Do 'bouncing universes' have a beginning?

In trying to understand the nature of the cosmos, some theorists propose that the universe expands and contracts in endless cycles.

Physicists find signatures of highly entangled quantum matter

Via large-scale simulations on supercomputers, a research team from the Department of Physics, the University of Hong Kong (HKU), discovered clear evidence to characterize a highly entangled quantum matter phase—the quantum ...

Deep learning for new alloys

When is something more than just the sum of its parts? Alloys show such synergy. Steel, for instance, revolutionized industry by taking iron, adding a little carbon and making an alloy much stronger than either of its components.

Estimating the informativeness of data

Not all data are created equal. But how much information is any piece of data likely to contain? This question is central to medical testing, designing scientific experiments, and even to everyday human learning and thinking. ...

Novel theory of entropy may solve materials design issues

A challenge in materials design is that in both natural and manmade materials, volume sometimes decreases, or increases, with increasing temperature. While there are mechanical explanations for this phenomenon for some specific ...

Wormholes help resolve black hole information paradox

A RIKEN physicist and two colleagues have found that a wormhole—a bridge connecting distant regions of the Universe—helps to shed light on the mystery of what happens to information about matter consumed by black holes.

New algorithm to measure entanglement entropy

A research team from the Department of Physics, the University of Hong Kong (HKU) has developed a new algorithm to measure entanglement entropy, advancing the exploration of more comprehensive laws in quantum mechanics, a ...

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Entropy

Entropy is a concept applied across physics, information theory, mathematics and other branches of science and engineering. The following definition is shared across all these fields:

where S is the conventional symbol for entropy. The sum runs over all microstates consistent with the given macrostate and is the probability of the ith microstate. The constant of proportionality k depends on what units are chosen to measure S. When SI units are chosen, we have k = kB = Boltzmann's constant = 1.38066×10−23 J K−1. If units of bits are chosen, then k = 1/ln(2) so that .

Entropy is central to the second law of thermodynamics. The second law in conjunction with the fundamental thermodynamic relation places limits on a system's ability to do useful work.

The second law can also be used to predict whether a physical process will proceed spontaneously. Spontaneous changes in isolated systems occur with an increase in entropy.

The word "entropy" is derived from the Greek εντροπία "a turning towards" (εν- "in" + τροπή "a turning").

This text uses material from Wikipedia, licensed under CC BY-SA