昨天的讨论为我们今天的话题奠定了基础——更准确地理解希格斯场如何赋予粒子质量，并揭开物理学的基础之谜。让我们从伽利略的相对性原理开始。
首先，伽利略的相对性原理否认了宇宙中存在绝对静止的参照系。这意味着，希格斯场不可能如常见类比中所述，是充满宇宙的某种“浓汤”，因为这会使其自身成为一个绝对静止的参照系。
其次，我们需要了解什么是质量。通常，我们从化学上认知的质量定义是指物质的量。虽然牛顿在他的力学中已经洞察到质量是对惯性大小的描述，但他仍采用了质量等同于物质的量的定义。爱因斯坦从他的狭义相对论却推导出一个颠覆性的结论：质量和能量是等价的，即著名的质能方程E=mc^2。
这个能量指的是物体内部包含的能量，这个公式告诉我们，通过压缩、拉伸弹簧或往手机里充电等方式增加物体内部能量，同时也增加了它们的质量。然而，由于能量需要除以光速的平方（一个极大的数值），这些日常现象中质量的改变几乎是观察不到的。
还有一个通俗且脑洞大开的例子可以帮助理解这一点：我们人类身体是由原子组成的，原子又由电子、质子、中子和夸克构成。如果按照通常意义下的质量定义，身体的质量应该等同于体内所有电子和夸克的质量总和。然而，事实是，我们身体内所有电子和夸克的质量加起来还不足我们自身重量的百分之一。如果质量就是物质的量的话,我们的身体会像纸一样轻,风一吹就会飘上天。为什么？因为我们的身体质量绝大部分来源于原子核的质量，而原子核的质量不是其包含的夸克的质量总和，而是通过强相互作用聚合成质子和中子，并将它们聚合成原子核的能量。想象强相互作用如同强大的弹簧，将夸克牢牢抓在一起，我们的大部分能量和质量正来源于这些“紧密的弹簧”中储藏的能量。
有了这些基本认识，加上量子力学中的另一个基本事实，我们就可以深入讨论希格斯场如何赋予基本粒子以质量。欢迎进入量子力学的领域！在这里，我们通常所说的原子、电子、质子、夸克和光子，它们真的都是粒子吗？量子力学告诉我们，这些微观粒子只是在某些情况下表现得像粒子，但实际上它们都是波，与我们日常生活中见到的波无异。波动的琴弦产生声波，水面在风吹下产生水波，同样，粒子也表现出波动的特性。
爱因斯坦因光量子理论而获得诺贝尔奖，这一发现解释了光电效应，即光既是波又是粒子。光子以光速运行，因此没有静止质量，但仍具有能量。能量可以通过一个简洁的公式表示：能量等于其振动频率乘以普朗克常量E=hv。既然能量等同于质量，能量等于振动频率，那么简单的逻辑推导便得出：质量就是振动。然而，这个简单的三段论式的逻辑推理却打开了一个脑洞：万事万物，包括我们自己，可能并不存在真正的实体，都不过是一堆振动而已。用诗意的语言来说，世界就像一首由基本物理场演奏的交响乐，优雅而空灵，这世界观竟与佛教的“无常”和“空”的世界观不谋而合。
Yesterday's discussion set the stage for what we're talking about today - understanding more precisely how the Higgs field gives mass to particles, and unlocking the fundamental mysteries of physics. Let's start with Galileo's principle of relativity.
First, Galileo's principle of relativity denied the existence of an absolutely stationary frame of reference in the universe. This means that the Higgs field cannot be some kind of "thick soup" that fills the universe, as the common analogy suggests, because that would make it itself an absolutely static frame of reference.
Secondly, we need to understand what quality is. In general, the definition of mass that we think of chemically refers to the amount of substance. Although Newton in his mechanics had the insight that mass was a description of the magnitude of inertia, he still adopted the definition of mass as the amount of matter. Einstein derived a subversive conclusion from his special theory of relativity: mass and energy are equivalent, known as the mass-energy equation E=mc^2.
This energy refers to the energy contained within objects, and the formula tells us that increasing the internal energy of objects by compressing or stretching a spring or charging a cell phone also increases their mass. However, since the energy needs to be divided by the square of the speed of light (an extremely large number), changes in mass in these everyday phenomena are almost invisible.
Another popular and imaginative example helps to understand this: our bodies are made up of atoms, which in turn are made up of electrons, protons, neutrons and quarks. If mass is defined in the usual sense, the mass of the body should be equal to the total mass of all the electrons and quarks in the body. However, the fact is that the combined mass of all the electrons and quarks in our body is less than one percent of our own weight. If mass were the amount of matter, our bodies would be as light as paper and would float up when the wind blows. Why? Because the vast majority of our body mass comes from the mass of the nucleus, and the mass of the nucleus is not the sum of the masses of the quarks it contains, but the energy that fuses them into protons and neutrons through strong interactions, and fuses them into the nucleus. Think of the strong interaction as a powerful spring holding the quarks together, and most of our energy and mass comes from the energy stored in these "tight springs."
With these basic insights, coupled with another fundamental fact in quantum mechanics, we can delve into how the Higgs field imparts mass to elementary particles. Welcome to the realm of quantum mechanics! In this case, are atoms, electrons, protons, quarks, and photons really particles? Quantum mechanics tells us that these microscopic particles only behave like particles in certain situations, but in fact they are all waves, no different from the waves we see in everyday life. In the same way that the fluctuating strings of a violin produce sound waves, the surface of the water under the wind produces waves, particles also exhibit the properties of waves.
Einstein won the Nobel Prize for his quantum theory of light, a discovery that explains the photoelectric effect, in which light is both a wave and a particle. Photons travel at the speed of light and therefore have no rest mass, but still have energy. Energy can be expressed by a simple formula: energy is equal to its vibration frequency multiplied by Planck's constant E=hv. Since energy is equal to mass, and energy is equal to vibration frequency, a simple logical deduction follows: mass is vibration. However, this simple syllogistic logic opens up the imagination that everything, including ourselves, may have no real entity, but is nothing more than a bunch of vibrations. In poetic terms, the world is like a symphony played by the basic physical field, elegant and ethereal, and this worldview is in line with the Buddhist worldview of "impermanence" and "emptiness".