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When we speak of natural laws or the laws of physics, we are dealing with state facts, which are derived from verifications with the scientific method. In other words, the laws of physics are born out of empirical observations. In other words, the laws of physics help to describe the behaviour of the world around us.
The laws of physics are simply the conclusions that, over time, have been learned from observations of nature and scientific experiments. Within the scientific method, experiments are repeated continuously, in varying conditions to infer with certainty about the phenomena studied, so that these conclusions are accepted worldwide. Scientific conclusions are repeatedly replicated and validated by the scientific community.
Some of the Important Laws of Physics are listed below:
Laws | Explanation |
Newton’s second law of motion | This law deals with the behaviour of objects when there is an imbalance in the existing forces. That is when an object is subjected to acceleration. |
The ideal gas law | The ideal gas law describes the equation of the state of gas under ideal conditions. This law has been crucial in defining the behaviour of many gases. |
Bernoulli’s principle | Bernoulli’s principle states that the velocity of a fluid is inversely proportional to the pressure within the fluid. |
The law of conservation of mass | The law of conservation of mass states that mass cannot be created or destroyed, but can only be transformed, in an isolated system. This law can be expressed in the following differential equation: ∂ρ∂t+▽(ρv)=0 |
Application of the Laws of Physics
Within science, theories and laws have evolved, leading to better approximations of reality. For example, in the beginning we assumed that the Earth was the centre of the universe. This then evolved with the hypothesis that the sun was the centre of the universe. After much scientific testing, we can now conclude that both approaches were wrong. Although the sun is the centre of our solar system, it is not the centre of the entire universe.
Another clear example is the application of Newton’s universal law of gravitation, which explained the behaviour of all the planets in the solar system. However, this law could not explain the behaviour of Mercury’s orbit and rotation period. This phenomenon remained unsolved until the arrival of Einstein and his general theory of relativity.
The laws of physics explain the behaviour of nature. To do this, certain properties are relevant:
– These laws apply under certain conditions
– The laws apply universally, they are omnipresent.
– They are a way of simplifying the representation of reality.
– They are absolute and do not depend on external factors
– They are stable over time
– They are homogeneous in time and space.
There are two basic classifications for the laws of physics:
- Classical physics: which explains the observable world around us.
- Atomic physics: which explains the interactions of the subatomic world (sometimes also called quantum physics).
Within Isaac Newton’s Philosophiae Naturalis Principia Mathematica postulate, the principles of classical mechanics can be understood, as well as Einstein’s theory of relativity.
In the following, we will look at the laws from their origin, i.e., from where they were derived.
Derivations of Definitions
Some of the laws of science come from theoretical definitions, derived from mathematical definitions. In general, laws are derived more from tangible phenomena. Clear examples are principles such as uncertainty, stationary action, or causality.
Laws Due to Mathematical Symmetries
Mathematical symmetries are often found in nature. We can list some examples such as the symmetric rotation of space-time, which is reflected in the Lorentz transformation. We can also find a homogeneity in space that can be seen in the conservation laws and in the Pauli principle, which speaks of the uniqueness of each electron. The laws may, however, have exceptions (or gaps), which become apparent after repeated experiments.
Derivations of Approximations
These are laws that come from modifications of other physical laws. An example is the law of general relativity which comes from an approximation of the Newtonian law of gravitation. This same law applies to Quantum Electrodynamics which is an application of Coulomb’s law.
Derivations of Symmetry Principles
Some symmetries, such as those of space-time, are derived in mathematical approximations that give rise to new fundamental physical laws. For example, the symmetry of time results in the conservation of energy. Another example is the conservation of momentum, derived from the symmetry of space.
