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Spending time in space and having an unrivalled view of
planet Earth is an experience many of us dream of, but the
human body evolved to function in the gravity of Earth. So fully
recovering from spending time in the weightlessness of space can
take years.
“It’s a fact that space is by far the most extreme
environment that humans have ever encountered and we’ve just
not evolved to handle the extreme conditions,” Professor Damian
Bailey, who studies human physiology, says. To begin with, the
heart and blood vessels have an easier time as they no longer
have to pump blood against gravity — and they start to weaken.
And the bones become weaker and more brittle. There should be
a balance between the cells breaking down old bone and those
making new, but that balance is disrupted without the feedback
and resistance of working against gravity. “Every month, about
1% of bones and muscles are going to wither away — it’s
accelerated ageing,” Professor Bailey says.
Microgravity also distorts the vestibular system, which is
how you balance and sense which way is up. In space, there is no
up, down or sideways. It can be disorientating when you go
up — and again when you return to Earth.
James Gallagher. What nine months in space does to the human body.
Internet: <bbc.com> (adapted).