Micro..changes..in air density

well it detected jonesy so i think it genuine. Also he demonstrates it working in the same way a metal detector works.

to me show exactly that ash have no idea of what to do in many occasions ...

Thats why i feel ash may not be programmed he may have free will and honestly believes in the company ethic and their reasons for having an example to study. After all the world is full of people that work for unscrupulous company's and believe in what they represent. If human nature is that Infallible why cant an android be equally morally corrupt or misguided.

Jeystone, I just watched alien again tonight.. and I it was the first time I noticed that she says "micro changes my ass", so I suspected that he had that planned before hand.. and then I read this.. lol.. But he did pause in an odd fashion before stating the micro changes.He proceeded to cut the leg/finger because Dallas demanded it. So maybe in Prometheus they will find out that the creatures have acid for blood. Maybe then Ash would know what would happen and that is why he made a cut in an area that would not harm Kane.. Once again.. that is funny you posted this and I never even noticed.. lol

i think the "micro changes my ass" is a " dont talk difficult ..talk simple, let me see how it work " ...she is quite pleased when she see how it work ...

It obviously works or else they wouldn't have found Jonesy.....It seems to me, (based on Ash's response to Ripley, the apparent malfunctions that both Ripley and Lambert experience, and Ash's expression as Dallas' death seems iminent with Lambert screaming over the comms), It's designed to function properly, but Ash, with a feel for machines, he himself being one, that he works in bugs meant to intentionally cause problems as they search......It would have to work somewhat or else he would bring too much attention to himself.

Craigamore, I freak'n love that.. that is so crafty...

Thanks @danrald

I don't think it's implied that Ash knew much of anything about the alien life-cycle before he was exposed to it, first-hand. He clearly thought the facehugger was still functional after it had fallen off of Kane, evidenced by his behavior during the search of the medical bay. He was also clearly shocked by what happened to Kane, evidenced by the fact he was concerned with relative trivialities like shoving a spoon in Kane's mouth so he wouldn't bite his tongue ( some kind of seizure ) when his chest was actually about to explode.

yeah I guess you are right, he didn't know much..but then how come the company are so excited 'crew expendable'...maybe they would like to know what type of extra terrestrial life it is before having the whole crew killed...could have been amoeba... Also changes in air density would be a terrible way to key on a xenomorph, what about all the steam etc from pipes....then again it is a movie lol

When something moves in an atmosphere, it compresses the air (in the direction of its movement). The air pressure behind it is proportionally decreased (i.e., a vacuum is created). The air density is a function of the object's velocity. The Alien moved at near human speed hence the term "micro changes in air density." With a supersonic aircraft, you get sonic booms.

I think the motion sensor is legit (or generally accepted as so - given its use in Aliens) but Ash knows far more than he lets on (i.e. given the weapons they have available, short of blowing up the ship, they have little chance of killing it with or without a motion sensor). I don't even think the motion sensor stops working. My interpretation is that Lambert assumes it's stopped working as the Xenomorph is able to avoid detection (by remaining impossibly still). Ash strongly advises Dallas against attempting to remove the facehugger (with "if it's feeding him oxygen, you might want to consider the possible effect of removing it" and the like), but ultimately he has to follow Dallas' orders or risk giving himself up. All of his actions are a fine balance between protecting the Xeno and keeping up the pretence - and there's only Ripley that picks up on it. Furthermore, with (I think) Ridley Scott having informed that Prometheus will contain the "DNA" of Alien but none of the sequels, I feel the crux of the issue regarding the link between Alien and Prometheus will be Ash (and the Company)'s knowledge of what happened on the Prometheus mission. It's possible that said knowledge doesn't extend to how the Xeno was going to birth from Kane. I also feel Ash only gives Ripley (and company) a glimpse into his insight when he's found out (because although he does sympathize with their situation, it's still his mission to protect it). I find what he reveals at this point very cryptic and can't help but draw more relevance to the bit about the Xeno having adapted quickly to the (Nostromo) environment - possibly the reason why the progenitor (if there is to be one in Prometheus) will look different to the previously established image.

Ash (or Weyland) knowing anything about xenomorphs/SJs/derelicts, etc. is dependant on whether or not anyone makes it back home to Earth in this movie. What with ships apparently exploding and Scott saying that 'they get stranded' maybe Weyland will still be pretty much in the dark.

I disagree Bunny, I feel it is assumed that the company knew everything and had a habit of placing robots whos primary concerns were aligned with the companies on every one of their space missions even those prior to the Nostromos.