|Dr. David Albert, Professor and Director of Philosophical Foundations of Physics, Columbia University, specializes in Philosophical Problems of Quantum Mechanics, Philosophy of Space and Time and Philosophy of Science. Albert is the author of Quantun Mechanics and Experience and has published numerous articles on quantum mechanics in Physical Review.
|Here is a problem that has confused philosophers and physicists from the 19th century to the present. Our most common experience of the world is that time has a certain direction. We are born, grow old, and die; eggs break; liquids mix; and our offices tend to get more disordered - not the other way round. This one-way behavior is captured by the second law of thermodynamics: the entropy of isolated systems usually increases and never decreases. However, in our most basic and most successful scientific theories time has no such direction. For any motion that produces these effects, there is another motion obeying the laws of microscopic-scale physics that produces the reversed effect. In other words, the fundamental physical laws are reversible.
There appears to be no scientific basis for our common sense conviction that by acting now we can affect the future but not the past. The issue is a subtle one, because one might be tempted to deny the existence of the past altogether and to regard our memories of it as mere illusions. Of course, such an attitude would violently contradict common sense. This tension between science and common sense is equally represented in the question of precisely how the past is different from the future.
Dr. Albert’s contribution to the present scientific and philosophical understanding of these matters is both at the most advanced level, and yet something in the nature of an elementary presentation on the subject accessible to interested high-school students.
Dr. David Albert is currently Professor of Philosophy at Columbia University and Director of the Program in the Philosophical Foundations of Physics.