Why Does a Star Shine?
There is a lot of phenomenon we take for granted. A child has asked me this question some time ago, “why does a star shine?” Well, most of us don’t even think this is a question and answer “it just does!”
Actually, there is a strong science behind this “ignorable” question – quantum tunneling.
Quantum tunneling refers to the quantum mechanical phenomenon where a particle tunnels through a barrier that is classically could not surmount. Think of this way, can a normal person go through a concrete wall directly? Of course not. But in quantum world, a particle can.
A star like our sun, it must fuse hydrogen to helium releasing huge amount of energy which is the heat we can feel and the light that shines. The problem is that in classical model, it is impossible to fuse hydrogen into helium. Why? Hydrogen has one proton in its nuclei which carries positive charge. To fuse helium, we need two hydrogen nuclei which both carry positive charge to somehow fuse together. As common sense, same charges repel each other. But the reality is they do fuse. Just not by “common sense” but by quantum tunneling – a proton tunnels itself through the repulsion barrier into the other side which the distance is close enough to the other proton that the Strong Nuclear Force (one of the Four Forces that governs the universe) can work its magic and hold these two protons together forming helium releasing energy and answering that child’s question.
You see, there is a whole new world that common sense doesn’t apply. We need to open our mind and ready to explore like a child.
Lao Zi, the founder of Taoism wrote in Tao Te Ching, “normal people are always trying to be clever with their eyes and ears; while wise people are always trying to learn from young children who look at this world with a pure heart.”
星星为什么会发光？
曾经有一个小朋友问过我这个问题：“星星为什么会发光？”这是一个太容易被我们当作理所当然的问题了。我们大部分人都是不把它当作一个问题而是连想都不想的就敷衍着回答：“它本来就发光啊！”
实际上，这是一个背后有强大科学理论和实验支撑的大问题。星星发光的原因是量子隧穿。量子隧穿是无法用经典力学来解释的一种量子效应；它是微观粒子能够穿越它们本来无法通过的障碍的现象。想想看，一个正常人能否直接穿越墙壁？肯定不能。但是量子可以。
星星的基本燃料是氢气，简单说，氢原子需要核聚变核成氦原子来释放能量，发光发热。但是问题在于，在常规模式下，两个氢原子是无法核成的。因为氢原子核中的质子是带正电的，两个带正电的质子由于同性相斥，远离还来不及呢，怎么核成？这就是量子隧穿的用武之地了。带正电的质子是可以通过量子隧穿穿越“相斥力屏障”到达屏障的“另一边”，和另外一个质子的距离近到可以让“强核力”（统治宇宙的四大力量之一）发挥作用而将两个质子“困”在一起而形成新的元素“氦”，释放能量，同时解答那个小朋友的问题。
其实你看，我们这个世界充满了魔幻版的奇迹，常规的思维模式往往是走不通的；我们真的要存有一颗童心，用这颗充满好奇的童心来上下求索。正如老子在《道德经》中曰：“百姓皆注其耳目，圣人皆孩之。”
