Bringing the Supermarket to the Apocalypse Chapter 419: Space-time

In general, to determine the size of an object, you need to know its shape and size. 》

For a cuboid, knowing its length, width, and height, the volume can be calculated using the formula of Euclidean geometry, as long as it knows the up, down, left, and front and rear distances relative to another static reference object of negligible size, It is also sufficient to use Euclidean geometry.

It is not enough to describe the instantaneous position of a moving object. You also need to know the instantaneous speed and acceleration. Thus, the concepts of three-dimensional space coordinate system and one-dimensional time coordinate can be abstracted. The nature and laws of the object's movement have a close relationship with the spatial coordinate system and time coordinates used to measure. In order to determine the inertial system, Newton abstracted the concepts of three absolute spaces and one absolute time. The absolute space satisfies the three-dimensional Euclidean geometry, and the absolute time elapses uniformly. Their nature is independent of any specific objects and their motions. The inertial system is the coordinate system of the reference object, which is a stationary or uniformly moving linear motion relative to the absolute space.

In classical mechanics, any object satisfies the Galilean transformation between the space coordinate and the time coordinate of different inertial coordinate systems. Under this set of transformations, position and velocity are relative; space length, time interval, and acceleration of moving objects are absolute or constant. The simultaneity in time measurement is also unchanged; it is invariable whether two events occur at the same time relative to a certain inertial frame of reference. Relative to two events occurring simultaneously in a certain inertial reference system, relative to two events occurring simultaneously in a certain inertial reference system, they must also be simultaneous with respect to other inertial reference systems, which is called absoluteness of simultaneity. All the laws of Newtonian mechanics, including the law of gravitation, have the same form under Galilean transformation. This can be abstracted as the Galilean principle of relativity; the mechanical law remains unchanged under the transformation of the inertial frame of reference. At the same time, invariance is closely related to conservation laws. The time translation invariance of a moving object under the Galilean transformation corresponds to the energy conservation of the object; the space translation and spatial rotation invariance under the Galilean transformation corresponds to the conservation of momentum and angular momentum of the object.

If there is absolute space, the motion of the object relative to the absolute space should be measurable. This is equivalent to requiring that certain laws of mechanical motion should contain absolute speed. However, there is no absolute speed in the laws of science. In other words, the accuracy of apocalypse's scientific laws does not require absolute space.

According to this type of transformation, the length and time interval of the ruler (that is, the speed of the clock) are not constant; the ruler of high-speed motion becomes shorter than the ruler of static motion, and the clock of high-speed motion becomes slower than the clock of static motion.

Simultaneousness is no longer constant (or absolute); for two events that occur simultaneously in one inertial reference system, it does not happen for another inertial reference system moving at high speed.

In the special theory of relativity, the speed of light is invariant, so the time-space interval (referred to as space-time interval) is also invariant; between some inertial systems, except for the energy conservation and momentum conservation corresponding to the invariance of time translation and space translation In addition, there is time-space translation invariance; therefore, there is an energy-momentum conservation law. According to this conservation law, the mass-energy relationship can be derived. This relationship is extremely basic in atomic physics and nuclear physics.

The principle of relativity in the narrow sense requires that all physical laws have the same form for the inertial reference system. However, incorporating the law of gravity into this requirement does not conform to the observation facts.

According to the general theory of relativity, if the inertial force or gravitational interaction between objects is considered, there is no large-scale inertial reference system, and there is only a local inertial system at any space-time point; between local inertial systems at different space-time points , Through mutual inertia or gravity. The spacetime with inertial force is still a straight four-dimensional Minkowski spacetime.

The spacetime with gravitational field is no longer straight, it is a four-dimensional curved spacetime, and its geometric properties are described by the four-dimensional Riemannian geometry with sign difference of the metric. The degree of curvature of space-time is determined by the energy-momentum tensor of matter (object or field) and its motion, determined by the gravitational field equation.

In general theory of relativity, time-space is no longer just a "stage" for the movement of objects or fields, but curved time-space itself is a gravitational field. The time-space properties that characterize gravity are closely related to the properties of objects and fields moving within them.

On the one hand, the energy-momentum of the motion of objects and fields is used as the source of the gravitational field. The strength of the gravitational field is determined by the field equations, and the degree of bending of the space is on the other hand. The nature of the motion of objects and fields.

If the sun is the source of the gravitational field, its mass causes the spacetime where the sun is located to bend, and its degree of bending characterizes the strength of the solar gravitational field. The trajectory of Mercury, which is closest to the Sun, is most affected, and starlight passing the edge of the Sun will also be deflected, and so on.

Soon after the general theory of relativity was proposed, astronomical observations showed that the theoretical calculation of general theory of relativity is consistent with the observation results.

The understanding of space and time has always been closely related to the understanding of the universe. Modern cosmology is based on cosmological principles and Einstein's gravitational field equations.

The principle of cosmology believes that the universe as a whole evolves in time, that is, there is a time arrow, and it is uniformly isotropic in space.

The spatial position and momentum, time and energy of the system described by quantum mechanics cannot be measured accurately at the same time, they meet the uncertainty relationship; the classical orbit no longer has precise meaning, etc. How to understand the essence of quantum mechanics and related measurement has been There is controversy. In apocalypse, the research on quantum entanglement, quantum teleportation, quantum information, etc. also brings new problems and challenges to the important concepts of causality and localization that are closely related to time-space.

The combination of quantum mechanics and special relativity results in a unified model of quantum electrodynamics, quantum field theory, and electroweak uniformity, including standard models that describe strong-acting quantum chromodynamics. Some challenging questions. While profoundly changing some important concepts about time-space, it also brings some principles.

If the vacuum is not empty, there is zero-point energy and vacuum fluctuations, it has greatly changed the understanding of physics about vacuum.

On the basis of here, quantum perturbation theory calculations of quantum electrodynamics can give results that are in exact agreement with experiments, but this perturbation expansion is unreasonable. The mechanism of symmetry breaking makes the intermediate boson, which transmits weak effects, gain mass. However, the expected value of the vacuum of the Hagers field and the aforementioned zero-point energy are equivalent to Changshu in a certain sense, but its value is better than that observed by astronomy. The cosmological constant is tens to hundreds of orders of magnitude larger.