Item 23. Open Questions updated 01-JUN-1993 by SIC -------------- original by John Baez While for the most part a FAQ covers the answers to frequently asked questions whose answers are known, in physics there are also plenty of simple and interesting questions whose answers are not known. Before you set about answering these questions on your own, it's worth noting that while nobody knows what the answers are, there has been at least a little, and sometimes a great deal, of work already done on these subjects. People have said a lot of very intelligent things about many of these questions. So do plenty of research and ask around before you try to cook up a theory that'll answer one of these and win you the Nobel prize! You can expect to really know physics inside and out before you make any progress on these. The following partial list of "open" questions is divided into two groups, Cosmology and Astrophysics, and Particle and Quantum Physics. However, given the implications of particle physics on cosmology, the division is somewhat artificial, and, consequently, the categorization is somewhat arbitrary. (There are many other interesting and fundamental questions in fields such as condensed matter physics, nonlinear dynamics, etc., which are not part of the set of related questions in cosmology and quantum physics which are discussed below. Their omission is not a judgement about importance, but merely a decision about the scope of this article.) Cosmology and Astrophysics -------------------------- 1. What happened at, or before the Big Bang? Was there really an initial singularity? Of course, this question might not make sense, but it might. Does the history of universe go back in time forever, or only a finite amount? 2. Will the future of the universe go on forever or not? Will there be a "big crunch" in the future? Is the Universe infinite in spatial extent? 3. Why is there an arrow of time; that is, why is the future so much different from the past? 4. Is spacetime really four-dimensional? If so, why - or is that just a silly question? Or is spacetime not really a manifold at all if examined on a short enough distance scale? 5. Do black holes really exist? (It sure seems like it.) Do they really radiate energy and evaporate the way Hawking predicts? If so, what happens when, after a finite amount of time, they radiate completely away? What's left? Do black holes really violate all conservation laws except conservation of energy, momentum, angular momentum and electric charge? What happens to the information contained in an object that falls into a black hole? Is it lost when the black hole evaporates? Does this require a modification of quantum mechanics? 6. Is the Cosmic Censorship Hypothesis true? Roughly, for generic collapsing isolated gravitational systems are the singularities that might develop guaranteed to be hidden beyond a smooth event horizon? If Cosmic Censorship fails, what are these naked singularities like? That is, what weird physical consequences would they have? 7. Why are the galaxies distributed in clumps and filaments? Is most of the matter in the universe baryonic? Is this a matter to be resolved by new physics? 8. What is the nature of the missing "Dark Matter"? Is it baryonic, neutrinos, or something more exotic? Particle and Quantum Physics ---------------------------- 1. Why are the laws of physics not symmetrical between left and right, future and past, and between matter and antimatter? I.e., what is the mechanism of CP violation, and what is the origin of parity violation in Weak interactions? Are there right-handed Weak currents too weak to have been detected so far? If so, what broke the symmetry? Is CP violation explicable entirely within the Standard Model, or is some new force or mechanism required? 2. Why are the strengths of the fundamental forces (electromagnetism, weak and strong forces, and gravity) what they are? For example, why is the fine structure constant, which measures the strength of electromagnetism, about 1/137.036? Where did this dimensionless constant of nature come from? Do the forces really become Grand Unified at sufficiently high energy? 3. Why are there 3 generations of leptons and quarks? Why are there mass ratios what they are? For example, the muon is a particle almost exactly like the electron except about 207 times heavier. Why does it exist and why precisely that much heavier? Do the quarks or leptons have any substructure? 4. Is there a consistent and acceptable relativistic quantum field theory describing interacting (not free) fields in four spacetime dimensions? For example, is the Standard Model mathematically consistent? How about Quantum Electrodynamics? 5. Is QCD a true description of quark dynamics? Is it possible to calculate masses of hadrons (such as the proton, neutron, pion, etc.) correctly from the Standard Model? Does QCD predict a quark/gluon deconfinement phase transition at high temperature? What is the nature of the transition? Does this really happen in Nature? 6. Why is there more matter than antimatter, at least around here? Is there really more matter than antimatter throughout the universe? 7. What is meant by a "measurement" in quantum mechanics? Does "wavefunction collapse" actually happen as a physical process? If so, how, and under what conditions? If not, what happens instead? 8. What are the gravitational effects, if any, of the immense (possibly infinite) vacuum energy density seemingly predicted by quantum field theory? Is it really that huge? If so, why doesn't it act like an enormous cosmological constant? 9. Why doesn't the flux of solar neutrinos agree with predictions? Is the disagreement really significant? If so, is the discrepancy in models of the sun, theories of nuclear physics, or theories of neutrinos? Are neutrinos really massless? The Big Question (TM) --------------------- This last question sits on the fence between the two categories above: How do you merge Quantum Mechanics and General Relativity to create a quantum theory of gravity? Is Einstein's theory of gravity (classical GR) also correct in the microscopic limit, or are there modifications possible/required which coincide in the observed limit(s)? Is gravity really curvature, or what else -- and why does it then look like curvature? An answer to this question will necessarily rely upon, and at the same time likely be a large part of, the answers to many of the other questions above. ******************************************************************************* * Item 24. updated 24-MAY-1993 by SIC Accessing and Using Online Physics Resources -------------------------------------------- (I) Particle Physics Databases The Full Listings of the Review of Particle Properties (RPP), as well as other particle physics databases, are accessible on-line. Here is a summary of the major ones, as described in the RPP: (A) SLAC Databases PARTICLES - Full listings of the RPP HEP - Guide to particle physics preprints, journal articles, reports, theses, conference papers, etc. CONF - Listing of past and future conferences in particle physics HEPNAMES - E-mail addresses of many HEP people INST - Addresses of HEP institutions DATAGUIDE - Adjunct to HEP, indexes papers REACTIONS - Numerical data on reactions (cross-sections, polarizations, etc) EXPERIMENTS - Guide to current and past experiments Anyone with a SLAC account can access these databases. Alternately, most of us can access them via QSPIRES. You can access QSPIRES via BITNET with the 'send' command ('tell','bsend', or other system-specific command) or by using E-mail. For example, send QSPIRES@SLACVM FIND TITLE Z0 will get you a search of HEP for all papers which reference the Z0 in the title. By E-mail, you would send the one line message "FIND TITLE Z0" with a blank subject line to QSPIRES@SLACVM.BITNET or QSPIRES@VM.SLAC.STANFORD.EDU. QSPIRES is free. Help can be obtained by mailing "HELP" to QSPIRES. For more detailed information, see the RPP, p.I.12, or contact: Louise Addis (ADDIS@SLACVM.BITNET) or Harvey Galic (GALIC@SLACVM.BITNET). (B) CERN Databases on ALICE LIB - Library catalogue of books, preprints, reports, etc. PREP - Subset of LIB containing preprints, CERN publications, and conference papers. CONF - Subset of LIB containing upcoming and past conferences since 1986 DIR - Directory of Research Institutes in HEP, with addresses, fax, telex, e-mail addresses, and info on research programs ALICE can be accessed via DECNET or INTERNET. It runs on the CERN library's VXLIB, alias ALICE.CERN.CH (IP# 128.141.201.44). Use Username ALICE (no password required.) Remote users with no access to the CERN Ethernet can use QALICE, similar to QSPIRES. Send E-mail to QALICE@VXLIB.CERN.CH, put the query in the subject field and leave the message field black. For more information, send the subject "HELP" to QALICE or contact CERN Scientific Information Service, CERN, CH-1211 Geneva 23, Switzerland, or E-mail MALICE@VXLIB.CERN.CH. Regular weekly or monthly searches of the CERN databases can be arranged according to a personal search profile. Contact David Dallman, CERN SIS (address above) or E-mail CALLMAN@CERNVM.CERN.CH. DIR is available in Filemaker PRO format for Macintosh. Contact Wolfgang Simon (ISI@CERNVM.CERN.CH). (C) Particle Data Group Online Service The Particle Data Group is maintaining a new user-friendly computer database of the Full Listings from the Review of Particle Properties. Users may query by paper, particle, mass range, quantum numbers, or detector and can select specific properties or classes of properties like masses or decay parameters. All other relevant information (e.g. footnotes and references) is included. Complete instructions are available online. The last complete update of the RPP database was a copy of the Full Listings from the Review of Particle Properties which was published as Physical Review D45, Part 2 (1 June 1992). A subsequent update made on 27 April 1993 was complete for unstable mesons, less complete for the W, Z, D mesons, and stable baryons, and otherwise was unchanged from the 1992 version. DECNET access: SET HOST MUSE or SET HOST 42062 TCP/IP access: TELNET MUSE.LBL.GOV or TELNET 131.243.48.11 Login to: PDG_PUBLIC with password HEPDATA. Contact: Gary S. Wagman, (510)486-6610. Email: (GSWagman@LBL.GOV). (D) Other Databases Durham-RAL and Serpukhov both maintain large databases containing Particle Properties, reaction data, experiments, E-mail ID's, cross-section compilations (CS), etc. Except for the Serpukhov CS, these databases overlap SPIRES at SLAC considerably, though they are not the same and may be more up-to-date. For details, see the RPP, p.I.14, or contact: For Durham-RAL, Mike Whalley (MRW@UKACRL.BITNET,MRW@CERNVM.BITNET) or Dick Roberts (RGR@UKACRL.BITNET). For Serpukhov, contact Sergey Alekhin (ALEKHIN@M9.IHEP.SU) or Vladimir Exhela (EZHELA@M9.IHEP.SU). (II) Online Preprint Sources There are a number of online sources of preprints: alg-geom@publications.math.duke.edu (algebraic geometry) astro-ph@babbage.sissa.it (astrophysics) cond-mat@babbage.sissa.it (condensed matter) funct-an@babbage.sissa.it (functional analysis) hep-lat@ftp.scri.fsu.edu (computational and lattice physics) hep-ph@xxx.lanl.gov (high energy physics phenomenological) hep-th@xxx.lanl.gov (high energy physics theoretical) lc-om@alcom-p.cwru.edu (liquid crystals, optical materials) gr-qc@xxx.lanl.gov (general relativity, quantum cosmology) nucl-th@xxx.lanl.gov, (nuclear physics theory) nlin-sys@xyz.lanl.gov (nonlinear science) To get things if you know the preprint number, send a message to the appropriate address with subject header "get (preprint number)" and no message body. If you *don't* know the preprint number, or want to get preprints regularly, or want other information, send a message with subject header "help" and no message body. (III) The World Wide Web There is a wealth of information, on all sorts of topics, available on the World Wide Web [WWW], a distributed HyperText system (a network of documents connected by links which can be activated electronically). Subject matter includes some physics areas such as High Energy Physics, Astrophysics abstracts, and Space Science, but also includes such diverse subjects as bioscience, musics, and the law. * How to get to the Web If you have no clue what WWW is, you can go over the Internet with telnet to info.cern.ch (no login required) which brings you to the WWW Home Page at CERN. You are now using the simple line mode browser. To move around the Web, enter the number given after an item. * Browsing the Web If you have a WWW browser up and running, you can move around more easily. The by far nicest way of "browsing" through WWW uses the X-Terminal based tool "XMosaic". Binaries for many platforms (ready for use) and sources are available via anonymous FTP from ftp.ncsa.uiuc.edu in directory Web/xmosaic. The general FTP repository for browser software is info.cern.ch (including a hypertext browser/editor for NeXTStep 3.0) * For Further Information For questions related to WWW, try consulting the WWW-FAQ: Its most recent version is available via anonymous FTP on rtfm.mit.edu in /pub/usenet/news.answers/www-faq , or on WWW at http://www.vuw.ac.nz:80/overseas/www-faq.html The official contact (in fact the midwife of the World Wide Web) is Tim Berners-Lee, timbl@info.cern.ch. For general matters on WWW, try www-request@info.cern.ch or Robert Cailliau (responsible for the "physics" content of the Web, cailliau@cernnext.cern.ch). (IV) Other Archive Sites There is an FTP archive site of preprints and programs for nonlinear dynamics, signal processing, and related subjects on node lyapunov.ucsd.edu (132.239.86.10) at the Institute for Nonlinear Science, UCSD. Just login anonymously, using your host id as your password. Contact Matt Kennel (mbk@inls1.ucsd.edu) for more information. ******************************************************************************* * END OF FAQ