth's surface interacts with geoelectrons (red dots) deep in Earth's mantle. The arrows on the geoelectrons indicate their spin orientations, opposite that of Earth's magnetic field lines (white arcs). Illustration: Marc Airhart (University of Texas at Austin) and Steve Jacobsen (Northwestern University). Credit Marc Airhart, University of Texas at Austin, and Steve Jacobsen, Northwestern University. Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.