How long can you stay in space?

Space travel changes the way the human body works in some surprising ways. One of the main reasons for these changes is gravity, or rather, the lack of gravity. 

When astronauts are in space, they do not walk on the floor like we do on Earth. Instead, they float around inside their spacecraft. This is because the International Space Station (ISS) is in free fall as it orbits the Earth. As it falls towards the Earth, it is also moving forward at a high speed, creating a feeling of weightlessness for the astronauts inside.

This lack of gravity has a big impact on the human body. For example, because astronauts do not have to fight against gravity to move or lift things, their muscles do not have to work as hard. In fact, the UK Space Agency has found that astronauts can lose as much as 40% of their muscle mass and 12% of their bone mass after just five months in space. This can cause problems when they return to Earth and have to readjust to the effects of gravity.

Another surprising effect of space travel is on eyesight. Due to change of pressure, fluid distribution inside human eye can get distorted.

Psychological effects like isolation and confinement also play a crucial role in determining the length of stay.

Russian cosmonaut Valeri Polyakov holds the record for the most days spent in space in one go. He spent 437 days in Russia's Mir space station between 1994 and 1995.

Overall, space travel affects almost every part of the human body, and the main reason for this is gravity. It is important for astronauts to understand these changes and to take steps to combat them, such as through exercise and proper nutrition. By studying the effects of space travel on the human body, scientists can better prepare for long-duration missions to places like Mars and beyond.