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Blue shift refers to a shortening of a transmitted signal's wavelength, and/or an increase in its frequency. The name comes from the fact that the shorter-wavelength end of the optical spectrum is the blue (or violet) end, hence, when visible light is compacted in wavelength, it is "shifted towards the blue", or "blue-shifted". Since the longer-wavelength end of the visible electromagnetic spectrum is red, the opposite effect, of a lengthening of a signal's wavelength, is referred to as redshifting.
These terms and conventions ("blue" = compaction, "red"=stretching) are used even when referring to signals outside the optical range (for instance, radio waves, x-rays and gamma rays). . The term is also used informally to refer to a hypsochromic shift in photochemistry.
[edit] Astronomy
Redshift is much more noted due to its importance to modern astronomy. While the general redshift of starlight is seen as evidence for an expanding universe, there are a few examples of blue shift in astronomy:
[edit] Cause of blueshift in astronomy
These are the known possible causes of blue shift in astronomy:
- Movement of the source towards us, as seen in
- the edge of a rotating galaxy moving towards us
- In blazars which propel relativistic jets towards us
- Some galaxies [1] and quasars [2]
- Gravitational effects. See gravitational redshift
[edit] Limit of blue shift
- See also: chronon
According to well accepted quantum theory, the limit of blue-shift is approached when a half-wavelength of light approaches the planck length. This corresponds to a half-wavelength of 1.616x10^-35 meters, and a frequency of 9.276x10^42 Hz (and defines a minimum period of 1.078x10^-43 seconds, which therefore must be the minimum increment of time in the universe).
[edit] See also
