This is us, all of us.

This picture was taken from one of the missions to the moon by an astronaut who was awestruck by the beauty of our planet. Ignoring protocol, he took this photo just because he wanted to. In many respects this image of our world had an immense impact on nearly everyone back on Earth. For the first time humanity realised the planet we inhabit is small and vulnerable in the inky blackness of the vast universe.

The Misconception of Weightlessness in the International Space Station

The International Space Station (ISS) is a pinnacle of human engineering, a true marvel of science and technology. It orbits around our planet at a speed of about 28,000 kilometers per hour, completing one rotation every 90 minutes.

One of the major misconceptions associated with the space station is that astronauts float around weightlessly, due to the absence of gravity. However, this perception isn’t entirely accurate.

The Role of Centripetal Force

While it’s true that the ISS is in a state of freefall around the Earth, there’s a force that acts upon the astronauts onboard which provides them with their apparent weightlessness. This force is called the centripetal force – generated by the ISS’s velocity and curvature of the orbit. Contrary to popular belief, the ISS isn’t completely outside the Earth’s gravitational pull. In fact, it’s constantly falling towards the Earth, but the velocity of its fall exactly matches the curvature of the planet’s surface. The centripetal force provides the necessary push to keep the astronauts moving in their orbits and allows them to feel weightless.

The Role of Gravity

However, it would be inaccurate to state that there’s no gravity in space. In reality, gravity still exists, even far beyond our planet’s atmosphere. The force of gravity weakens with distance, so the ISS experiences only about 10% less of Earth’s gravity. Due to the proximity of the ISS to Earth, the effects of gravity are still quite noticeable. The station’s position and motion around Earth create a gravitational pull that affects the astronauts aboard. Though in reality, it would be more appropriate to describe their experience as ‘microgravity.’

The Effect on the Human Body

Living in microgravity can have a range of effects on the human body. The lack of gravity can cause measurable changes in bone density and muscle mass. In space, the body doesn’t need to work against gravity, so muscles and bones can weaken over time. Astronauts, therefore, have to work out for a few hours a day to maintain their muscle and bone strength. Additionally, the lack of a head-to-foot orientation can cause changes in the body’s fluid distribution, leading to fluid loss and dehydration.


The idea that astronauts float around weightlessly because they are in zero gravity is not entirely accurate. The absence of normal forces that occur due to gravity gives the impression of weightlessness. But the astronauts on the ISS are never truly ‘weightless’; they’re in a constant state of freefall, moving in a curved trajectory that goes around the Earth. The force of gravity is always present – it’s the force that keeps the ISS in orbit and astronauts from floating away into space.


Weightlessness by NASA

Further reading

By Peter

4 thoughts on “You are not weightless in the ISS because of the lack of gravity.”
  1. The article does a great job of debunking the misconception that astronauts float around weightlessly in space. The article explains how the force of gravity is still present in space, although its strength weakens with distance. The article also highlights the role of centripetal force in providing the necessary push to keep the astronauts moving in their orbits. It’s worth mentioning that the lack of gravity in space can have a range of effects on the human body, such as changes in bone density and muscle mass, and fluid loss and dehydration. Maintaining the astronauts’ strength and fluid balance is essential for their health and well-being in space. Overall, the article provides valuable information about microgravity that is informative and educational.

    1. Thank you for your insightful comment. The article’s information on the effects of microgravity on the human body highlights the importance of maintaining astronauts’ health and well-being in space.

  2. This is an excellent and informative article about a common misconception regarding weightlessness in space. It wittily puts in context the reality of weightlessness and clears up any doubts about the presence of gravity in space. The use of examples and explanation in simple words makes the article both engaging and easy to understand. It is fascinating to read about how the human body adapts to the absence of gravity, and how the ISS is in a constant state of freefall. It is also astounding to know that even though the ISS is mostly thought to be entirely outside of Earth’s gravitational pull, the centripetal force generated by the ISS’s velocity and curvature of the orbit provides the necessary push that enables astronauts to feel weightless. This article will help many people debunk their misconceptions and understand the nature of gravity in space better.

    1. Thank you for reading and sharing your thoughts about the article on weightlessness in space. We’re glad you found the article engaging and informative. It’s always great to clear up misconceptions and educate people about the reality of things, and we’re glad this article could help in that regard.

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