1.5 Nature of physical laws

Nature of Physical Laws: Physicists explore the universe. Their investigations, based on scientific processes, range from particles that are smaller than atoms in size to stars that are very far away. In addition to finding the facts by observation and experimentation, physicists attempt to discover the laws that summarise (often as mathematical equations) these facts. The concept of energy is central to physics and the expressions for energy can be written for every physical system. When all forms of energy e.g., heat, mechanical energy, electrical energy, etc., are counted, it turns out that energy is conserved. The general law of conservation of energy is true for all forces and for any kind of
transformation between different forms of energy.  According to Einstein’s theory, mass m is equivalent to energy E given by the relation \(E=m c^{2}\), where c is the speed of light in vacuum. In a nuclear process, mass gets converted to energy (or vice-versa). This is the energy that is released in a nuclear power generation and nuclear explosions.

The physical quantities that remain unchanged in a process are called conserved quantities. Some of the general conservation laws in nature include the laws of conservation of mass, energy, linear momentum, angular momentum, charge, parity, etc. Some conservation laws are true for one fundamental force but not for the other. Conservation laws have a deep connection with the symmetries of nature. Symmetries of space and time and other types of symmetries play a central role in modern theories of fundamental forces in nature.