In the early days of television, small-screen science fiction generally ignored the laws of nature, technology and common sense. Take the 1960s TV series Lost in Space. In one early segment a comet’s heat somehow threatens to fry a couple of members of the spacefaring Robinson family. Pretty far-fetched, considering that comets are made of ice, rock and dust.

Even quality shows like The Twilight Zone made gaffes, as in the 1962 episode “The Little People,” which postulated humanoids hundreds of feet high. Unfortunately, as a body’s height is squared, its volume is cubed. So these fictional life-forms would in reality collapse under their own weight.

Then, in 1966, came Star Trek, setting the new gold standard of scientific plausibility in TV entertainment. This year the cult series celebrates the 50th anniversary of its September 8 premiere.

The goal of scientific accuracy began with the creator and executive producer, Gene Roddenberry. “Roddenberry told me, ‘I wanted scientists to be able to watch our show, believe it, enjoy it and not laugh at it,’” says Marc Cushman, co-author of These Are The Voyages, a three-volume set about the making of the series. “He said, ‘I wanted to know that if it’s not probable, it’s at least possible.’”

Many of the details that gave Star Trek its futuristic feel—medical monitors, hand-held communications devices, automatically sliding doors—have become reality. What, after all, was Mr. Spock’s “library computer” but an early imagining of the internet? What about those square record tapes, packed with digitized information, which the crew slipped into convenient slots for everything from readouts to meals? They were no more than 23rd-century floppy disks.

Admittedly, Star Trek sometimes reached too far. We likely won't see faster-than-light travel, aka “warp drive,” achieved anytime soon. Not to mention the transporter—a device that broke down bodies and objects into energy, “beamed” the particles to a certain point and then rearranged them into their original components. “Of everything they had on Star Trek,” Jerry Pournelle, former president of the Science Fiction and Fantasy Writers of America, said in 1978 in the magazine Science Fantasy Film Classics, “the transporter is the toughest of the lot. It’s going to be the longest one coming.”

Nevertheless, the makers of Star Trek did try to get things largely right and reasonable, starting with the first pilot episode, “The Cage.” Roddenberry contracted with Harvey P. Lynn, Jr., a RAND Corporation physicist, to provide technical advice for a nominal fee. As later documented in a book about making the series, Lynn’s comments were varied and astute. For example, he picked up on one particular line of dialogue from the pilot script: “Any oxygen planets?” the commander asks. In his feedback on the episode Lynn wrote, “Technically, a planet could have oxygen and still be unsuitable to sustain life for many other reasons.” Hence, in the final version an Enterprise underling reports, “Our reading shows an oxygen–nitrogen atmosphere, sir. Heavy with inert elements but well within safety limits.”

Elsewhere, Roddenberry had written that the home planet of the featured alien race, the telepathic Talosians, had a gravity that was “1.3 of Earth.” But he also described the inhabitants as small and slim, with elongated heads. “This is not consistent with a gravity of 1.3,” Lynn pointed out at the time, “but it is consistent with a gravity of less than that of the Earth. Why not substitute ‘0.85,’ ‘point 85,’ or ‘85 percent’?” So the line was changed to “zero point nine of Earth.”

When Star Trek became a regular series, the show's producers turned to the De Forest Research, Inc., to provide scientific and legal guidance. “What [Roddenberry] was trying to avoid was the standard television clichés of bug-eyed monsters,” according to 89-year-old company founder Kellam de Forest.

The majority of script review fell to de Forest's then-associates, Joan Pearce and Peter Sloman. “Most of the time, the science was not at the level that I had to do too much consulting,” Sloman, 66, recalls. “Once in awhile I would call someone at U.C.L.A. in the physics department, but in most cases I knew enough. Unless it was an active violation of physical laws, I would tend to let it go, because so much had been established in science fiction. Like time travel. Wells did it, Heinlein did it, so we did it.”

Some problematic matters were solved with the stroke of a pen. In the popular comedic episode “The Trouble with Tribbles” episode writer David Gerrold conceived a species of cute, purring, rapidly breeding little fluff balls. But de Forest’s team pounced on the creatures' “asexual” nature. “Asexual means reproducing by fission,” they wrote. “Better make it bisexual, meaning the creature is both male and female.” So Gerrold rewrote accordingly.

Similarly, the episode “By Any Other Name,” envisioned the Enterprise crew being captured by the Kelvans, a race that could freeze their enemies’ nerve impulses. Pearce objected. “If all nerve impulses were paralyzed,” she wrote in a feedback memo, “the organism will die because the automatic as well as the voluntary muscles will be affected.” The solution: The head Kelvan intones, “You are all paralyzed by a selective field that neutralizes nerve impulses to the voluntary muscles.”

“Joan did not suffer fools gladly,” Sloman says with a chuckle. “She didn’t suffer them at all. She loved words and liked to use them properly and got pissed off when they were not.” Hence, Pearce seized on this utterance by the navigator, Ensign Pavel Chekov (Walter Koenig), in “Bread and Circuses” on approaching the planet 892-IV: “Only one sixteenth parsec away, Captain. We should be there in seconds.”

“This is equivalent to the driver of an automobile traveling at 60 miles per hour, saying, ‘Only a few feet away. We should be there in seconds,’” Pearce protested. “Suggest the Enterprise will be traveling at low sublight speed (for example, 5,000 kilometers per second) and the system be 100,000 kilometers away.”

Perhaps the most nettlesome scientific conundrum that Star Trek encountered occurred in “The Devil in the Dark,” written by producer Gene L. Coon. The script called for a hideous, corrosive-spitting blob of a creature that eats solid rock, moving as easily through that medium as Homo sapiens move through the air. This “horta” was made of compounds based not on carbon but on its nearest elemental relative, silicon.

Stern words came back from de Forest and company: “Silicon-based life could only develop and be sustained under conditions of extreme heat—perhaps an environment comparable to that prevailing on the planet Mercury. It could not possibly exist in the oxygen atmosphere. In the presence of oxygen the silicon compounds would undergo spontaneous chemical transformation—that is, they would burn.”

Ultimately, the Star Trek crew skirted the issue with a synthesized, artificially created, human-friendly, underground environment. That scenario still allowed for a skeptical Dr. McCoy (DeForest Kelley) to argue, “Silicon-based life is physiologically impossible—especially in an oxygen atmosphere.” To which the ever-logical Mr. Spock (Leonard Nimoy) responds, “It may be, doctor, that the creature can exist for brief periods in such an atmosphere before returning to its own environment.” It may have been fudging but it was also an honest attempt to reconcile scientific law and artistic license.

As Star Trek flew on, its penchant for plausibility turned out to be a double-edged sword. Fans picked up on, and began dissecting, the show’s self-assured techno-jargon. “A stereotypical letter,” co-producer Robert H. Justman mused in a later memoir, “might say: ‘In act three of last week’s show Capt. Kirk’s narration indicated a star date of 4891.4, but he’d already mentioned star date 4323.7 in act one. This means he made love to Phobos 7’s four-breast alien maiden princess before he arrived and beamed down. How can this be?”

Peter Sloman once received a letter from a high school classmate who skewered him for allowing the hull skin temperature of the show’s Galileo shuttlecraft to reach an impossibly high threshold upon reentering a planetary atmosphere. “You do realize,” Sloman’s friend wrote, “that this temperature is 500 degrees above the recrystallization point of iron?”

There were other blunders: In “The Omega Glory,” McCoy remarks that the human body is about 96 percent water. The actual figure is approximately 60 percent. In “Court Martial,” Capt. Kirk explains how to enhance the power of the Enterprise’s computer auditory sensor. “By installing a booster, we can increase that capability on the order of 1 to the fourth power.” Alas, the good captain didn’t grasp that 1 raised to the fourth power is still 1.

Sloman, who majored in linguistics at Georgetown University, had a particular prejudice against the “universal translator,” a handheld device that, in the episode "Metamorphosis," turned extraterrestrial thoughts (not even language) into English. Unless the gizmo had bona fide telepathic powers, he argued, it was unworkable. “It was like something out of Captain Video,” a series that predated Star Trek by about 15 years.

In the end, though, when it came to serving both the god of drama and the caesar of science, Star Trek more than held its own. No less than science fiction giant Isaac Asimov said as much: “That’s what makes the difference between Star Trek and all the other science fiction series that I have seen,” he said in an interview in the mid-1970s. “Star Trek was the only one when, whoever it was who was involved, Gene—and I mention no names—insisted on people knowing something about science and preparing. And it showed, you know! You could see that even when you broke the laws of science, you were doing it intelligently and plausibly.”