# Force fields Definition and 8 Discussions

In speculative fiction, a force field, sometimes known as an energy shield, force shield, force bubble, defence shield or deflector shield, is a barrier made of things like energy, negative energy, dark energy, electromagnetic fields, gravitational fields, electric fields, quantum fields, plasma, particles, radiation, solid light, or pure force. It protects a person, area, or object from attacks or intrusions or even deflects energy attacks back at the attacker. This fictional technology is created as a field of energy without mass that acts as a wall, so that objects affected by the particular force relating to the field are unable to pass through the field and reach the other side, are deflected or destroyed. This concept has become a staple of many science-fiction works, so much that authors frequently do not even bother to explain or justify them to their readers, treating them almost as established fact and attributing whatever capabilities the plot requires.
The ability to create forcefields has become a frequent superpower in superhero media.

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1. ### I Why must a pure force depend on the four-velocity?

Disclaimer: Please read in the following formulas ##E/c^2## instead of ##m##, because W. Rindler used relativistic mass, what might be confusing with today's usage of the term "mass". I am reading the chapter "38. The formal structure of Maxwell's theory" in Wolfgang Rinder's book "Introduction...
2. ### ID4 force field

What is the closest thing we can come up with that does the same thing as ID4's force field?Assuming we have unlimited energy, unlimited space and somehow won't kill anyone in the process.
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### I Experimentally measure gravitational force

Can we experimentally measure the very weak gravitational force between two objects just like we can detect magnetic field lines by a deflecting compass.
4. ### Problem on a question about the gravitation potential

Hello everyone 1. Homework Statement In the solution of a question, regarding the gravitational force fields and gravitational potential when the mass is inside Earth (where the height of the mass is lower than the radius of earth), the step where we take the integral of the force in order to...
5. ### What amount of energy is needed to make a field of plasma?

How much energy would be required to generate a spherical field of plasma using an EM field? I have heard that EM fields can excite atoms in the air to create plasma- however, this may be incorrect. If correct, how much energy would be needed and would it fry anything inside because of the...
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### I Question about the formal definition of conservative force

So, I was reading the mathematical description of a conservative force o wikipedia : https://en.m.wikipedia.org/wiki/Conservative_force and at the line "Many forces (particularly those that depend on velocity) are not force fields. In these cases, the above three conditions are not...
7. ### Is Gravitational Force conserved at the origin (r=0)?

I know gravity is a conservative force field and can be treated as such for all intents and purposes, but I was just thinking that in order to show that a vector field is conservative that vector field must be defined everywhere (gravitational force field is not defined at r=0). I was thinking...
8. ### Whether or not a force is conservative depends on our choice of reference frame, True or False?

We generally take the force of gravity to be conservative, but what if the source of gravity is moving through space? Then the force would only be conservative relative to the source, correct? As another example, consider someone in a balloon ascending with constant speed relative to earth...