Various technologies are employed in this fictional world, and help define it. Among these are:
Rat Things, also known as semi-autonomous guard units, are cybernetic personal defensive guards found in and around Mr. Lee's Greater Hong Kong. Approximately the size of an adult Pit Bull, Rat Things are named for their long, flexible tail. Rat Things are made from pit bull terriers, surgically augmented with cybernetic components. Rat Things were invented by Mr. Ng, of Ng Security Industries, who was severely handicapped after a helicopter accident in Vietnam. Like the Rat Things, Mr. Ng is also a cyborg.
Rat Things remember their previous lives as dogs. They can also communicate with other Rat Things by "barking" in the Metaverse. Although their minds are largely controlled by their implants, they can sometimes act independently of their programming. When in the Metaverse and not performing guard duties, Rat Things experience running on endless beaches, playing in the surf, eating steaks that grow on trees, and blood-drenched Frisbees floating around, waiting to be caught.
Like other technology in Snow Crash, Rat Things are powered by a nuclear isotope battery, which requires extensive cooling due to the massive amount of waste heat generated. The Rat Things are passively cooled by a system of heat sinks that are only effective when the Rat Thing runs fast enough to move ambient air across the fins. To prevent rapid overheating when stationary, they must remain in their hutches (effectively dog houses), where they are continuously sprayed by jets of refrigerant. Through running, Rat Things are capable of breaking the sound barrier (about 768 mph at sea level), although this is not typically permitted by Mr. Lee's Greater Hong Kong's "good neighbor" policies due to noise reasons. Because they must be either moving at high velocities or actively cooled in their hutches, Rat Things are rarely seen by human eyes and few people know what they look like.
A fictional type of wheel prominently used on skateboards and advanced motorcycles. They consist of small segments of contact surface mounted on telescoping spokes, allowing the wheel to take the shape of cracks, curbs, and bumps. They have a passing mention in The Diamond Age as being used on a wheelchair belonging to a minor character.
Reason is a railgun in a rotary cannon configuration which fires depleted uranium flechettes. It is mounted to a large, wheeled ammunition box and is equipped with a harness for user comfort, a nuclear battery pack, and a water-cooled heat exchanger. The weapon, created by Ng, was still in beta testing, and suffers a software crash during a battle. Hiro is later able to apply a firmware update, and uses it until its ammunition supply is depleted. It bears, in inscription on its nameplate, the Latin phrase Ultima Ratio Regum, "the last argument of kings" (i.e. violence).
The Metaverse is a collective virtual shared space, created by the convergence of virtually enhanced physical reality and physically persistent virtual space, including the sum of all virtual worlds, augmented reality, and the internet. The word metaverse is a portmanteau of the prefix "meta" (meaning "beyond") and "universe" and is typically used to describe the concept of a future iteration of the internet, made up of persistent, shared, 3D virtual spaces linked into a perceived virtual universe.
Stephenson's Metaverse appears to its users as an urban environment, developed along a single hundred-meter-wide road, the Street, that runs the entire 65536 km (216 km) circumference of a featureless, black, perfectly spherical planet. The virtual real estate is owned by the Global Multimedia Protocol Group, a fictional part of the real Association for Computing Machinery, and is available to be bought and buildings developed thereupon.
Users of the Metaverse gain access to it through personal terminals that project a high-quality virtual reality display onto goggles worn by the user, or from low-quality public terminals in booths (with the penalty of presenting a grainy black and white appearance). Stephenson also describes a sub-culture of people choosing to remain continuously connected to the Metaverse by wearing portable terminals, goggles and other equipment; they are given the sobriquet "gargoyles" due to their grotesque appearance. The users of the Metaverse experience it from a first person perspective.
Within the Metaverse, individual users appear as avatars of any form, with the sole restriction of height, "to prevent people from walking around a mile high". Transport within the Metaverse is limited to analogs of reality by foot or vehicle, such as the monorail that runs the entire length of the Street, stopping at 256 Express Ports, located evenly at 256 km intervals, and Local Ports, one kilometer apart.