Q: In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.
This letter represents a quantity defined as Gibbs free energy per surface area in the Young-Laplace equation. Relativistic mass equals rest mass times a quantity represented by this letter, which is equal to the derivative of time with respect to proper time. That quantity is also expressed as one divided by the square root of one minus v squared over c squared, known as the (*) Lorentz factor. In addition to symbolizing surface tension and photons, this letter names a type of high-energy decay and radiation carrying more energy than X-rays. For ten points, identify this third letter of the Greek alphabet.
A:
Science