preindustrial Europe first and second sleep lighting

Europeans once commonly slept in two shifts

In preindustrial Europe, many people slept for a few hours, woke for a period in the middle of the night, and then slept again. As artificial lighting made nighttime activity easier, this pattern faded. By the 1920s, the idea of a "first" and "second" sleep had largely disappeared.

A deaf child can create a home sign system

A deaf child without access to an established sign language may create signs used within the family and develop a few rules for combining them. Without support or feedback from a wider community, the system does not become a full language.

Lake Nyos could release gas without an outside trigger

In 1986, deep water in Cameroon’s Lake Nyos held carbon dioxide and was unstable because of temperature-based layering. Rising bubbles could pull up more gas-rich water, setting off an overturn that released gas and fed on itself. No landslide or other outside event was needed.

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preindustrial Europe first and second sleep lighting

Europeans once commonly slept in two shifts

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