- 1. The Green's function to the Helmholtz equation has two solutions: the advanced and retarded time solutions.
There is no mathematical reason for why the field cannot be produced before the particle moves, but this process is
observationally never observed in nature, and would be in serious conflict with the intuitive principle of causality.
- 2. The second law of thermodynamics states that entropy increases with time.
- 3. In quantum mechanics, a the expectation values of a system can be computed, but it can never be known with
certainty in what quantum state it resides unless a measurement is made. After making a measurement, the system assumes
one of its eigenstates and remains there.
- 4. Big Bang cosmology demonstrates that the universe Eric Weisstein's World of Astronomy expands with time.
- 5. Subjective time notes that, while information about the past is readily available, it is not possible to
examine records of the future.
Entropy, Second Law of Thermodynamics
© 1996-2007 Eric W. Weisstein
