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Physics Stack Exchange，Stack Exchange 上的物理学问答社区，面向研究人员、学生与物理爱好者。

Relative speed conservation in Elastic Collisions (One dimensional)

Why is relative speed conserved in elastic collisions? The algebraic derivation of the equation: $u_1 - u_2 = v_2 - v_1$ or $|u_1 - u_2| = |v_1 - v_2|$ is relatively (no pun intended) straightforw...

收藏1 天前

相同的量子实验，在相同的宇宙中却得出不同结果？[重复]

这是一篇物理问答社区（Physics Stack Exchange）的重复问题帖，核心疑问是：即使完全掌握量子态的所有物理相关参数，为何仍无法预测单次测量的确切结果？该限制究竟是认识论的（缺少隐藏数据）还是本体论的（物理态本身不含预定值）？追问还包括：若存在更深层决定论理论，实验上需要改变什么才可验证？若无法改变，那该主张是否已超出物理进入哲学？以及在根本随机性的世界里，因果性该如何表述？帖子带有"duplicate"标记，说明社区已存在同源问题。

收藏1 天前

«两个物理上完全相同的宇宙能否产生不同的量子测量结果？» [已关闭]

Physics Stack Exchange 上的一个已关闭问题：如果两个宇宙在量子态、环境、历史和所有微观自由度上完全相同，且同时执行相同的量子实验，结果是否可能不同（如一个得 0、另一个得 1）？提问者追问，在不存在任何物理差异的前提下，这种差异的依据是什么，是否说明量子测量结果本质不确定、非决定论，还是暗示存在隐藏变量或比标准量子力学更深层的规律。问题聚焦测量结果的随机性语义——若两宇宙"原则上"无任何差异，说一个"随机"得到 0、另一个"随机"得到 1 究竟意味着什么。属于量子诠释层面的思辨讨论，非实验或工程内容。

收藏1 天前

在某些电荷构型具有平移对称性的情况下，为什么势必须沿该直线保持恒定？

When there is translational symmetry along a charge configuration why is it must that potential always remains constant along that line, it may be said that electric field will remain constant at ever...

收藏1 天前

Is QFT actually relativistic?

In any interactive quantum field theory in four dimensions, interactions are modeled as products of distributions at single space-time points. To my understanding, there is no sense in which QFT can a...

收藏1 天前

Calculation of cross product square in formula

I have a difficulty with the formula for the power radiated by a charge with arbitrary motion, \begin{equation} P_{rad} = \frac{q^2 c \gamma^6 \mu_0}{6\pi}\Big[\dot{\boldsymbol{\beta}}\cdot\dot{\bolds...

收藏1 天前

Can two bodies be at thermal equilibrium while having different temperatures?

I am learning about thermodynamics and while doing so i came across this question; at first i was confident that the answer would be 'no' however the teacher said it is possible and the answer is yes,...

收藏1 天前

Single Photon "size" [closed]

When a single hydrogen atom transitions from n=2 (-13.60eV) to n=1 (-3.40 eV), it emits a λ = 122 nm photon. A. How many photons are emitted? B. How many 122 nm cycles are emitted? C. What is the dura...

收藏1 天前

What are the perspectives of trapped-ion quantum computing in 2026? [closed]

Cold trapped ions are believed to be one of the leading candidate systems for building a quantum computer. The development of trapped-ion quantum computers was rapid and impressive for decades. Howeve...

收藏1 天前

Theoretical interpretation of CHSH correlation loss: Classical phase-space thermal noise vs. non-unitary decoherence

I am examining the theoretical bounds of CHSH correlation degradation under a deterministic phase-space framework (in the spirit of local-realist / hidden-variable foundational models). Consider an em...

收藏1 天前

Condition to fall into $1/r^2$ potential

Suppose we have a particle of mass $m$ coming from infinity towards the neighborhood of the origin in a potential of the form $-1/r^2$. It is clear that the behaviour of the particle depends on the im...

收藏2 天前

What is the electromagnetic field due to an alternating current in an anisotropic medium?

We know that an infinite, alternating, straight line current generates an outward cylindrically propagating electromagnetic field with the axial electric field expressed as a Hankel function of the ra...

收藏2 天前

正负导体静电排斥的实验比较

一位物理 Stack Exchange 用户提问：库仑定律预言同号电荷相互排斥，且 +Q/+Q 与 −Q/−Q 的排斥力应相同，但在普通导体中两者物理机制不同——负电荷是加入电子，正电荷是移走电子。作者想知道是否有人实际做过实验，定量比较两个正电导体与两个负电导体之间的静电力，尤其关注正电荷通过光电发射产生、且电荷量独立于力测量而确定的实验。寻求经典或现代实验的文献指引。属于基础物理的细致追问，信息增量有限但视角独特，对物理爱好者或教学场景有讨论价值。

收藏4 天前

气体之间的相互作用压力

物理问答：两个不同压力的气体被移除隔板后，直接相互作用时，根据牛顿第三定律每个粒子施加强相等且方向相反的压力，问题是这种相互作用压力与两个气体各自初始压力的关系是什么？属于基础气体动力学/热力学问题，讨论深度有限。

收藏4 天前

如果我们抛弃惯性参考系，只在需要时添加虚拟力，经典力学仍然可行吗？

一位物理爱好者提问：能否完全抛弃惯性参考系和牛顿第一定律，只靠"在任何非直线运动时都加一个虚构力"来描述力学？发帖人想确认这种做法在分析运动时是否足够，或者某些情况下是否会出问题。这是 Physics Stack Exchange 上的讨论帖，属于基础力学概念辨析。对科技读者来说，内容偏学术问答，信息增量有限，讨论入口较窄，预计互动量不高。

收藏4 天前

单粒子可以有熵吗？

提问者描述了一个思想实验：一个粒子被关在小盒子里，小盒子通过孔与一个远大于它的大盒子相连。若大盒子体积趋于无穷，粒子最终几乎必然出现在大盒子中。他由此困惑：熵学通常认为熵是多粒子系统的性质，单粒子不能有熵；但这个单粒子"从高浓度区扩散到低浓度区"的过程看起来像熵增，是否说明单粒子也能被赋予熵？问题核心在于把宏观热力学熵（统计概念）套用到单个量子/经典粒子上时是否自洽。答案一般指向：熵是系综或概率分布的量，不是单个粒子的内禀属性；单粒子的"扩散"可以用相空间体积增长或贝叶斯信息熵（观察者知识）来描述，但这不等于热力学熵增。

收藏4 天前

Does Galileo's thought experiment suggest that we can not ever check if absolute space exists?

In particular I am talking about Galileo's thought experiment of the ship. In my understanding of the experiment, we can not ever check absolute motion (which I guess would be motion in absolute space...

收藏4 天前

Does the correspondence principle already cover this connection between classical orbits and quantum transitions? [duplicate]

I was contrasting the classical orbit of a planet with hydrogen energy levels. In the former case, change of energy leads to a continuous change of orbit (for example $a=-\frac{GMm}{2E}$), whereas in ...

收藏4 天前

Physics Stack Exchange

Relative speed conservation in Elastic Collisions (One dimensional)

相同的量子实验，在相同的宇宙中却得出不同结果？[重复]

«两个物理上完全相同的宇宙能否产生不同的量子测量结果？» [已关闭]

在某些电荷构型具有平移对称性的情况下，为什么势必须沿该直线保持恒定？

Is QFT actually relativistic?

Calculation of cross product square in formula

Can two bodies be at thermal equilibrium while having different temperatures?

Single Photon "size" [closed]

What are the perspectives of trapped-ion quantum computing in 2026? [closed]

Theoretical interpretation of CHSH correlation loss: Classical phase-space thermal noise vs. non-unitary decoherence

Condition to fall into $1/r^2$ potential

What is the electromagnetic field due to an alternating current in an anisotropic medium?

正负导体静电排斥的实验比较

气体之间的相互作用压力

如果我们抛弃惯性参考系，只在需要时添加虚拟力，经典力学仍然可行吗？

单粒子可以有熵吗？

Does Galileo's thought experiment suggest that we can not ever check if absolute space exists?

Does the correspondence principle already cover this connection between classical orbits and quantum transitions? [duplicate]

Inconsistency in Witten's superstrings [closed]

Is Friction conservative or non-conservative force?

Canonical ensemble - Proportionality of probabilities - Huang Section 7.1 [duplicate]

Acoustic interference of non-collinear waves

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