According to the theory of general relativity, a galaxy must have a certain amount of mass to be held together by gravity.

His idea: gravity can exist without any mass at all. The study explores a different solution to the same equations that normally describe gravity—both in Newtonian theory and in general relativity.

The electromagnetic force rules objects with excess charge (like electrons, protons, and socks shuffling over a fuzzy carpet), and gravity steers objects with mass. The first three forces largely ...

Despite keeping us grounded and warping light that travels through space, gravity is actually quite a weak force. The smaller the mass, the less gravity appears to have any pull, until at quantum ...

Let's start with a definition. Gravity, or gravitational attraction, is the tendency of mass to gather toward itself, drifting together even across great distances due to curvature in spacetime.

As gravitational force fundamentally involves the warping of space-time itself, it enables all objects to interact with each other, whether they have mass or not. Massless photons, for example ...

A new paper proposes an alternative hypothesis, showing how gravity could exist without mass and produce many of the same effects we ascribe to dark matter. Einstein’s theory of general ...

Slowly these became the planets. Some newly formed planets had a large enough mass, and with it, a large gravitational force, to pull on and capture smaller objects that were moving past them. These ...