Universe Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! === Particles === [[File:Standard Model of Elementary Particles.svg|thumb|upright=2.2|Standard model of elementary particles: the 12 fundamental fermions and 4 fundamental bosons. Brown loops indicate which bosons (red) couple to which fermions (purple and green). Columns are three generations of matter (fermions) and one of forces (bosons). In the first three columns, two rows contain quarks and two leptons. The top two rows' columns contain up (u) and down (d) quarks, charm (c) and strange (s) quarks, top (t) and bottom (b) quarks, and photon (γ) and gluon (g), respectively. The bottom two rows' columns contain electron neutrino (ν<sub>e</sub>) and electron (e), muon neutrino (ν<sub>μ</sub>) and muon (μ), tau neutrino (ν<sub>τ</sub>) and tau (τ), and the Z<sup>0</sup> and W<sup>±</sup> carriers of the weak force. Mass, charge, and spin are listed for each particle.|alt=A four-by-four table of particles. Columns are three generations of matter (fermions) and one of forces (bosons). In the first three columns, two rows contain quarks and two leptons. The top two rows' columns contain up (u) and down (d) quarks, charm (c) and strange (s) quarks, top (t) and bottom (b) quarks, and photon (γ) and gluon (g), respectively. The bottom two rows' columns contain electron neutrino (ν sub e) and electron (e), muon neutrino (ν sub μ) and muon (μ), and tau neutrino (ν sub τ) and tau (τ), and Z sup 0 and W sup ± weak force. Mass, charge, and spin are listed for each particle.]] {{Main|Particle physics}} Ordinary matter and the forces that act on matter can be described in terms of [[elementary particle]]s.<ref>{{cite book |author=Veltman, Martinus |title=Facts and Mysteries in Elementary Particle Physics |url=https://archive.org/details/factsmysteriesin0000velt |url-access=registration |publisher=World Scientific |year=2003 |isbn=978-981-238-149-1}}</ref> These particles are sometimes described as being fundamental, since they have an unknown substructure, and it is unknown whether or not they are composed of smaller and even more fundamental particles.<ref name=PFIp1-3>{{cite book |first1=Sylvie |last1=Braibant |first2=Giorgio |last2=Giacomelli |first3=Maurizio |last3=Spurio |year=2012 |title=Particles and Fundamental Interactions: An Introduction to Particle Physics |url=https://books.google.com/books?id=e8YUUG2pGeIC&pg=PA1 |edition=2nd |pages=1–3 |publisher=[[Springer (publisher)|Springer]] |isbn=978-94-007-2463-1 |access-date=January 27, 2016 |archive-date=August 26, 2016 |archive-url=https://web.archive.org/web/20160826133823/https://books.google.com/books?id=e8YUUG2pGeIC&pg=PA1 |url-status=live }}</ref><ref name=Close>{{cite book |author-last=Close |author-first=Frank |year=2012 |title=Particle Physics: A Very Short Introduction |publisher=Oxford University Press |isbn=978-0-19-280434-1 }}</ref> In most contemporary models they are thought of as points in space.<ref>{{Cite web |last=Mann |first=Adam |date=August 20, 2022 |title=What Are Elementary Particles? |url=https://www.livescience.com/65427-fundamental-elementary-particles.html |access-date=August 17, 2023 |website=Live Science |archive-date=August 17, 2023 |archive-url=https://web.archive.org/web/20230817161504/https://www.livescience.com/65427-fundamental-elementary-particles.html |url-status=live }}</ref> All elementary particles are currently best explained by [[quantum mechanics]] and exhibit [[wave–particle duality]]: their behavior has both particle-like and [[wave]]-like aspects, with different features dominating under different circumstances.<ref>{{cite book |last=Zwiebach |first=Barton |title=Mastering Quantum Mechanics: Essentials, Theory, and Applications |publisher=MIT Press |year=2022 |isbn=978-0-262-04613-8 |page=31 |author-link=Barton Zwiebach}}</ref> Of central importance is the [[Standard Model]], a theory that is concerned with [[Electromagnetism|electromagnetic]] interactions and the [[Weak interaction|weak]] and [[Strong interaction|strong]] nuclear interactions.<ref name="Oerter2006">{{cite book |author=Oerter |first=R. |url=https://archive.org/details/theoryofalmostev0000oert |title=The Theory of Almost Everything: The Standard Model, the Unsung Triumph of Modern Physics |publisher=[[Penguin Group]] |year=2006 |isbn=978-0-13-236678-6 |page=[https://archive.org/details/theoryofalmostev0000oert/page/2 2] |format=Kindle |url-access=registration}}</ref> The Standard Model is supported by the experimental confirmation of the existence of particles that compose matter: [[quark]]s and [[lepton]]s, and their corresponding "[[antimatter]]" duals, as well as the force particles that mediate [[fundamental interactions|interactions]]: the [[photon]], the [[W and Z bosons]], and the [[gluon]].<ref name=PFIp1-3 /> The Standard Model predicted the existence of the recently discovered [[Higgs boson]], a particle that is a manifestation of a field within the universe that can endow particles with mass.<ref name="OnyisiFAQ">{{cite web |last=Onyisi |first=P. |date=October 23, 2012 |title=Higgs boson FAQ |url=https://wikis.utexas.edu/display/utatlas/Higgs+boson+FAQ |publisher=[[University of Texas]] ATLAS group |access-date=January 8, 2013 |archive-date=October 12, 2013 |archive-url=https://web.archive.org/web/20131012130340/https://wikis.utexas.edu/display/utatlas/Higgs+boson+FAQ |url-status=live }}</ref><ref name="strasslerFAQ2">{{cite web |last=Strassler |first=M. |date=October 12, 2012 |title=The Higgs FAQ 2.0 |url=http://profmattstrassler.com/articles-and-posts/the-higgs-particle/the-higgs-faq-2-0/ |work=ProfMattStrassler.com |access-date=January 8, 2013 |quote=[Q] Why do particle physicists care so much about the Higgs particle?<br />[A] Well, actually, they don't. What they really care about is the Higgs ''field'', because it is ''so'' important. [emphasis in original] |archive-date=October 12, 2013 |archive-url=https://web.archive.org/web/20131012042637/http://profmattstrassler.com/articles-and-posts/the-higgs-particle/the-higgs-faq-2-0/ |url-status=live }}</ref> Because of its success in explaining a wide variety of experimental results, the Standard Model is sometimes regarded as a "theory of almost everything".<ref name=Oerter2006 /> The Standard Model does not, however, accommodate gravity. A true force–particle "theory of everything" has not been attained.<ref name="Weinberg2011">{{cite book|first=Steven|last=Weinberg|title=Dreams of a Final Theory: The Scientist's Search for the Ultimate Laws of Nature|publisher=Knopf Doubleday Publishing Group|isbn=978-0-307-78786-6|date=2011}}</ref> ==== Hadrons ==== {{Main|Hadron}} A hadron is a [[composite particle]] made of [[quark]]s [[bound state|held together]] by the [[strong force]]. Hadrons are categorized into two families: [[baryon]]s (such as [[proton]]s and [[neutron]]s) made of three quarks, and [[meson]]s (such as [[pion]]s) made of one quark and one [[antiparticle|antiquark]]. Of the hadrons, protons are stable, and neutrons bound within atomic nuclei are stable. Other hadrons are unstable under ordinary conditions and are thus insignificant constituents of the modern universe.<ref name=Allday2002/>{{rp|118–123}} From approximately 10<sup>−6</sup> seconds after the [[Big Bang]], during a period known as the [[hadron epoch]], the temperature of the universe had fallen sufficiently to allow quarks to bind together into hadrons, and the mass of the universe was dominated by [[hadron]]s. Initially, the temperature was high enough to allow the formation of hadron–anti-hadron pairs, which kept matter and antimatter in [[thermal equilibrium]]. However, as the temperature of the universe continued to fall, hadron–anti-hadron pairs were no longer produced. Most of the hadrons and anti-hadrons were then eliminated in particle–antiparticle [[annihilation]] reactions, leaving a small residual of hadrons by the time the universe was about one second old.<ref name=Allday2002>{{cite book|last1=Allday|first1=Jonathan|title=Quarks, Leptons and the Big Bang|date=2002|publisher=IOP Publishing|isbn=978-0-7503-0806-9|edition=2nd}}</ref>{{rp|244–266}} ==== Leptons ==== {{Main|Lepton}} A lepton is an [[elementary particle|elementary]], [[half-integer spin]] particle that does not undergo strong interactions but is subject to the [[Pauli exclusion principle]]; no two leptons of the same species can be in exactly the same state at the same time.<ref>{{cite encyclopedia |title=Lepton (physics) |url=http://www.britannica.com/EBchecked/topic/336940/lepton |encyclopedia=[[Encyclopædia Britannica]] |access-date=September 29, 2010 |archive-date=May 11, 2015 |archive-url=https://web.archive.org/web/20150511203531/http://www.britannica.com/EBchecked/topic/336940/lepton |url-status=live }}</ref> Two main classes of leptons exist: [[electric charge|charged]] leptons (also known as the ''electron-like'' leptons), and neutral leptons (better known as [[neutrino]]s). Electrons are stable and the most common charged lepton in the universe, whereas [[muon]]s and [[tau (particle)|taus]] are unstable particles that quickly decay after being produced in [[high energy physics|high energy]] collisions, such as those involving [[cosmic ray]]s or carried out in [[particle accelerator]]s.<ref>{{cite book | last=Harari | first=H. | year=1977 | chapter=Beyond charm | title=Weak and Electromagnetic Interactions at High Energy, Les Houches, France, Jul 5 – Aug 14, 1976 | editor1-last=Balian | editor1-first=R. | editor2-last=Llewellyn-Smith | editor2-first=C.H. | series=Les Houches Summer School Proceedings | volume=29 | page=613 | publisher=[[North-Holland Publishing Company|North-Holland]] }}</ref><ref>{{cite conference |author=Harari H. |title=Three generations of quarks and leptons |url=https://www.slac.stanford.edu/cgi-bin/getdoc/slac-pub-1974.pdf |book-title=Proceedings of the XII Rencontre de Moriond |editor1=E. van Goeler |editor2=Weinstein R. |page=170 |year=1977 |id=SLAC-PUB-1974 |conference= |access-date=May 29, 2020 |archive-date=May 13, 2020 |archive-url=https://web.archive.org/web/20200513180308/https://www.slac.stanford.edu/cgi-bin/getdoc/slac-pub-1974.pdf |url-status=live }}</ref> Charged leptons can combine with other particles to form various [[composite particle]]s such as [[atom]]s and [[positronium]]. The [[electron]] governs nearly all of [[chemistry]], as it is found in [[atom]]s and is directly tied to all [[chemical property|chemical properties]]. Neutrinos rarely interact with anything, and are consequently rarely observed. Neutrinos stream throughout the universe but rarely interact with normal matter.<ref>{{cite press release |publisher=[[Massachusetts Institute of Technology|MIT News Office]] |date=April 18, 2007 |title=Experiment confirms famous physics model |url=http://web.mit.edu/newsoffice/2007/neutrino.html |access-date=June 2, 2015 |archive-date=July 5, 2013 |archive-url=https://web.archive.org/web/20130705100832/http://web.mit.edu/newsoffice/2007/neutrino.html |url-status=live }}</ref> The [[lepton epoch]] was the period in the evolution of the early universe in which the [[lepton]]s dominated the mass of the universe. It started roughly 1 second after the [[Big Bang]], after the majority of hadrons and anti-hadrons annihilated each other at the end of the [[hadron epoch]]. During the lepton epoch the temperature of the universe was still high enough to create lepton–anti-lepton pairs, so leptons and anti-leptons were in thermal equilibrium. Approximately 10 seconds after the Big Bang, the temperature of the universe had fallen to the point where lepton–anti-lepton pairs were no longer created.<ref>{{cite web|title=Thermal history of the universe and early growth of density fluctuations|url=http://wwwmpa.mpa-garching.mpg.de/~gamk/TUM_Lectures/Lecture4.pdf|work=Guinevere Kauffmann|publisher=[[Max Planck Institute for Astrophysics]]|access-date=January 6, 2016|archive-date=August 21, 2016|archive-url=https://web.archive.org/web/20160821041542/http://wwwmpa.mpa-garching.mpg.de/~gamk/TUM_Lectures/Lecture4.pdf|url-status=live}}</ref> Most leptons and anti-leptons were then eliminated in [[annihilation]] reactions, leaving a small residue of leptons. The mass of the universe was then dominated by [[photon]]s as it entered the following [[photon epoch]].<ref>{{cite web|title=First few minutes|work=Eric Chaisson|publisher=Harvard Smithsonian Center for Astrophysics|url=https://www.cfa.harvard.edu/~ejchaisson/cosmic_evolution/docs/fr_1/fr_1_part3.html|access-date=January 6, 2016|archive-date=December 4, 2013|archive-url=https://web.archive.org/web/20131204050252/https://www.cfa.harvard.edu/~ejchaisson/cosmic_evolution/docs/fr_1/fr_1_part3.html|url-status=live}}</ref><ref>{{cite web|title=Timeline of the Big Bang|work=The physics of the Universe|url=https://www.physicsoftheuniverse.com/topics_bigbang_timeline.html|access-date=January 6, 2016|archive-date=March 30, 2020|archive-url=https://web.archive.org/web/20200330140345/https://www.physicsoftheuniverse.com/topics_bigbang_timeline.html|url-status=live}}</ref> ==== Photons ==== {{Main|Photon epoch}} {{See also|Photino}} A photon is the [[quantum]] of [[light]] and all other forms of [[electromagnetic radiation]]. It is the [[force carrier|carrier]] for the [[electromagnetic force]]. The effects of this [[force]] are easily observable at the [[microscopic scale|microscopic]] and at the [[macroscopic scale|macroscopic]] level because the photon has zero [[rest mass]]; this allows long distance [[fundamental interaction|interactions]].<ref name="OpenStax-college-physics"/>{{rp|1470}} The photon epoch started after most leptons and anti-leptons were [[annihilation|annihilated]] at the end of the lepton epoch, about 10 seconds after the Big Bang. Atomic nuclei were created in the process of nucleosynthesis which occurred during the first few minutes of the photon epoch. For the remainder of the photon epoch the universe contained a hot dense [[plasma (physics)|plasma]] of nuclei, electrons and photons. About 380,000 years after the Big Bang, the temperature of the universe fell to the point where nuclei could combine with electrons to create neutral atoms. As a result, photons no longer interacted frequently with matter and the universe became transparent. The highly redshifted photons from this period form the cosmic microwave background. Tiny variations in temperature and density detectable in the CMB were the early "seeds" from which all subsequent [[structure formation]] took place.<ref name=Allday2002 />{{rp|244–266}} {{Big Bang timeline|state=collapsed}} Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). Do not submit copyrighted work without permission! Cancel Editing help (opens in new window) Discuss this page