Plane waveIn physics, a plane wave is a special case of wave or field: a physical quantity whose value, at any moment, is constant through any plane that is perpendicular to a fixed direction in space. For any position in space and any time , the value of such a field can be written as where is a unit-length vector, and is a function that gives the field's value as dependent on only two real parameters: the time , and the scalar-valued displacement of the point along the direction . The displacement is constant over each plane perpendicular to .
Standing waveIn physics, a standing wave, also known as a stationary wave, is a wave that oscillates in time but whose peak amplitude profile does not move in space. The peak amplitude of the wave oscillations at any point in space is constant with respect to time, and the oscillations at different points throughout the wave are in phase. The locations at which the absolute value of the amplitude is minimum are called nodes, and the locations where the absolute value of the amplitude is maximum are called antinodes.
Future generationsFuture generations are cohorts of hypothetical people not yet born. Future generations are contrasted with current and past generations, and evoked in order to encourage thinking about intergenerational equity. The moral patienthood of future generations has been argued for extensively among philosophers, and is thought of as an important, neglected cause by the effective altruism community. The term is often used in describing the conservation or preservation of cultural heritage or natural heritage.
Intergenerational equityIntergenerational equity in economic, psychological, and sociological contexts, is the idea of fairness or justice between generations. The concept can be applied to fairness in dynamics between children, youth, adults, and seniors. It can also be applied to fairness between generations currently living and future generations. Conversations about intergenerational equity occur across several fields. It is often discussed in public economics, especially with regard to transition economics, social policy, and government budget-making.
