You’re an astronaut on the International Space Station, orbiting the Earth 15.7 times per day, looking down at a blue marble 330 to 410 kilometres below your feet.
The force of gravity in the space station is only a millionth of what it is on the Earth’s surface — just enough to stop the station from drifting off into space, but not enough to keep human spines from extending.
The human body has evolved to live in Earth’s gravity. When an astronaut travels into space, weightlessness complicates everyday life; from eating to sleeping, and yes, even going to the toilet.
The most difficult changes occur inside astronauts’ bodies. These changes cause health problems both in space and on the return to Earth.
Nearly every astronaut experiences “space sickness” caused by the disruption of balance sensors located in a person’s inner ear. This disturbance is triggered by the near-absence of gravity, and results in vomiting, headaches, disorientation, and even problems locating your own limbs.
Space sickness is the least of an astronaut’s worries, though, and the problems usually disappear in a few days.
On Earth, bodily fluids such as blood and mucous are usually pulled down by the force of gravity. In space, there is not enough gravity to do that, so the fluids migrate from an astronaut’s legs to his or her head.
This causes “space sniffles,” which involves nasal congestion and a puffy face, similar symptoms to the seasonal colds we experience on Earth.
These sniffles last throughout the entire mission. Imagine having to deal with the nuisances of a cold for months at a time.
What’s more, with so little gravity to work against, the heart has to pump less to get blood circulating around the body. This causes heart tissues to begin to shrink, a potentially huge problem when astronauts return to Earth.
To combat this, astronauts must exercise to reverse the shrinkage and keep their hearts strong.
“[In space] we exercise about two and a half hours each day. These exercises are divided between weightlifting, cycling, and treadmill routines, “ astronaut Don Pettit said.
By constantly conditioning the heart, it will take less time to recover upon their return to Earth.
In space, astronauts no longer walk to get from place to place; they float, meaning their leg bones need to support less weight. This leads to bone breakdown and a release of calcium into the body, which causes its own problems, namely, painful kidney stones and even bone fractures.
In addition to all the bad, there might be a positive body change — at least for those vertically challenged space walkers — that happens to some astronauts in space. In an almost gravity-free environment, astronauts get a bit taller, some five to eight centimeters, to be exact.
On Earth, gravity compresses the spinal cord. Without that pull on the spine, the soft discs between the bony vertebrae expand and astronauts grow taller. Not surprisingly, backaches and nerve problems make this an uncomfortable experience.
Back on Earth, astronauts shrink back to their normal heights, but it can take two to three years depending on the duration of their time in space.
Seven more space launches are scheduled in 2012, with one even happening on Oct. 31. Follow the story on the NASA website, http://www.nasa.gov/news/index.html.
Erica Sawula is a grad student in Laurentian University’s Science Communication program. Have a burning science question that can be answered in Northern Life’s new science column, Talking Science? Send your question to firstname.lastname@example.org.