A.T. Field
An A.T. Field (short for "Absolute Terror Field") is a nearly impenetrable force-field barrier which Angels can generate. Conventional weapons such as those used by the combined military forces of the United Nations are effectively useless in penetrating an A.T. Field. Essentially, the only thing that can penetrate an A.T. Field is another A.T. Field, such as those created by the Evangelions.
Besides Evangelions, only two human-made weapons are capable of effect against Angels. The first is the N² Mine, the most powerful non-nuclear weapons ever created. N² mines have succeeded at stunning or even seriously injuring some of the weaker Angels (albeit temporarily because wounded Angels have always regenerated), but against some of the more powerful Angels, even multiple N² mines have failed to do any damage whatsoever.
There was one other instance where an A.T. Field was breached without the use of the Evas, the fight against Ramiel, where a prototype positron rifle using the electricity of the entire power grid of Japan penetrated Ramiel's A.T. Field and killed the Angel. However, such a weapon is subject to power and range limitations, as witnessed in the battle against Arael where a positron rifle (of a different model from that used against Ramiel) failed to harm the orbiting Angel.
The one weapon practically capable of piercing any A.T. Field is the Spear of Longinus: an extraterrestrial artifact of incredible power, shaped like an Eva-sized javelin. Artificial replicas of the Spear of Longinus are also capable of piercing an A.T. Field.
((A.T. Fields are also capable of preventing attacks originating inside of the field from expanding outwards. For example in the battle against Zeruel, Eva 00's A.T. Field was extended to maximum, allowing her to detonate an N² Mine within the GeoFront, but muffle the blast so it did not kill everyone in the GeoFront itself. Later, Rei would also keep Eva 00's A.T. Field at maximum in order to temporarily constrain the Angel Armisael to keep it from spreading.))
Later in the series, Kaworu Nagisa reveals that every living thing possesses an A.T. Field: Angels and Evangelions just have A.T. Fields so strong that they are easily detectable and can stop even physical attacks. "A.T. Fields" which regular humans generate are what literally holds individual beings' egos together, separating individuals. Ultimately this is the cause of loneliness and pain in the world, keeping individual people apart.
Another secret revealed later in the series is that each Evangelion has a human soul bonded to it: A.T. Fields are actually generated by the human soul contained within the Eva (seemingly amplified beyond the level of a "normal" human A.T. Field by the Eva's body). The A.T. Field of an Angel is also generated specifically by the Angel's soul. This is why Kaworu's A.T. Field is the strongest ever measured: his physical body is a vessel for the soul of Adam, the powerful First Angel. This is also why Rei Ayanami can generate an A.T. Field: Rei's physical body is a vessel for the soul of Lilith, the Second Angel. Both Adam and Lilith are Seeds of Life, thus Lilith is actually a co-equal being to Adam, and this is why the A.T. Field which Rei can generate is of equal strength to the incredibly powerful A.T. Field that Kaworu can generate. It must be remembered, though, that within the storyline the "soul" is not so much an ethereal/theological concept but essentially an energy/thought pattern which has been defined and can actually be manipulated by "Metaphysical biology", an advanced field of science which exists by the future date of 2015.
In the climax of The End of Evangelion, the Rei/Adam/Lilith hyper-being generates, along with the Mass Production Evangelions and Evangelion Unit-01, a massive "Anti A.T. Field" which neutralizes all A.T. Fields across the world, causing all of humanity to revert into the primordial soup of LCL, merging into a single super-organism in the climax of the Human Instrumentality Project.
Typically, A.T. Fields are invisible. A.T. Fields can interact with objects to cause them to move and is hypothesized that it is the source of some of the Angel's ability to levitate (most notably, Kaworu). When they are raised or when they interact with an object, a slight blur can be seen. In Episode 03, when Evangelion Unit-01 raises an A.T. Field, a slight blur can be seen momentarily. When the Spear of Longinus is pulled from the moon in Episode 26', the same blur can be seen momentarily. During the fight between Evangelion Unit-01 and Unit-02 (controlled by Kaworu) in Terminal Dogma, a momentary blur can be seen followed by the Nerv staff detecting an A.T. Field. Although they are invisible, A.T. Fields can often be seen when they come in contact violently with something physical or with energy weapons, forming concentric octagonal yellow lines. This can be seen in Episode 02 when Evangelion Unit-01 collides with Sachiel's A.T. Field, in Episode 22, Arael's A.T. Field can be seen when it deflects a blast from a positron rifle. The blur caused by its physical manifestation and the visible yellow lines can also be seen in many other places throughout the series. Ramiel's A.T. Field was so powerful, however, that it could be seen with the naked eye when it was fired upon. Kaworu was stated to have the most powerful A.T. Field ever detected, so his A.T. Field was probably even more powerful than Ramiel's and also clearly visible, i.e. when Eva-01 tries to stab him and his A.T. Field stops the blade.
Although A.T. Fields were originally seen to be a purely defensive ability, during the course of the series it is demonstrated that A.T. Fields can be used offensively. The first instance of this was when the Angel Sahaquiel used its A.T. Field in Episode 12 to crush several nearby satellites attempting to observe it in Earth orbit. Leliel's bizarre multi-dimensional pocket-dimension is apparently created by inverting its A.T. Field in some way. Arael's mind-probe attack is based on a special projection of its A.T. Field. Eva-01 itself shockingly wielded its A.T. Field as a weapon in Episode 19 at the climax of her battle against the Angel Zeruel, when with a wave of her hand like an symphony conductor, she tore Zeruel's body to bloody shreds and crippled it. By Eva 02's final battle in The End of Evangelion, Asuka's piloting abilities had increased to the point that she wielded Eva-02's A.T. Field against advancing JSSDF hoverjet squadrons and tank battalions, crushing them with a wave of her hand.
Notes
- The phrase "Absolute Terror Field" is never actually mentioned within the series itself. It only appears in the opening credits.
- Since the very earliest days of Evangelion analysis, there has been a rumor that A.T. Field is a genuine psychological term that describes the barrier that separates autism patients from the world around them. However, extensive searching of online psychology researches and forums has failed to find any use of the term other than in reference to NGE. Therefore, this rumor can safely be dismissed as false.
- Although when an A.T. Field is visible, it's usually concentric octagons. However, there are 2 instances where this is not the case. First, in Episode 06 when Nerv staff reviews an energy blast that deflects off of Ramiel's A.T. Field, it is seen as hexagons on the display, even though they were octagons earlier; this is a visual continuity error. The second instance is in Episode 13 when lasers were deflected by Ireul's A.T. Fields which were purple hexagons and were not concentric; this is most likely a reference to the movie The Andromeda Strain.
- Ritsuko Akagi makes it a point that an Eva's A.T. Field "erodes" that of an Angel, most Nerv personnel tend to loosely refer to the process as one A.T. Field "neutralizing" or "canceling-out" the other A.T. Field.
