Welcome to Physics Gives You Wings.
This site is dedicated to all things physics related. Explore. Learn. Have fun.

Marcus Afshar

A little about me:

  • I teach physics at Glendale Community College, in Southern California.
  • I have a PhD in physics from Univ. of California at Davis and a bachelor's in physics from Univ. of California at Berkeley.
  • My PhD research was in quantum gravity. My thesis was titled Quasilocal Energy in FRW Cosmology and was based primarily on my paper in the journal Classical and Quantum Gravity.
  • I can be contacted via email at: mafshar@glendale.edu

Course websites:

A few of my favorite physics websites:

  • arXiv Here you'll find preprints of scholarly papers in physics. Almost every physics paper published since 1990 can be found here.
  • MyPhysicsLab Here you'll find, among other things, simulations of periodic motion such as springs and pendulums with good explanations.
  • Falstad's Applets Here you'll find Java applets demonstrating a variety of phenomena in physics, from classical mechanics to electromagnetism to quantum mechanics.
  • PhET Simulations Here you'll find a large number of Java applets demonstrating various concepts in physics, chemistry and biology.
  • Dr. QuantumIn this YouTube video the animated Dr. Quantum explains the mysterious quantum double slit experiment -- one of my favorite animations of all time.
  • Magnetic LevitationIn this YouTube video you can see a demonstration of magnetic levitation using quantum locking of flux tubes -- far more astonishing than ordinary magnetic levitation.
  • Journey into a Blackhole In this YouTube video you can see a physically accurate simulation of a journey to the heart of a blackhole.

A few of my favorite papers in physics:

  • W. B. Bonnor, Size Of A Hydrogen Atom In The Expanding Universe, Class. Quantum Grav. 16 (1999) 1313 - 1321. This paper addresses the question of whether a hydrogen atom expands as the universe expands. On a related note, one may wonder if atoms and molecules in our bodies are expanding as the universe expands.
  • J. D. Bekenstein, Black Holes and Entropy, Phys. Rev. D 7 (1973) 2333 - 2346. In this classic paper, Bekenstein first proposes that a black hole must have entropy.
  • A. Einstein, B. Podolsky and N. Rosen, Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?, Phys. Rev. 47 (1935), 777 - 780. In this classic paper, which forms the basis of the famous EPR paradox, Einstein and collaborators propose that quantum mechanics is an incomplete and possibly inconsistent theory. Although Einstein believed the cosmological constant to be his "biggest mistake," in fact this paper may have been a bigger mistake.
  • K. Eppley and E. Hannah, The Necessity of Quantizing the Gravitational Field, Foundations of Physics 7 (1977) 51 - 68. In this paper the authors show that a non-quantized gravitational field can be used to violate fundamental principles of quantum mechanics. So general relativity and quantum mechanics are fundamentally at odds with each other.

In physics news:

  • Superluminal Neutrinos: On September 23, 2011, physicists from the OPERA collaboration announced results indicating that neutrinos travel faster than light. A pre-print of their announcement can be found in the arXiv database. As of today -- October 2, 2011 -- their finding has not yet been published in a refereed journal. So in some respects the announcement is premature. If true, this finding contradicts one of the tenets of special relativity, namely that nothing can travel faster than light. Perhaps the following information will help you form your own opinion:
      • What is a neutrino? A neutrino is a fundamental particle. Like electrons, neutrinos are believed to be indivisible building blocks of matter. They have mass, but are extremely light. They are electrically neutral, and rarely interact with ordinary matter. In fact, a neutrino can easily pass through the entire diameter of Earth without interacting with a single particle.
      • Has the speed of neutrinos ever been measured before? Yes. Approximately 168,000 years ago, Supernova 1987A exploded somewhere in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud. The explosion emitted large numbers of both photons and neutrinos, which arrived on Earth almost simultaneously on February 23, 1987. This was seen as strong indication that neutrinos have nearly the same speed as photons. If the speeds were different, as the OPERA data suggests, then the neutrinos should have arrived considerably earlier. So there is direct conflict between these two experiments. It should be noted however that the neutrinos in the OPERA experiments had vastly different energies than the neutrinos emitted by Supernova 1987A.
      • Why do we believe that nothing can travel faster than light? There are several reasons for this. One of the most compelling is that if objects are allowed to travel faster than light, then causal relations can be violated. Consider two events that are causally related, such as the kicking of a ball and the subsequent rolling of the ball. Suppose event A is the cause and event B is the effect. For every observer, event A should precede event B. In other words, the cause should come before the effect. Special relativity respects this simple relation between cause and effect. However an observer traveling faster than light may observe event B to precede event A. Remember that the act of observation necessarily involves interaction with light. This reversal of cause and effect disturbs the very foundation of science. Since this is clearly an undesirable situation, we postulate that nothing can travel faster than light -- not even neutrinos. In science fiction novels, this reversal of causality is often viewed as time travel. How bizarre would it be if a neutrino could see its own demise before its own creation?
      • What would it mean if the OPERA data is in fact correct? If superluminal propagation, i.e. faster-than-light motion, is possible, then special relativity, general relativity and quantum field theory would all have to be revised. This would be the biggest upheaval in physics in at least 50 years. It is difficult to be specific about the changes. Perhaps the Lorentz transformations, which form the foundation of special relativity, would have to be modified to allow speeds beyond the speed of light. Perhaps the speed of neutrinos would have to be introduced as a new fundamental constant, or as the new speed limit of nature. The report from the OPERA experiment does not indicate whether the speed of neutrinos is constant for all inertial observers. Up to now only mass-less particles, like photons, have had this privilege. Note however that almost all the physics taught in the first two years of college would remain unchanged. Changes in the behavior of ordinary objects -- with ordinary speeds and ordinary energies -- would be too miniscule to perceive.


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The Uncertainty Principle

Last Updated: 26Aug2015