1.
Introduction
Every branch of Science is
categorized into theoretical and experimental parts. However, in the areas of
Physics and Chemistry the distinction between the two becomes prominent. In
this essay, I would like to discuss these two different aspects in Physics and
their significance by isolating examples from historical discoveries.
We
have no knowledge about the exact origin of Science. One can say it originated
through a series of simple experiments (both practical and theoretical)
conducted by people when they started observing nature; through astronomical observations
made by the Babylonians and the mathematical discoveries of Euclidean Geometry;
through Archimedes Principle and the Pythagorean Theorem. There were advances
in experimental as well as mathematical and theoretical sides of Science. At
that stage, the concepts were too tender and could not be broken down into
simpler statements. Almost all of them were empirical. Why the Pythagorean
Theorem holds? – Nobody knows, of course one can derive it but those
derivations themselves involved some fundamental axioms[1]. But philosophers and scientists of that time
used these fundamental theorems to construct models which described reality along
with some predictions. These predictions in turn could be verified by experiments,
which transform them into “a law”. Prior to that, it is simply regarded as a
theory. No matter how beautiful, elegant or intuitive it is, there exists no obligation
to accept it as a law. With simple mathematical tools, philosophers of the past
determined the radius and circumference of Earth, without even traversing the
entire Earth. Their predictions were later verified through experiments.
However, as time went by, there were significant developments both in theory
and experiments. It was realized that Physics could be split into its theoretical
and experimental parts. Thus arose two branches of Physics: Theoretical Physics
and Experimental Physics. In the present day, people choose to specialize in
one or the other. Despite, the distinction these two branches overlap
inevitably and according to my belief the experimental part shall continue to
hold an upper hand. After all, experiments distinguish reality from fantasy.
The act of observation is what completes Physics as well as Science.
Nevertheless, one should not deny the importance and potential possessed by
Theoretical Physics. In the history of Physics, there are two great examples in
which a discovery was made in one of the branches and later extended into the
other. These examples are the two main pillars of Modern Physics : 1.) Einstein’s
Theory of Relativity and 2.) Quantum Physics.
2.) Special and
General Theory of Relativity
Einstein’s
Theory of relativity was a special modification of Galileo’s Theory of
Relativity. In the early 20th century, a series of experiments
showed that electromagnetic radiations travelled through space at a constant
velocity. These experiments also ruled out the concept of hypothetical luminiferous
aether as a medium for the propagation of electromagnetic radiations[2]. Physicists were baffled when this constancy
of velocity was not maintained in Galilean Relativity. Since, the existence of
ether was disproved and repeated experiments confirmed the velocity of
electromagnetic radiations to be unchanged, there was no option left but to
reject or modify Galilean Relativity to accommodate the experimental
observations. In the year 1905, which was also called as Annus mirabilis (miracle year) for Albert Einstein, he published
four papers in the Annalen Der Physik
scientific journal. The third paper titled – “On the Electrodynamics of Moving
Bodies”[3] carried the idea of Special Theory of
Relativity. The paper suggested brilliant modifications of the equations of
Galilean Relativity so that the constancy of the velocity of electromagnetic
radiations can be preserved. Even though, Albert Einstein was accredited for
this genius theory. The equations involved in it are called as – “Lorentz
Transformation Equations”, named after a Dutch physicist – Hendrik Lorentz, who
originally derived those equations. But, Lorentz chose to adhere with the
previous idea of hypothetical aether and interpreted his theory accordingly[4]. The genius of Einstein was to use these
results by Lorentz to explain the constant velocity of light. This clearly
points out the fact that even though Lorentz’s theory was correct, the way he
interpreted it made a lot of difference about the perception of reality. The
Special Theory of Relativity was for inertial frame of references (objects
moving with constant velocity with respect to another object). A much more
general theory was required for non-inertial (accelerating) reference frames.
It took Einstein nearly ten years and a number of failed attempts to come up
with a General Theory of Relativity. He borrowed the mathematics from Differential
Geometry and Tensor Calculus to demonstrate how space and time is curved by
mass and energy giving rise to Gravity. It is believed that when Einstein was
working for a General Theory of Relativity. There was yet another German
mathematician named David Hilbert who was also simultaneously working for it.
He was thought to be closer to discovering it, but Einstein won the race[5]. General Relativity was later confirmed by a
number of experiments and observations. In 1915, Einstein predicted the existence
of Gravitational Waves using his theory – these are ripples in the fabric of
spacetime. He believed that it would be impossible to detect these waves.
However, nearly a century after its prediction, the LIGO (Laser Interferometer
Gravitational – Wave Observatory) observed these waves and confirmed its
existence. General Relativity also predicted the existence of Black Holes. In
April 2017, the first image of a Black Hole was captured using the Event
Horizon Telescope and Einstein’s Theory of Relativity passed another test.
This
long tale of the Theory of Relativity is a supreme example of how powerful a
theory can be. If forged properly by considering all pre-existing laws, it can
be a vital tool for understanding reality and even yielding testable predictions.
The sheer power of mathematics and imagination allowed Physicists to predict
something which had never been observed before. Yet, they were so precise that
those assertions were verified in the same form as predicted, almost a century
later.
3.) Quantum Physics
On
the contrary, there is another contender on the stage. A theory which arose
from a set of observations conducted in the early and mid twentieth century –
Quantum Physics. It is known for its unintuitive and chaotic character. Quantum
Mechanics was discovered when Physicists started conducting experiments with
small scale objects and the nature of radiations. They observed the laws of
classical mechanics failed to explain the behavior of these objects and a new
theory was necessary. The subject introduces an unavoidable element of
uncertainty and randomness into the quantum realm. Unlike the Theory of
Relativity, Quantum Physics is not theoretically rigid. It is associated with a
number of different theories or “interpretations” for the same experimental
observations. The most orthodox explanation is the – Statistical Interpretation[6] or the Copenhagen Interpretation because it
was mostly formulated by Niels Bohr and Werner Heisenberg in Copenhagen,
Denmark. Another well known interpretation was formulated by Louis De-Broglie
and later used by David Bohm to present the Pilot Wave Theory or Bohmian
Mechanics[7]. Of course, there are other interpretations
like Hugh Everett’s Many Worlds Interpretation[8]
or the Spontaneous Collapse Theories. All these different theoretical
formulations of Quantum Physics debate on whether reality is deterministic or
stochastic. Inspite of this, one should not forget that the core of these
theories is the fundamental observations made through experiments. These
interpretations are nothing but different models of the same reality and till
date one has no reason to believe in one and disregard the other.
4.) Conclusions
Why
are there different theories associated with Quantum Physics but not with
Relativity? I believe it boils down to the sequential manner of theory and
experiment. Special and General Relativity was first predicted theoretically
through a series of “thought experiments”. Hence, when actual experiments were
conducted later, there was no ambiguity in the conclusions because they were
conducted with the purpose of testifying Relativity. On the other hand, Quantum
Physics was first hinted from experiments conducted with small scale objects.
Owing to this, physicists had the experimental results in hand but the task of
formulating a theoretical model for them got tedious. Each model had the
potential to describe these results in their own manner whilst having their own
imperfections. Had relativity not been discovered by Albert Einstein, then we
would have certainly obtained hints of it. Perhaps from the errors in Global
Positioning System satellites; and from the precession of perihelion of planet
Mercury; and from the Gravitational Lensing observed near a galaxy or a black
hole. However, the chances of formulating the Theory of Relativity in its exact
form as we have today from these observations would have been less. The Theory
of Relativity would then have been one amongst many other seemingly possible
interpretations of those observations. This might demonstrate how sometimes
psychological aspects decide how we view reality. To conclude, both theory and
experiments are paramount in Physics. Although, practical experiments should be
viewed as keys to unlocking the secrets of Universe, for they are depict reality.
Our theories are merely viewpoints on this Universe and are doomed to change
with time. With each experiment conducted with increasing precision, these
theories would be discarded or refined to fit into reality. The inverse of this
cannot be true.
5.) References