ALPHA experiment at CERN observes the influence of gravity on antimatter

Isaac Newton's historic work on gravity was apparently inspired by watching an apple fall to the ground from a tree. But what about an "anti-apple" made of antimatter , would it fall in the same way if it existed? According to Albert Einstein's much-tested theory of general relativity, the modern theory of gravity, antimatter and matter should fall to Earth in the same way. But do they, or are there other long-range forces beyond gravity that affect their free fall? In a paper , the ALPHA collaboration at CERN's Antimatter Factory shows that, within the precision of their experiment, atoms of antihydrogen - a positron orbiting an antiproton - fall to Earth in the same way as their matter equivalents. "In physics, you don't really know something until you observe it," says ALPHA spokesperson Jeffrey Hangst. "This is the first direct experiment to actually observe a gravitational effect on the motion of antimatter. It's a milestone in the study of antimatter, which still mystifies us due to its apparent absence in the Universe." Gravity is the attractive force between any two objects with mass. It is by far the weakest of the four fundamental forces of nature.