ORAC or Orac may refer to:
- Oxygen radical absorbance capacity, a scalar value derived in the laboratory for comparing the antioxidant content of different foods or nutritional supplements
- Office of the Registrar of Aboriginal Corporations, former name of the Australian government agency now called Office of the Registrar of Indigenous Corporations (ORIC)
- Orac (Blake's 7), a fictional computer from the science fiction television series Blake's 7
- Orac (MD program), a classical molecular dynamics program for solvated biomolecules
- Orac, Leova, a commune in Moldova
- Orac, an early poker-playing computer program developed by Mike Caro
- ORAC, Wilhelm Reich's abbreviation for his orgone accumulator
- Orac, pseudonym of David Gorski, cancer surgeon and blogger critical of alternative medicine
- Costel Orac (born 1959), Romanian footballer
- Daniel Orac (born 1985), Romanian footballer
Orac is a fictional character from the British science fiction television series Blake's 7. Orac was voiced by series regular Peter Tuddenham, except for the series 1 finale "Orac" (which introduced the character) when the voice was provided by Derek Farr (who played Orac's creator Ensor in that episode).
Orac is a highly advanced supercomputer developed by the scientist Ensor, brought aboard the Liberator by Blake and the others at the end of the first series. Ensor was a particularly irascible character and Orac inherited some of his traits: Orac is terse, short-tempered, and frequently unhelpful. Avon often lamented that Orac was too valuable to dump. Orac is activated by a "key", which is removed by the crew to shut him up if he prattles on too much.
There is evidence that Orac was still functional in the "off" mode, as his response to activation would be one of impatience, "What is it now?" indicating that he was performing other self-preoccupied activities.
Orac has the ability to communicate with all other computers that carry tarriel cells—the basic component of all computer systems, designed by Ensor at a young age. He is therefore able to provide the Liberator crew with priceless knowledge. Through calculation of probability, Orac can also predict the future as seen in the series 1 cliffhanger episode (also called "Orac") in which he makes a prediction apparently showing the Liberator being destroyed. However, in episode 1 of series 2 ("Redemption") it is a sister ship, identical to Liberator, which is destroyed. Orac admits, somewhat smugly, that this is what he had predicted. Orac is also able to use his limitless information to derive effective strategies or deduce critical information.
All these systems and abilities combined make Orac an extremely valuable and sought after prize for the Federation. Initially, his creator was planning to sell him to the Federation paid for in part with medical aid for his heart condition. Servalan offered 100 million credits for Orac—an amount that astonished Travis and Blake, although Servalan and Ensor both believed Orac was worth ten times that much. However, Servalan, knowing that Ensor would die without help, sabotaged the returning shuttle, killing both Ensor's son and the medic. She then attempted to steal Orac, only to be stopped by Blake. Unfortunately, Ensor died before he could be brought aboard the Liberator for surgery.
Orac quickly proved his worth when Liberator was re-taken shortly after this by her builders, The System. Even their advanced technology proved no match for Orac, which within hours had completely (and quite possibly lethally) compromised The System itself, as well as deleting their backdoor access into Liberator's computer Zen. He would prove his worth again and again, helping devise strategies for penetrating Federation facilities or producing critical information for the crew. Perhaps his greatest service to humanity was when he hacked into the Federation master command strategic computers in the episode 'Star One', alerting Servalan from outside the Galaxy to the invasion force from Andromeda and mobilizing the Federation. It was never explained how "tarriel" compatible systems were to be found on the non-Federation Liberator, or the master control of The System.
Orac's systems are multi-dimensional; he projects a carrier beam through the same dimension that allows telepaths to transfer thoughts. It is through the hijacking of this beam that an unnamed psychic-being attempted to invade the physical plane. It was defeated through Cally's telepathy boosted by proximity to telepathic plants called Moondiscs. To prevent any future incursion by the being, Avon fitted a bomb to Orac that would detonate if his power fluctuated outside of his normal parameters.
This is not the last time that he endangered the crew. Orac had an unquenchable thirst for knowledge. His desire to study a black hole was so great that he took control of the Liberator and steered it dangerously close. He states that gaps in his knowledge are "intolerable" and castigates the crew for their lack of interest in the more fascinating aspects of the Universe. This behaviour was contrasted in "Headhunter", when Orac kept insisting that he must be deactivated to avoid being forcefully merged with Muller's android. Muller had also been a student of Ensor, so the technologies were similar, and the Android was also fitted with a 'circuit influencer' giving it access to non-computer devices beyond Orac's control. Orac kept insisting that such a union with the Android would lead to the extermination of humanity or technological slavery. It was never clear whether Orac's genuine concern was for humanity or for self-preservation.
Orac, on one occasion, had a Federation computer perform routine design work for him, leading Avon to comment that one of Orac's more human-like qualities is that "it does not like to work." Orac is able to reduce his dimensions and mass to what can be carried in a hand via The Theory of Matter Reduction (also called Controlled Atomic Implosion), which enabled Avon and Vila to sneak him into a casino and win massive stakes at the computer-controlled tables.
Orac was damaged during the destruction of the underground facilities on Terminal ("Rescue"). Repairing him proved beyond even Avon's abilities (without the appropriate tools) but Dorian, who had studied with Ensor, was able to get him operating again. In Tony Attwood's non-canonical Afterlife, Ensor is shown to have made a twin of Orac for his own use—called Caro. Orac was able to sense the presence of Caro, but unable to read its system.
Orac was not present during the final shootout on Gauda Prime in Blake, and his survival or whearebouts are unknown.
Cancer surgeon and blogger David Gorski uses the pseudonym 'Orac' in homage to the Orac of Blake's 7.
Orac is a classical molecular dynamics computer program (written in FORTRAN language) for simulating complex molecular systems at the atomistic level. The code was written originally in 1989-90 by Massimo Marchi during his stay at IBM, Kingston (USA). The code was further developed at CECAM in 1995 and released under the GPL license in 1997. The latest release of Orac may be run in parallel using the standard Message Passing Interface libraries, allowing replica exchange simulations, multiple walkers metadynamics simulations and multiple steered molecular dynamics nonequilibrium trajectories.