Space and the Human Body

Shariq Ali
Valueversity

Consider a situation for a moment: two identical twin brothers — the same DNA, the same upbringing, the same environment. Now imagine that one brother remains on Earth while the other spends an entire year in space.

The research question was simple yet profound: what happens to human physiology when gravity is almost absent?
To explore this, NASA conducted the “Twins Study.”

The astronaut Scott Kelly, who traveled to space, and his identical twin brother Mark Kelly, who stayed on Earth, were studied comparatively.
Scott spent nearly 340 days aboard the International Space Station, where there is neither a complete day nor night, and the body continuously exists in a microgravity environment.

One of the first major physiological challenges in space affects the bones. On Earth, our bones constantly bear weight. In space, this load disappears. As a result, bone mineral density begins to decrease, and calcium is lost from the body.

That is why astronauts perform specific daily exercises to keep their bones and muscles active.
Interestingly, the study also observed changes at the cellular level.

The length of Scott’s DNA end-caps, known as telomeres, altered during his time in space and changed again after his return to Earth. This suggests that the human body does not respond only at the level of muscles and bones — its physiology reacts even at the cellular level.

Furthermore, the immune system in space functioned almost as it does on Earth. This raised hope that long-duration space travel may be possible, provided we understand human physiology more deeply.

This study reminds us that the human body is remarkably adaptable. Yet as we step into new environments — such as space — it becomes equally essential to understand the changes that unfold within it.