Neutronium

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Neutronium is a term originally used in science fiction and in popular literature to refer to an extremely dense phase of matter composed primarily of neutrons; historically, the word was coined by scientist Andreas von Antropoff in 1926 (scil., before the discovery of the neutron itself) for the conjectured 'element of atomic number zero' that he placed at the head of the periodic table. However, the meaning of the term has changed over time, and from the last half of the 20th century onward it has been used legitimately to refer to extremely dense phases of matter resembling the neutron-degenerate matter postulated to exist in the cores of neutron stars.

1 Neutronium and neutron stars
2 Neutronium and the periodic table
3 Neutronium in fiction
4 See also
5 References

[edit] Neutronium and neutron stars

The term neutronium is used in popular literature to refer to the material present in the cores of neutron stars (stars which are too massive to be supported by electron degeneracy pressure and which collapse into a denser phase of matter). This term is very rarely used in scientific literature, for two reasons:

There is no universally agreed-upon definition for the term "neutronium".
There is considerable uncertainty over the composition of the material in the cores of neutron stars (it could be neutron-degenerate matter, strange matter, quark matter, or a variant or combination of the above).

A more detailed discussion of the structure of neutron stars is presented in the neutron star article. When neutron star core material is presumed to consist mostly of free neutrons, it is typically referred to as neutron-degenerate matter in scientific literature. However, some scientists treat neutronium (a bare neutron) as element 0 even today. It is thought to be the first element that emerged after the big bang.

[edit] Neutronium and the periodic table

The term neutronium was coined in 1926 by Professor Andreas von Antropoff for a conjectured form of matter made up of neutrons with no protons, which he placed as the chemical element of atomic number zero at the head of his new version of the periodic table. It was subsequently placed as a noble gas in the middle of several spiral representations of the periodic system for classifying the chemical elements, such as the Chemical Galaxy (2005).

Although the term is not used in the scientific literature either for a condensed form of matter, or as an element, there have been reports that, besides the free neutron, there may exist two bound forms of neutrons without protons. However, these reports have not been further substantiated. Further information can be found in the following articles:

Free neutron: Isolated neutrons undergo beta decay with a half-life of approximately 10 minutes, becoming protons (the nucleus of hydrogen).
Dineutron: The dineutron, containing two neutrons, is not a bound particle, but has been proposed as an extremely short-lived state produced by nuclear reactions involving tritium.
Tetraneutron: A tetraneutron is a hypothetical particle consisting of four bound neutrons. Reports of its existences have not been replicated, and its existence would require revision of current nuclear models.

A trineutron state consisting of three bound neutrons has not been detected, and is not expected to be stable even for a short time. Calculations indicate that the hypothetical pentaneutron state, consisting of a cluster of five neutrons, would not be bound.<ref>Bevelacqua, J. J. (June 11, 1981). "Particle stability of the pentaneutron". Physics Letters B 102 (2-3): 79-80.</ref>

[edit] Neutronium in fiction

The term neutronium has been popular in science fiction since at least the middle of the 20th century. It typically refers to an extremely dense, incredibly strong form of matter. While presumably inspired by the concept of neutron-degenerate matter in the cores of neutron stars, the material used in fiction bears at most only a superficial resemblance (usually depicted as an extremely strong solid under Earthlike conditions, while all proposed forms of neutron star core material are fluids and are extremely unstable at pressures lower than that found in stellar cores).

Noteworthy appearances of neutronium in fiction include the following:

In Star Trek, neutronium is an extremely hard and durable substance, often used as armor, which conventional weapons cannot penetrate or even dent. The alien "planetkiller" seen in the Star Trek: The Original Series episode "The Doomsday Machine", had a hull comprised of indestructible neutronium.
In Star Wars Expanded Universe, neutronium is a rare heavy metallic element, which together with other fictional elements makes up an alloy known as durasteel.
In Doctor Who, neutronium is a substance which can shield spaces from time-shear when used as shielding in time-vessels.
In the webcomic Schlock Mercenary neutronium is used in "annie plants," a type of total conversion power generator used for running everything from gigantic warships to personal sidearms. Gravitic technology is used to generate the neutronium from ordinary matter. (This form of neutronium is more closely based on true neutron-degenerate matter: it is similarly fluid and similarly unstable, and is a favored fuel for "annie plants" because of its extreme density.)
In Peter F. Hamilton's The Neutronium Alchemist, neutronium is created by the "aggressive" setting of a superweapon.
In Stargate SG-1, neutronium is a substance which is the basis of the technology of the advanced Asgard race, as well as a primary component of human-form Replicators.
In the Known Space fictional universe of Larry Niven, neutronium is actual neutron star core material. Niven does not make assumptions about its strength, but imagines that small blobs of it would remain stable (and inevitably spherical) under their own gravity.
In Greg Bear's The Planet-Killers (or The Law) duology, neutronium and anti-neutronium are used to destroy planet Earth.
In the computer games Master of Orion and Sid Meier's Alpha Centauri, neutronium is a possible armor type that can be researched.
In VGA-Planets it is used as fuel for spaceships.
In the book Die Herren der Schwarzen Festung by the German writer Wolfgang Hohlbein, neutronium is capable of holding two black holes away from each other.
In the computer game Independence War II: Edge of Chaos, neutronium is referred to as material needed to build hulls for space faring vessels. It is also one of the more expensive and rare materials in the game second only to anti-matter.
In the "Golden Age" trilogy by John C. Wright a rotating torus of neutronium, when brought near the event horizon of a black hole, allowed access to the inner region of the black hole presumably due to the counteracting gravitational force.

No analogous material is expected to exist in the real world. The ultra-dense material in the cores of neutron stars is only stable at the extremely high pressures found there. Under Earth-like conditions, it would immediately revert to being normal matter, exploding with great force in the process.