Factual error: In between the scenes when they are leaving Earth and passing through the Jupiter system, you can see stars flying by on the viewer. How could they be flying by stars if they haven't even left the Solar System?
Factual error: Right before Epsilon XI gets vaporized by V'Ger, Lieutenant Commander Branch (the person talking during the transmission seen during the meeting on the Recreation Deck) states that V'Ger is 82 AU's in diameter. Something that big would not even fit in our solar system, as 82 AU's is about 2.7 times the distance Neptune is from the Sun (corrected in the Director's Edition).
Factual error: The cloud surrounding V'ger is noted as being 82 AU (Astronomical Units) across. This is more than the distance from the Sun to Pluto and back. As such, V'ger would never have been able to approach Earth. This was adjusted to 2 AU in the special edition DVD.
Answer: Deltans exude an intensely potent and effective chemical substance known as pheromones, which act as signals arousing an intense sexual reaction in other species (in other ST material it's inferred that its potency is so extreme that a non-Deltan risks insanity in a sexual encounter with a Deltan). Upon entering Starfleet, Deltans must swear "an oath of celibacy" so as not to influence or take advantage of crewmembers. That is why Lt. Ilia stated that her "oath of celibacy" was on record.
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