How is matter different from mass? These and other questions about the deepest levels of physics, answered inside.

How do you weigh one of the largest objects in the entire universe? Very carefully, according to new research.

NASA's James Webb Space Telescope recently zeroed in on the Bullet Cluster—delivering highly detailed images that show a ...

Scientists believe dark matter must exist to account for astronomical observations that suggest an unidentified source of mass in the cosmos. Dark matter has evaded a wide variety of detection ...

For ordinary matter, momentum is given by the formula P = mv, where P is momentum, m is mass, and v is velocity. Even tiny amounts of matter can have vast amounts of momentum if the matter is ...