The Journey Inward

1. If a pion (mass = 139.6 MeV) were the only exchange particle for the strong force, what would be the range of the strong force? What fraction of the diameter of a proton is this? If the W particle (mass = 80.5 GeV) were the only exchange particle for the weak force, what would be the range of the weak force? What fraction of the diameter of a proton is this?
   如果π介子（质量=139.6 MeV）是强相互作用的唯一交换粒子，那么强相互作用的范围是多少？这相当于质子直径的多少分之一？如果W粒子（质量=80.5 GeV）是弱相互作用的唯一交换粒子，那么弱相互作用的范围是多少？这相当于质子直径的多少分之一？
Resources:

Exchange forces 交换力

Range of forces 力的作用范围

Nuclear sizes 核尺寸

2. If quarks are what all the heavy particles like protons and neutrons are made of, why haven't we seen one?
   如果夸克是构成所有重粒子如质子和中子的基本粒子，为什么我们还没有看到它们呢？
Resources:

Quarks 夸克

Confinement of quarks 夸克禁闭

Bag model 袋模型

3. What is a neutrino and how can you detect one?
   中微子是什么，如何探测中微子？
Resources:

Neutrinos 中微子

Detection of neutrinos 中微子的探测

Cowan & Reines Cowan & Reines（专名或术语）

Super Kamiokande 超 Kamiokande

4. How can you say that the electromagnetic and weak forces are "unified" when they seem so different?
   你如何说电磁力和弱力是‘统一’的，它们看起来如此不同？
Resources:

Exchange forces 交换力

Electroweak unification 电弱统一

Spontaneous symmetry breaking 自发对称破缺

5. Almost all the heavy particles are unstable, even the neutron. But the proton is stable - no one has ever seen the decay of a proton. Why? Resources:

   Proton 质子

   Conservation laws 守恒定律

   Conservation of baryon number 重子数守恒

   几乎所有的重粒子都是不稳定的，即使中子也不例外。但质子是稳定的——没有人曾观察到质子的衰变。为什么？参考资料：
6. Why is it necessary to have high energies to investigate small things? Assume that the wavelength necessary to see an object is equal to the size of the object, and that the wavelength is given by the deBroglie wavelength relationship. What energy electron would be necessary to see an atom (size 0.3 nm)? a carbon nucleus (5.8 fm)? a proton (2.4 fm)? to probe to the current limit of resolution of 0.001 fm? Resources:

   Why high energies? 为何需要高能？

   DeBroglie wavelength 德布罗意波长

   DeBroglie calculation 德布罗意计算

   为什么需要高能量来研究小物体？假设要观察一个物体，所需的波长等于该物体的尺寸，并且波长由德布罗意波长关系给出。要观察一个原子（尺寸0.3 nm）需要多高的电子能量？要观察一个碳核（5.8 fm）？要观察一个质子（2.4 fm）？要探测到目前的分辨率极限0.001 fm？参考资料：