[Reading Science] What Happens If You Recklessly Use Force Without 'Gravity' in Space?

What would happen if a human applied force to another object in the zero-gravity environment of outer space?
[Photo by YouTube screen capture]

[Asia Economy Reporter Kim Jonghwa] There is no gravity acting in outer space. The absence of gravity means that the 'normal force' is '0'. The normal force is the force acting perpendicular to a surface. In other words, if gravity does not act, the weight becomes '0'.

A rock that weighs 1 ton (t) on Earth will weigh 0 in outer space where gravity does not act. In outer space, this rock would feel like a weightless sheet of paper, unlike on Earth. What if you tried pushing or throwing this rock just for fun?

In outer space, because there is no gravity, carelessly moving or touching an object placed in the middle can cause unexpected problems. Experimentally touching or moving the rock is more likely to lead to bad outcomes. This is due to the 'law of action and reaction'.

All matter has 'mass'. Mass is an intrinsic quantity of matter that does not change under any circumstances. This mass remains constant even in outer space where there is no gravity. Even though the rock that weighed 1t on Earth becomes 0 in weight in outer space, its mass remains 1t.

Weight is the product of mass and gravitational acceleration (g), representing the force an object experiences due to Earth's gravity. An adult man weighing 70 kg on Earth would weigh 0 kg in outer space, but his mass remains 70 kg. In other words, a mass of 70 kg never changes.

What happens if you push a rock with a mass of 1t that feels weightless in outer space? According to the law of action and reaction, the person pushing also receives a force. The force transmitted to the person pushing is equal to the force the rock receives, which is somewhat like giving yourself a flick on the head while looking in the mirror.

The easiest example to understand the law of action and reaction is a balloon. When you blow up a balloon, block its opening with your hand, and then release it, the air escaping from the balloon causes it to shoot off in the opposite direction.

At this moment, the balloon moves in the opposite direction to the escaping air. The principle of a rocket launching into outer space is the same as the balloon releasing air. When a rocket burns fuel and expels gas at tremendous speed downward, it gains thrust in the opposite upward direction.

Returning to outer space, if a person pushes the rock, the rock moves in the direction it was pushed, and the person is pushed in the opposite direction. In outer space, without friction, neither the rock nor the person will stop but will continue moving. They might only stop if caught in a planet's orbit or gravity, or if they collide with a meteor.

Astronauts floating in outer space. For everyone's safety, they do not engage in any behavior outside the rules.
[Photo by YouTube screen capture]

One important point to remember is that if a man with a mass of 70 kg pushes a rock with a mass of 1t, the forces applied to both objects are equal, but their momenta differ. The man with the smaller mass of 70 kg will be propelled at a much higher speed than the rock. In this case, the 70 kg man has touched something he should not have.

In science fiction (SF) movies, characters use thrusters or are connected by wires when flying or moving in outer space. Scenes where they desperately grab onto something to stop when bumping into a spaceship also have a reason. They know they would otherwise keep floating forever in space.

Isn't life on Earth the same? Unnecessary displays of force often cause backlash and trouble. Should such cases be called the 'butterfly effect'? Or is it more accurate to call it the law of action and reaction or the 'law of mass invariance'? While inanimate objects do not know, human behavior might better be described as the 'law of reaping what you sow'.