View source for Terminology

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== Terminology ==
<big>[[Index|Back to the Index page]]</big><br>
A list of frequently used terms.

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{| class="wikitable sortable" style="width: 95%;"
|+ Terminology 
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! Term !! Brief description

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| [[Terminology/Airy disk|Airy disk]] || Airy disk - In optics, the Airy disk is described as the best-focused spot of light that a perfect lens with a circular aperture can make.

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| [[Terminology/Anisotropy|Anisotropy]] || Anisotropy - Structural property of non-uniformity in different directions, as opposed to [[Terminology/Isotropy|Isotropy]]. 

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| [[Terminology/Axis of Evil|Axis of Evil]] || Axis of Evil - The "axis of evil" is a name given to the apparent correlation between the plane of the Solar System and aspects of the [[Terminology/Cosmic Microwave Background|Cosmic Microwave Background (CMB)]] in which the location of Earth is shown to have a greater "significance" than might be expected by "chance".

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| [[Terminology/Coulomb's Law|Coulomb's Law]] || Coulomb's Law - force between two electrically charged particles at rest

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| [[Terminology/Cosmic Microwave Background|Cosmic Microwave Background]] || Cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe. 

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| [[Terminology/Covariance|Covariance]] || Covariance is a measure of the relationship between two known variables and to what extent, they change under transformation. Example: Lorentz Transformations facilitate a change in the x-axis (distance) and t-axis (time) as a function of the Gamma factor: 
Length contraction: <br>
<math>L = L_0\sqrt{1 - \dfrac{v^2}{c^2}}</math>

Time dilation: <br>
<math>\Delta t = \gamma \Delta \tau = \dfrac{\Delta \tau}{\sqrt{1 - \dfrac{v^2}{c^2}}}</math>

By using using covariance (a change in the x and t coordinate) the speed of light will remain constant in all frames that use this transformation.

Special Relativity makes use of linear orthogonal transformations for frames moving at a constant velocity.

The General Theory expands covariance to accelerated frames, but maintains the same changes to the x and t coordinates.

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| [[Terminology/Classical mechanics|Classical mechanics]] || Classical mechanics is a physical theory describing the motion of objects.

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| [[Terminology/Dynamics|Dynamics]] || Dynamics - Predictions of future motion based on real forces with respect to a fix lab frame. Real forces are defined relative to the analysis, often including variables like: friction, resistance, mass, momentum, and energy. 

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| [[Terminology/Experiment|Experiment]] || Experiment - A test under controlled conditions that is made to demonstrate a known truth, examine the validity of a hypothesis, or determine the efficacy of something previously untried.

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| [[Terminology/Flatness problem|Flatness problem]] || Flatness problem - The flatness problem (also known as the oldness problem) is a cosmological fine-tuning problem within the Big Bang model of the universe, problems arise from the observation that some of the initial conditions of the universe appear to be fine-tuned to very 'special' values.

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| [[Terminology/Horizon problem|Horizon problem]] || Horizon problem (also known as the homogeneity problem) - is a cosmological fine-tuning problem within the Big Bang model due to the difficulty in explaining the observed homogeneity of causally disconnected regions of space

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| [[Terminology/Isotropy|Isotropy]] || Isotropy - In physics and geometry, isotropy is uniformity in all orientations, as apposed to [[Terminology/Anisotropy|Anisotropy]].

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| [[Terminology/Kinematics|Kinematics]] || Kinematics - Future predictions of motion based on observation - no regard for causal mechanism or forces.

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| [[Terminology/Invariance|Invariance]] || Invariance - Any physical quantity is invariant when its value remains unchanged under specific coordinate transformations.

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| [[Terminology/Inverse-square law|Inverse-square law]] || The Inverse-square law applies to strength of Light and radio waves over distance.

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| [[Terminology/Rayleigh criterion|Rayleigh Criterion]] || Rayleigh Criterion - determines the minimum angle between two point objects that can be resolved by a circular aperture, lens, or mirror. 

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| [[Terminology/Statics|Statics]] || Statics - Statics is the branch of classical mechanics that is concerned with the analysis of force and torque acting on a physical system that does not experience an acceleration, but rather is in equilibrium with its environment. 

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| [[Terminology/Tired light|Tired light]] || Tired light - A class of hypothetical redshift mechanisms that was proposed as an alternative explanation for the redshift-distance relationship.

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| [[Terminology/Twilight|Twilight]] || Twilight - light produced by scattering sunlight in the upper atmos, when the Sun is below the apparent horizon.  

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===See Also===
* [[Tech|Technology]]

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