As Kirk finally gets an idea of what to do and as the crew is now watching, he gets up and comes from behind a rock, but at first it is kind of a white ghost image that you see and then suddenly you can see that it is Kirk.
When Kirk is about to kill the Gorn captain, he puts the obsidian spike on his throat, but, in the next cut, the weapon is gone. The camera goes back to the original angle and the weapon appears again.
Kirk heaves a rock at the Gorn, striking it in the abdomen and coming to rest to the Gorn's right. In the next shot, when the Gorn approaches, the rock has disappeared, and another rock on the ground is in a noticeably different spot.
Near the end, Kirk is talking with the Metron. From the close-up shot, the Metron is facing Kirk. From the long shot, his body is at 45 degrees.
When Kirk is coming down the hill after pushing the rock on the Gorn, his left side is leading. In the next shot, his right side is leading.
Gunpowder is a low explosive: it has to be contained to explode. Otherwise it simply burns. Even if Kirk had real gunpowder, it wouldn't have exploded.
Kirk could not have made black gunpowder with just the dry ingredients. First, all of the base chemicals would need to be ground very finely, then mixed with pure isopropyl alcohol into a slurry, dried, then ground again.
Proportions would need to be 75% potassium nitrate, 15% charcoal and 10% sulfur.
Lastly, the explosive force from the ignition of the powder would not be sufficiently contained by a plant like bamboo. It would probably have killed Kirk.
Proportions would need to be 75% potassium nitrate, 15% charcoal and 10% sulfur.
Lastly, the explosive force from the ignition of the powder would not be sufficiently contained by a plant like bamboo. It would probably have killed Kirk.
The boulder that Kirk pushes off the edge of a cliff to try and crush the Gorn is very large and requires Kirk to push it slightly uphill to get it to topple off the edge. A boulder this large would easily weigh over 1000 lbs, and there is no way Kirk could have managed to push it uphill to get it over the edge by himself.
Sulu said they were "clear across the galaxy 500 parsecs from where we were". The galaxy is about 40000 parsecs across, so they were moved 1/80 of the way across the galaxy. This would be the same as saying that, when travelling from Los Angeles toward New York City, Pomona is clear across the country.
Mini Myth Mayhem (2009) tried to recreate the battle with the Gorn, and proved that Kirk's gun-making procedure would not have worked, due to the nature of bamboo, wood, and other factors. However, the official novelization of Arena, probably reflecting the original script, explains that chemical compounds on Cestus III are very different from their Terran analogs. Thus, within the parameters of the story, Cestan wood and bamboo are indeed capable of accomplishing what Kirk did with them.
Kirk finds a large hollow tube and he starts filling it with potassium nitrate, diamonds, sulfur, etc. However, it is a hollow tube and he keeps carrying it straight up and down which means everything he has just put into would be falling out the bottom. Note that if the tube Kirk used is a piece of bamboo, as it appears to be, the plant regularly creates seams, which divide individual chambers in the plant's stem to provide structure and rigidity. Thus, the tube would not be hollow. The tube contains an obvious seam, which would create a point in the tube capable of holding all the ingredients. Also, the tube in question is growing on an alien planet and may only superficially resemble bamboo.
After Kirk orders Sulu to, "Keep those screens (usually called "shields") up...!" he turns to Spock and says, "If they lower those screens to beam us up they'll be open to phaser attack". Obviously, Spock would be well aware of that fact and would not need an explanation for Kirk's order. However, the writers were probably aware of that, but used artistic license to make that point to the viewing audience - not Spock.
In the beginning, the Metrons say they have prepared a planet for the two combatants. Several times during the fight, a rock-paved road is visible. However, the Metrons could have prepared the road too.
Captain Kirk rolls a large rock off a cliff and it does not stop the Gorn, but a crude cannon made from a wooden tube and black powder does. If the rock weighed 400 lbs. and it fell 100 feet per second it would generate over 60,000 ft.lbs. of energy, much more energy than a small, wooden cannon utilizing crude black powder could produce.
While the crew is watching the picture the Metrons provide on the view screen, the picture noticeably shifts up and down in the frame of the screen, apparently due to a poor (or hastily done) video overlay.
The Metron camera (on the Enterprise view screen) conveniently zooms in on the charcoal, before Kirk notices it. As if the Metrons knew what was coming.
When Kirk first spots the large boulder on the rock ledge above the Gorn, it is in full sunlight. As he approaches it supposedly only seconds later, it is already partly shadowed.
The supposedly heavy boulder Kirk struggles to roll onto the Gorn shakes quite a bit.
(at around 37 mins) As Kirk is preparing to fire a mortar round at the Gorn, a stage hand's shadow is seen moving across the actors.
When Kirk spots the large rock that he will soon roll off the cliff onto the Gorn, the next close-up shot of it reveals a cord tied around it anchoring it to a smaller rock to the lower right of it.
While Kirk is climbing the rocks after first meeting the Gorn, shadows can be seen from the reflectors used to illuminate the set. They are from two directions and inconsistent with the sunlight.
Spock readily identifies the "white substance encrusting that rock" as potassium nitrate before Kirk even discovers its bitter taste. Countless other white crystalline substances also occur in nature (e.g., salt, gypsum, chalk) so Spock's easy identification seems highly implausible.
Early in their fight, Kirk and the Gorn are interlocked. The Gorn, with its great strength could have fatally crushed Kirk's chest and back and could have caused fatal injury by biting Kirk's head, ending the fight very quickly.
A sensor scan of Cestus III should have revealed that it had been attacked.
The Metrons stop the Gorn ship several minutes before they stop the Enterprise. The Enterprise is traveling at Warp 8 for a couple of minutes after the Gorn ship has been stopped. Traveling at Warp 8 the Enterprise, would have reached the stopped Gorn ship almost instantaneously and the Enterprise still has operable weapons at this point.
The Metrons pronounce their name "Meh-trahn" but Kirk mispronounces it as "Meh-trohn" every time, and Spock uses both forms.
On Cestus III, Spock informs Capt. Kirk that the arsenal is "about one hundred yards in that direction". As the metric system was already standard, meters should have been used as the estimate.
Captain Kirk refers in his log to the Arena planet as an "asteroid" which it clearly isn't.
When Kirk fires the mortar, he, Spock, and the blue shirt move to the back of the foxhole, which offers far less protection from the blast than they would have had if they had ducked down below the lip of the front of the foxhole.