Neutronium

Neutronium is the indestructible rock-like element that forms the outer boundary of the world and is also used in certain ruin structures and the material under some geysers. In normal play it cannot be mined or destroyed, and it acts as a hard limit on map expansion. Its temperature varies by location: border neutronium is extremely cold at -272.2 °C, ruin structures made of neutronium are around 21 °C, and neutronium beneath geysers generally matches the temperature of the biome it is embedded in.

Neutronium does not transfer heat. Its thermal conductivity and specific heat capacity are both zero, so neutronium tiles and prefab structures made from it do not heat up or cool down from surrounding temperatures, even in extreme environments. One exception is interaction with Tempshift Plates placed next to it, which can force heat exchange with a neutronium tile. Another exception appears during rocket launch, when rocket exhaust can raise its temperature.

In standard gameplay, neutronium is effectively impossible to remove. In debug mode it can be excavated, and when sampled in sandbox tools it appears as a very large mass per tile. Debug excavation drops 10 t of neutronium and the resulting debris behaves like normal dropped material, including showing its temperature and carrying a decor penalty of -10. If neutronium is forced to reach 10000 K, the game crashes instead of producing a molten form.

A few interactions make neutronium notable in edge cases:

• Sweepy can interact with neutronium and move it into a Sweepy Dock.
• A Duplicant with the Super Productive buff could previously excavate neutronium instantly, but this caused skill point overflow and prevented learning new skills.
• After update U42-508497, mining tasks for neutronium are automatically canceled instead.
• In the Spaced Out! DLC, radiation can destroy neutronium by repeatedly bombarding it; because 1 unit of radiation removes 1 g of material, a 20 t tile requires 20 million units of radiation, which is far beyond a standard Radbolt Generator’s output.

The element is also associated with the game’s lore. Gravitas scientists treated neutronium as a kind of universal quarantine material, formed to seal off foreign matter and prevent contamination. Some descriptions also imply the existence of refined neutronium, which was apparently produced for advanced technology such as the Anti Entropy Thermo-Nullifier.