Why can’t time run backwards?
Nobel Laureate Sir Anthony J. Leggett asked that very question during a recent visit to Lehigh University, exploring its scientific, philosophical and theological ramifications.
Leggett, widely acclaimed for his expertise in the theory of low-temperature physics, visited the Bethlehem campus as a guest of both the P.C. Rossin College of Engineering and Applied Science and the College of Arts and Sciences.
The 75-year-old Camberwell, London native shared nearly every minute of his time with the university community, presenting two lectures, meeting with students and faculty as well as spending time with a number of fellow scientists.
Leggett's explored the subject of time during the John J. Karakash Distinguished Lecture, exploring the "origin of the 'arrow' of time."
"We can remember the past and predict the future, not vice versa," Leggett explained. "At the very basic level, the laws of physics make no distinction between past and future … the fundamental microscopic laws of classical or quantum-mechanical physics look exactly the same if the direction of time is reversed."
Leggett listed the five "arrows of time" as:
- Thermodynamic: with entropy, or disorder, increasing over time;
- Psychological: people remember the past and try to affect the future;
- Biological: plants and animals grow;
- Electromagnetic: stars and light bulbs emit radiation but do not absorb it;
- Cosmological: the universe is expanding over time
"That the past causes the present and the present causes the future, has never been challenged," said Leggett. "But a revolution on the scale of quantum mechanics could change our ideas regarding the arrow of time."
Leggett offered a second lecture the next day as guest of the department of Physics in Lehigh's College of Arts and Sciences, at the Frank J. Feigl Lecture, titled “Bell’s Theorem, Entanglement, Quantum Teleportation and all that.”
Leggett was the 2003 recipient of the Nobel Prize for Physics for his contributions to the theory of superconductors and superfluids, shaping the theoretical understanding of normal and superfluid helium liquids and other strongly coupled superfluids. A member of the National Academy of Sciences, the American Philosophical Society and the American Academy of Arts and Sciences, Leggett was also knighted by Queen Elizabeth II in 2004 "for services to physics."
He currently serves as a Professor of Physics at University of Illinois.
Read more about Leggett's visit to Lehigh in the university news archive.