At the end of a lecture on astronomy, describing how the planets orbit the Sun, a little old lady at the back of the room ...

An astrophysicist has shown that gravity may be able to exist without mass, a theory that suggests dark matter may not be necessary to explain phenomena observed in our universe. Dark matter is a ...

New findings suggest that ordinary sound has negative gravitational mass. This is an Inside Science story. (Inside Science) -- The sound of a sonic boom may produce about the same magnitude of ...

Most of the matter in our universe is invisible. We can measure the gravitational pull of this “dark matter” on the orbits of stars and galaxies. We can see the way it bends light around itself and ...