News tagged with speed of light
Study finds single photons cannot exceed the speed of light
(PhysOrg.com) -- The rule that nothing can travel faster than the speed of light, c, is one of the most fundamental laws of nature. But since this speed limit has only been experimentally demonstrated for ...
Jun 24, 2011 |
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Researchers analyze the future of transistor-less magnonic logic circuits
(PhysOrg.com) -- As one of the newest research areas today, the field of magnonics is attracting researchers for many reasons, not the least being its possible role in the development of transistor-less logic ...
Jun 28, 2010 |
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Post-Quantum Correlations: Exploring the Limits of Quantum Nonlocality
(PhysOrg.com) -- When it comes to nonlocal correlations, some correlations are more nonlocal than others. As the subject of study for several decades, nonlocal correlations (for example, quantum entanglement) ...
May 07, 2009 |
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Physicists Propose Method for Entangling Moving Material Particles
(PhysOrg.com) -- When physicists experiment with quantum entanglement, they usually work with photons, the intangible particles of light. In the past few years, however, scientists have begun to broaden their ...
Jan 16, 2009 |
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First, fast, and faster
(Phys.org) -- Scientists in PML's Quantum Measurement Division have produced the first superluminal light pulses made by using a technique called four-wave mixing, creating two separate pulses whose peaks ...
Apr 06, 2012 |
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'Faster-than-light' particles fade after cross-check
Neutrinos do not go faster than light, according to fresh measurements of a test last year that had suggested the particles broke the Universe's speed limit, CERN said on Friday.
Mar 16, 2012 |
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First results from Daya Bay find new kind of neutrino transformation
The Daya Bay Reactor Neutrino Experiment, a multinational collaboration operating in the south of China, today reported the first results of its search for the last, most elusive piece of a long-standing puzzle: ...
Mar 08, 2012 |
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Computer simulations suggest graphynes may be even more useful than graphene
(PhysOrg.com) -- The past several years have seen a virtual explosion in the amount of research dedicated to graphene and as a result there has been a nearly constant stream of news pertaining to new discoveries ...
Nanotechnology / Nanomaterials
Mar 05, 2012 |
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Chandra finds fastest wind from stellar-mass black hole
Astronomers using NASA's Chandra X-ray Observatory have clocked the fastest wind yet discovered blowing off a disk around a stellar-mass black hole. This result has important implications for understanding ...
Feb 21, 2012 |
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Physicist creates scale model of LHC ATLAS experiment of out LEGO blocks
(PhysOrg.com) -- The Large Hadron Collider at the European Organization for Nuclear Research (CERN) in Switzerland has generated a lot of news of late, e.g. the announcement that a team had found what it believes ...
Dec 30, 2011 |
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Earth's outer core deprived of oxygen: study
The composition of the Earth's core remains a mystery. Scientists know that the liquid outer core consists mainly of iron, but it is believed that small amounts of some other elements are present as well. Oxygen ...
Space & Earth / Earth Sciences
Nov 23, 2011 |
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Scientists take fresh look at 'faster-than-light' experiment
Scientists who threw down the gauntlet to physics by reporting particles that broke the Universe's speed limit said on Friday they were revisiting their contested experiment.
Oct 28, 2011 |
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Exotic galaxy reveals tantalizing tale
(PhysOrg.com) -- A galaxy with a combination of characteristics never seen before is giving astronomers a tantalizing peek at processes they believe played key roles in the growth of galaxies and clusters ...
Aug 25, 2011 |
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A hint of Higgs: An update from the LHC
The physics world was abuzz with some tantalizing news a couple of weeks ago. At a meeting of the European Physical Society in Grenoble, France, physicists -- including some from Caltech -- announced that ...
Aug 16, 2011 |
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Scientists drag light by slowing it to speed of sound
(PhysOrg.com) -- Scientists at the University of Glasgow have, for the first time, been able to drag light by slowing it down to the speed of sound and sending it through a rotating crystal.
Jul 06, 2011 |
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Speed of light
The term speed of light generally refers to a fundamental physical constant of spacetime that limits the rate of transfer of matter or information. The speed of light is the speed of not just visible light, but of all electromagnetic radiation in vacuum (also called free space), and usually is denoted by the symbol c. Speeds faster than that of light are encountered in physics but, in all such cases, no matter or information is transmitted faster than c. The speed of light also plays a role in general relativity, and is believed to be the speed of gravitational waves.
In SI units, the magnitude of the speed of light in vacuum is exactly 299,792,458 metres per second (m/s) because of the way the metre is defined. More about this topic is found below in Speed of light set by definition.
For many practical purposes, the speed of light is so great that it can be regarded to travel instantaneously. An exception is where long distances or precise time measurements are involved. For example, in the Global Positioning System (GPS), a GPS receiver measures its distance to satellites based on how long it takes for a radio signal to arrive from the satellite. In astronomy, distances are often measured in light-years, the distance light travels in a year.
The speed of light when it passes through a transparent or translucent material medium, like glass or air, is less than its speed in vacuum. The speed is inversely proportional to the refractive index of the medium. In specially-prepared media, the speed can be tiny, or even zero.
For many years the speed of light was the subject of speculation, some believing it to be infinite. The first effective measurements of the speed of light were made in the seventeenth century, and these were progressively refined until, in 1983, the speed of light in vacuum was fixed by definition.
For more information about Speed of light, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
