Some forces act across a gap. A magnet pulls iron and pushes or pulls another magnet without touching it. Rubbing can separate electric charge, and charged objects attract or repel each other from a distance. Like charges repel, unlike charges attract, and the force weakens as the distance grows. Scientists explain these forces with fields, maps of the force that surrounds an object and acts on another object at a distance. Gravity is a field too, and its pull grows with mass.