What is the Guinness World Record for the longest time spent in space, and who holds it?

The Guinness World Record for the longest time spent in space is held by Russian cosmonaut Valeri Polyakov, who spent 437 days, 17 hours, and 58 minutes aboard the Mir space station from January 1994 to March 1995. Polyakov's mission was part of a joint program between Russia and the United States to study the effects of long-term spaceflight on the human body.

Polyakov, a medical doctor, conducted various experiments during his time in space, including studying the effects of weightlessness on the cardiovascular system and the body's ability to adapt to changes in posture and movement. He also tested new exercise equipment designed to prevent muscle and bone loss during extended stays in space.

Polyakov's record still stands today, but it may be surpassed in the future as space agencies plan longer missions to the moon and Mars. However, it will remain a remarkable achievement and testament to the resilience and endurance of the human body in space.