The day is not far when people will travel to outer space frequently. But before you dream of Martian colonies and spacewalks, know how the human body changes when it leaves the Earth’s atmosphere
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Shifting bodily fluids
When you orbit Earth, you’re effectively in a free-fall around the planet, weightless. This means there’s nothing to force blood and other bodily fluids toward your feet. The fluid shifting from your legs to your head could fill a two litre bottle.
Reduced bone density
If you don’t exercise while in space, you’ll lose about 12 per cent of your bone density. Researchers are still trying to understand why this happens, though micro fractures in bones caused simply by walking around on Earth seem to be important to maintaining bone health.
Increased height
Since gravity isn’t pushing you down, fluid-filled discs between each of the bony vertebrae in your spine don’t get compressed, stretching your height by about 4 per cent. After Scott Kelly’s time in space, he returned two inches taller than his twin brother. But returning to Earth-like gravity reverses that effect.
Cancer risk
Radiation bombarding your body outside of Earth’s protective magnetic field can increase your risk of getting cancer. NASA currently limits male astronauts’ lifetime radiation exposure to 3,250 millisieverts, which is equivalent to about 400 CT scans of the abdomen. Female astronauts typically have more tissue that’s susceptible to radiation, so their lifetime limit is 2,500 mSv.
Changed DNA
DNA is life’s basic blueprint. However, it’s equally important when and how much those genes are expressed, or turned on and off. A lot of that has to do with a person’s environment. A study found that about seven per cent of Scott Kelly’s genes expressed a bit differently after a year in space than they did on the ground, and didn’t return to normal.
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