# The arrow of time

- kind: problem
- status: open
- year: 1876

**Statement.** Why did the universe begin in a state of such low entropy?

The laws of physics are nearly time-symmetric, and the second law explains the direction of time only given a low-entropy past. Why the early universe was so special, the past hypothesis, is a question for cosmology that physics has not answered.

## Sources

- [Wikipedia: Arrow of time](https://en.wikipedia.org/wiki/Arrow_of_time)

[Fluids and many bodies](/wiki/Space:matter-in-motion.md) · [Physics](/wiki/Continent:physics.md)

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