Why do the astronauts seem to be floating inside the space stations and shuttles?

The Problem:

You must have seen, on TV shows, that astronauts seem to be floating inside the space station or the space shuttle. It seems that they are weightless. And they actually are. But the question is how and why are they in that condition?

The Solution:

This is a classic question and one of my favorites which I have asked to numerous people and I usually get one of the following answers:

1. There is no gravity in the space. (90-95% people give this answer).
2. The gravitational pull is balanced by centrifugal force. (Some more learned guys give this answer).

Unfortunately both are wrong. Lets us see why.

1. The force of gravitation is inversely proportional to the square of distance. The space stations are at a height of nearly 400 kms. Now at a height of 400 kms, if you so dome calculations, you would find that the acceleration due to gravity is 90% of that on Earth's surface. So if you weigh 100 N on Earth then on space station it would be 90 N and not zero as you might think. SO it is definitely not ZERO GRAVITY out there.

2. Take a stone attached to a string and whirl it around. Do you really think that the stone would feel weightless? Think for yourself.

SO the question is what is the real answer. 

Weight is a force with which the Earth attracts everything towards itself. The acceleration imparted by Earth is 9.8 m/s^2. Now if you are in an elevator and it accelerates upwards at an acceleration of 9.8 m/s^2 then your weight will double out.This is because the weight tends to add up only when there is a normal reaction being imparted by the surface on which you are standing. In case of falling down the surface on which you are standing also tends to be in free fall with the same acceleration due to gravity. This means there will be no normal reaction and hence the apparant weight of yours will be zero.

This is precisely what happens inside a spacecraft. It is continuously freely falling towards the center of the Earth. Which leads to a weightless condition. The only catch is that the spacecrafts have a tangential velocity of nearly 25000 km/h which tends to make them go around the Earth in an orbit.

It is like the spacecraft is falling towards the Earth and the Earth is curving away from it thereby forcing the spacecraft to never really reach the Earth's surface.

Comments