space medicine: Absence of Day and Night

The absence of the earthly cycle of day and night during space travel produces subtle effects, both physiological and psychological. The period from sunrise to sunset in a quickly orbiting spacecraft may be as little as 11⁄2 hours long. All body rhythms, such as heartbeat, respiration, and changes in body temperature, are regulated by biological clocks (see rhythm, biological). These rhythms are related to human patterns of sleep and wakefulness, which in turn are based on the alternation of day and night. On most flights, adherence to “home” schedules maintains normal human cycles.

Sections in this article:

• Introduction
• A Closed Environment
• Absence of Day and Night
• Ionizing Radiation
• Inertial Forces
• Weightlessness
• Bibliography

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2024, Columbia University Press. All rights reserved.

See more Encyclopedia articles on: Medicine