====== Physical constants ======

==== Constants variability : ====

Many physics calculations rely on the assumption that the [[http://en.wikipedia.org/wiki/Physical_constant|‘physical constants’]] e.g. light-speed, gravity, etc etc are, in fact, constant. Extremely accurate experimental procedures strongly suggest that they (mostly) are. But the experiments can only be carried out on a ‘local’ scale, and in a very short timeframe (cosmologically speaking). Thus the possibility exists that some constants may vary at extreme distances and/or timescales. If so, current explanations of many cosmological phenomena may have to be completely re-evaluated.

//Further reading:// [[https://web.archive.org/web/20120113035927/www.sheldrake.org/experiments/constants/|The Variability of Fundamental Constants ]] [archived] (by [[https://www.sheldrake.org/|Dr Rupert Sheldrake]] //)//

=== Example: Possible light-speed variation. ===

In 2007, the [[https://magic.mpp.mpg.de/|MAGIC]] telescope array at La Palma, Canary Islands (Spain) found that high energy photons arriving from distant [[content:physics:cosmology:gamma_ray_bursts|gamma ray bursts]] arrived at different times - the delay (max. of several minutes) being determined by the photon's wavelength (i.e. energy).

See [[https://www.ucdavis.edu/news/gamma-ray-delay-may-be-sign-new-physics|'Gamma Ray Delay May Be Sign of 'New Physics'' ]] (UC Davis).

==== The 'Anthropic Principle' : ====

As the physical constants have been measured with increasing accuracy, many scientists and philosophers have asked why the constants have the values which they do. Although no-one has been able to answer the question, it's been pointed out that if (many of) the constants had even slightly differing values, then the Universe could not exist in its present form.

This is the so-called //Anthropic Principle// -  which (broadly) states that constants //must// have the values which they do, or we would not be here to analyse them.

Further details : [[http://abyss.uoregon.edu/~js/cosmo/lectures/lec24.html|University of Oregon, US]]

----

Also see : [[content:physics:cosmology:gravitational_constant]] and [[content:physics:quantum_physics:fine_structure_constant]]

~~stars>4/5~~