Astrophysics

Dark matter is as tangible as stars and planets to most astronomers. We routinely map it out. We conceive of galaxies as lumps of dark matter with dabs of luminous material. We understand the formation of cosmic structure, as well as the evolution...

For the third time in less than two years, physicists have detected billion-year-old ripples in the fabric of space-time. The new recording, like the two others before it, was made using the Laser Interferometer Gravitational-Wave Observatory (LIGO)...

What struck me was some regularity in the anomaly. The rotational velocities were not just larger than expected, they became constant with radius. Why? Sure, if there was dark matter, the speed of stars would be greater, but the rotation curves...