Speed of light: Difference between revisions
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<onlyinclude>The '''speed of light''', almost always written as ''c'' (for celerity, an archaic term for swiftness of motion), is a | [[File:Speedoflight.jpg|thumb|The speed of light, c, is constant in a vacuum.]] | ||
<onlyinclude>The '''speed of light''', almost always written as ''c'' (for celerity, an archaic term for swiftness of motion), is the constant value for velocity of a [[photon]] (packets of [[light]]) in a [[vacuum]]. It is a strange consequence of Einstein's theory of [http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/relcon.html relativity] and has been measured to be 299 792 458 meters per second. <ref>BIPM. (2006). "The "explicit-constant" formulation", [Online], Avaliable: https://web.archive.org/web/20140811195806/http://www.bipm.org/en/si/new_si/explicit_constant.html</ref> </onlyinclude> Einstein's theories also led to the rather surprising consequence that [[mass]] and [[energy]] are related by the speed of light in what has become the most famous equation in physics: | |||
<math> E = mc^{2} </math> | <math> E = mc^{2} </math> | ||
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*''m'' is mass (often a mass difference, for example in [[nuclear fission|nuclear reaction]]s) | *''m'' is mass (often a mass difference, for example in [[nuclear fission|nuclear reaction]]s) | ||
*''c'' is the speed of light. | *''c'' is the speed of light. | ||
Light travels extremely fast. But, on a galactic scale, light still takes a very long time to reach observers. | |||
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<iframe width="560" height="315" src="https://www.youtube.com/embed/nQUwHdSAhmw" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe> | |||
</html> | |||
To learn more about the speed of light and its strange effects please see [http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/relcon.html hyperphysics], for the equation <math> E = mc^{2} </math> specifically please see the hyperphysics article on [http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/releng.html#c1 relativity]. | To learn more about the speed of light and its strange effects please see [http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/relcon.html hyperphysics], for the equation <math> E = mc^{2} </math> specifically please see the hyperphysics article on [http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/releng.html#c1 relativity]. | ||
==Mass Defect and Nuclear Decay== | |||
Mass defect is the difference between the measured and calculated mass of the nucleus. By Einstein's energy-mass equivalence equation, "missing" mass is accounted for by considering any mass converted into energy during the formation of the atom. This principle also exists in nuclear decay. There is a slight difference in mass before and after an isotope decays and any difference was simply converted into energy. This phenomenon proves especially useful because we can then harness this energy for electricity production, such as is done in [[nuclear power]] plants. | |||
==For Further Reading== | |||
For further information please see the related pages below: | |||
* [[Radioactivity]] | |||
* [[Energy]] | |||
* [[Isotope]] | |||
* [[Mass]] | |||
* Or explore a [[Special:Random|random page]] | |||
==References== | |||
<references/> | |||
[[Category:Uploaded]] | [[Category:Uploaded]] | ||
Revision as of 20:52, 25 June 2026
The speed of light, almost always written as c (for celerity, an archaic term for swiftness of motion), is the constant value for velocity of a photon (packets of light) in a vacuum. It is a strange consequence of Einstein's theory of relativity and has been measured to be 299 792 458 meters per second. [1] Einstein's theories also led to the rather surprising consequence that mass and energy are related by the speed of light in what has become the most famous equation in physics:
Where:
- E is energy
- m is mass (often a mass difference, for example in nuclear reactions)
- c is the speed of light.
Light travels extremely fast. But, on a galactic scale, light still takes a very long time to reach observers.
To learn more about the speed of light and its strange effects please see hyperphysics, for the equation specifically please see the hyperphysics article on relativity.
Mass Defect and Nuclear Decay
Mass defect is the difference between the measured and calculated mass of the nucleus. By Einstein's energy-mass equivalence equation, "missing" mass is accounted for by considering any mass converted into energy during the formation of the atom. This principle also exists in nuclear decay. There is a slight difference in mass before and after an isotope decays and any difference was simply converted into energy. This phenomenon proves especially useful because we can then harness this energy for electricity production, such as is done in nuclear power plants.
For Further Reading
For further information please see the related pages below:
- Radioactivity
- Energy
- Isotope
- Mass
- Or explore a random page
References
- ↑ BIPM. (2006). "The "explicit-constant" formulation", [Online], Avaliable: https://web.archive.org/web/20140811195806/http://www.bipm.org/en/si/new_si/explicit_constant.html