Lesson 1, Topic 1
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Nature of Physical Laws

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By nature, laws of Physics are stated facts which have been deduced and derived based on empirical observations. Simply put, the world around us works in a certain way, and physical laws are a way of classifying that “working.”

Physical laws are just conclusions drawn based on years (or however long it takes) of scientific observations and experiments which are repeated over and over under different conditions to reach inferences which can be accepted worldwide. These are continuously validated by the scientific community over time.

Application of Laws Of Physics

In the beginning, it was assumed that the earth was the centre of the universe. Then it was hypothesized that our sun is the centre of the universe. We now know that both these conclusions are wrong. The sun may be the centre of our solar system, but it is not the centre of the universe.

Another example is the odd behaviour of the planet, Mercury. Newton’s universal law of gravitation was able to explain all the other planets in the solar system but the orbit and rotational period of Mercury was a bit off, and for some time no one knew why. Later, Einstein came to the rescue with his general theory of relativity.

The different properties of laws of Physics which shed information about their nature are given below:

  • True, under specified conditions
  • Universal and do not deviate anywhere in the universe
  • Simple in terms of representation
  • Absolute and unaffected by external factors
  • Stable and appear to be unchanging
  • Omnipresent and everything in the universe is compliant (in terms of observations)
  • Conservative in terms of quantity
  • Homogeneous in terms of space and time
  • Theoretically reversible in time

Basic laws of physics that govern our universe can be categorized in two ways. Classical physics that deals with us, the surrounding environment and the observable universe around us. Apart from this, there is also atomic physics that deals with subatomic particles and their interactions (quantum mechanics).

Philosophiae Naturalis Principia Mathematica by Isaac Newton tells us the theories of classical mechanics and the theory of relativity by Einstein. Some other laws are the laws of thermodynamics and Boyle’s law of gas.

We’ll take a look at the laws from their point of origin or wherever they were derived or conceptualized from. So put on seatbelts as things are going to get interesting from here on!

Laws derived from Definitions

Few laws of science are derived from math definitions, for instance, the uncertainty principle, the principle of stationary action or causality. These laws are not mathematical as they are empirical and just explain what we perceive from our five senses.

Laws due to Mathematical Symmetries

The mathematical symmetries that are found in our nature, for instance, the rotational symmetry of space-time is reflected in the Lorentz transformation, the homogeneity of space is reflected in the conservation laws and the uniqueness of electrons is represented in the Pauli exclusion principle. Sometimes evidence appears in repeated experiments proving that the law is invalid or has loopholes, although it is highly unlikely that the physical laws would change.

Laws derived from Approximations

Sometimes general laws are modified or changed to form some of our physical laws. For instance, Special reactivity under low-speed approximations is Newtonian dynamics. General relativity in a low mass approximation is Newtonian Gravitation, when a situation that factors in large distances comes into play Quantum Electrodynamics is approximated into Coulomb’s law.

Laws derived from Symmetry Principles

Spacetime and such other symmetries result in mathematical consequences which are some approximated to create fundamental physical laws. For instance, when the symmetry of times shifts the conservation of energy is born as a consequence. The symmetry of space gives birth to the conservation of momentum.