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I'm confused by the end of Alien 3, when they drown the Xenomorph in molten lead.

  • The Xenomorph manages to survive being plunged into boiling hot lead, but previous Xenomorphs were killed by and gravely scared of flamethrowers. Why?
  • As the lead is poured, some shouts / screams are heard which sound like the preacher who sacrificed himself to keep the Xenomorph busy. However, he's just been covered with molten lead, so that doesn't seem likely. Who was shouting?
  • The Xenomorph emerges from the lead relatively intact, then it explodes(!) after being showered with a bit of water. What caused it to explode?

Were these all just goofs / plot-holes, or are there reasonable explanations for them?

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  • It's possible to make explanations but the exploding alien is quite silly. A definite case of 'did not do the research' – user8416 Jan 2 '13 at 11:58
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The aliens were shown in previous movies to be mostly impervious to heat. The aliens didn't like being hit by the flamethrowers but we never saw an alien killed by one. In Aliens, Vasquez and Drake kept the aliens from killing their whole squad by re-enabling their smart guns and blasting the aliens with automatic weapons fire.

In Alien 3, there were no shouts from the preacher (Dillon) after the lead was poured. Ripley and the character at the furnace controls, Morse, grunted as the lead was poured, no doubt because of the intense heat they were exposed to by being so close to the 600°F+ lead. Dillon shouted and cursed as the alien was ripping into him, but his cries had stopped by the time the lead was poured.

At the end of Alien 3 the alien's demise was meant to be due to the same forces that make glass and some metals brittle after casting unless they are annealed to relieve internal stresses. The alien was heated and then quenched which would make its exoskeleton brittle. Eventually the increased internal pressure due to immersion in the hot lead caused the alien's brittle covering to burst apart. Conversion of water in the alien's body to steam would be more than enough pressure to cause an explosion given the thousandfold increase of volume when water is converted to steam at normal atmospheric pressures.

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  • The explosion still doesn't fit perfectly: Inside the outer shell the alien would have to boil I assume, which might have killed it. But at the same time it might be possible that the alien's body is under pressure all the time (i.e. initially not just for a simple, earth-like atmosphere, so the heat added just a bit (if at all)), although the difference would have to be rather big. – Mario Dec 31 '12 at 10:05
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    @mario why would the alien need to boil? The contents of the inside of any container exert force on the outside of the container. We have no idea of HOW much force is being exerted in the case of a xenomorph. – sarge_smith Dec 31 '12 at 14:56
  • Yes, but having such a high pressure under standard conditions (i.e. not heated) sounds odd (cause they didn't just explode when cut, impaled or shot at). So I assume the additional pressure has been caused by heat (although it's debatable whether this would be that significant for it to be considered boiling). – Mario Dec 31 '12 at 15:06
  • @mario I don't remember one ever being cut, but they do explode every time they are shot (at least the location shot does). I would say that given their survival range, vacuum to high pressure, would make me think that they would likely implode instead of explode, but hey, they chose another direction. – sarge_smith Dec 31 '12 at 15:12
  • @sarge_smith Didn't they cut the Facehugger in the first movie? Been a while, though. – Mario Dec 31 '12 at 16:33
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No goofs, no plot-holes, just physics at work (and probably a bit of imagination).

It's been a bit since I've seen the movie and it's also a bit speculation, but this is what I'm thinking:

  • Hot isn't the same as being hot. This sounds stupid, but not all flames are the same temperature and molten stuff isn't necessarily the same as well. As a extreme example, take water and molten iron. Lead melts at around 600 K or 330 °C, which isn't "that hot". I don't really remember what exactly they had in those pots, but it obviously hasn't been hot enough to kill the Xenomorph. Just for reference, silicon (what Xenomorphs are based on) melts at around 1700 K or 1400 °C. Burning wood or gas can be about three times as hot as molten lead and would therefore be nearly enough to definitely damage the Xenomorph. However, thinking about this point, there's still one open question: What about the new Xenomorph growing inside Ripley? Shouldn't it be able to survive the lead as well? Or would it be just too sensitive to environmental stuff such as great heat?

  • I don't remember the specific shouts or screams. Maybe they reused something or it's really just some imagination. Can't comment on this point.

  • As you might have learnt in school, different materials change their volume based on temperature. This can be easily reproduced with water: Fill a bottle with water and put it into the fridge. When freezing, the water will expand and crack the bottle (it might actually explode depending). Or fill a glass with water and put it outside. Once the water freezes it will raise (not because the ice is lighter, but because the ice fills a bigger volume). In a similar way, this happens with the Xenomorph: Its body would be able to adjust to both temperatures, but due to the change happen too fast it can't adapt properly, probably having its exoskeleton destroyed by a thermal shock (different parts deforming/expanding at a different rate). The explosion might have been portrayed a bit too extreme, but it's far from being (completely) unrealistic.

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  • I'll concede on the first point, but I disagree on the 3rd. The Xenomorphs demonstrated a need for a seriously tough outer shell of silicon-based polymers (as mentioned in the first movie) but internally were soft and relatively fragile. It seems illogical that they could increase their internal temperature to 330°C and survive. Even if we just consider the external shell as being the part that matches the temperature of its surroundings, a violent explosion of its entire body when sprayed with a little water seems very far-fetched. – Polynomial Dec 30 '12 at 23:07
  • I agree, the explosion might have been a bit overdone, but still being not completely unrealistic (considering that the water most likely wouldn't drop the temperature that fast). – Mario Dec 30 '12 at 23:11
  • Updated the answer, as this might not be just due to temperature changes, but due to thermal shock as well. It's still a bit overkill though. – Mario Dec 30 '12 at 23:25
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The script and the novelisation both strongly imply that it's the temperature differential between the hot lead and the cold water that cause the Xenomorph to explode, in much the same way that the mould explodes when rapidly cooled.

then - large water duct - the chain pulls open the seal - water gushes out

  1. then - Ripley being drenched - hanging on for her life - the water cascades

  2. then - the freezing water hits the Alien - its head explodes!! then - a huge explosion! the entire mould goes up --

Aliens III, Final Draft Script

and

Water erupted from the large bore quencher that hung over the lip of the mold. She found herself tangled up in the chain, unable to get loose. The torrent of water drenched her, sweeping her around in tight spirals. But the chain would not let her go.

The cold water struck the alien and its hot metal coat. The head exploded first, then the rest of the body. Then the mold, vomiting chunks of supercooled metal and steam. Morse was thrown to the floor of the crane’s cab as it rocked on its supports, while the commando unit ducked reflexively for cover.

Warm water and rapidly cooling metal rained down on the chamber.

Alien 3 (novel)

You can see a similar reaction in the video below.

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Yes, but take into account nobody knows what other chemicals and/or materials make up a Xenomorph. For all we know, Xenomorph insides could contain a chemical compound that explodes when it reacts with lead, due to some lead on its exoskeleton and water causing its heated exoskeleton to cool and become brittle, it could in conjunction with pressure changes blow it apart if atmospheric conditions were just right.

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Take a look at this experiment https://sciencebasedlife.wordpress.com/2012/03/06/why-you-can-stick-your-hand-in-molten-lead-but-shouldnt/ If the xenomorph has a layer of water or similar fluid like the acid on it's skin the dense lead won't let the liquid evaporate and would protect it from the molten metal for a time

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