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Post by rmc on Aug 15, 2014 16:30:54 GMT
Discussion involves the 1989 movie, The Abyss.
I'm not clear if this has been mentioned before, and, admittedly, I am really just nit-picking here with something that probably Director James Cameron has already fielded and explained. But, not seeing it discussed anywhere before, myself, I'll start this thread; at least until I discover any earlier discussion about it...
Best witnessed during the scene with the Water Tentacle, there is a problem for the crew of the Deep Core: The open-ended, diving-bell-like submersible launching bay could not work the way depicted. And to correct the problem there is a reasonably-simple alteration that could have been shown, but then this alteration would have made the Water Tentacle scene, itself, nearly impossible to depict.
Here's my logic: A diving bell, an open-ended diving bell, uses air pressure to keep the level of the water at the base-level of the so-called bell. The depths that the Deep Core was depicted operating was the sea floor of open ocean. True, there was the Abyss-depth that the Deep Core never attempts getting down to, and, that canyon may have been several miles deep too, but the average depth of the open ocean, the depth that the Deep Core is specifically depicted operating at is at least a mile to two miles deep. That would mean that the water pressure on the hull of the Deep Core would be at least a ton per square inch. Air would need to be pumped into that submersible launching bay until the AIR had also reached pressures of over a ton per square inch. The crew of the Deep Core could not have survived such air pressure. The reasons are centered around the physics of gas mixtures. Even if replacing the Nitrogen with Helium, the ton-or-better "air" pressure becomes toxic, I believe. (may be wrong here, if enough He is used in place of O2, but it's a moot point, as the Deep Core, depicted, did not use a He/O2 mix) Possibly, at those pressures, the gases involved may even behave differently than at the surface on the human body. And the whole compartment of the Deep Core would have, apparently, needed to be at that specific air pressure, as proved by the scene where the 'Water Tentacle' roams freely around the various rooms of the Deep Core, after having originated from out in the open ocean, using the open-ended submersible launching bay to enter the Deep Core.
The alteration allowable (at least for better movie-physics purposes) would have been to make the submersible launching room a sealed off quarters, only opening to the ocean once the air pressures are high enough (or maybe skip pumping in air into the bay -- and let in water, slowly, until water pressure equals outside water pressure and then open a hatch of some sort for the exiting submersible) Something like that. But, admittedly, then our Water Tentacle has no open path for viewing the interior of the Deep Core as it would have to get past the sealing mechanism I am introducing here.
Not too sure if there is a means for the Mythbusters to test this movie-myth, specifically. So, I posted it here in the Strange Ideas forum.
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Post by the light works on Aug 15, 2014 17:56:39 GMT
yeah, gonna be hard to demonstrate. been a long time since I watched it - and I had not thought about the pressure and the effects of the gas concentration. I know extreme deep divers have nearly 100% helium for their breathing air due to oxygen toxicity at that concentration.
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Post by wvengineer on Aug 15, 2014 19:59:44 GMT
The design of the deep core is actually very reasonable. Humans can survive high air pressure environments, as long as they have time to adjust. If you remember when the marines first arrived at the Deep core, they spend several hours in a small compression chamber. That is based on real life diving practices. It takes between hours to several days to for the internal air pressure in the body (epically in the blood stream) to equalize the surrounding air. If you slowly increase the pressure of the chamber, you can safely transition from surface air pressure to high pressure deep diving pressure.
The danger comes from rapid changes in pressure. Rabid drops in air pressure can result in the bends. The rapid drop of air pressure causes nitrogen dissolved in the blood to come out and firm bubbles. This can be deadly. If you remember the last scent they comment on how they never decompressed when the came up to the surface and should be dead.
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Post by rmc on Aug 15, 2014 20:59:16 GMT
Have been a certified diver. I am aware of decompression and pressurization. I was speaking more about the gaseous mixture, in that it presents a danger itself while at high pressure; irregardless of the decompression techniques used later.. or the equalization process used during descent. Too much of either gas at pressure simply results in a toxic scenario for people. One cannot escape this fact even by reducing O2 or Nitrogen alternatively at certain pressures, because there is simply too much of the other chemical in the gaseous mixture acting upon the human blood stream as a result of compressing the chemical in question. Also, apparently Helium was not used here anyway, as the voices all seem to be at normal "sea-level" O2/Ni mixture levels. So, any idea about attempting to alter the mixture to a better blend than Oxygen and Nitrogen, I feel, is apparently out. Not directing this post to anyone in particular, just including it now to support, further, what I originally posted: Oxygen Toxicity: scuba.about.com/od/scubaterminology/f/What-Is-Oxygen-Toxicity.htmAnd the other mixture problem if using Nitrogen (in typical air, as apparently they were) Nitrogen Narcosis: en.wikipedia.org/wiki/Nitrogen_narcosis |
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Post by the light works on Aug 15, 2014 21:49:44 GMT
Have been a certified diver. I am aware of decompression and pressurization. I was speaking more about the gaseous mixture, in that it presents a danger itself while at high pressure; irregardless of the decompression techniques used later.. or the equalization process used during descent. Too much of either gas at pressure simply results in a toxic scenario for people. One cannot escape this fact even by reducing O2 or Nitrogen alternatively at certain pressures, because there is simply too much of the other chemical in the gaseous mixture acting upon the human blood stream as a result of compressing the chemical in question. Also, apparently Helium was not used here anyway, as the voices all seem to be at normal "sea-level" O2/Ni mixture levels. So, any idea about attempting to alter the mixture to a better blend than Oxygen and Nitrogen, I feel, is apparently out. Not directing this post to anyone in particular, just including it now to support, further, what I originally posted: Oxygen Toxicity: scuba.about.com/od/scubaterminology/f/What-Is-Oxygen-Toxicity.htmAnd the other mixture problem if using Nitrogen (in typical air, as apparently they were) Nitrogen Narcosis: en.wikipedia.org/wiki/Nitrogen_narcosisso here is a submyth: if you are in a high pressure helium environment - as it would be if you were actually in a deep sea rig like that - WOULD you have "helium voice?" - or to make it more general and less specific - does atmospheric pressure have an effect on your voice in the same manner as denser or less dense breathing air does? |
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Post by rmc on Aug 16, 2014 16:47:20 GMT
Sorry. I took my mother to the ER for a problem.. Looks like she is on the mend as we apparently took her in soon enough! As to the other questions about gases under pressure, if there is any way to check for signs that sound behaves differently in a given gas subjected to increasing pressures, I say, sure! Why not look at that?
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Post by mrfatso on Aug 16, 2014 17:32:32 GMT
Another factor might be that your hearing might be affected by increased gas pressure, the tympanic membrane might move to a reduced degree due to the greater pressure on it.
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Post by the light works on Aug 16, 2014 19:14:35 GMT
Sorry. I took my mother to the ER for a problem.. Looks like she is on the mend as we apparently took her in soon enough! As to the other questions about gases under pressure, if there is any way to check for signs that sound behaves differently in a given gas subjected to increasing pressures, I say, sure! Why not look at that? good to hear your mother is on the mend. it has been a rough weekend, here, so far. If I was pulling a day shift as well, I would probably be well on my way to threatening the record for the busiest 24 hour period. how could we practically test the gas pressure thing? short of putting people in a pressure chamber, the only thing I can come up with is a recorder (or other simple reed instrument) and an oscilloscope (or more modern visual displays). I don't know if putting a microphone inside the chamber would allow people outside to hear any pitch change or not. - they could supply the recorder with a variety of different gases both inside and outside their pressure chamber. |
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Post by rmc on Aug 16, 2014 22:23:00 GMT
If I remember correctly, we did an experiment involving a vacuum chamber and alarm in calculus-based physics. As air was pumped out (obviously becoming *less dense*, with regard to molecule spacing ) all the pitch did was get fainter until unheard. Now, admittedly, that's the opposite direction of what you are suggesting testing. And, the number of pounds per square inch involved for each situation is greatly different. But, an early guess is that varying the pounds per square inch does nothing for some reason. While varying the so-called density by choosing different makeups of chemical gases (nitrogen vs helium, for instance) for some reason does. I'd like to go on further and speculate that it has more to do with the molecules themselves, rather than the actual spacing between, that causes a variance in whatever pitch is heard. My guess is that some physicist out there somewhere can spell out, point blank, what should and would happen in each case, including yours. All I can really do is guess.
Thank you for the well-wishes, by the way. I just got back from her room and got to watch as they removed the tube that had been placed down her nasal passage and throat. Now all we have to do is a little observation for a day or so, and we are in the clear (as far as that bowel blockage was concerned anyway)
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Post by the light works on Aug 16, 2014 22:31:38 GMT
If I remember correctly, we did an experiment involving a vacuum chamber and alarm in calculus-based physics. As air was pumped out (obviously becoming *less dense*, with regard to molecule spacing ) all the pitch did was get fainter until unheard. Now, admittedly, that's the opposite direction of what you are suggesting testing. And, the number of pounds per square inch involved for each situation is greatly different. But, an early guess is that varying the pounds per square inch does nothing for some reason. While varying the so-called density by choosing different makeups of chemical gases (nitrogen vs helium, for instance) for some reason does. I'd like to go on further and speculate that it has more to do with the molecules themselves, rather than the actual spacing between, that causes a variance in whatever pitch is heard. My guess is that some physicist out there somewhere can spell out, point blank, what should and would happen in each case, including yours. All I can really do is guess. Thank you for the well-wishes, by the way. I just got back from her room and got to watch as they removed the tube that had been placed down her nasal passage and throat. Now all we have to do is a little observation for a day or so, and we are in the clear (as far as that bowel blockage was concerned anyway) a mechanically driven speaker should produce the same frequency regardless of the atmosphere it is in - barring such a thick atmosphere that it impedes the motion of the speaker. however, I am not sure if a reed (or a larynx) would vibrate at a different frequency in a different atmospheric pressure. the resonant frequency of the reed would seem to say no, but if it was only the resonant frequency of the reed, then changing the gas you vibrate it with should also have no effect. |
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Post by silverdragon on Aug 20, 2014 12:23:06 GMT
Thinking on this one.
If the dive is deep enough and the thing doesnt crush anyway, and I am referring to what happened to the dive helmet when Buster went decompression into the helmet experiment....
Deep Diving and Air.
If and open ended tube full of water is submersed with the air at the top, juts how long until the air compresses beyond usable?...
At what depth would it be possible that air may be compressed into liquid state?....
Can humans even survive anywhere near that depth at those pressures?...
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Post by Lokifan on Sept 6, 2014 7:04:23 GMT
I remember seeing a documentary about deep sea divers. One sequence was shot in a decompression chamber with helium/oxygen mix.
Their voices were squeaky.
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Post by Lokifan on Sept 6, 2014 7:15:40 GMT
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Post by rmc on Sept 7, 2014 2:46:26 GMT
Here again, the declared mix described in the afore-mentioned literature, doesn't match what the audience actually hears. The lack of squeak tells us that they are actually depicting an O2, Nitrogen mix similar to sea level. And, even at 500 meters depth, the typical sea-level mix becomes toxic... Even Hydreliox produces Hydrogen Narcosis at about 500 meters, per the link you supplied.
The easy fix for the various scenes would have been to allow a certain amount of squeak in the character's voices. Even though that would go against being acceptable for general audiences (or so the powers that be may have thought so) The squeak would have told us (the viewers) that a special mix including helium was being used. But, it's not there.
Plus, what "abyss" is easily accessible from a ledge starting as shallow as 500 meters? The depiction of an endless edge drop, like that found at say the Marianas Trench for instance would have required a base depth of about one mile to start getting to such an Abyss. That's just how the sea floor works in reality. So, finding an abyss at 500 meters is, yet another myth, it would appear.
However, as I stated in the original post, these are things that were attempted to be patched together in order to make the story flow, but they just don't follow your typical oceanographic facts.
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Post by the light works on Sept 7, 2014 3:43:46 GMT
Here again, the declared mix described in the afore-mentioned literature, doesn't match what the audience actually hears. The lack of squeak tells us that they are actually depicting an O2, Nitrogen mix similar to seal level. And, even at 500 meters depth, the typical seal-level mix becomes toxic... Even Hydreliox produces Hydrogen Narcosis at about 500 meters, per the link you supplied. The easy fix for the various scenes would have been to allow a certain amount of squeak in the character's voices. Even though that would go against being acceptable for general audiences (or so the powers that be may have thought so) The squeak would have told us (the viewers) that a special mix including helium was being used. But, it's not there. Plus, what "abyss" is easily accessible from a ledge starting as shallow as 500 meters? The depiction of an endless edge drop, like that found at say the Marianas Trench for instance would have required a base depth of about one mile to start getting to such an Abyss. That's just how the sea floor works in reality. So, finding an abyss at 500 meters is, yet another myth, it would appear. However, as I stated in the original post, these are things that were attempted to be patched together in order to make the story flow, but they just don't follow your typical oceanographic facts. I guess at this point - we have demonstrated that the movie was done in a studio and not at the depth implied, specified, or shown - which leaves the question of whether it is possible to even have a setup like the movie - with breathing mixtures, etc. |
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