For astronauts on lengthy journeys, extraterrestrial weightlessness - the experience of floating through space inside of one's craft - is both a blessing and a punishment. Canadian astronaut Chris Hadfield observes that "bodies are made to work with gravity. The blood is pushed to your feet and your heart squeezes it to your head; if gravity were to suddenly disappear, your heart would continue to do this, but gravity would no longer force the blood back to your feet, causing your head to swell.
Physiologist Alan Hargens and his colleagues at NASA discovered in the 1980s that newborn giraffes' blood arteries swiftly enlarge after birth, frequently enabling them to walk within their first hour of life outside of the womb. With the help of this finding, the Lower Body Negative Pressure Device (LBNP), which functions like a regular vacuum cleaner to "provide negative pressure across the lower body," became more effective. In turn, this mimics Earth-like conditions and stops astronauts returning home from passing out.
