Then Meets Now
Physics of old and new
Newtonian physics is often referred to as classical physics after the development of modern physics in the 1920's
In the old days physics dealt with those phenomena of the inanimate world which do not involve too deep a change in the structure of matter. Thus in terms of energy concentration, physics was restricted to phenomena at room temperature where the energy exchange per atom was no more than one electron volt which at best modified only the secondary bonds in condensed matter. On the other hand, chemistry dealt with high temperature, where chemical changes were brought about through the changes of covalent bonds involving several electron volts per atom or molecule. In respect of size of objects dealt with in Newtonian Physics, human size was the limit. Thus atomic objects constituted chemistry, while celestial objects belonged to astronomy. Since Pasteur showed that a living creature can only be derived from other living ones, the living world was separated from the non-living physical world by boundaries never to be crossed. Classified physics was also constrained by a velocity limit which had to be much less than the velocity of light. Physicists are interested in repressing their invented laws in compact general quantitative terms. Mathematicians, too, play an essential role. However, physicists are not as free as mathematicians who can create the whole abstract imaginary world based entirely on postulates and logical deductions without the constraints of verifiability by experimental observations.
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