Title page
Title: The paradox between quantum mechanics and classical mechanics
Li Yip Cheung
UID:3036388044
Course name: CCST9026 Scientific Revolutions and their Impact on Modern
Societies
20 October, 2024
The discovery of quantum mechanics started in the study of black body radiation. It is
a body which does not reflect light, instead it emits light, the sun is one of the
approximate examples. Physicists found out the color of light that the black body
emits solely depends on its temperature, and they can formulate a black body
radiation curve, to describe the color of light in a given the temperature.
However, physicsts cannot articulate the obsserved spectrum of raiation emitted by
the black bodies using classical wave theory, especially at high frequencies, this
problem is known as the ‘ultraviolet catastrophe’. In 1900, Max Planck derive a
mathematical formula to describe the curve, but one must assume that electromagnetic
radiation is emitted in a discrete energy form and is quantized. This is how quantum
mechanics emerges.
Later, Albert Einstein built work on Planck’s discovery and explain the photoelectric
effect by assuming light behaves like particle,which is called photon. This further
shows that the inadequate of classical wave theory.
According to Thomas Kuhn in his book The Structure of Scientific Revolutions, a
scientific revolution goes through 5 phrases, which are pre-science and normal
science, model drift, model crisis, model revolution and paradigm change. In the
following, I will discuss how the discovery of quantum mechanics paradox with
classical mechanics and how this episode support Khun’s idea.
First, before quantum mechanics was discovered, mechanics was based on Newton’s
law of motion for people to study motion of object in macroscopic world over 200
years. With addition to Lagrangian mechanics and Hamilton mechanics and work
from other physicist, classical mechanics worked well and people could already
describe the motion of macroscopic objects using mathematics. Classical mechanics
was going through pre-science and normal science phrases, where people had a
scientifically based model of understanding that works.
However, classical mechanics could not explain the phenomenon of photoelectric
effect and black body radiation, anomalies started to accumulate. Followed by atomic
spectra showed discrete energy level and doublet slit experiment’s observer effect, the
growing number of anomalies made physicist to struggle since none of these
examples could be explained by classical mechanics, the model started to drift and
having a crisis.
In 1900, Planck presented his hypothesis, he proposed that energy is absorbed or
emitted in a discrete form, in order to explain the black body radiation problem. This
conecpt fundementally changed the classical view of energy is continuous, marking
the beginnning of model revolution.
In 1905, Einstein’s proofed that light behaves like particle, carries quantized enrgy
and lead to the concept of wave-particle duality, which is light exhibit both wave-like
and particle -like properties. This concenpt further proofed the inadquate of classical
mechanics.
Furthermore, in 1913, Bohr’s atomic model was introduced and it explained the
stability of the atom from his prostulates, for instances, the energy levels of electrons
and angular momentum are quanized, electrons in these stable orbits do not emit
radiation, the transition of electron between different energy levels is by the electron
itself emitted or absorbing the exact amount of energy which is the difference between
the two energy levels.
The above model are challengeing the classical view of mechanics and yet they can
articulate the microscopic phenonmena. Following by the inevitable paradigm shift
from classical to quantum mechanics.
Despit the fact that the above model can explain microsopic problems, as quantum
mechanics developed, the unpredictability of quantum mechanics caused a debate
between Bohr and Einstein. Einstein insisted that everything in this world can
accurately predicted using mathematical formula, while Bohr argued that quantum
mechanics was probabilistatic, there is no way that we can accurately predict the
behaviour of an object in microscopic world.
Until now, the concept of quantum mechanics is generally accepted by the vast
majority of physicists. The paradigm shifted and a new normal science era has
commenced.
