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What is Free Fall? | Free Fall in General Relativity

August 19, 2022
written by Adeel Abbas

Free fall occurs when a body falls freely under its own weight. Free fall is normally only experienced in outer space, where the lack of air pressure causes objects to float around without friction.

What is Free fall?

Freefalling is the act of falling without any external force acting upon the body. Freefalling is a natural occurrence that happens at high speeds. When we jump off something, we fall freely until our bodies hit the ground. If you were to jump out of a plane, you would experience freefall.

In order to experience free fall on Earth, we need to be in thin air (i.e., low atmospheric pressure) at high altitudes. In order to achieve this condition, we would need to travel thousands of miles above sea level and beyond the stratosphere.

The closest place to experience true free fall on Earth is inside the Space Station, which orbits the planet at approximately 400km above sea level. However, even though the ISS is located at these heights, it still experiences atmospheric pressures that cause objects to sink instead of float away. This is because the low-pressure area surrounding the station is smaller than the volume of the station itself and is unable to lift everything inside.

Free fall can occur in many situations, but the most common is when an object falls from a great height.

Free fall causes air to expand and become less dense. The air around the object then tries to expand and it pushes the object upwards. This causes the object to accelerate and it goes through a parabolic curve. After a while, the object stops moving upwards and it starts falling downwards. During this process, the air also returns back to its original state.

As you see, the air gets compressed, it expands and then the object falls and the air returns to its original position.

The reason why this happens is because of the gravitational force. When the air gets compressed, the mass of the object increases. It is because of this increase in the mass that the object starts falling.

Free fall is essential for our survival. We cannot live without air, but if it is not compressed, there will be no free fall. This phenomenon is important because it is necessary for our survival.

Free Fall Example

The planets are in free fall because of the Sun’s gravity. There is a condition of weightlessness for astronauts in space because both the spaceship and the astronauts are in free fall.

 there are some more examples of free fall.

  • A spaceship in space with some sort of engine. On a suborbital trajectory, the ballistics are going up for a few minutes and then down.
  • There is an object at the top of the drop tube.
  • A person jumping off the ground at a low speed is an object thrown upward. As long as the air resistance is not much compared to the weight.

Free fall in general relativity

In general relativity, an object in free fall is not subject to force and is moving along a geodesic. The Newtonian theory of free fall agrees with general relativity, which is far away from any of the sources of space-time curvature.

General relativity is the only one that can account for the precession of orbits, the orbital decay or inspiral of compact binaries due to gravitational waves, and the relativity of direction. The experimental observation that all objects in free fall accelerate at the same rate, as noted by Galileo and then embodied in Newton’s theory as the equality of gravitational and inertial mass, was confirmed to high accuracy by modern forms of the Eötvös experiment.