Bringing the Supermarket to the Apocalypse Chapter 415

Energy is one of the basic concepts of physics. From classical mechanics to relativity, quantum mechanics and cosmology, energy is always a core concept. ↑

In general common sense or popular science readings, energy refers to a system that can be released or obtained from it, which can be equivalent to doing a certain amount of work. For example, 1 kilogram of gasoline contains 12 kilowatt-hours of energy, which means that if all the chemical energy in 1 kilogram of gasoline is applied, it can do 12kwh.

Energy is the physical quantity of physics that describes a system or process. The energy of a system can be defined as the sum of work from a state of zero energy to the state of the system. How much energy a system has in physics is not a certain value, it changes as the system is described. In the course of life activities, all life activities require energy, such as synthetic reactions of material metabolism, muscle contraction, and glandular secretion. And this energy is mainly from food. The nutrients contained in animal and plant foods can be divided into five categories: carbohydrates, lipids, proteins, minerals and vitamins, plus water in six categories. Among them, carbohydrates, fats and proteins can be oxidized in the body to release energy. The three are collectively referred to as “capacity nutrients” or “heat source materials”.

The law of conservation of energy indicates that energy does not occur out of thin air, nor does it disappear from the air. It can only be transformed from one form to another, and the total amount of energy remains the same. Energy is scalar, not vector, no direction. As for positive matter and antimatter, it is not that the mass is positive or negative, but the electrical properties of the nucleus are opposite. After the encounter, the mass is converted into energy. Energy is needed for any sport. There are many forms of energy, such as light energy, sound energy, heat energy, electrical energy, mechanical energy, chemical energy, nuclear energy, and the like. As an example, observe the energy of a solid with a mass of 1kg:

In classical mechanics, the energy is the sum of the work done from static acceleration to the existing speed.

In classical thermals, the energy is the sum of the work done by heating the existing temperature from absolute zero.

In physical chemistry, the energy is the sum of the work added to the raw material when the solid is synthesized.

In atomic physics, the energy is the sum of the work done to the existing state from the state in which the atomic energy is zero.

The opposite method can also be used to define the energy contained in this solid. Give two examples:

The internal energy of the solid is the sum of the work released by cooling it to absolute zero.

The atomic energy of the solid is the kinetic energy of its binding energy released into a reaction product in the nuclear fission or fusion reaction.

Although energy is a common and basic physical concept, it is also an abstract physical concept.

In fact, physicists did not really understand the concept of energy until the mid-19th century. Before that, they were often confused with concepts such as force and momentum.

The energy requirement of the human body refers to the individual who can maintain a good health condition for a long time, has a good body shape, body composition and activity level, achieves energy balance and can maintain the energy intake necessary for production labor and social activities.

In Einstein's special theory of relativity, energy is a component of four-dimensional momentum. In any closed system, each component of the vector (one of which is energy and the other three is momentum) is conserved when viewed in any inertial system. If it does not change with time, the length of this vector will be conserved (Mkowski model length) The length of the vector is the static mass of a single particle, and is also the constant mass (ie, constant energy) of the system composed of multi-mass particles.

Therefore, as long as the observer's reference system has not changed, the conservation of energy versus time in the special theory of relativity is still true, and the energy of the whole system remains unchanged. The observers in different reference systems will measure different amounts of energy, but each observation The amount of energy measured by the person will not change with time. The invariant mass is defined by the energy-momentum relationship, which is the minimum of the system mass and energy that all observers can observe. The constant mass is also conserved, and the values ​​measured by the observers are the same.

In quantum mechanics, the energy of a quantum system is described by a self-adjoint operator called a Hamiltonian, which acts in the Hilbert space of the system (or the wave function space). If the Hamiltonian is a non-time-varying operator, the measurement of its probability does not change with time as the system changes, so the expected value of energy does not change with time. The localized energy conservation under quantum field theory can be obtained by using the energy-momentum tensor operator with the Nobel theory. Since there is no global time operator in quantum theory, the uncertainty relationship between time and energy will only be established under certain conditions, and the uncertainty relationship between position and momentum is the essence of quantum mechanics. Different (see the principle of uncertainty). The energy at each fixed time can be accurately measured without being affected by the uncertain relationship between time and energy, so even in quantum mechanics, energy conservation is a well-defined concept.

Energy must follow the law of conservation of energy. According to this law, energy can only be changed from one form to another and cannot be produced or eliminated. Energy conservation is the mathematical conclusion of temporal translational symmetry (translation invariance).

According to the law of conservation of energy, the energy flowing in is equal to the energy flowing out plus the change in internal energy. This law is a fairly basic criterion in physics. According to the translational symmetry of time (translation invariance), the laws of physics (theorems) hold at any time.

The law of conservation of energy is a feature of many laws of physics. From a mathematical point of view, conservation of energy is the result of Novo's specific theory. If the physical system satisfies continuous symmetry in time translation, its energy (the conjugate physical quantity of time) is conserved. Conversely, if the physical system has no symmetry in time shifting, its energy is not conserved, but if the system is exchanged with another system and the synthesized system does not change with time, the energy of the larger system will Wherein Since any time-varying system can be placed in a large, time-invariant system, energy conservation can be achieved by appropriate redefinition of energy. For the physics theory in flat spacetime, since quantum mechanics allows for non-conservation in a short time (for example, positive-antiparticle pairs), energy conservation is not observed in quantum mechanics, and in the special theory of relativity, the law of conservation of energy is converted into mass. Can keep the law.

The law of conservation of mass energy means that in an isolated system, the sum of relativistic kinetic energy and static energy of all particles remains unchanged during the interaction process. The law of conservation of mass energy is a special form of the law of conservation of energy.

Energy, what Lin Feng is very eager for, can't do anything without enough energy. What you can do now is to constantly enhance your energy.

Chapter end