Engineering

A gnu way to control room temperature

Heating, ventilation, and air conditioning systems—called HVAC systems—can be a delicate balance. There are many factors to consider, from air flow between rooms to the effect of human body heat. In the past decade, researchers ...

Energy & Green Tech

At 50, Europe's oldest nuclear plant not ready to retire

Europe's oldest functioning nuclear reactor, at Switzerland's Beznau plant, will turn 50 next week—a lifespan deemed dangerously long by environmentalists who are demanding that it be shut down immediately.

Energy & Green Tech

Suitable energy mix for smaller communities

Solar thermal, geothermal, photovoltaic—what form of energy supply is most suitable for a particular municipality? Representatives of smaller communities are overwhelmed by a huge amount of information, which tends to exacerbate ...

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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