List of unsolved problems in physics

Some of the major unsolved problems in physics are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result. The others are experimental, meaning that there is a difficulty in creating an experiment to test a proposed theory or investigate a phenomenon in greater detail.

Unsolved problems by subfield

The following is a list of unsolved problems grouped by the broad area of physics into which they fall.

Cosmology, and general relativity

Cosmic inflation

Is the theory of cosmic inflation correct?, and if so, what are the details of this epoch? What is the hypothetical inflaton field giving rise to inflation? If inflation happened at one point, is it self-sustaining through inflation of quantum-mechanical fluctuations, and thus ongoing in some impossibly distant place?^[1]

Horizon problem

Why is the distant universe so homogeneous, when the Big Bang theory seems to predict larger measurable anisotropies of the night sky than those observed? Cosmological inflation is generally accepted as the solution, but are other possible explanations such as a variable speed of light more appropriate?^[2]

Future of the universe

Is the universe heading towards a Big Freeze, a Big Rip, a Big Crunch or a Big Bounce? Or is it part of an infinitely recurring cyclic model?

Gravitational wave

Can gravitational waves be detected experimentally?^[3][4]

Baryon asymmetry

Why is there far more matter than antimatter in the observable universe?

Cosmological constant problem

Why does the zero-point energy of the vacuum not cause a large cosmological constant? What cancels it out?

"Thirty Unsolved Problems in the Physics of Elementary Particles". Progress in Physics 4. 

^ Nakamura; et al (2010). J. Phys. G 37 (075021) http://pdg.lbl.gov/2011/reviews/contents_sports.htmlBare URL needs a title. 

^ Ferrarese, Laura; Merritt, David (2000), "A Fundamental Relation between Supermassive Black Holes and their Host Galaxies", The Astrophysical Journal 539: L9–L12, arXiv:astro-ph/0006053, Bibcode 2000ApJ...539L...9F, doi:10.1086/312838, http://adsabs.harvard.edu/abs/2000ApJ...539L...9F

^ "Scientists Find That Saturn's Rotation Period is a Puzzle". NASA. June 28, 2004. Retrieved 2007-03-22. 

^ Kenneth Chang (July 29, 2008), "The Nature of Glass Remains Anything but Clear", The New York Times, http://www.nytimes.com/2008/07/29/science/29glass.html

^ P.W. Anderson (1995), "Through the Glass Lightly", Science 267: 1615, doi:10.1126/science.267.5204.1615-e, "The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition."

^ Cryogenic electron emission phenomenon has no known physics explanation. Physorg.com. Retrieved on 2011-10-20.

^ doi:10.1209/0295-5075/89/58001

^ Proceedings: Mathematical, physical, and engineering sciences (Royal Society) 453, 1997, "An unsolved problem in modern physics concerns the phenomenon of sonoluminescence"

^ Goldstein, Melvyn L. (2001). "Major Unsolved Problems in Space Plasma Physics". Astrophysics and Space Science 277 (1/2): 349–369. Bibcode:2001Ap&SS.277..349G. doi:10.1023/A:1012264131485. 

^ Yoshida, Beni (2011). "Feasibility of self-correcting quantum memory and thermal stability of topological order". Annals of Physics 326 (10). arXiv:1103.1885. Bibcode:2011AnPhy.326.2566Y. doi:10.1016/j.aop.2011.06.001. Retrieved 8 April 2012. 

^ Podolsky, Dmitry. "Quantum Hall effect. One open question". NEQNET. Retrieved 23 April 2012. 

^ Schlein, Benjamin. "Graduate Seminar on Partial Differential Equations in the Sciences - Energy and Dynamics of Boson Systems". Hausdorff Center for Mathematics. Retrieved 23 April 2012. 

^ Mukherjee, Prabir K. (1998). "Landau Theory of Nematic-Smectic-A Transition in a Liquid Crystal Mixture". Molecular Crystals & Liquid Crystals 312: 157–164. doi:10.1080/10587259808042438. Retrieved 28 April 2012. 

^ A. Yethiraj, "Recent Experimental Developments at the Nematic to Smectic-A Liquid Crystal Phase Transition", Thermotropic Liquid Crystals: Recent Advances, ed. A. Ramamoorthy, Springer 2007, chapter 8.

^ The Nobel Prizes in Physics 1901–2000. Nobelprize.org (2000-02-09). Retrieved on 2011-10-20.

^ The Office of Science – What is Physics?. Sc.doe.gov. Retrieved on 2011-10-20.

^ Nielson, Micheal; Chuang, Isaac (2004). http://www.squint.org/qci/QINFO-book-nielsen-and-chuang-toc-and-chapter1-nov00.pdf. Cambridge University Press. ISBN 978-0-521-63503-5. 

^ "Alcohol constrains Physical Constant in the Early Universe". Max-Planck-Institut für Radioastronomie. December 2012. Retrieved December 15, 2012. 

^ Turyshev, S.; Toth, V.; Kinsella, G.; Lee, S. C.; Lok, S.; Ellis, J. (2012). "Support for the Thermal Origin of the Pioneer Anomaly". Physical Review Letters 108 (24). arXiv:1204.2507. doi:10.1103/PhysRevLett.108.241101.  edit

^ http://www.nytimes.com/2012/07/24/science/mystery-tug-on-pioneer-10-and-11-probes-is-einsteins-i-told-you-so.html?

^ "The MKI and the discovery of Quasars". Jodrell Bank Observatory. Retrieved 2006-11-23. 

^ Hubble Surveys the "Homes" of Quasars Hubblesite News Archive, 1996-35

External links

• What don't we know? Science journal special project for its 125th anniversary: top 25 questions and 100 more.
• Physics News Update A weekly physics news bulletin hosted by the American Institute of Physics.
• List of links to unsolved problems in physics, prizes and research.
• Ideas Based On What We’d Like to Achieve
• 2004 SLAC Summer Institute: Nature's Greatest Puzzles
• Dual Personality of Glass Explained at Last

Unsolved problems by discipline   Biology Chemistry Computer science Economics Linguistics Mathematics Neuroscience Philosophy Physics Statistics