Because astronauts like the ones on the
International Space
Station (ISS) are moving so quickly, they're also
aging a bit more slowly than the rest of us. Due to a principle of
physics known as time dilation,
after a six-month stint on the ISS, returning astronauts are just a
tiny bit younger than the rest of us. But before you book a ticket
that'll take you literally out of this world, understand this isn't
exactly a fountain of youth we're talking about. Your six-month
effort at age reduction will only garner you about 0.007 seconds of
extra life, according to the calculations of one ISS astronaut
[source:
Lu].
But that's not really the issue we're talking about when we
discuss how humans age in space. Let's start with a rundown of how
the aging process typically proceeds on
Earth. Until scientists muster
up a way to make us all immortal, most of us will go through the
process of aging. This typically involves metamorphoses like bones
becoming brittle, blood vessels hardening, muscles wasting away,
joints stiffening up, bowels turning irritable, bladders becoming
unpredictable, teeth decaying, vision growing dim, skin wrinkling
up, and so on.
While for most people, it takes decades to really start to feel
the effects of the aging process, humans stationed in space
experience some of them in fast-forward. They're often reversible
once an astronaut returns home, although sometimes a few of the
changes can be permanent.
A lack of
gravity is the main cause for
these intense alterations. Gravity is one of the most important
forces at work on Earth, and it plays an immense role in the
majority of our bodily systems. Take the muscles, for example.
Older peoples' muscles tend to shrink and atrophy as they age and
become less mobile. Astronauts' muscles react in a similar way
because they are barely used. That's why astronauts in space for
extended periods of time use special exercise machines to help
mitigate this effect.
A similar process takes place in the bones. After a certain age,
people on Earth start to lose mass in their bones, typically at a
rate of about 1-to-2 percent a year. But in space, those people
lose bone mass at a greatly accelerated rate: as much as 1-to-2
percent a month. Because the astronauts' skeletal systems don't
need to support their weight, the bones begin to decrease
production of new bone material and increase the amount of old bone
absorption. Luckily, their skeletal systems usually return to
normal once they've spent some time back on terra firma [source:
NASA].
Even though they're saving 0.007 seconds, astronauts still
experience some of the symptoms of a drawn-out aging process.
Researchers are working to figure out the mechanics of why these
changes occur, as well as what can be done to prevent them. This
information could not only to help make spaceflight easier on the
human body, but to help improve life on Earth as well.
Space tourism is possible