Fundamental Forces | 基本相互作用力

📚 Fundamental Forces | 基本相互作用力

All interactions in the universe can be reduced to four fundamental forces. They explain everything from the orbits of planets to the stability of atomic nuclei.

宇宙中所有相互作用都可以归结为四种基本力。它们解释了从行星轨道到原子核稳定性的各种现象。

1. What are fundamental forces? | 什么是基本力？

In physics, a fundamental force is an interaction that cannot be explained by a more basic force. When we push a door, the contact force is actually the result of electromagnetic repulsion between surface atoms.

在物理学中，基本力是指无法用更基础的力来解释的相互作用。当我们推门时，接触力实际上是表面原子之间电磁排斥的结果。

CIE A-Level physics recognises four fundamental forces: gravitational, electromagnetic, strong nuclear, and weak nuclear. All other forces are macroscopic manifestations of these.

CIE A-Level 物理确认四种基本力：引力、电磁力、强核力和弱核力。所有其他力都是这些基本力的宏观表现。

2. Gravitational force | 万有引力

Gravity acts between all objects that have mass or energy. It is always attractive and has an infinite range, but it is by far the weakest fundamental force on the microscopic scale.

引力作用于所有具有质量或能量的物体之间。它始终是吸引力，作用范围为无限远，但在微观尺度上它是最弱的基本力。

Newton’s law of universal gravitation gives the force between two point masses as:

牛顿万有引力定律给出两个质点之间的引力为：

F = G m₁m₂ / r²

where G = 6.67 × 10⁻¹¹ N m² kg⁻², m₁ and m₂ are the masses, and r is their separation.

其中 G = 6.67 × 10⁻¹¹ N m² kg⁻²，m₁ 和 m₂ 是两个物体的质量，r 是它们之间的距离。

Although gravity is extremely weak at particle scales, it dominates on astronomical scales because it is always attractive and long range.

尽管引力在粒子尺度上极其微弱，但由于它始终为引力且作用范围远，在天文尺度上它占据主导地位。

3. Electromagnetic force | 电磁力

The electromagnetic force acts between charged particles. It can be attractive or repulsive, depending on the signs of the charges, and it has an infinite range.

电磁力作用于带电粒子之间。根据电荷符号的不同，它可以是吸引力或排斥力，作用范围为无限远。

Coulomb’s law describes the force between two point charges:

库仑定律描述两个点电荷之间的力：

F = k q₁q₂ / r²

where k = 8.99 × 10⁹ N m² C⁻², q₁ and q₂ are the charges, and r is the separation.

其中 k = 8.99 × 10⁹ N m² C⁻²，q₁ 和 q₂ 是电荷量，r 是距离。

The electromagnetic force is about 10³⁶ times stronger than gravity between two protons. It binds electrons to nuclei, forms atoms and molecules, and gives rise to contact forces such as friction and tension.

两个质子之间的电磁力约比引力强 10³⁶ 倍。它将电子束缚在原子核周围，形成原子和分子，并产生了摩擦力和张力等接触力。

4. Strong nuclear force | 强核力

The strong nuclear force is the strongest of the four fundamental forces. It has a very short range of about 10⁻¹⁵ m, roughly the diameter of a nucleon.

强核力是四种基本力中最强的。它的作用范围非常短，约为 10⁻¹⁵ m，大致相当于核子的直径。

At the most fundamental level, the strong force acts between quarks via gluons. The residual strong force, sometimes called the nuclear force, binds protons and neutrons together in the nucleus and overcomes the electrostatic repulsion between protons.

在最基本层面上，强核力通过胶子在夸克之间起作用。剩余的强核力（有时称为核力）将质子和中子束缚在原子核内，克服了质子之间的静电排斥。

The strong interaction is independent of electric charge; it affects quarks and gluons, and is responsible for holding hadrons such as protons and neutrons together.

强相互作用与电荷无关；它作用于夸克和胶子，并负责将质子、中子等强子束缚在一起。

5. Weak nuclear force | 弱核力

The weak nuclear force is responsible for processes that change one type of quark into another, for example beta decay. It is much weaker than the strong force but still stronger than gravity at short distances.

弱核力负责将一种夸克转变为另一种夸克的过程，例如 β 衰变。它比强核力弱得多，但在短距离上仍比引力强。

Its range is extremely short, about 10⁻¹⁸ m, which is less than the diameter of a proton. The weak force is mediated by the W⁺, W⁻, and Z⁰ bosons.

它的作用范围极短，约为 10⁻¹⁸ m，小于质子的直径。弱力由 W⁺、W⁻ 和 Z⁰ 玻色子传递。

In beta minus decay, a neutron changes into a proton, emitting an electron and an antineutrino. At the quark level, a down quark changes into an up quark.

在 β⁻ 衰变中，一个中子转变为一个质子，释放出一个电子和一个反中微子。在夸克层面，一个下夸克转变为一个上夸克。

6. Relative strengths and ranges | 相对强度与作用范围

The table below compares the four fundamental forces in terms of approximate relative strength and range.

下表比较了四种基本力的近似相对强度和作用范围。

Force	相对强度	Range	作用对象
Strong nuclear	1	~10⁻¹⁵ m	quarks, hadrons
Electromagnetic	~1/137	infinite	charged particles
Weak nuclear	~10⁻⁶	~10⁻¹⁸ m	quarks, leptons
Gravitational	~10⁻³⁹	infinite	all mass/energy

The relative strengths depend on the distance scale, but this comparison is valid for interactions between protons at typical nuclear separations.

相对强度取决于距离尺度，但这一比较适用于在典型核间距下质子之间的相互作用。

7. Exchange particles and force mediation | 交换粒子与力的传递

In the Standard Model, forces are transmitted by exchange particles called gauge bosons. Each fundamental force has its own mediator: the photon for electromagnetism, the gluon for the strong force, the W and Z bosons for the weak force, and the hypothetical graviton for gravity.

在标准模型中，力由称为规范玻色子的交换粒子传递。每种基本力都有自己的媒介粒子：光子传递电磁力，胶子传递强力，W 和 Z 玻色子传递弱力，假想的引力子传递引力。

These exchange particles are virtual, meaning they exist for a very short time and cannot be directly detected. The limited range of the strong and weak forces arises because their mediators are massive or confined.

这些交换粒子是虚粒子，它们存在时间极短，无法被直接探测。强力和弱力作用范围有限，是因为它们的媒介粒子具有质量或受到禁闭。

8. The Standard Model and unification | 标准模型与统一

The Standard Model describes the electromagnetic, strong, and weak forces within a single quantum field theory. It classifies all known fundamental particles into quarks, leptons, and gauge bosons.

标准模型在同一个量子场论框架内描述了电磁力、强力和弱力。它将所有已知的基本粒子分为夸克、轻子和规范玻色子。

Electromagnetism and the weak force have been unified into the electroweak theory. At high energies, they behave as a single force. Physicists hope to include the strong force in a Grand Unified Theory, but gravity remains difficult to incorporate.

电磁力和弱力已经被统一为电弱理论。在高能量下，它们表现为同一种力。物理学家希望将强力纳入大统一理论，但引力仍然难以纳入。

Gravity is described by Einstein’s general relativity, not by a quantum exchange particle confirmed by experiment. The graviton has been proposed but not yet observed.

引力由爱因斯坦的广义相对论描述，尚未通过实验证实其量子交换粒子。引力子已被提出，但尚未被观测到。

9. Weak interaction and beta decay | 弱相互作用与 β 衰变

Beta decay is a key example of the weak interaction. In beta minus decay, a neutron in an unstable nucleus decays into a proton:

β 衰变是弱相互作用

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Fundamental Forces | 基本相互作用力