# Force fields are possible

## Big Bang Physics 6, textbook

Fields 95 The electric field 25 Analogous to the gravitational field, the following also applies here: If the field lines are narrower, ie in the vicinity of the charges, the electric field is also stronger (Fig. 25.6). There is only one type of mass, but there are two types of charges, positive and negative. It has been agreed that the field lines run from plus to minus. So you indicate the direction of the force that acts on a positive test charge. Info: Semolina field line images Tab. 25.1 gives you an overview of the various fields. The “force fields” in science fiction are fascinating, but have more to do with fiction and less with science. Info: Scifi force fields type of field vector / scalar example temperature field scalar field weather map (Fig. 25.1) pressure field scalar field weather map (Fig. 25.1) gravitational field vector field gravitational field of the earth (Fig. 25.3) electric field vector field field under a thunderstorm cloud (see Fig 25.23, p. 100) magnetic field vector field magnetic field of the earth (see Fig. 26.9, p. 106) Tab. 25.1: Examples of fields Semolina grain field line images With semolina grains in castor oil you can show the electric field lines very nicely (Fig. 25.4) . The voltage between the electrodes must be in the range of 10,000V. But why do uncharged semolina grains align in an electric field? Because the electrical force first causes a charge shift within the grains. This is called polarization (F4; see chap. 22.1.4, p. 75). This turns them into small electrical dipoles and aligns themselves in the electrical field (Fig. 25.5). i Fig. 25.4 Fig. 25.5 Fig. 25.6: The direction of the field lines Summary If one can assign a certain property to every point in a room (such as a temperature or a force), then one speaks of a field. Force fields can be represented by field lines. They show the size and direction of the total force at each location. The electric field lines lead by definition from plus to minus and indicate the direction of force on a positive test charge. Scifi force fields How could force fields be generated in practice (F4)? There are four known forces in this universe (see Tab. 10.1, Chapter 10.1, "Big Bang 5"). Weak and strong interactions have extremely short ranges of one proton diameter or less and are therefore not suitable for generating extensive force fields. You also need a repulsive force so that the force field cannot be crossed. The only known repulsive forces are the electrical and the magnetic force, which, however, are a consequence of the electrical. Nevertheless, force fields would be difficult to implement even with this. First of all, the field of each charge extends to infinity and the force field could not be limited to a thin curtain. In addition, you could only block objects with the same charge, but not neutral ones like people or a laser beam. The situation is different with the protective shields of the spaceships (Fig. 25.7). In the Star Trek universe, these shields function at least theoretically in such a way that the entire space-time is curved around the spaceship. Einstein already discovered that this is possible in principle within the framework of his general theory of relativity, and we will come back to this in “Big Bang 8”. i Fig. 25.7: The Voyager's protective shields in action Z For testing purposes only - property of the publisher öbv

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