The speed of light (more generally, the speed of propagation of electromagnetic radiation) in a vacuum, denoted c, is an important fundamental physical constant in many areas of physics. It has an exact value of 299,792,458 meters per second, because the meter length unit is redefined based on this constant and the standard second. According to special relativity, c is the maximum speed that all energy, matter, and information in the universe can reach. It is the speed at which every massless particle bound to physical fields (including electromagnetic radiation such as light photons) propagates in a vacuum. It is also the propagation speed of gravity (such as gravitational waves) predicted by current theories. Particles and waves travel with velocity c regardless of the motion of the source or of the observer’s inertial frame of reference. After Einstein founded relativity, it became known that the speed of light is indeed very fast, because this is the upper limit of the local speed in the universe, and no other speed can be exceeded. through it. Moreover, regardless of the medium in the frame of reference, the measured speed of light is exactly the same. Based on the principle of the constant speed of light in relativity and the highly accurate measurement of the speed of light, physicists have also determined the speed of light to be 299,792,458 meters/second without affecting the speed of light. affect the current physical quantity. In this way, people no longer have to worry about accurately measuring the speed of light, and can also solve the problem of errors in the equipment used to determine the clock. The speed of light propagating in a vacuum is independent of both the motion of the light source as well as of the observer’s inertial frame of reference. The constancy of the speed of light was postulated by Einstein in his 1905 paper on special relativity. Physicists can now only experimentally confirm the speed of light by methods above two Two-way speed of light is frame-independent, because the speed of light cannot be measured in one-way speed of light, ignoring some conventions of uniformity. synchronization between the clock at the source and the clock at the receiver. Whether it’s electron transition, nuclear fusion, nuclear fission, or the annihilation of yin and yang matter, these processes produce light. Once light is created, their speed will immediately reach the speed of light, and they will always travel at this speed. If light were not absorbed by matter, they would not be dissipated in the universe, and the speed would always remain at the speed of light. For example, the first photons created in the universe 13.8 billion years ago are still present today, and they travel through the universe at the speed of light. So, how did light reach the speed of light? How does light maintain the speed of light? What is the driving force that drives the light forward? If it is explained from the point of view of the particle nature of light, then light is composed of photons with no rest mass. According to special relativity, since the static mass of photons is zero, their speed can only be the speed of light. According to the Higgs mechanism of the Standard Model of Particle Physics, when photons without static mass pass through the Higgs field throughout the universe, the photons will not be coupled, so they will not gain static mass, and their speed will not decrease. Once the photons are generated, their speed will directly reach the speed of light, and there is no acceleration from zero to the speed of light. Propagation of photons does not require energy to propagate, if they were not absorbed by matter or a black hole, they would always travel aimlessly through a vacuum at the speed of light. On the other hand, if explained from the evaporation of light, the nature of light is electromagnetic wave. Maxwell’s equations of electromagnetism show that electricity and magnetic fields are essentially unified, that a changing electric field excites a magnetic field, and a changing magnetic field excites a repeated electric field, creating out electromagnetic waves. Since electromagnetic fields are formed at the speed of light, electromagnetic waves travel at the speed of light. The generation and existence of electromagnetic fields are independent of the medium, so light can travel at the speed of light in a vacuum. Although the spatial structure continues to expand, light propagating through space will appear redshift, but they will not completely disappear in the universe.

According to the excavation team of the Archeology Institute, this architectural vestige is completely located in the cultural class of Tran dynasty, below the culture class of the Le so, Le Trung Hung and Nguyen dynasties at a depth of 1.95m, from the ground ground. current area. This cultural layer is dense with Tran tiles, including red cover tiles, lotus-nosed tiles, and pointed tiles. Round architectural traces Architectural vestiges of the Tran dynasty are circular in shape under the Tran dynasty clay and brick layers, about 0.4m – 0.6m thick and built entirely of cover bricks. Round architectural brick cover bricks are all rectangular, bright red bricks arranged in two staggered rows and only one layer, the outer row is lower than the inner row. Outside the circle in the East – West – South directions are a number of pebbles with many different sizes arranged relatively flat but not in a certain shape. Implementing the direction of the Standing Committee of the City Party Committee and Hanoi People’s Committee at Notice No. 152-TB / TU dated March 6, 2021 at the meeting with the Thang Long Heritage Conservation Center – Hanoi; Decision No. 3624 / QD-BVHTTDL dated December 4, 2020 of the Minister of Culture, Sports and Tourism on archaeological excavations at Thang Long Citadel Center – Hanoi, Heritage Conservation Center Thang Long – Hanoi has coordinated with the Archeology Institute to conduct excavation and exploration in the East – North area of ​​Kinh Thien electrical base relic with a total area of ​​nearly 1,000m2. The exploration excavation in 2021 is considered to have the largest scale in more than 10 years, the Archeology Institute conducted the excavation at Thang Long Citadel – Hanoi. Exploring the circular architecture found that the clay foundation mixed with the Tran debris was compacted firmly. There are a few bricks on the face that are arranged in an East-West direction, but they are no longer neat. In this group of bricks, the first brick from the West, at the edge has two Chinese characters “Thuong Tan Quoc”. In the past, I met at 18 Hoang Dieu a brick in the Tran dynasty with the word “Thuong Tan Quoc”. At the same time, there was another brick with the word “Thuong Tan Vien”. At a depth of 0.7m compared to the circular architecture, there is a small rock base in the Tran dynasty that no longer has its original position. Outside, to the south, 78cm from the circular architecture, there is a large terracotta pot (mouth diameter 1.2m, depth 55cm) bright red, good materials, the outer rim of the mouth is decorated with lotus flowers, apricot flowers and “Lien Chau” is characteristic of the Tran dynasty. The pot has a drainage hole set on one side of the perineum. This is probably the largest terracotta pot ever in the Tran dynasty. Outside the round vestige to the East there are traces of two underground sewers in the Tran dynasty: one was built of brick cover, the other was built by specialized circular water pipes. The brick sewer is 3.64m far from the circular architectural vestige to the East and 0.35m lower, and 4.64m long running in the North – South direction. The sewer section in the North was cut by architectural foundations of the Nguyen Dynasty. The culvert consists of three parts of the cap, wall and bottom. The manhole cover and bottom are placed horizontally, the sides of the manhole are placed vertically on the two edges of the bottom and the manhole cover forms the sewer with a cross-section of nearly square as the space for drainage. The type of brick used to build the culvert is a rectangular red cover brick with a cut surface of the brick (characteristic of architectural materials of the fourteenth century). Currently the sewer has been destroyed, so the actual length in the past has not been determined. The manhole cover is covered with a single row of remaining 6 bricks, the North is left with 5 bricks, the first 2.28m long, bolted by broken rectangular bricks (21cm wide, 6cm thick) printed with Han characters, Vinh Ninh Truong. The male is left with one 40cm long pill. The round water sewer is 3.5m from the brick sewer to the East. The two ends of the sewer that were cut by the late architecture remain only a section of 2.97m in length, running in the East-West direction. There are still 8 round terracotta water pipes, the head is wider than the tail, the end of the tube has a ledge to assemble so that it fits from the end of one tube to the other. Terracotta sewer pipes are 37-39cm long, 13-15cm in diameter. This sewer appears in the same strata as the brick sewer and is 0.35m lower than the circular architecture. Chronology and values According to the results of stratification of Thang Long culture, the relic has a circular structure in the Tran cultural class. Two large underground culverts and terracotta pots distributed around circular architecture all date to the Tran dynasty. Relevant relics in the area revealed such as bricks, tiles, and chinaware all dating back to the Tran dynasty. Therefore, it is possible to initially identify vestiges of circular architecture dating back to the Tran dynasty in the XIII-XIV century. For those who directly excavated, the round structure of Tran dynasty that appeared this year in the Northeast of Kinh Thien Palace could be classified into a type of “strange” architecture. The status quo, this circle is intact, the structure is quite simple. Other traces appeared around such as large terracotta pots, brick sewers, circular underground sewers with the same age, but it is not possible to confirm whether they are related to each other or not. The current state of the monument has not seen any signs that can remind the excavators of the architecture’s function. The area is under further excavation Some people suggest that this could be a small flower garden scene in the Tran Palace. Is there also the thought of a structure related to some kind of spiritual ritual? However, all that are just initial speculations without any evidence to explain. Previously, the round architecture of Tran dynasty was met by archaeologists in a few places. In 1998, excavation in the North of Doan Monmon discovered a circle of late Tran dynasty cut into the vestiges of the wall / or the road with frill lines “lemon flowers” dating back to the earlier Tran dynasty in the southwest position. This circle is noteworthy because there are vertical bricks inside in the style of “diagonal triangles” filling the round architectural surface. At Bao An pagoda (Gia Lam), archaeologists also encountered a type of circle with the form close to the circle in Doan Mon. Thus, at least in archeology, at present, there have been 3 circular structures in Tran dynasty in three different places, in which the structure in Doan Mon is somewhat closer than the round structure in Bao An pagoda. The circular structure in the Northeast of Kinh Thien is not clear whether it is the same as the two above structures because the surface layer has been destroyed, only the circle is dashed. However, they have the same circle and have two nearly the same vertical brick lines, so it can be deduced that they have nearly the same structure. But all three of these architectural vestiges are functionally unknown. The three circular structures in 3 different places also show that there seems to be a style of building brick circles in the architecture in the Tran dynasty, as well as in the Le Lieu period. . “What is that structure to do and what it reflects in Tran architecture in Thang Long or in a temple (Bao An pagoda) is still a mystery that needs to be studied for a long time. Therefore, archaeologists temporarily consider traces of circular architecture in the Northeast of Kinh Thien Palace in 2021 as a remarkable “strange” architecture type of Tran Dynasty in Thang Long Palace area. It also shows that Thang Long Palace still has many unexpected undiscovered values ​​under the ground of a World Heritage, ”said the excavation team of the Archaeological Institute. Hope to soon restore Kinh Thien Palace If in 2019, with an excavated area of ​​900 square meters, the Vietnam Archeology Institute discovered many traces of gardens, lakes, and artifacts with architecture of the Le primitive and Le Trung Hung dynasties, making the hypothesis of Thuong ien garden, Can Chanh power was first discovered at the Imperial Citadel of Thang Long – Hanoi, in 2021, the results of exploration and excavation revealed more unique evidences, artifacts and relics. With the narrowed position of archaeological results in 2021 is considered to have touched the space of Can Chanh Palace, an overall part of the overall space of the Kinh Thien Palace in the Le early period. Previously, Hanoi also made specific moves with the project of restoring Kinh Thien power, which is the introduction of a roadmap: Phase 1 (2020 – 2025) completing pre-feasibility study report, reporting feasibility study report and basic design; Phase 2 (2025 – 2030) to implement the project of restoring Kinh Thien power. According to scientists, experts, architectural traces and relic systems discovered in the excavation in 2021 continue to reflect the complex evolution of historical and cultural relics Thang Long – Hanoi. underground. Thereby, it has contributed more documents to clarify the great, rich and diversified values ​​with three globally outstanding criteria of the World Heritage Site Center of Thang Long Citadel. At the same time, contribute some valuable materials to serve the research on recovering the space of Kinh Thien main hall. The new discoveries create favorable conditions for scientists, speed up the recovery process, and satisfy the aspirations of the masses of people and researchers. Posts and photos: Bao Thoa