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.