Zero Point Module

"It's kind of like a miniature universe in a bottle."

- Rodney McKay

A Zero Point Module, often abbreviated ZPM, is a power source built by the Ancients. Utilizing Zero point energy, it is the cleanest energy source in the known universe. Given its vast power generation capabilities and small size, it is among the most valuable of the Alteran's innovations.

Overview
"It extracts vacuum energy from [an] artificial region of subspace-time until it reaches maximum entropy."

- Radek Zelenka

A Zero Point Module is a large, translucent group of crystals about two feet tall with a circular base. The devices glow yellow when active, and are a dark shade of orange red when inert. A ZPM houses a pocket of subspace-time known as the quantum foam (subatomic wormholes constantly opening and closing and fading in and out of subspace). Zero point energy is extracted from this pocket until it reaches maximum entropy, at which point the pocket collapses, leaving behind a useless shell.

The life of a ZPM is directly proportional to the power demands placed on it, but is still capable of lasting for remarkable periods of time even under the most extreme conditions. The power generated by three of them (sequentially rotated every 3.3 thousand years) enabled Atlantis' shield to survive the pressure of several Hundred feet of ocean for 10,000 years, though the rest of the city had been powered down to maximize output. Based on atmospheric pressure calculations and the shield's surface area, derived from approximate atlantis dimensions, these ZPM's were each capable of functioning at an output of between 100-200 Terawatts for a duration of about 3,300 years (roughly 2×1025 Joules: five times the solar energy received by the Earth per year, or 1/18th the output of Earth’s sun per second). A single ZPM, at nearly full power, could provide enough energy to resist constant bombardment by Wraith Hive ships for days.

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 (there are also green colored crystals on ZPM's, but it is unclear if they have any specific purpose or function). The crystals of a ZPM are virtually indestructible and can remain functional for hundreds of thousands of years. (MGM: "SGC Intelligence Briefing")

History
"I couldn't believe my eyes: three ZPMs right in front of me."

- Elizabeth Weir

Although the Ancients and Asurans were able to produce ZPMs as needed, every ZPM discovered and used by the Tau'ri and Wraith have been obtained from either leftover Ancient technology and outposts or the Asuran homeworld. Since the knowledge behind their construction eludes both sides, their only option is to locate existing ones.

Atlantis, and every other known City-ship, relied on Zero Point Modules in groups of three to supply power to the city simultaneously, and so is typically unable to properly function with other means due to insufficient power generation. After the Ancients returned to Earth, three ZPMs were left behind to power Atlantis' shield. By the time the Atlantis expedition arrived 10,000 years later, two of them were completely depleted and the third was drained soon after.

The first ZPM encountered by the Tau'ri was on the planet of Proclarush where it had been powering a shield protecting the outpost there. It was taken to power the Drone weapons of the Ancient outpost in Antarctica to destroy the Goa'uld fleet under the control of Anubis. It was later connected to the Stargate to facilitate dialing the intergalactic address leading to Atlantis in the Pegasus Galaxy which depleted it entirely, resulting in the Atlantis expedition being left stranded in the Pegasus Galaxy for a year. It was then used in a ruse against Ba'al. In an alternate reality, the Tau'ri never learned the location of Atlantis, and the ZPM was instead drained fending off an Ori attack.

Dr. Meredith Rodney McKay, Chief Science Officer of the Atlantis Expedition and a member of the First Atlantis Reconnaissance Team discovered a ZPM on M7G-677, where it was being used to power an Electromagnetic field generator protecting a series of villages on the planet from Wraith attack. McKay brought it to Atlantis in the hope of using it to power the city, but soon returned it after learning that it was much too depleted to be of any use to them.

Camulus discovered a 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. 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, which held a roughly 50% charge, could have possibly encompassed the entire solar system, and at the very least would have completely destroyed Earth.

A ZPM, known to the locals as the Potentia, was left on Dagan by the Ancients, who entrusted the Quindosim to safeguard it for them. Repeat cullings by the Wraith wiped out their membership and thus the location of the ZPM, but the new Brotherhood was able to locate it with the help of the Atlantis expedition.

However, because the expedition were not Ancients themselves, the new Brotherhood refused to part with it, instead choosing to hide it in the belief that the Ancients would return and eventually reward them although the group were not aware of the fact that the Ancients were long gone and would never ever return to the Pegasus Galaxy.

SG-1 discovered a ZPM in Egypt that had previously belonged to the Goa'uld Supreme System Lord Ra, who was apparently unaware of its properties and used it as an object in religious rituals. They used a Time Jumper to travel back in time and steal it, so they could plant it for future discovery where they knew it would remain safe.

This ZPM was later used to dial Atlantis and send reinforcements, to prepare for the coming Wraith attack, then installed on the Daedalus to increase its hyperdrive efficiency so it could arrive in time to be of use during the Battle of Atlantis. Upon arrival, the ZPM was used to power Atlantis' shield. Following a successful ruse to trick the Wraith into thinking the city was destroyed, the ZPM provided a steady power supply to Atlantis for nearly two more years. It was depleted to allow an alternate Rodney McKay to return to his own reality.

A depleted ZPM had been filed away in the Genii archives for hundreds of years. Realizing what it meant to Atlantis, Ladon Radim used it in his coup d'etat as part of a scheme to capture Lt. Colonel John Sheppard and a large strike team, which would be enough to bring Cowen out in the open. It was presumably destroyed in the nuclear explosion Ladon used to kill Cowen and his inner circle.

A ZPM was used to power the sublight engines of the Tria during its near-lightspeed journey from the Pegasus galaxy to the Milky Way. The effects of relativity meant that very little time had passed for the Ancients crewing the vessel. After being rescued by the Daedalus and returned to their city, the Ancients took control and asked expedition to leave, using the ZPM to power the city and dial Earth directly. After the Asurans attacked and subsequently occupied Atlantis, they installed at least two more ZPMs to power the stardrive. Sheppard's team was able to destroy the Asurans, acquiring their ZPMs. Despite McKay's vehement protests, two were sent back to Earth: one to power the Antarctic outpost and another to power the Odyssey. The remaining ZPM was nearly depleted when the Asurans attacked Atlantis using a satellite weapon, eventually reaching critical levels and stranding Atlantis in space.

With their ZPM incapable of powering the Stardrive, the expedition raided Asuras for a replacement module. Upon successful completion of their mission, the ZPM was used to repower Stardrive, then the expedition finished their journey to M35-117, which served as Atlantis' new home. The ZPM then took on the role of powering Atlantis, with plenty of power levels left to suit their needs.

When the Wraith fought alongside the Tau'ri and Travelers in the Battle of Asuras, Todd managed to steal a cache of ZPMs from Asuras before the planet was destroyed. Three were used to power a Wraith cloning facility to bolster their numbers enough to defeat the Tau'ri and rival Wraith in the same manner they defeated the Ancients. These ZPMs were presumably destroyed with the rest of the facility when the Hive ship Atlantis had commandeered was driven into it. He also used an unknown number of ZPMs to power a Hive ship, enhancing every system to nigh-unbeatable levels. Its improved hull was virtually impervious to attack, including the Asgard plasma beam weapon which would have previously destroyed a hive ship. Its weapons could punch through the shields of an BC-304 in seconds, and its hyperdrive was capable of intergalactic travel. It was so powerful it was able to withstand Atlantis itself at full power and win and it took a nuclear weapon detonated inside of the ship to destroy it. Presumably the ZPMs were destroyed also.

In addition to the ZPMs powering the Hive ship, Todd provided Atlantis with two additional ZPMs to power their Stardrive, having been convinced to by Sheppard as an act of spite against his treacherous underling who had stolen the Hive ship. Using the ZPMs, Atlantis was able to reach Earth through a combination of its hyperdrive and an experimental Wormhole drive. Ultimately, the city lacked the firepower to defeat the Hive, and in the attempt was forced into the atmosphere. Unable to regain orbit, the city landed in San Francisco, cloaked to ensure the continuing secrecy of the Stargate program.

Eventually it was decided to return Atlantis to Pegasus due to the efforts of General Jack O'Neill and Richard Woolsey forcing the IOA's hand. With three ZPMs powering the hyperdrive, Atlantis would be able to make the journey between Earth and Lantea in just nine days, but seven days into the journey, on the edge of the Pegasus Galaxy, one of the hyperdrive induction arrays malfunctioned from battle damage and began drawing massive amounts of power to widen the hyperspace corridor. Though dropping out of hyperspace fixed this, the damage was already done: the hyperdrive was damaged beyond the Tau'ri's ability to repair and the ZPMs were drained to twenty percent power. The crew managed to land Atlantis on a relatively close planet that was marginally habitable, but the process drained the ZPMs to nine percent.

Behind the scenes

 * The American characters in both shows pronounce the "Z" in "ZPM" as "Zee", whereas Dr. Rodney McKay, a Canadian and other expedition members pronounces the "Z" as "Zed". This became clear in the first episode of season 1 of Stargate Atlantis.
 * The name "Zero Point Module" was made up by the Tau'ri. It is unknown what the Ancients and Asurans referred to the devices as. Both Ancients and Asurans expressed confusion at the term, making it clear that their name for it is quite different. The Ancient term could be "Potentia" - used by the Brotherhood of the Fifteen, which was given a ZPM to protect from the Lanteans themselves.
 * The MGM Tech Journal mentions that a singularity exists within the module, which somewhat contradicts on-show descriptions of the ZPM. It is possible, however, that the singularity is either a wormhole that leads to the pocket of subspace-time or the pocket itself rather than the heart of a black hole.