Understanding Astronauts' Weight in Spaceship

Astronauts inside a spaceship, especially one in orbit like the International Space Station (ISS), experience a sensation of zero weight. This is often referred to as weightlessness or microgravity.

The Concept of Freefall

The primary reason for this feeling is that the astronauts and the spaceship are in a continuous state of freefall around the Earth. Although Earth's gravity is still significant at orbital altitudes (about 90% of its strength at the surface), it's constantly pulling the spaceship and everything inside it towards the planet.

However, the spaceship is also moving horizontally at a very high speed. This forward velocity combined with the constant downward pull of gravity causes the spaceship to continuously "miss" the Earth, resulting in an orbit.

Sensation vs. Reality

Inside the orbiting spaceship, both the astronauts and the objects around them are falling together at the same rate. Because there is no external force pushing down on them (like the ground does on Earth) or pulling them apart, they don't feel their own weight. It feels as though gravity has disappeared, but in reality, they are constantly falling.

Conclusion

Therefore, astronauts inside an orbiting spaceship feel zero weight due to the state of continuous freefall.