In classical physics, matter is any substance that has mass and takes up space by having volume.[1][2] In the microcosm, atomic matter consists of subatomic particles, such as the atomic nucleus composed of protons and neutrons, and orbiting electrons.[3][4]

States of matterEdit

Matter exists in states (or phases): the classical solid, liquid, and gas; as well as the more exotic plasma, Bose–Einstein condensates, fermionic condensates, and quark–gluon plasma.[5]

General relativityEdit

Theorems in general relativity and cosmology, equate matter as anything that contributes to the energy–momentum of a system, specifically, anything that is not purely gravity.[6][7] In this view, light and other massless particles and fields are all part of "matter".

Fundamental particlesEdit

Massless particles, such as photons, are not considered matter, because they have neither rest mass nor volume. However, not all particles with rest mass have a classical volume, since fundamental particles such as quarks and leptons (sometimes equated with matter) are considered "point particles" having no effective size or volume. Nevertheless, quarks and leptons together make up "ordinary matter", and their interactions contribute to the effective volume of the composite particles that make up ordinary matter.


  1. R. Penrose (1991). "The mass of the classical vacuum". in S. Saunders, H.R. Brown. The Philosophy of Vacuum. Oxford University Press. p. 21. ISBN 0-19-824449-5. 
  2. "Matter (physics)". McGraw-Hill's Access Science: Encyclopedia of Science and Technology Online. Archived from the original on 17 June 2011. Retrieved 2009-05-24. 
  3. P. Davies (1992). The New Physics: A Synthesis. Cambridge University Press. p. 1. ISBN 0-521-43831-4. 
  4. G. 't Hooft (1997). In search of the ultimate building blocks. Cambridge University Press. p. 6. ISBN 0-521-57883-3. 
  5. Brookhaven National Laboratory (18 April 2005). "RHIC Scientists Serve Up "Perfect" Liquid". Press release. Retrieved 2009-09-15. 
  6. S.M. Caroll (2004). Spacetime and Geometry. Addison Wesley. pp. 163–164. ISBN 0-8053-8732-3. 
  7. P. Davies (1992). The New Physics: A Synthesis. Cambridge University Press. p. 499. ISBN 0-521-43831-4. "Matter fields: the fields whose quanta describe the elementary particles that make up the material content of the Universe (as opposed to the gravitons and their supersymmetric partners)." 
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