Speed of light
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