Astronauts are surprisingly good at judging distances without gravity

According to new research published in the journal Astronauts, astronauts have an uncanny ability to judge distances in the weightlessness of space. npj microgravity. The findings revealed that astronauts have a surprisingly accurate ability to estimate distances traveled in a microgravity environment such as the International Space Station (ISS).

It is a collaborative effort led by York University in collaboration with the Canadian Space Agency, NASA and other international space agencies. But why embark on such a study? Venturing into space presents astronauts with unique challenges, not least of which is the absence of gravity.

This lack of gravity affects various bodily functions and senses, including how we perceive movement and orient ourselves in space. Given the critical nature of precise movement and navigation in spacecraft or when conducting space missions, understanding and improving the spatial awareness of astronauts in microgravity is critical.

„The perception of gravity has been shown repeatedly to affect cognitive ability. The most profound way to see the influence of gravity is to take it, which is why we took our research into space,” said Lawrence Harris, professor and director of psychology. Multisensory Integration Lab.

„We've had a steady presence in space for a quarter of a century, and as space ventures grow with plans to go to the Moon and beyond, answering health and safety questions is increasingly important. Based on our findings, it appears that humans can surprisingly compensate for the lack of an Earth-normal environment by using vision.

The research focused on two main groups: astronauts performing missions on Earth and in the microgravity environment of the ISS, and a control group that underwent similar testing only on Earth. The astronaut group consisted of 15 individuals (8 women and 7 men) who, however, did not complete the study due to various reasons, such as delays in their space flight or inability to complete the second test session within a certain time frame.

Thus 12 astronauts (6 male and 6 female) completed all aspects of the test protocol. The control group initially consisted of 22 participants, and 20 completed the study due to discontinuation due to motion sickness in some cases.

The researchers used virtual reality (VR) technology to simulate a three-dimensional hallway, which served as the primary setting for the experiments. The hallway is designed with light spots on the walls to create visual flow, reflecting the visual cues one experiences while moving through the space.

The experimental procedure was carefully designed to assess participants' ability to judge distance in a simulated environment. Participants viewed a target at various distances in a virtual hallway and were asked to estimate the egocentric distance to the target. Once they made their judgment, they were shown the start of the trial, and the target disappeared, replaced by optic flow simulating movement toward the target's location.

Participants indicated when they felt they had reached the goal level. This process was repeated over multiple trials and distances without providing any feedback on performance to ensure that learning effects did not influence the results.

The astronauts were tested at five different stages: before their spaceflight, early and late during their mission on the ISS, and early and late after their return to Earth. While on Earth, experiments were conducted with the astronauts sitting and lying down (lying face up) to simulate different orientations relative to gravity.

A key finding of the research was that visual cues, or visual flow, play an important role in astronauts' perception of movement and distance in space. Visual flow refers to the pattern of apparent movement of objects, surfaces, and edges in a visual scene caused by relative movement between an observer and the scene. In the weightless state of space, where vestibular cues related to gravity are unavailable, astronauts rely heavily on these visual cues to determine how far they have traveled.

The study also found that posture affects the perception of distance on Earth. Specifically, participants tended to judge the distance as shorter when they were in a supine position (lying face up) compared to when they were sitting upright. This finding was consistent with the hypothesis that the absence of conventional gravity cues may result in over-reliance on visual information to estimate distances.

Also, the results showed no significant difference in the astronauts' performance before and after their spaceflight. This indicates that the experience of microgravity does not adversely affect the astronauts' ability to perceive distance when they return to Earth. This is an encouraging sign for long-duration space missions, suggesting that astronauts can quickly re-adjust to Earth's gravity without lasting impairments in spatial perception.

However, the study has its limitations, including a small sample size and the exclusion of data from participants who did not complete all testing sessions. Furthermore, the astronauts were not tested immediately upon reaching the ISS, meaning that the initial adaptation phase to microgravity was not captured.

The researchers call for further studies to explore these findings, particularly the long-term effects of space travel on spatial orientation and to understand how these insights may benefit people with balance disorders on Earth.

study,”Effects of long-term exposure to microgravity and body orientation in relation to gravity on perceived distance traveled”Bjorn Georges, Nils Buri, Megan McManus, Ambika Bansal, Robert S. Allison, Michael Jenkin, and Lawrence R. Written by Harris.