Facts

• The nucleus of an atom is made up of various hadrons. Neutrons and protons are two forms of hadrons, and are called fermionic hadrons. Hadrons are composed of subatomic particles called quarks and gluons which are bonded together by strong interactions; quarks cannot be separated from hadrons. The six types of quarks, or flavors, are up, down, charm, strange, top and bottom. Only the up and down quarks are considered stable. As of 2009, the quark is believed to be the smallest particle that makes up our universe.
  
  

History

• In 460 BC, Democritus, a Greek philosopher, conceptualized that the atom is the smallest particle of matter, but this was not based on scientific fact until 1803, when John Dalton revived the term atom and developed the atomic theory. In 1897, J. J. Thompson, an English physicist, discovered that the electron was a smaller particle than the atom, and Ernest Rutherford discovered the nucleus and the proton in 1911. In 1923, Rutherford's assistant, James Chadwick, discovered the neutron.
  
  

Discovery

• In the 1950s and 60s, many types of hadrons were discovered. Apart from the proton and neutron, hadrons are very unstable and only exist for a millionth of a second. According to HyperHistory Online, unstable hadrons do not form part of normal matter. In the 1960s, the theory of quarks was proposed by Murray Gell-Mann and George Zweig to explain the hadrons.
  
  

Considerations

• While scientists still look at our current Standard Model theory to understand structures of subatomic particles, it is not a complete theory since it does not take into consideration the force of gravity or the general Theory of Relativity. With the discovery and research of black holes, scientists are now realizing the shortcomings of the Standard Model and interest has been renewed in the Unified Field Theory.
  
  

String Theory

• String theory hypothesizes that one master equation is at the foundation of all matter and it may demonstrate that everything that happens in the universe, from the subatomic dance of quarks to the big bang theory and creation of galaxies, is a reflection of this master equation,according to HyperHistory Online. String theory may prove Einstein's belief that everything is built from the space-time continuum.