One of the many reasons that humanity has gone to space is to discover more about ourselves and our biology. Putting humans in space provides us with a lot of data about our bodies and our psychology as we are able to see the impacts that zero gravity and isolation have on us. One area that has been illuminating has been the sleep lessons derived from humanity’s experiences in space.
One of the things that is important to consider about space is the environment and how this may impact sleep. For starters, there is almost no gravity in space (well there is no gravity in deep space but the closer an astronaut is to a planet or star the greater the level of gravity though even in orbit there is minimal gravitational effects). Zero-g has a wide range of physiological impacts on the human body, with many we are still learning about. As well as the lack of gravity though there are also other environmental factors including the isolation and the different day night cycle depending on where the astronaut is, with those in orbit experiencing up to 30 day night transitions in a 24 hour period. Put bluntly, it is a drastically different environment from that which we have evolved in.
The first lesson
The first lesson taken from humanity’s time in space is that our bodies do not naturally stick to the 24 hour cycle. This may seem strange considering we have evolved on a planet with just such a cycle but it is true. In fact, they have found that most people will settle at about 25.4 hour cycles after a long enough period in space, though no one can explain exactly why.
The second lesson
The second lesson learned is that humans are heavily reliant on external cues for sleep. Without the light-dark transitions we have in a normal 24 hour day, and the other contextual signals we experience here on Earth, your ability to regulate sleep times can be a mess. Over time the astronauts struggled with sleep, their regular habits were harder and harder to keep and their sleep cycles became much shorter.
The third lesson
The third lesson is that we are not very good at judging our own sleep levels or quality. Many of the astronauts were reporting that their sleep levels and quality were good but because they are so heavily monitored whilst in space the controllers could tell that this was not the case and that most were not sleeping as well or as long as they thought.
The final lesson
The final lesson is one for all of us down here on Earth. We need to be careful with our own sleep as we are nearly as vulnerable as the astronauts as we modify our own environments down here to the point that they impact our sleep quality and we are just as bad at judging it. Be warned.
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