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Loading contentA measure of disorder that, on cosmic scales, only increases — giving time its direction.
The second law of thermodynamics says total entropy never decreases. The Universe began in a remarkably low-entropy state, and its steady rise defines the arrow of time. Black holes carry enormous entropy proportional to their horizon area — a clue linking gravity, quantum mechanics, and information.
Facts on this topic will be cited from these primary and reference sources.
Mission data, planetary science, space telescopes, and public-domain imagery.
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