In everyday life, objects appear to be stationary, but in the microscopic world, we can’t accurately measure the position and momentum of an electron at the same time. This is because, according to Heisenberg’s uncertainty principle, the smaller the particle, the greater the disturbing effect of light on the observation. This principle is an important foundation of quantum mechanics and has contributed to the development of physics through debate among scientists.
In our daily lives, when we read a book or work on a document on a laptop, we take it for granted that the book or laptop stays where it is, without questioning it. This sense of stability is also due to the invisibility of the physical interactions of the environment around us, as we assume that the book or laptop is fixed in place unless the desk shakes or some other special circumstance occurs. If you think about the concept of “balance of forces” from your middle school or high school physics class, everything around us is actually affected by the interaction of multiple forces, but it’s hard to feel this in real life. For example, a book on your desk is interacting with the earth through gravity, and the desk is counteracting that force to keep the book in place. But we don’t recognize this complex physical process; we simply feel that the book is in place.
As we’ve learned in physics, all objects are affected by various forces, such as gravity and contact forces, but we don’t think of these forces as moving objects. This is because the forces we actually experience in our daily lives are so insignificant. For example, the force of light on a book, or the universal force of attraction between objects, is too small to move a book, so we are convinced that a book or laptop always stays where it is.
But this common sense intuition doesn’t hold true for the microscopic world, or for tiny particles like electrons. This is because the laws of physics apply in ways we can’t imagine. For example, the fact that we can’t know exactly where an electron is located goes against our everyday experience. This phenomenon can be explained by Heisenberg’s uncertainty principle. The uncertainty principle is an important theory for understanding physical disturbances that occur in the microscopic world.
When we look at an object, we can see it because light is reflected off of it and enters our eyes. Whether we’re looking at a book or an electron, in either case, light is reflected off of it and into our eyes. However, in the microscopic world, the effects of the disturbances that light causes on objects are more pronounced. When we look at a book, the disturbance of light on it is so small that it is negligible. Therefore, we feel that the book is always fixed in place. For a particle like an electron, on the other hand, the effect of light on its kinetic state is relatively large and must be taken into account.
According to the principle of indeterminacy, the amount of disturbance applied to an object makes it impossible to know exactly where it is. This is especially true for small particles, where the wavelike nature of light makes it difficult to accurately measure the position of an electron. To know the state of motion of any object, you need to know its momentum and position. Momentum is defined as the product of the object’s mass and velocity. If we know these two values accurately, we can get a clear picture of an object’s state of motion. However, in the microscopic world, we can’t avoid disturbances caused by light, so we can only observe in a way that minimizes them.
Consider the case of observing an electron: if we use light with a small momentum to disturb the electron less, the wavelength of the light will be long, making the measurement of the electron’s position inaccurate. A wavelength is simply the interval between oscillations of light as it travels. The longer the wavelength, the wider the range of light in the space where the electron is located, making it impossible to measure accurately. Conversely, if you use light with a shorter wavelength, you can pinpoint the electron’s location more precisely, but the electron’s momentum is greatly disturbed. This is because shorter wavelengths of light have more energy and therefore have a greater impact on the electron.
In the end, the momentum and position of an electron cannot be accurately measured at the same time. The two values are inversely proportional, meaning that if you try to measure one accurately, the other will become more inaccurate. Heisenberg mathematized this principle and found that the product of the change in momentum and the change in position is always greater than a constant value. This leads to the conclusion that the state of an electron is completely unpredictable.
Heisenberg’s uncertainty principle provided a very important foundation for the development of quantum mechanics. Many scientists used this principle to study new physical phenomena, which led to breakthroughs in quantum physics. Albert Einstein was skeptical of the uncertainty principle and tried to refute it with a hypothetical thought experiment, but Niels Bohr defended it and proved its importance to quantum mechanics. The debate between Einstein and Bohr remains an important topic of study among physicists to this day, and it spurred the development of quantum physics.
As such, the uncertainty principle has given us a new perspective on the physical world. Small interactions of forces that are easily ignored in everyday life make a decisive difference in the micro world. This principle shows how the micro and macro worlds are governed by different physical laws and suggests that the world as we know it is not all there is.
