# Tag Info

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The average lifetime of a particle "at birth" is $1/\lambda$. The average lifetime of the collection of particles that are alive at a given time is longer, because that is a biased sample. ...
• 1,317

### Is the concept of entropy a result of limited technology?

I know that entropy is the energy within a system that is unable to do useful work. This doesn’t really bear scrutiny. Entropy and energy have different units, for one. But even an approximate ...
• 19.7k

### Is the concept of entropy a result of limited technology?

Totally wrong. Entropy is NOT "the energy within a system that is unable to do useful work." Instead entropy is the thermal charge that does work as it moves from a higher temperature to a ...
• 12.2k

### The average of a continuous value: $\overline{O} = \int O(x) \rho(x) dx$, but coordinate invariant

lpz is correct that you are including an erroneous factor of $|dy/dx|$ in your transformation of $O(x)$. You may be getting misled by the transformation of the density, which uses the same symbol for ...
• 546