To begin our discussion of protective technologies, notionally, there are four types of shielding:

• particle shielding;
• ray shielding;
• gravity shielding;
• irreality shielding.

Particle & Ray Shielding

The most important and most common of these, of course, are the first two: particle shielding and ray shielding. Naturally, both of these are complete misnomers, thanks to wave/particle equivalence, and have an inconvenient degree of overlap, and yet they are the accepted engineering terms.

The technical definition of particle shielding is that it is intended to affect fermions, the particles which chiefly constitute matter, including quarks, the composite particles made up of them, and leptons; while ray shielding is intended to affect gauge bosons, such as the photon, gluon, and the various asthenons.

Thus, in the informal engineering view, particle shielding begins with conventional armor, Whipple shields, laser point-defense grids, and the like, while ray shielding can be considered to include such simple devices as high-reflectivity surfaces, HICAP and other high-Z materials, and even thermal dissipation systems or sheer mass. (Drunkwalking, of course, can be considered both.)

Later developments in particle shielding included a variety of technologies including sacrificial defense drones, semi-ablative fluff, fluid-foam armor, droplet nanoclouds, and gravimetric bubbles, the forerunners of the modern kinetic barriers.

Meanwhile, the story of attempts to advance ray shielding is a complex mess of dismissed technologies, ranging from entirely failed attempts such as FAT NINJA through variations on many others: magnetic plasma bubbles, dazzle nanoclouds, EM blisters, Meng mirrors, wormhole mouth-drones, antithetikon emitters, polariton photon-walls, stasis hyperspheres, claudications, and other metric warps, none of them achieving nearly the same success or general applicability as their particle counterparts.

All of which is to mostly ignore the inevitable overlap between technologies (for example: while often classified as “rays”, kinetic barriers are effective against particle beams; and attempts at producing kinetic barriers strong enough to deflect photons, which after all do have mass, continue – thereby classifying them as ray shielding, too), not to mention such bizarre entries in the field as the uncertainty sheath, singularity-lock armor, the blink displacer, UNMOVED MONAD, and its weaker cousin, the probability unseller.

Gravity Shielding

Intended to protect you from gravity and weapons that function on gravitic principles. Entirely hypothetical, unless you count “get your own equal and opposite gravity”.

Irreality Shielding

Intended to protect you from having the laws of physics you’re using edited out from under you, which also conveniently protects you from hypothetical dangers like extrauniversal invasions that bring their own physics along with them, falling through nilgularities, or outbreaks of primordial chaos within the brane. Currently consists of a single technology, the selective ontology evocation system, programmed with its most boring use, ensuring that everything stays exactly as it is.

– introduction to “Shielding” chapter, Celestime Technology Review