neutronium n.

an extremely dense material composed entirely of free neutrons

In SF, neutronium is typically conceived of as a solid. Astrophysical research suggests that the condensed neutron material present in neutron stars is predominantly in a superfluid state.


  • 1930 E. E. Smith Skylark Three in Amazing Stories Sept. 564/1 page image Edward E. Smith bibliography

    We're going to project a fourth-order force out to grab us some dense material, a pretty close approach to pure neutronium.

  • 1930 E.E. Smith Skylark Three in Amazing Stories Sept. 564/1 page image Edward E. Smith bibliography

    ‘Neutronium? Pure mass?…I have been under the impression that it does not exist. Of what use can such a substance be to you?’ ‘Can’t get pure neutronium, of course…couldn’t use it if we could. What we need and are going to get is a material of about two and a half millionspecific gravity.’

  • 1930 E. E. Smith Skylark Three in Amazing Stories Oct. 615/1 page image Edward E. Smith bibliography

    Ten enormous supporting forces held the lens of neutronium immovable in the exact center of the upper end; at intervals down the shaft similar forces held variously-shaped lenses and prisms formed from zones of force; in the center of the bottom or floor of the towering structure was the double controlling system, with a universal visiplate facing each operator.

  • 1931 J. Williamson The Stone from the Green Star in Amazing Stories Nov. 748/1 page image Jack Williamson bibliography

    Thanks to her indestructible neutronium hull, the flier was not injured.

  • 1935 ‘M. Leinster’ Proxima Centauri in Astounding Stories Mar. 43/2 page image Murray Leinster bibliography

    He’d explain the disintegration field, which collapses the electrons of hydrogen so that it rises in atomic weight to helium, and the helium to lithium, while the oxygen of the water is split literally into neutronium and pure force.

  • 1938 J. Binder If Science Reached Earth's Core in Thrilling Wonder Stories Oct. 98 (caption) Jack Binder bibliography

    In the future, scientists will be able to isolate or control the element neutronium. Neutronium, composed of collapsed atoms, would weigh sixty million tons per cubic inch.

  • 1942 ‘H. Clement’ Proof in Astounding Science Fiction June 103/1 page image Hal Clement bibliography

    The first cities were of neutronium, like those of today, but it was necessary to stabilize the neutrons with fields of energy; at core temperature, as you know, neutronium is a gas.

  • 1942 I. Asimov Black Friar of Flame in Planet Stories Spring 24/1 page image Isaac Asimov bibliography

    The treaty of Draconis has hung like neutronium around our neck these twenty years.

  • 1944 T. Sturgeon Killdozer! in Astounding Science Fiction Nov. 8/1 page image Theodore Sturgeon bibliography

    An insulator. The terminal product or by-product of all energy research—neutronium.

  • 1949 F. Brown Gateway to Darkness in Super Science Stories Nov. 22/1 page image Fredric Brown bibliography

    It negates the force that holds the electrons to the nucleus. In effect, it collapses matter into neutronium.

  • 1966 L. Niven Neutron Star in Worlds of If Oct. 18/2 page image Larry Niven bibliography

    The rocket motor would send the Skydiver crashing into eleven miles of neutronium.

  • 1977 J. Varley Ophiuchi Hotline (1994) 18 John Varley bibliography

    Far down the slope of the hole, halfway to infinity, a tiny mass of neutronium that had been Lilo was orbiting at almost the speed of light, releasing energy as it was stressed to the limits of matter before it finally decayed into oblivion.

  • 1981 T. Pratchett Strata 19 page image Terry Pratchett bibliography

    You plate the underside with neutronium for gravity.

  • 1984 D. Duane My Enemy, my Ally xii. 190 Diane Duane bibliography

    McCoy…timed about half his pieces out, preparing to dump them on her like a ton of neutronium in six very visible moves.

  • 1996 J. Gunn Joy Machine xiv. 209 James E. Gunn bibliography

    It wouldn’t be difficult to jury-rig a device—say an antimatter payload contained within a neutronium shell.

  • 2000 A. Reynolds Revelation Space xxviii. 376 Alastair Reynolds bibliography

    The relativistic projectile weapons were only slightly tardier, and reports of their success followed a few seconds later; spectacular stuttering pulses as the projectiles rained home, slugs of neutronium and antimatter slamming into the world.

Research requirements

antedating 1930

Earliest cite

E.E. 'Doc' Smith, "Skylark Three"

Research History
Brian Ameringen submitted a 1949 cite from Fredric Brown.
Jonathan Stone posted a 1947 E.E. Smith cite to sci.physics that was verified and submitted by Mike Christie.
Steinn Sigurdsson suggested Baade & Zwicky's PNAS paper in about 1938, or Gamow in his book "Atomic Nuclei"; however, earlier cites have now been submitted, so we no longer need to find these references.
Mike Christie submitted a cite from a 1978 reprint of Murray Leinster's 1935 story "Proxima Centauri"; Alistair Durie verified this in its first magazine appearance.
Bill Seabrook located and Mike Christie confirmed a 1944 cite from Theodore Sturgeon's "Killdozer!"
Imran Ghory submitted a cite from a 1973 reprint of Isaac Asimov's "Black Friar of the Flame", which Fred Galvin verified in the 1942 first publication.
Rick Hauptmann submitted a 1931 cite from Jack Williamson's "The Stone from the Green Star".
Isaac Wilcott submitted a cite from the magazine serialization of E.E. Smith's "Skylark Three" (Amazing Stories, December 1930). Fred Galvin submitted cites from an earlier issues of the magazine serialization of E.E. Smith's "Skylark Three" (Amazing Stories, September 1930).
Clive Shergold submitted a 1981 cite from Terry Pratchett.

Earliest cite in the OED: 1967
Updated in September 2003 with a new earliest date of 1935.

Last modified 2023-08-21 12:54:34
In the compilation of some entries, HDSF has drawn extensively on corresponding entries in OED.