(Phys.org)—One of the first observations suggesting the existence of an invisible dark matter came in 1933 when astronomer Fritz Zwicky noticed that galaxy clusters were more energetic than they ...

The equivalence principle is one of the more fascinating ideas in modern science. It asserts that gravitational mass and inertial mass are identical. Einstein put it like this: the gravitational force ...

Physicists report that electrons in semiconductor crystals have a negative inertial mass when strongly accelerated in an electric field. Physicists of the Max Born Institute in Berlin report in the ...

I've been trying to explain quantum physics, forces, relativity, and space-time to my kid and we had a question that I'm finding difficult to find a solid answer to. Background you can skip if you ...

Moment of inertia is an important parameter when sizing and selecting a linear system. But it’s critical to know which type of inertia—planar moment of inertia or mass moment of inertia—is given and ...

Antimatter is anti- a lot of things, but it’s not supposed to be antigravity. An antimatter particle does have the opposite electric charge of its ordinary matter counterpart. But the mass of both ...

At the heart of Einstein’s theory of gravity (general relativity) is the equivalence principle. The equivalence principle says that there is no difference between being stationary and subject to ...