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| Positive energy. From website www.djerm.com |
These days I'm having some brief discussions in other forums with some buff miracle solutions and conspiracy theory. Following the line of magical thinking which corresponds to an illiterate society and disrespectful to the actual scientific knowledge, proponents of miracle solutions to the problem of energy are often people with little or no knowledge of elementary physics, but that although they believe that actually comprise an abstract concept such as energy, and are convinced that nature really offers us an inexhaustible energy spectrum easily usable for our purposes, and if not it's because we are leveraging of a global conspiracy. The funny thing is that according to them we are also actively participating in this malevolent conspiracy of us who have dedicated many years of our life to the study of the fundamental laws of the universe, and therefore our opinion, it is always covered by a deep insight, healthy skepticism and a long process of reflection, is easily overruled by the doubts of our honesty with that ad hominem argument ahead easily fall into the disqualification Faltona and impertinent. I believe therefore appropriate to make this post in which I'll review it a little more understandable some basic concepts of physics in relation to energy, I have little faith that serve to placate the vacant infected progress unlimited, but at least it may serve to clarify some ideas to those who intend to try to understand the problems we face.
What is energy? Like other widely used concepts in physics such as force, work or power, the common language use this term with great latitude that encompasses many meanings, sometimes contradictory to the scientific and precise definition is given in Physics. I do not intend here to look back at the elementary grades of high school, because I think the basic knowledge about all the readers already have them, so I will focus on the interpretation and meaning of these concepts, but at some point I will have to use some formulas and a little math.
One of the first things we are taught in school about sums up the energy the following aphorism: "Energy is neither created nor destroyed: only transformed." The phrase is very true and condenses much of the scientific knowledge of the twentieth century is indeed the central claim of one of the cornerstones of thermodynamics, the First Principle. However, the phrase itself is much denser than it might seem, and its implementation is so far removed from everyday experience (where we see that objects spend and lose energy) and thus we take it as a phrase mantra, like one of those questions and answers of the Catechism, which did not fully understand but we accept as undisputed principle. And as with the Catechism, to reach our teens we put everything in question, and how deep we have not understood that that energy is neither created nor destroyed, then the very thing we foolishly challenged, more so if we rebel against authority imposed and levied against the deceptions that make up what we call reality. However, that energy is neither created nor destroyed is a tautology , since the definition of energy is built to be a conserved quantity, something that never changes. What happens is that we are not interested in the total energy, but the energy that can be exploited: the mechanical work. And here comes the Second Law of Thermodynamics, which tells us that in any conversion of energy sources in usable work we have to pay a toll, as a part of the energy be dispersed. But explain this a little more detail.
In the following I will rely on the basic laws of classical mechanics, which describes with precision of several orders of magnitude our everyday experience. All concepts and relations to which I refer can actually be generalized to the context of quantum mechanics (describing the laws governing the very small) and relativistic mechanics (describing the laws governing that moves very fast ), but before going on to discuss more complex concepts one must understand at least the simplest. Unfortunately, the complexity and lack of insight raised by the explanation of quantum and relativistic phenomena, sometimes exacerbated by news reports merely gimmicky and not very rigorous, makes some "witch of the tribe", sales of smoke, seek to rely on these exotic effects to justify the violation of the First or the Second Law of Thermodynamics. Nothing is further from reality, because despite the difficulties of generalizing the theoretical framework of thermodynamics or relativity to quantum field theory these two are perfectly compatible with it, and the principles deriving from it are perfectly applicable to your area ( There is an interesting question about the effect of the gravitational interaction that would violate the Second Law of Thermodynamics, but has no practical effect on what is here and their discussion goes far beyond the conceptual framework of this blog ). In summary, there is no such thing as an infinite source of energy based on the Zero Point Energy , bad interpretation of a key concept in quantum field theory (the quantum vacuum fluctuations ), though there many popular videos on the subject available on the internet, for more aberration, these videos are usually based on electromagnetic effects that can be described within the framework of Classical Electrodynamics -part, then, classical mechanics and nothing to do with the zero-point energy and greater affront regularly invoke the name of Nikola Tesla in vain, which must be turning in his grave.
Consider, then, what is the energy from the point of view of classical mechanics. The laws of Newton , verified with great accuracy after many careful experiments tell us that for any particle in motion:
F = m * a
or, which is, force equals the mass times acceleration. The left side of the equation, force, represents the dynamic quantity, is the agent of change, and has a prior existence independent of that over which it operates. The right side, which contains the product of mass and acceleration, kinematic quantity, which depends on the state of motion and the peculiarities of the particle. Mass is a property of this particle, its inertia or resistance ability to change the state of motion: a body with twice the mass of twice the acceleration needed to change the way their movement. As for acceleration, is an absolute reference (not dependent on the inertial reference frame) and measures the pace at which changes the speed of the particle. If we take this expression and integrate over a piece of the trajectory of the particle we get the following:
K W = change
where by "variation" means the difference between the final moment and initial piece of history considered. The left side is the mechanical work done by force, by definition, since work Physics is defined as: the integral of the force along the path. The right side is the change in kinetic energy , K = 1 / 2 mv ^ 2, half of mass times velocity squared, which is obtained by applying differential calculus elemental to the right of the first equation. The interpretation of this second equation, which results from the first, is that all work performed results in a modification of the kinetic energy of the particle. In short, if the force exerted on the particle work it will win or lose speed (as if the work is accelerating or braking) according to the mathematical expression. The beauty of this relationship is that the left side of the field is by force of external causes movement, while the right side is a feature specific particle moves there. On the other hand, making this relationship is extremely powerful do not need to know what has made the particle, just how much work has had on her, to see how it has changed its speed (at least in magnitude). However, the work carried out depends on what path is followed (remember the history of the particle), while the kinetic energy depends only on the initial and final point.
If the force field is the type called "conservative ", this expression can be further refined. A conservative force field is one that is derived from a potential (technically, is the gradient changed sign of a scalar function called energy potential). The advantage of conservative force fields is that, as evidenced by a little calculation work in the last equation does not depend on the path to be followed, but only depends on the initial and final point, and in fact corresponds corresponds to the variation of the potential change of sign. Therefore, for a conservative force field we
- variation of U = change in K
from which it follows that
0 = change in (U + K) = change in E
A magnitude E, which is equal to the sum potential energy and kinetic energy, is called mechanical energy of the particle. This is the definition of energy in physics, and is defined according to this reasoning, that is, precisely defined to be a conserved quantity. Not a chance, in cases where that takes into account other types of interactions more complex than I discuss here (eg, electromagnetic) are introduced to define appropriate terms of energy (eg radiation electromagnetic energy emitted by the moving charges) so that energy is always a conserved quantity. And that is precisely what we want is that energy is a conserved quantity, because then we can easily characterize the physical state of a system without having to know all its evolution. The definition of energy is also a reproductive character of the equations of motion of the particle through Hamiltonian formulation. In short, the movement of a particle under the action of conservative forces preserves, by construction, energy and also can regenerate the whole movement with the equations derived from it ( Analytical Mechanics).
What we have discussed so Now a simple case: a single particle under the action of a conservative force field. You have to say that all the elemental forces we know (gravitational, electromagnetic, strong nuclear and weak, all others are derivations of them) are conservative, so ask the force to be conservative is not a big restriction. However, the introduction of complex bodies, which contain many particles, it does trigger a change in practice the concept of energy. So, assuming the linear superposition principle (the resultant force is the sum of all the fundamental forces) that we total system power (understood as the sum of the kinetic energy of all particles the sum of the potential energy of all particles) is a conserved quantity, as in the case of a single particle. However, with a complex object consisting of many particles we distinguish two types of energy: its center of mass and heat. The center of mass is that corresponding to the object behaves as a whole, is the kind of energy that is often interesting to do useful work, and that is what is macroscopic: the piston moves upward to compressing the combustion chamber, the rotor blade that is moved by water, etc. But the macroscopic body has a second type of motion, smaller scale, in which position changes are smaller in the case of solids: the thermal motion, which corresponds to the agitation of the molecules that form the object and that is precisely what we measure when we measure the temperature of an object (it can be shown by the Statistical Physics the temperature is actually a measure of this kinetic energy). This second type of motion is chaotic, random. The movement of the center of mass (including the solid rotation of rigid bodies) is readily usable para hacer un trabajo; el térmico, por el contrario, sólo puede ser usado para transmitir una agitación semejante a un cuerpo puesto en contacto con él (contacto térmico y transferencia de calor).
Cuando utilizamos una fuente de energía cualquiera (porque quemamos un combustible o hacemos otro tipo de reacción física o química) generalmente desencadenamos un proceso térmico: de golpe una gran cantidad de energía potencial contenida en el combustible es convertida en energía cinética, pero con un grado de desorden considerable (por ejemplo, en la gasolina que se quema las moléculas de los gases producidos move in all directions and with very different speeds.) With a suitable apparatus (eg, confining the explosion inside a cylinder with a piston phone) can ensure that these molecules move randomly transfer part of its movement in one direction to the macroscopic element perform the useful work want. Part of the energy of the disordered molecules is transmitted to a system in which the movement is mostly ordered, solid, and therefore useful for us. However, we can not avoid that part of the newly released kinetic energy is never utilized and is dispersed in the form of heat, random movements of molecules. That is exactly what it says the Second Law of Thermodynamics: never recover all the energy that was stored for useful work, one part will be dispersed as heat. Worse, this dispersion is irreversible, can never be recovered (if not at the expense of generating even more dispersion). We know well the day to day costs more to sort that mess, fixing to break, linking to separate, clean up that mess ... The energy is not lost, but little by little scattering in random movements, thermal, which are useless for us. The energy is unchanged, but its usefulness to us decreases, and once used is not recovered.
Finally, the post is long and certainly not affordable to everyone, and I have not entered into the technical details of the issue. But I would conclude by making clear a few concepts.
regard to inexhaustible energy sources need to be clear about one thing: he claims that is a source of infinite energy, or do not understand the concept of energy or is a trickster (or both). Put another way: if someone says he can have the desired inexhaustible source of energy should be able to show which of the basic postulates of classical mechanics fails, typically will be the conservative nature of the forces acting on the system. Curling up with complicated devices that attempt, as the magician's trick to divert attention from what actually happens is a deception, if the merchants of the gullibility of others have such power source, demonstrating that they have discovered a new type of interaction , strength, which is not conservative, that careful experiments and measurements show rigorous to support it. On the other hand, would be a drama to be true. If there is a fundamental force conservative and can not inject energy into our system, then would be like if we had an inexhaustible source of energy. But that energy would be dispersed equally to the use, so we go slowly increasing the temperature of our system (planet, solar system, galaxy, universe ...) until you reach a time when it would melt everything. Think for a moment: what they think would happen if there were a magic tap that gave us all the oil we wanted? That would burn continuously until the atmospheric concentration of CO2 in the Earth was like Venus and land surface temperatures were equally searing. On the other hand, it is logical that there is no such kind of forces in our universe, exist because it would destabilize even destroy the possibility of intelligent life organized matter and that observed ( anthropic principle). Our universe seems to work as a system of cause-reaction that compensates for the cause, always keeping a delicate dynamic balance.
And regarding the optimal use of energy sources, it must be clear that the Second Law of Thermodynamics is, in essence, pure statistics. Classic example: what is the probability that in a container with two chambers, one empty and one filled with gas, by removing the wall that separates the gas fills the entire container? Just because the molecules move randomly, the theory predicts and practice confirms that in a moment of gas molecules occupy all the volume equally, the probability is 1. What is the probability that a given instant of time all the molecules are concentrated in a single chamber, so that if we were to place the wall would return quickly to have the gas contained? The probability of this event tends to zero exponentially with the number of particles. That means pure chance sets a direction of time, which always leads to increased disorder, and can not expect that the molecules of CO2 and water produced by burning gasoline with the ambient heat to react spontaneously to return to form gasoline.
all: the total energy of the universe never changes, but the useful energy we can leverage decreases with use. Anyway, I hope that, having taken the trouble to write a post so long, it can serve as reference for anyone who needs to shake off the heavy lunatics of the chimera of infinite energy. Indeed, as anxiety about our situation will become acute over Proponents of miracle solutions, and society will be at a crucial moment, which must decide whether to hear mermaids singing promise you never accessible Arcade and again, or grow up and accept that things must change.
Salu2,
AMT
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