Did you know … astronauts forget about gravity when they return to Earth?

Many of us have dreamed about going to space at least once in our lifetime. I certainly did. However, neither life in space nor coming back to Earth seems to be as glamorous as we imagine it can be. Some of this has to do with gravity and how those who spend certain amount of time in space forget about it.

Well, they don’t literally forget about gravity. However, their muscles, bones, and balance systems need some time to readjust to the gravity we experience on Earth, because well, things are different in space.

In space, there is what’s called microgravity. There, the astronauts’ bodies adapt to microgravity, meaning their muscles and cardiovascular systems do less work to counteract gravity. When astronauts return from their missions, they undergo physical rehabilitation to completely recover.

Astronauts’ bodies go through a lot of changes and adaptations when they return to this planet. They often experience orthostatic intolerance (also called postural hypotension) which is a condition where the body struggles to adjust to Earth’s gravity in an upright position.

Orthostatic intolerance

Orthostatic intolerance is described as a form of low blood pressure that happens when standing after sitting or lying down. Orthostatic hypotension can cause dizziness or lightheadedness and sometimes fainting.

There are several degrees of orthostatic hypotension. When the condition is mild, episodes may be brief. However, long-lasting orthostatic hypotension can signal more-serious problems. The Mayo Clinic advises that it is important to see a health care provider if you frequently feel lightheaded when standing up.

According to the Mayo Clinic, occasional orthostatic hypotension is usually caused by something obvious, such as dehydration or lengthy bed rest. The condition is easily treated. However, chronic orthostatic hypotension is usually a sign of another health problem, so treatment depends on the cause.

According to the Mayo Clinic, the most common signs and symptom of orthostatic hypotension is lightheadedness or dizziness when standing after sitting or lying down. Symptoms usually last less than a few minutes.

Orthostatic hypotension signs and symptoms include: Lightheadedness or dizziness upon standing, blurry vision, weakness, fainting (syncope), and confusion.

Sometimes, whilst standing, other people must stay by their side to assist the astronaut in case of loss of balance or the astronaut appears he/she is going to fall onto the ground due to dizziness. Imagine a feeling of your legs being like pudding.

This condition happens because when they are in space, their bodies adapt to microgravity, which weakens leg muscles and causes cardiovascular changes. Back on Earth, the simple fact of standing up can lead to a sudden drop in blood pressure, resulting in fainting or lightheadedness.

It takes some time for their bodies to readjust and function normally again in Earth’s gravity.

Things such as driving, for instance, can also become a challenge due to the perception of speed, even if someone else is driving the car.

In an interview with the Museum of Science, Bob Hines, who served as the pilot on NASA’s SpaceX Crew-4 mission to the International Space Station, once said that returning to Earth and trying to adapt back to gravity after 170 days (almost six months) in space felt like his feet “were stuck to ‘giant electromagnets.’

Hines explains that when coming back from space, astronauts are banned from driving for a least a few weeks. From someone who just came back from space, even a little speed can be perceived as going really fast.

This phenomenon of orthostatic intolerance underscores the challenges of shifting between different gravitational environments. If humans will ever become a multiplanetary species or even live more permanently in space stations or for extended periods of time, science will have to overcome this challenge first.