Tau
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|
| Greek alphabet | |
|---|---|
| Α α Alpha | Β β Beta |
| Γ γ Gamma | Δ δ Delta |
| Ε ε Epsilon | Ζ ζ Zeta |
| Η η Eta | Θ θ Theta |
| Ι ι Iota | Κ κ Kappa |
| Λ λ Lambda | Μ μ Mu |
| Ν ν Nu | Ξ ξ Xi |
| Ο ο Omicron | Π π Pi |
| Ρ ρ Rho | Σ σ Sigma |
| Τ τ Tau | Υ υ Upsilon |
| Φ φ Phi | Χ χ Chi |
| Ψ ψ Psi | Ω ω Omega |
| obsolete letters | |
| [[Digamma|Template:Polytonic Digamma]] | [[San (letter)|Template:Polytonic San]] |
| [[Qoppa|Template:Polytonic Qoppa]] | [[Sampi|Template:Polytonic Sampi]] |
Tau (upper case Τ, lower case τ) is the 19th letter of the Greek alphabet. In the system of Greek numerals it has a value of 300.
The lower-case letter τ is used as a symbol for:
- Torque, the rotational force in mechanics.
- The elementary tauon particle in particle physics.
- The lifetime of a spontaneous emission process.
- The time constant in an RC circuit.
- A coefficient of correlation — see Kendall's tau.
- The Golden ratio 1.618... (although φ (phi) is more common)
- Tau in astronomy is a measure of opacity, or how much sunlight cannot penetrate the atmosphere
- Tau in biochemistry is a protein associated to microtubules
Other uses of Tau:
- Tau is the name of an island near Kilinailau, Greenwich Island, and Ocean Island.
- In Games Workshop's Warhammer 40,000 science fiction gaming universe, the Tau are an alien race.
- Tau is a symbol used from antiquity and is represented by a type of cross. There are those who accuse Christ of being the pirate of this ancient symbol, but it did not become a symbol of Christianity until a later date. As with Christianity, other ancient societies who used the "Tau" symbol also evolved its use to represent resurrection, reincarnation and blood sacrifice.
- The prefix of many cosmic entities, fictional or not. Notably Tau Ceti Five from System Shock 2de:Tau