Uploaded on March 9, 2011
Which end is up? - Science on the International Space Station
2011-03-09 - Canadian Astronaut Bob Thirsk is a test-subject for the ground-breaking Canadian experiment BISE (Bodies in the Space Environment), which examines how humans distinguish up from down in weightlessness.
(Credit: Canadian Space Agency)
Robert Thirsk: I’m astronaut Bob Thirsk at the Canadian Space Agency. Welcome to the first Canadian expedition mission to the International Space Station.
Narrator: Look around. Your eyes are scanning thousands and see hundreds of objects at a glance. Your brain is expending effort to block out most of the input and help you focus on a single image. What do you then perceive? A tree, its branches reaching toward the sky. The initial message sent to the brain – the plant is upright. The second and less obvious idea is that you are too. But it takes more than just visual clues to determine what is upright. It also depends on another crucial component of human physiology, your proprioceptive system, where gravity sensors reside.
Robert Thirsk: After adapting to weightlessness, we no longer sense gravity. So we’re missing key sensory information to help us sort up from down. We have to rely almost entirely upon visual cues. Consider that when I see a colleague enter a module with her or his head pointing the opposite direction, it’s quite natural for me to assume that my crewmate is upside down, since I will determine the up direction in a weightless environment, based on wherever the top of my head is pointing.
Narrator: “Bodies in the Space Environment” is a study designed to better understand the impact of long-term exposure to the space environment on sensory perception. Dr. Laurence Harris and his York University team have enlisted Canadian astronaut Bob Thirsk to be a test subject for BISE.
Robert Thirsk: On this tunneled laptop computer, I’ll view a series of foreground and background images to the exclusion of the environment around me. The background will appear in random order and at various degrees of rotation with respect to my body. The foreground consists of a rotating letter. I will perceive that letter as either a P or a D depending upon how much the letter is rotated. If I perceive it as a P, I push one button. If I perceive it as a D, I push another button.
Narrator: York University will use this data to discern Bob’s perceptual upright. Onboard results will be compared with trials performed on Earth before and after the mission. The complete studies will help scientists to better understand how vision in relation to body cues determines the test subject’s sense of up in near weightlessness.
Robert Thirsk: On a practical level, BISE may contribute to the introduction of better, clearer layouts for equipment and interiors of spacecraft, reducing confusion and even disorientation for future space explorers. On Earth, we can apply these findings to designing optimal living environments for people with balance and movement control disorders and potentially help their recovery.