The Heisenberg Uncertainty Principle is one of a handful of ideas from quantum physics to expand into general pop culture. It says that you can never simultaneously know the exact position and the exact speed of an object and shows up as a metaphor in everything from literary criticism to sports commentary. Uncertainty is often explained as a result of measurement, that the act of measuring an object's position changes its speed, or vice versa. The real origin is much deeper and more amazing. The Uncertainty Principle exists because everything in the universe behaves like both a particle and a wave at the same time. In quantum mechanics, the exact position and exact speed of an object have no meaning. To understand this, we need to think about what it means to behave like a particle or a wave. Particles, by definition, exist in a single place at any instant in time. We can represent this by a graph showing the probability of finding the object at a particular place, which looks like a spike, 100% at one specific position, and zero everywhere else. Waves, on the other hand, are disturbances spread out in space, like ripples covering the surface of a pond. We can clearly identify features of the wave pattern as a whole, most importantly, its wavelength, which is the distance between two neighboring peaks, or two neighboring valleys. But we can't assign it a single position. It has a good probability of being in lots of different places. Wavelength is essential for quantum physics because an object's wavelength is related to its momentum, mass times velocity. A fast-moving object has lots of momentum, which corresponds to a very short wavelength. A heavy object has lots of momentum even if it's not moving very fast, which again means a very short wavelength. This is why we don't notice the wave nature of everyday objects. If you toss a baseball up in the air, its wavelength is a billionth of a trillionth of a trillionth of a meter, far too tiny to ever detect. Small things, like atoms or electrons though, can have wavelengths big enough to measure in physics experiments. So, if we have a pure wave, we can measure its wavelength, and thus its momentum, but it has no position. We can know a particles position very well, but it doesn't have a wavelength, so we don't know its momentum. To get a particle with both position and momentum, we need to mix the two pictures to make a graph that has waves, but only in a small area. How can we do this? By combining waves with different wavelengths, which means giving our quantum object some possibility of having different momenta. When we add two waves, we find that there are places where the peaks line up, making a bigger wave, and other places where the peaks of one fill in the valleys of the other. The result has regions where we see waves separated by regions of nothing at all. If we add a third wave, the regions where the waves cancel out get bigger, a fourth and they get bigger still, with the wavier regions becoming narrower. If we keep adding waves, we can make a wave packet with a clear wavelength in one small region. That's a quantum object with both wave and particle nature, but to accomplish this, we had to lose certainty about both position and momentum. The positions isn't restricted to a single point. There's a good probability of finding it within some range of the center of the wave packet, and we made the wave packet by adding lots of waves, which means there's some probability of finding it with the momentum corresponding to any one of those. Both position and momentum are now uncertain, and the uncertainties are connected. If you want to reduce the position uncertainty by making a smaller wave packet, you need to add more waves, which means a bigger momentum uncertainty. If you want to know the momentum better, you need a bigger wave packet, which means a bigger position uncertainty. That's the Heisenberg Uncertainty Principle, first stated by German physicist Werner Heisenberg back in 1927. This uncertainty isn't a matter of measuring well or badly, but an inevitable result of combining particle and wave nature. The Uncertainty Principle isn't just a practical limit on measurment. It's a limit on what properties an object can have, built into the fundamental structure of the universe itself.
海森堡測不準原理,或"不確定性原理" 是少數可以從量子物理領域 拓展到普羅大眾文化的物理原理之一 它指出我們無法既確定一個物體的位置 又同時精準測得這它的速率。 這在許多領域被當成隱喻使用 從藝文評論到體育播報領域都有 測不準原理常常被認為源自於測量行為 測量物體位置的動作 同時會改變其速度,反之亦然 但是真正的原理更加深奧 也更加驚奇有趣 之所以會有測不準原理 是因為宇宙中的任何東西 都同時兼具「粒子」和「波」的兩種性質 在量子力學中,一個物體的 確切位置和速度是沒有意義的 為了理解它 我們需要釐清一下: 表現得像「粒子」或像「波」的含意 粒子可在某一時間存在於特定位置 我們能利用在特定位置 發現此物體的機率圖形 來呈現這個定義 圖形上會有一個高峰值 物體在某個特定位置 出現的機率是 100%,在他處則都是 0% 而波則是「擾動」在空間中傳播的現象 就像是湖面上的漣漪 我們可將「波」視為整體 然後確認其性質 其中最重要的就是波長 波長是相鄰兩個波峰或波谷之間的距離 但是我們無法確認波的位置 波在各種不同的位置出現的機率都很大 波長在量子物理學不可或缺的 因為物體的(物質波)波長與其動量有關 動量 = 質量 Χ 速度 一個快速運動的物體具有很大的動量 伴隨著波長很短的物質波 很重的物體即使動得不快 仍具有很大的動量 同樣的,也代表了它的波長很短 這就是我們無法察覺 日常物體波動性質的原因 如果你丟出一個棒球 它的波長是1公尺的10的33次方之一 因為實在是太小了,所以不可能被測到 但微小的物體,例如原子或電子束 波長就大到足以用物理實驗量測出來 如果我們有一個純粹的波 就可以測量它的波長 進而算出它的動量 但是卻無法測出它的確實位置 另一方面,我們很容易確知粒子的位置 但它卻並沒有波長 所以我們不知道它的動量大小 為了同時得到 一個粒子的位置與動量 我們需要融合兩種圖像 創造一個侷限 在很小區域的波圖像 那該如何進行呢? 方法是:藉由疊加數個不同波長的的波 因為一個波一種動量 這代表賦予物體具備不同動量的可能性 當我們將兩個波疊加起來時 波峰對齊的地方會形成更高的波峰 在另外一些位置 因波峰與波谷對齊而相互抵銷 結果就是有些地方我們看得到波 另一些地方,則什麼都沒有 如果我們再加上第三個波 那些波被抵銷的區域變大了 加上第四個,持續變大 而有波的區域逐漸變窄 如果我們持續疊加更多的波 就能得到一個波包 在一個很小的區域內有一個確定的波長 這就得到了一個 同時擁有波與粒子屬性的物體 但是這樣一來 位置和動量都無法準確測得 物體並非侷限在一個單一位置上 在波包內的範圍裡 我們發現物體的機率都很高 我們透過疊加多個波得到波包 意味著我們就有可能找到 與其中一個物體相對應的動量 導致位置與動量都無法精確測量 這都與測不準原理有關 如果你想更精確的測量位置 就得用更多的波疊加起來, 加以建造出更小的波包 波數增加使動量更不確定 如果你想更明確的得到動量值 就需要一個更大的波包 結果位置就更不確定 這就是海森堡測不準原理 最初由德國物理學家 Werner Heisenberg 於1927 年提出 這種測不準的特性與測量的精確度無關 是結合波和粒子 兩種性質之後不可避免的結果 測不準原理不僅僅 是測量上的實際限制 它是物體只能表現出 一種(波或粒子)性質的限制 已被建入宇宙基本構造之中