ZPM

A Zero Point Module, often abbreviated ZPM, is a power source, created by the Ancients, capable of supplying tremendous amounts of energy. It is one of the most formidable power sources known to exist, having been developed by the Ancients several million years ago during their original habitation of the Milky Way galaxy

Overview
Visually, a Zero Point Module resembles a large, translucent group of primarily orange-colored crystals approximately one foot in height with a roughly cylindrical shape. When activated, a ZPM emits a yellow glow from its center, with a small red circle at the top of illuminating once the device has been fully engaged. This illumination ceases once the ZPM has been disconnected from whatever it was powering or has become fully depleted.

The device itself serves as an enclosure for an artificially created pocket of subspace-time. Zero point energy is extracted from this pocket until it reaches maximum entropy, at which point the pocket collapses, leaving behind a useless shell.

Like many types of Ancient technology, Zero Point Modules are crystal-based. The crystals that compose the shell of the ZPM are similar in many ways to the crystals adapted by the Goa'uld and Tok'ra: red crystals contain the necessary programs to allow ZPMs to provide power to Ancient technology when a ZPM is interfaced with a conduit, while yellow crystals act as a buffer to prevent catastrophic overload. The crystals of a ZPM are virtually indestructible and can remain functional for hundreds of thousands of years.

The life of a ZPM is directly proportional to the power demands placed on it. If not in use, a ZPM will maintain its power level indefinitely. However, even if exposed to constant strain, ZPMs will still supply power for thousands of years, depending on the degree of the strain; The power generated by three of them enabled Atlantis' shield to survive the pressure of several hundred feet of ocean for 10,000 years. A single ZPM, at nearly full power, could provide enough energy to resist constant bombardment by Wraith Hive ships for days before depleting.

Ancient use
The Zero Point Module was created by the Ancients several million years ago during their original habitation of the Milky Way galaxy. Several outposts in the galaxy powered by ZPMs are known to have existed, including Taonas on Praclarush, the Antarctic outpost on Earth, and Atlantis. However, many other Ancient sites in the galaxy appear to be powered by other means, potentially indicating that the ZPM was developed relatively late in their time in the galaxy.

While most outposts required only a single ZPM to be fully powered, City-ships, including Atlantis, are designed to function at full power only when powered by a trio of Zero Point Modules simultaneously, though one ZPM is generally sufficient to activate most systems. ZPMs are among the only known power sources capable of effectively powering control chairs as well as the shield and stardrive of a city-ship. During the First siege of Atlantis, Atlantis was powered by three ZPMs, which ultimately proved capable of sustaining the city's shield meanwhile holding back several hundred feet of ocean for 10,000 years, until the city's discovery by the Atlantis expedition.

ZPMs dating back thousands of years may still be found on a number of worlds in the Pegasus and Milky Way galaxies; once colonized by the Ancients. However, they are quite rare, with many simply having been lost over the centuries.

Tau'ri use
The first ZPM encountered by the Tau'ri was on the planet of Proclarush where it had been powering a shield to protect an Ancient outpost. It was disconnected from the outpost's control chair and taken to power the Drone weapons of the Ancient outpost  in Antarctica to defend Earth against Anubis' fleet (the original ZPM of the Antarctic outpost having already been depleted). It was later connected to the Stargate at the SGC to facilitate dialing the intergalactic address for Atlantis in the Pegasus Galaxy, which depleted it entirely. It was then used in a ruse against Ba'al. The Goa'uld Camulus discovered a half-charged ZPM in an Ancient outpost. Unable to use it himself, he coated it with a volatile compound that would react explosively to an electrical charge. He led the Tau'ri to it in the hopes that they would destroy themselves. Despite Camulus' best efforts, the plan ultimately failed when Dr. Bill Lee discovered the compound by mistake when it became necessary to flood the base with Gamma rays. The estimated blast radius of the ZPM could have possibly encompassed the entire solar system, and at the very least would have completely destroyed Earth.