The universe is expanding faster than physicists would expect. To figure out what processes underlie this fast expansion rate, some researchers are first trying to rule out what processes can’t.
Spiral galaxies like M100, pictured here, may hold answers about the nature of dark matter.
NASA Spitzer Space Telescope/NASA/JPL-Caltech
A comparison of star-forming galaxies suggests, surprisingly, that dark matter and visible matter do interact – taking us closer to understanding what keeps the galaxies together.