CEBAF turns on the charm

The world's most advanced particle accelerator for investigating the quark structure of the atom's nucleus has just charmed physicists with a new capability. The production of charm quarks in J/ψ (J/psi) particles by CEBAF ...

Demonstrating a weak topological insulator in bismuth iodide

Topological insulators are one of the most exciting discoveries of the 21st century. They can be simply described as materials that conduct electricity on their surface or edge, but are insulating in their interior bulk. ...

Four questions: Here there be monsters

On April 10, the world got to see the first image taken of a black hole in space, taken by the Event Horizon Telescope, a worldwide collaboration of astronomers and astrophysicists including a substantial team at the University ...

Striking a balance between climate action and social equality

At a referendum held in February, residents of Freiburg im Breisgau voted in favour of building a site in their city that will combine environmental and societal targets. The plan is supported by ICLEI – Local Governments ...

Building a better turbine

Imagine a world in which half of our electricity is generated renewably by offshore wind farms. Now imagine a powerful hurricane hitting the coast where that farm is located. If developers, engineers and policy makers haven't ...

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Energy

In physics, energy (from the Greek ἐνέργεια - energeia, "activity, operation", from ἐνεργός - energos, "active, working") is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law. Different forms of energy include kinetic, potential, thermal, gravitational, sound, light, elastic, and electromagnetic energy. The forms of energy are often named after a related force.

Any form of energy can be transformed into another form, but the total energy always remains the same. This principle, the conservation of energy, was first postulated in the early 19th century, and applies to any isolated system. According to Noether's theorem, the conservation of energy is a consequence of the fact that the laws of physics do not change over time.

Although the total energy of a system does not change with time, its value may depend on the frame of reference. For example, a seated passenger in a moving airplane has zero kinetic energy relative to the airplane, but non-zero kinetic energy relative to the Earth.

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