_ _ _ _ First of all, I want to be sure of you: the phenomenon of "slowly shrinking the clock with your feet" is absolutely real! The word physics comes from Greek, which means "nature". In ancient times, physics was an important part of "natural philosophy", and it was not separated from philosophy until after16th century. There is a very special relationship between physics and philosophy. Because physics is the basic discipline of natural science and the laws of physics are the most basic and universal laws in nature, the research results of physics will always directly promote the development of philosophy; At the same time, philosophy provides research tools and thinking standards for physics, and major breakthroughs in physics often come from ideological breakthroughs and philosophical enlightenment. Ignoring the guiding role of philosophy can only hinder the development of physics.
_ _ _ _ When I was in high school physics, I developed a strange habit that others thought: when I argued with my physics teacher about a physics theorem or a sentence, I used Chinese grammar to analyze these sentences very harshly, for example, to find out who is the subject, who is the object and who is the modifier. Also, I think it is impossible to learn physics well without learning math well. You can only make a face in junior high school at most. In the later high school physics and college physics, there was no mathematics, and it was simply daydreaming who wanted to learn physics well! In other words, if you want to learn physics well, you must form your own effective view of nature and strive to learn mathematics well. Mathematics is meaningless if it is not applied. You know, mathematics is just a quantitative analysis tool.
_ _ _ At the beginning, I still want to talk about the theory of the phenomenon of "the foot shrinks slowly". The content of "Development from Classical Mechanics to Relativity" is as follows:
_ _ _ _ In classical mechanics based on Newton's law of motion, there is a physical quantity such as space interval (length) L, time t and mass m, which has nothing to do with the speed of motion of an object. A ruler is so long when it is still at rest and so long when it is moving; Whether the clock is stationary or moving, its speed remains the same; The mass of a stationary object is the same as that of a moving object. This is the concept of absolute time and space in classical mechanics.
From _ _ _ to the end of19th century, classical mechanics encountered insurmountable difficulties in the face of the "strange" phenomenon of some fast-moving microscopic particles. Facing new things, Einstein broke the traditional concept of absolute time and space, published a paper entitled "On Electrodynamics of Moving Objects" in 1905, put forward the principle of relativity in a special sense and the principle of invariance of light speed, and founded the special theory of relativity. The special theory of relativity points out that length, time and mass all change with the speed of motion. The relationship between length, time, mass and speed can be expressed by the following equation:
L = (LO) * (L-V 2/C 2) 0.5, (commonly known as "scale effect")
T = (to)/( 1-V 2/C 2) 0.5, (commonly known as "clock slow effect")
M = (mo)/( 1-V 2/C 2) 0.5, (commonly known as "mass-velocity relation")
_ _ _ _ In the above categories, V is the speed of the object, C is the speed of light in vacuum, and lo and L are the length of the object measured in the direction of speed V in the relatively static and moving systems respectively; L0 and t are the time measured in a relatively stationary and moving system, respectively; Mo and m are the mass of the object measured in a relatively static and moving system, respectively.
_ _ _ _ However, when the speed of macroscopic objects is much less than the speed of light (V
_ _ _ _ Following the special theory of relativity, Einstein established the general theory of relativity in 19 15, pointing out that space-time cannot exist independently without matter, and the structure and nature of space depend on the distribution of objects, which greatly deepened human understanding of time, space and gravity. "Special relativity" and "general relativity" are collectively called relativity.
_ _ _ The popularization of the theory of relativity is reflected in all kinds of sci-fi movies about time, such as the time machine, back to the future series, and the 100-curtain triangle, which fully embodies the human exploration of the most mysterious thing in the world-time, and all of them permeate the common people's understanding of the theory of relativity. At present, Hawking's A Brief History of Time, the greatest theoretical physicist, has become a must-read book for ordinary people, which just fulfilled his old man's wish.
_ _ _ _ According to the British "Daily Mail" reported on July 28th, mallet, 62, is a professor of physics at the University of Connecticut. His time machine is based on Einstein's general theory of relativity. General relativity points out that gravity is a time-space curve, that is, a strong gravitational field can bend light and slow down the passage of time.
_ _ _ _ marlett's conception is nothing like the sleigh in the novel "Time Machine" by British science fiction writer Hg Welles, nor is it like the time machine in the movie "Back to the Future". Instead, his shuttle will look like a cylindrical vortex of light several feet in diameter. In fact, it is a huge gravitational field caused by a series of laser beam rings, and the intensity of the field center is enough to distort time and space.
_ _ _ _ Therefore, if a particle is placed in the middle of the halo, it will be pulled by the gravitational field. If you are close to the gravitational field, the clock and biological clock will slow down. If a person walks into this "time tunnel", he may appear at some time in the past.
_ _ _ _ One-way limited "time travel". Marlett believes that he can see the world's first "time machine" in his lifetime. He hopes to get 65438+200,000 pounds (US$ 250,000) to build a prototype in the laboratory. However, marlett also has strict requirements for sponsors.
"We hope to obtain non-military sources of funds. I don't want this plan to eventually become' highly confidential', so that we can't follow up ourselves. "
_ _ _ _ However, this imaginary "time machine" is not free to go back and forth as described in science fiction, reaching a certain point at will, and at most returning to the point when the machine was just started. For example, if you start the machine on June 65438+1 October 1 day and let it run for three months, then you can enter the "time machine" in March, and at most you can only go back to June 65438+1October1day. So it is impossible to go back to the Middle Ages to explore or travel to ancient Rome, and it is impossible to reach the future world.
_ _ _ _ cannot rewrite the fate of his father's death. This result is actually tantamount to announcing that mallet's original intention of building a "time machine" cannot be realized. At the age of 10, Marlette's beloved father died of a heart attack. The pain of losing his father made marlett feel that the whole world was destroyed. He couldn't believe it.
I will never see my father again, and I will never see the picture of a happy family again. In young Maretheu's view, his father's death was related to his serious habit of smoking and drinking. If we can go back in time and remind my father that all this may be rewritten.
_ _ _ _ From then on, mallet began to study time. The science fiction "The Time Machine" became his first reading. The hero in the book told him that "time is a kind of space, and we can shuttle back and forth in it, just like in space". Mallet also sprouted the idea of making a "time machine". A few years later, Einstein's special theory of relativity and general theory of relativity came out one after another, which made mallet realize that his dream was not impossible.
_ _ _ _ Although my imaginary "time machine" can't change my father's fate, mallet said, "If this equipment can be successful, future generations can use it to stop the tragedy I experienced. At least this is gratifying. "
_ _ _ _ The simplest idea of a "time machine". Before marlett, many scientists, inspired by the theory of relativity, had put forward several ideas of "time machine". 1974, Frank Tippler, a physicist in tulane university, New Orleans, USA, conceived to build a huge cylinder and made it.
Spin may distort the surrounding time and space, and there will be many "time portals" into the past. If you jump in, you will go back in time.
_ _ _ _ But according to his calculation, the cylinder must be at least as heavy as the sun, and it must be contained in a tube 60 miles long and 40 miles in diameter. This is obviously impossible.
_ _ _ In the 1980s, Kip S Thorne, a professor of theoretical physics at California Institute of Technology, put forward the famous "wormhole" theory-fair access connecting two places in time and space. These two places may be completely different universes, or they may be two places in the same universe. Matter can quickly reach another space-time destination through the entrance of a "wormhole". However, creating a "wormhole" in the space-time structure may require the energy of a star or dozens of atomic bombs, and even control negative energy, which is beyond the reach of modern technology.
_ _ _ _ Compared with predecessors, marlett's idea is much simpler and more feasible. 200 1 The American magazine New Scientist, which first reported mallet's thoughts, said in its comments: "mallet is not crazy, and the known physical theory does not deny the possibility of' time travel'. In theory, traveling through time and space is not that difficult. "
_ _ _ _ The inevitable paradox of time. However, even if many technical problems are overcome, the emergence of "time machine" will open a Pandora's box full of logical paradoxes. If it is assumed that there is only a single universe, with the passage of time, everyone wants to enter.
Trying to go back to the past or the future will lead to logical confusion.
_ _ _ _ The first paradox is that a time traveler enters the past and kills himself as a baby, so he will exist and not exist, because he can't grow up to finish the murder. The second contradiction is more subtle. The time traveler ran ahead of time. His name was engraved on the tree. When he came back to the present, he cut down the tree and made it disappear from the future. We will encounter contradictions again. At some point in the future, trees exist or not.
_ _ _ _ These paradoxes make the concept of causality in trouble. If this is the case, people may not be able to do whatever they want, but they finally have the freedom to travel through time and space, but they lose the freedom to act. It is not a huge loss to watch history pass quietly, but they are unable to change anything.
_ _ _ _ _ _ Multiple universes coexist? David deutsch, an expert in time travel, uses some laws of quantum physics to solve these contradictions. In the subatomic world, quantum uncertainty dominates: an electron hitting a proton may turn left or right, and there is no law to follow. According to some physicists such as deutsch, this uncertainty leads to the "multiplicity" of the universe. Every time an electron turns right, it forms a new universe with an electron that turns left.
_ _ _ _ That is to say, there is not only one world, but many parallel worlds. You go back to the past, but it's not your own world, but a world similar to your history. If you interfere with history, the future will be a different world from when you came.
_ _ _ _ This idea is crazy, but there are many famous physicists besides deutsch who believe in the existence of parallel worlds. Hawking said in A Brief History of Time: Another possible way to solve time travel is to choose the historical hypothesis. The idea is that when a time traveler goes back to the past, he enters another history that is different from the historical record. In this way, they can move freely and are not bound by the original history.
_ _ _ _ Everyone knows that time is produced by the movement of matter, such as the expansion of the universe, and the rising and setting of the sun also implies the passage of time. If all matter stopped moving, including air and celestial bodies, and everything was still, would you still feel the existence of time? Yes, time has stood still! So time has something to do with material movement. And space is also matter. Without matter, there is no space, even if there is matter in a vacuum. The matter here is a broad matter, including energy and spirit, not a material in the narrow sense of materialism. The volume occupied by tangible matter is its space, while the matter in the form of energy fills the space but does not occupy it. The reason why it does not occupy space means that tangible substances can directly occupy the space where energy is located. To put it bluntly, matter is space, and space is matter. The curvature of space is related to the density of matter. Since time and space are related to matter, they can be unified. The universe explodes at the singularity to produce matter, and time and space really make sense at that time! There was no concept of time and space before matter came into being!
_ _ _ _ Since time and space can be unified, they can also be transformed into each other. Time is produced by the movement of matter, which includes external movement and internal rotation. When matter freezes at rest and approaches absolute zero, internal rotation tends to be stationary, mass tends to be zero, time tends to be stationary, and volume tends to be infinite! There is as much space as there is volume, and then time is transformed into space.
_ _ _ _ Of course, the bigger the circle of knowledge, the wider the contact with the unknown! Human understanding of nature is still quite limited, and there are still many phenomena that cannot be scientifically and effectively explained.
_ _ _ _ Physics is an experimental science. The theory of physics is based on quantitative experiments, because no experiment can be absolutely accurate, and more importantly, because it is impossible to find out all the connections between each phenomenon and other phenomena, the conclusions can only be approximate and can only be applied in a certain range. This determines the approximation, restriction and relativity of any physical non-theory, and we must never treat them as unconditional things. People's understanding of objective physical phenomena always goes from ignorance to knowledge, from incomplete knowledge to relatively complete knowledge, from relative truth to absolute truth, but this process can never be finally completed.