Time marks our lives. The perception of time is not absolute, but varies in relation to the changing environment.

Two orders of time coexist on the International Space Station: an internal, artificial one and an external, natural one. The former reproduces the Earth’s 24-hour cycle, with day and night phases regulated by artificial light. It is a time controlled by human beings to plan activities on board.

The second, astronomical and independent of human will, is a time perceived by looking outside the ISS that alternates sunrises and sunsets every 90 minutes due to orbital velocity. This time, measured by the natural light cycle, is equivalent to perceiving the passage of 16 Earth days in a 24-hour period, generating the sensation of an accelerated rhythm.

Space Design must design these “time machines” by questioning how perceptions influence the physiology, psyche, thoughts, emotions and behaviours of the crew, with the aim of mitigating spatial and temporal disorientation and improving overall well-being.