[SCIENCE WORLD]The limits of language

According to a Buddhist saying, you should look at the moon, not the finger pointing to it. The moon stands for the ultimate truth, which cannot be revealed through language or concept. The finger is a symbol of the language or letters used to express the truth.

It sounds like a cliche that has little relevance to real life, but looking around our environment, we find many things that cannot be described with the concepts or language that we use.

The mind of someone who counts stars in the night sky is one example. But you can also find other examples that are easier and closer to everyday life -- for instance, it is practically impossible to describe the taste of Coca Cola.

In the scientific world, where objective facts are the subject of studies, scientists were confronted with the limitations of their language with the development of quantum mechanics.

It was possible to express objective elements in mathematical languages before the turn of the 20th century. And the faith that this principle was always applicable guaranteed the objectiveness of science. But faith in this belief collapsed when scientists discovered the wave properties of particles and the particle properties of waves.

In classical physics, wave properties and particle properties are two different physical attributes.

Modern physics introduces wave/particle duality, the notion that an entity simultaneously possesses localized (particle) and distributed (wave) properties.

The idea was introduced into modern physics to account for observations in which particles of matter interact to produce effects that appear to be identical to the effects that occur when waves diffract and interfere.

In classical physics, waves and particles were not interchangeable. That concept of waves and particles was changed fundamentally with the advent of quantum mechanics.

Light should be a wave, because it shows the typical properties of a wave: interference and diffraction. Light is regarded as a wave in classical physics. But scientists found that under certain circumstances, light shows particle properties. In contrast, electrons, which were considered particles by classicists, show wave properties in certain environments.

All objects possess wave properties and particle properties simultaneously. This phenomenon is called duality.

The world of nature is the world of complementarity: objects are described by both wave and particle attributes. If we try to understand an object only by its wave or its particle attributes, we can describe only one aspect of the object. When we try to grasp an object with only one description, we will inevitably face contradiction. When we stick to the choice of either waves or particles, we fail to understand the entirety of an object.

Nature is more than just what can be described by language or concept.

The writer is a professor of physics at Korea University.

by Yang Hyung-jin