Goofs

When Kate and Marek are examining the monastery cave-in, they see a decorated section of the wall, which is damaged. When Kate and Chris go to the same section of the wall in 1357, it is decorated differently, and they break out a larger section of wall than what was missing in the present.

When the group is first handed their markers, Kramer tells them, "You can use any one of them to call for your return at any time. Frank will explain the intricacies of how they work once you arrive. Most importantly, one marker will bring all of you back. Do not lose them." However, when Barreto is shot with the arrows, he presses his marker to return to the present time, but no one else is transported with him.

When Chris and Kate are in the monastery in 14th century France, and first discover the tunnel and start to crawl through it, one of them knocks over a candle. In the next shot it is back standing upright, as if it was never knocked over, without anyone picking it up.

After Chris, Kate, Marek, Professor Johnston, and Gordon escape the manor house, all five can be seen stepping on to a balcony. The next shot reveals that all are stepping on to the balcony but Marek, who stops to go and rescue Lady Claire.

While hiding in a village hut from Lord Oliver, Kate turns her wrist to look at the blood on her hand twice.

Decker yells "Fire!" to the archers at the river. But "fire" was an expression that only developed after the invention and widespread use of gunpowder and firearms. Before then, archers were commanded to "shoot" or to "loose" their arrows.

The hand grenade has "M-7204-F Fragmentation" clearly marked on the outside of it. There's no such grenade in existence. Also, fragmentation grenades are smaller and rounder in shape, rather than cylindrical. The grenade is in fact a repainted replica of a standard military-issue M-18 smoke grenade.

When explaining to the group how they would travel to 1357, it is explained that the fax machine was developed 30 years ago. In fact, it was first patented in 1843 by Alexander Bain, and commercially introduced and patented 119 years later in 1964 by Xerox Corporation.

The archer who kills Baretto is nonsense. He's trying to use an English longbow while riding a horse. Although the longbow was a deadly weapon in the hands of an experienced bowman, being capable of piercing armour if it shot a bodkin arrow, it had limitations. It was exclusively an infantry weapon because it was about five feet long and therefore impossible to use properly from horseback. And more, it took serious upper body strength to draw one, which would have been impossible while riding a horse. In any case, English archers were traditionally hunters and peasants and could not have afforded the cost of owning a riding horse, so could not have learned to ride or the art of horse archery. The medieval English never had any mounted horse archers because of these limitations. It was only later in Eastern Europe and in Mongolia that the medieval era began to develop composite recurve bows, which were short enough to be used on horseback, but still strong enough to take down an armoured soldier.

When the team are initially told about the wormhole, they are shown photographs of the sky, and it is explained the difference in the positions of the stars is how they were determined to be taken 600 years ago. 600 years is not long enough for a perceptible movement in stars. The star with the greatest noticeable proper motion is Barnard's star, which would take about 350 years to travel 1 degree in the sky. This would not be seen on a photograph as depicted.

Being their only way home, they're told their markers are "very precious", and yet they just casually wear them outside their clothes where they could easily snag on a branch, be snatched by a thief or simply lost as they fight to stay alive.

When Marek and De Kere are falling down the steps, a "dead" soldier lifts his head up.

When Lord Arnaut is in the tunnel with Chris and Kate after the explosion, one of the "rocks" on the ground is obviously made of foam.

Kate was disguised to look like a 14th century peasant, yet she reveals underwear not invented until the 19th Century.

When Gordon is killed, he falls to the ground and is dragged by the rope tying him to the cart. But despite the fact that he's supposed to now be dead, we can clearly see his hands holding tightly to the rope as he's dragged along.

The film completely misrepresents the languages being spoken at the time. In 1357, when the film takes place, neither modern French nor modern English would have been spoken. The English would have been speaking Middle English (a language closer in pronunciation and vocabulary to Old English) and the French would have been speaking Occitan - a combination of Middle French and Latin. Certain members of both sides would have spoken Latin, especially the clergy. Michael Crichton details these languages in his book but the film ignores them.

If the only way to see the time remaining on a marker was by pressing a notch with a thumbnail, then it would have been impossible for Decker to find out the time remaining on Gordon's marker while wearing thick leather gloves.

When Claire and Marek are floating down the river, the raft she is in is held together by industrial staples.

When Doniger is trapped in the machine, after he says he doesn't have his marker, when he says the words "I'll never get home!" his mouth isn't moving.

When the team see the star chart images, taken in 14th Century France, they clearly show the constellations of Centaurus and the Southern Cross, not visible from France, now or 1357.

Greek fire was a liquid which burned fiercely and which could not be doused by contact with water. It was invented and used by the Byzantines for naval warfare. The problem is that no person living today, not even a historian or an archaeologist, knows what the true ingredients of Greek fire were. Its recipe was such a closely guarded military secret that it has been lost to history. The professor would therefore not have been able to make it for the English. There's also another problem: Different scholars have different theories about it, but it seems probable that it was based on some form of naphtha, which is a liquid hydrocarbon mixture similar to gasoline or petroleum. The word itself comes from the Greek word for "wet." But in the film the ingredients they are given to work with are all dry, yet somehow the final product ends up wet and looking like ordinary pitch, which the medieval already knew about and used to defend castles against sieges.

At the beginning of the movie, Marek tells the grad students about the death of Lady Claire, which galvanized the French forces and led to them winning the battle. Later, Marek shows Chris the sarcophagus of the knight and his lady. He points out the knight is missing an ear. This is later shown to be Marek, as we see him lose his ear in the battle in the past. The lady with him in the sarcophagus is at the end revealed to be the Lady Claire. This means Marek was always destined to go into the past, and Lady Claire was never destined to die in the battle, despite Marek's lecture stating that her death was instrumental to the French's victory.

The European trebuchets of the 14th century were not mounted on wheels. They were too big and exerted far too much force on their frames to be free-standing. They were literal installations built of heavy timbers that had to be disassembled, transported on carts for a siege and then rebuilt in place and staked to the ground to stop them from ripping themselves apart or falling over.

The "transcription process" which is supposed to break someone down in one time and reassemble them in another is apparently based on their DNA, which shows a fundamental misunderstanding of how DNA works. DNA is a recipe for making an organism, like a chocolate cake recipe is a recipe for a specific kind of cake. But no matter how many times you follow the identical chocolate cake recipe, every time you make it you end up with an entirely new cake, not the exact same cake you originally made. Even if you could somehow break the original cake down to its basic ingredients and start over, the new cake will still be different from the original. And more, the new cake is not going to be able to "remember" the experiences and the memories of the original cake.

Also, there's a further logical paradox: how does the person get reassembled when they arrive in the past? There's no time machine in the past to do it. Nor is there any time machine in the past to disassemble someone in order to send them back to the future. Relying on a machine in the future to do the reassembly or disassembly means a wait of 650 years before either process can take place, because time can't be sped up.

They are told that no modern equipment can go through the wormhole, however - they are bringing the markers - which are electronic and also a grenade.

The markers should not work at all - if in actuality, they would have to depend on other data connection to transfer them back, which did not exist at that time.

It is possible that "no modern equipment" was so that it would not pollute the time line, or so that none of the members would stand out. Wearing a watch or using glasses would definitely draw attention to themselves, which is why Francois had to go without his glasses.