Physicists in Switzerland have taken the first peek inside atoms of antimatter. The new experiments, which probed antihydrogen atoms, show no sign that physical laws differ between this exotic matter and ordinary matter. The new observations set the stage for far more precise comparisons that researchers say will test the foundations of modern physics.
Prevailing theories hold that antihydrogen and hydrogen are identical except for having constituents with opposite electrical charges. An atom of antihydrogen comprises a positively charged positron–the antimatter twin of the electron–orbiting a negatively charged antiproton. Scientists made the first atoms of antihydrogen in the mid-1990s within an accelerator, but those particles moved too quickly to be closely studied.