The Restless universe
|Introduction to The restless Universe|
1 The lawful Universe2 The clockwork Universe
5 The uncertain Universe
Other titles in the Physical World series
Answer and comments
(ii) Thermodynamics deals with processes involving energy transfers, including heat, and clarifies ideas about equilibrium and irreversibility.
(iii) Statistical mechanics interprets thermodynamics in terms of the statistical behaviour of a large number of particles.
(iv) Electromagnetism deals with electricity and magnetism. It replaced the concept of action at a distance by that of a field, and showed that electric and magnetic fields have their own dynamics, leading to the interpretation of light and radio waves as electromagnetic waves.
(v) Special relativity is based on the idea that all observers in uniform motion should agree about the laws of physics. When the laws of electromagnetism were included, this led to a revolution in our ideas of space and time, which were merged together into space-time. Different observers, in different states of uniform motion, disagree about which events are simultaneous in space-time.
(vi) General relativity grew from the desire to express physical laws in the same way for all observers, even those who were not moving uniformly. It became a theory of gravity in which the motion of bodies was determined by the curvature of space-time, caused by sources of gravitation.
(vii) Quantum mechanics describes systems of particles in the atomic domain. It asserts that the fundamental laws of physics involve probability in an intrinsic and unavoidable way, and so casts doubt on simple realism.
(viii) Quantum field theory extends the ideas of quantum mechanics and special relativity to fields. Particles are interpreted as quanta of excitation of the field and may be created or annihilated as the field becomes more or less excited.
Relevant LinksA note on powers of ten and significant figures
|S207 The Physical World|