After 186 days in orbit, European Space Agency (ESA) astronaut Tim Peake is finally going home. How will he readjust to life on terra firma?

To the Earth-bound observer, floating in microgravity on board the International Space Station (ISS) may seem harmless, even fun or restful. However, the rigors of the seemingly entertaining space flight carry lasting effects on one's health.

As Peake plummets back to Earth this coming Saturday, the ESA astronaut will most likely experience and suffer from a condition called Entry Motion Sickness (EMS). This includes pallor sweating, nausea, vomiting, dizziness and headaches.

After spending six months in microgravity, reentering and readjusting to the Earth's gravity will become a challenge, even for trained astronauts.

When Peake lands on Earth, his body will need to readjust to the normal gravity back home. While the ISS has about 90 percent of our planet's normal gravity, the continuous free-fall of the ISS during orbit allow the onboard astronauts to experience the weightlessness.

The period wherein an astronaut reenters and readjusts to the planet's gravity is called the "readaptation." This period can take as little as six weeks to three years. It takes a long while for the body to return to its pre-spaceflight conditions.

In space, the vestibular system receives little data from the brain, which is the one in control of gravity, orientation, motion and equilibrium. In space, the human brain adjusts accordingly. But returning to terra firma can cause an astronaut's sensors to go into overdrive. This causes vertigo and dizziness because the brain is trying to relearn what's up from what's down.

In space, the lips and tongue also adjust to the weightlessness when they speak. When the astronauts return, they often struggle with speaking normally.

"On Earth, a complex, integrated set of neural circuits allows humans to maintain balance, stabilize vision and understand body orientation in terms of location and direction," said U.S. National Space Biomedical Research Institute head Dr. Dorit Donoviel.

Returning astronauts also feel a strong sense of heaviness in their limbs. This is because the fluids are trying to flow from the upper body and head back to the lower body. In space, the heart shrinks in size and blood volume decreases. Due to the reduced blood volume, the astronauts then have a blood shortage in their upper body and head.

Dr. Steve Taylor, Leeds Beckett University's senior lecturer in psychology, said that Peake's work will help him readjust to the life back on Earth. Taylor has interviewed many astronauts about their lives during and after spaceflight.

"He has had a major responsibility during his mission and hopefully he will feel his work has been of value to a wider community. Tim seems like a very positive person and I'm sure he'll feel he has been of use of the whole human race by testing the extremities of existence," added Taylor.

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