Why do astronauts float inside the ISS

When you experience a push or a pull, we say that a force is acting upon you.Gravity is a special force said to result when two masses attract each other, but w hat is mass? No one has ever answered that question clearly. All scientists say is "mass is the amount of stuff in an object (which, actually, isn't very helpful). An object that has a large mass is harder to push, and engineers have designed scales to measure mass. Bathroom scales have a spring in them, and the more mass you put on the scale, the more the spring compresses and the higher the reading (the number shown on the scale). So we can measure mass even if we don't quite know how to define it.

You know that bathroom scales measure your weight, so how can they measure mass also? Your weight is the force of the Earth's mass pulling on your mass. This force increases as your mass increases. For example, if your mass doubles, then your weight on Earth doubles. Then why have two different things - mass and weight? Although your mass won't change if you go to the Moon, your weight will be less because the Moon has less mass and won't attract you as strongly as the Earth does. We need both ideas to fully understand and define how objects behave in gravity. Are you confused? Don't worry; it took scholars centuries to get these concepts straight.

Galileo (1564-1642) made careful observations of falling bodies. He demonstrated that all bodies fall at roughly the same rate. Kepler (1571-1630) proposed three laws governing how planets move around the Sun. Neither Galileo nor Kepler developed a correct theory of gravity. However, their contributions were extremely valuable to the progress of science. Newton (1642-1727) built on the ideas and observations of Galileo, Kepler, and other scholars to explain gravity. His idea was that gravity was a force that resulted from masses attracting each other. Newton was able to explain the motion of the planets around the Sun with this idea. Einstein (1879-1955) refined Newton's concept of gravity to say that mass affects space. In his theory, the planets follow a path in the "warped" space around the Sun's mass.

So that’s a very brief history of gravity, now for the ISS.

The main gravity force at the International Space Station (ISS) comes from the Earth because it is the closest large body. The farther away a mass is, the smaller its gravity force, so the Moon and Sun don't have as much effect because they are a lot farther away from the ISS. (The mass of an object also plays a role, but that is another lesson!) An object is in free fall when the major force acting upon it is from gravity. For example, when astronaut David Scott dropped a hammer on the Moon, where there is almost no air resistance, the hammer was in free fall.

The ISS free-falls as it orbit’s the Earth. If there were no forces acting on the ISS, it would travel in a straight line away from the Earth. Because the Earth pulls the ISS towards it and is travelling 7900 meters per second (26,000 feet per second) parallel to the Earth's surface, the ISS moves around the Earth in a circle.

The force of gravity on both the astronauts in the ISS and the ISS itself is about nine-tenths of what it is at the Earth's surface. Why do you think NASA astronauts in the ISS feel weightless? You only feel weight when something pushes against you. The ISS can't push the astronauts because both the ISS and the NASA astronauts free-fall at the same rate. (They are travelling at the same speed and in the same direction.) Astronauts in the ISS appear to be floating, but it is more correct to say they are in "free fall."