A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

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The property of some materials by which individual atoms decay, emitting energy or particles often transforming into different elements in the process.
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Randomness covers questions having to do with the concept of randomness in physical processes and questions about determinism vs indeterminism or interpretations thereof. Question related to concepts …
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a particular coordinate system chosen to represent physical entities. The notion is most often used in special and general relativity to dentoe particular coordinates chosen on th…
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Change in the direction of propagation of a wave when its transmitting medium changes.
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The union of special (SR) and general (GR) relativity. Use this tag if both SR and GR apply.
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Energy sources that do not rely on the consumption of an exhaustible fuel. Tidal, geothermal, and the direct and indirect solar energies (direct: photovoltaics, CSP, solar thermal; indirect: wind, wav…
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an ensemble of techniques which serves to treat the infinities which appear in quantum field theory or statistical mechanics.
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applies to questions that arise in graduate and post-secondary work. These questions often require domain-specific knowledge and could not be answered from a general source or …
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to electrical resistance. DO NOT USE THIS TAG for non-electrical resistance.
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a good book about X?" or more generally, "What should I read to learn about X?", typically where there is not a single authoritative reference. Please READ THE GUIDANCE IN ME…
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The potential for a thermodynamic process to be reversed in time. Alternatively, a quantification of how far an irreversible process is from being reversible, which relies on a comparison to a corresp…
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Colloquially referred to as one of the hardest professions, rocket science is actually a common name for spacecraft/space-systems engineering. However, one can also generalize this to include all form…
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Circular motion about a central point or axis
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A tag for questions about the mechanical interactions of rotating objects, including torque and angular momentum.