Wikipedia:Reference desk/Archives/Science/2015 June 1

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June 1

Question (Silene undulata preparation)

When the ancient shamans used Silene undulata for vision quests they boiled it in a tea and drank the froth. Why does this work better than simply swallowing the roots whole? — Preceding unsigned comment added by 117.166.81.87 (talk) 00:02, 1 June 2015 (UTC)

Why do you think it "works better"? Maybe it's just part of the ritual, similar other herbs are smoked or chewed, various ways of igesting it probably affect the duration and onset of the effects. What is "better" seems subjective in this case. Vespine (talk) 02:11, 1 June 2015 (UTC)

See extract and tincture for related concepts. The active ingredient in a natural plant product often exists in low concentrations, and in certain cases would require the user to consume large quantities of the plant to ingest physiologically-relevant amounts of the active substance. A tea of this type is just a form of extract, which likely concentrates the active ingredients which may be of too low a concentration in the plant itself to be useful. Think of it this way: It's easier to get drunk off of whiskey than beer, and easier to get drunk off of beer than orange juice, though all three contain non-zero amounts of the active substance, ethanol. Why? Because the concentrations are different. In the case of the above ceremony, the reason for creating the tea may very well be to concentrate the psychoactive substances which may not exist in high enough concentrations to be useful in the original root. --Jayron32 02:19, 1 June 2015 (UTC)

That makes sense, although an additional reason for creating a tea is not wanting to consume the parts that aren't water soluble. For example imagine eating the contents of a Lipton tea bag. Looie496 (talk) 14:12, 1 June 2015 (UTC)

Or the sludge at the bottom of a beer kettle. Oh wait, people do that. Still, a good point also. --Jayron32 15:57, 1 June 2015 (UTC)

I added to your title, to make it actually useful. StuRat (talk) 04:09, 1 June 2015 (UTC)

Spatial disorientation

I was reading about the death of John F. Kennedy, Junior. He died when his private airplane crashed. I read that the cause of the crash might have been spatial disorientation. I then read further about spatial disorientation and I also spoke with some people who are pilots. In a nutshell, they said that it is possible (when spatial disorientation kicks in) that a pilot does not know his position relative to the earth. In other words, the pilot could be right-side-up, or he could be upside-down, or he could be "tilting to the left", or he could be "tilting to the right", and he would not even know it. I found it hard to believe, especially the example of being "upside-down" and not knowing it. My pilot friends basically said that, with no visual cues (such as the horizon or a coast-line, etc.), the pilot cannot determine his orientation relative to the earth. So, my question. However, if a person is "upside down" while piloting a plane, wouldn't that person – at the very least – feel the effects of gravity? Wouldn't they feel like they were being "pushed downward"? I'd imagine that I could tell that I am "upside down" because I would feel my body pushing down (due to gravity) against the seat-belts. And the seat-belts would be "holding me" or "suspending me". (This is similar to when I ride on a roller-coaster that actually loops around in a circle, so that at some point, I am completely upside down and being "held in" by the seat-belt.) Also, if the pilot did not even have a seat-belt on, wouldn't the pilot simply tumble out of the seat when he is upside down? So, none of this makes sense to me. Can anyone explain? Thanks. Joseph A. Spadaro (talk) 06:14, 1 June 2015 (UTC)

John Junior was only a VFR rated pilot, meaning he was only trained to fly, navigate and maintain aircraft attitude during daylight by essentially using visual references viewed from the cockpit. He was not trained in "flying blind" which is called IFR. With this additional rating, pilots are trained to fly the plane using only the instruments (maybe your pilot friends were only VFR rated, hence the nature of their advice, as an IFR pilot would have explained how to fly with the instruments only and not get disoriented). In the case of the spatial disorientation in the way you are asking, the principle instrument that would keep you level and "stop you flying upside down" is the artificial horizon. As John Junior was only Visual Flight Rules rated, I would hazard to guess he panicked when it got dark and did not pay attention to that very important instrument. As for sensing if you are inverted, if the plane was basically flying level I would think that you would feel gravity pulling you down, but if the plane was in an inverted dive that was looping down, then the centrifugal force created by the upside down looping dive might counteract or neutralise gravity depending on the speed of the dive and the radius of the loop. Ironmungy (talk) 08:11, 1 June 2015 (UTC)

Chapter 16, Aeromedical Factors, of the Airplane Flying Handbook, explains spatial disorientation, and explains how optical illusions, inner ear turmoil, hypoxia, and the forces experienced during uncoordinated flight can all contribute to poor pilot decision making and inability to positively control the aircraft. In particular, take a look at the diagrams of forces experienced during a skidding turn, which is a classic entry to a graveyard spiral. The pilot may feel that he is sliding horizontally, and may roll the aircraft - or even worse, slam on the rudder - to reduce that force. This is a wrong procedure and may cause a spin. The correct procedure is to coordinate yaw and roll during every turn, especially when flying in poor weather conditions.

Regarding belief: many people do not believe that their sensory perceptions can be so absolutely incredibly wrong. Yet, this is a fact: sensory perception can have complete dissociation from objective reality. In the application of aviation, it is very important to establish this fact. For this reason, aviators train for unusual attitude recovery. In this scenario, the pilot in training wears a view limiting device while an instructor pilot takes the aircraft into an other-than-normal situation, like the entry to a spin, or a power-off stall, or dives the aircraft toward the ground. The aviator in training must recover the aircraft. Even pilots trained only for VFR still need to perform this training, but experiencing it during training does not innoculate the aviator against all possible future hazardous situations.

Nimur (talk) 13:56, 1 June 2015 (UTC)

I suffer from vertigo, which is similar. In my case the inner ear balancing function doesn't seem to be very strong, leaving me almost exclusively dependent on visual cues to determine up and down. Without a flat plane in front of me, I get dizzy. Note that, at an intellectual level I may well know which way is up, but at a more basic level, I feel dizzy and like I am spinning or falling. For me the cure is to avoid such situations, or to close my eyes to avoid the confusing visual cues. Flying a plane while having a vertigo attack might well be difficult. StuRat (talk) 15:03, 1 June 2015 (UTC)

As stated above, you need centrifugal force to masquerade as gravity; i.e., to push you into your seat with a force roughly equal to that of gravity. To confuse upside-down with right-side-up would require being in an inverted loop, which is both unlikely from a practical standpoint and beyond the capability of most aircraft except for stunt planes; they simply lack sufficient power compared to their weight. I'm not sure even that would be enough centrifugal force to simulate gravity. You would need double your weight in force, to both neutralize the downward pull of gravity and then simulate it in the upward direction. So I'd say the upside-down thing was an exaggeration for dramatic effect. ―Mandruss ☎ 15:20, 1 June 2015 (UTC)

User:Mandruss, with due respect, you seem to have all the intuition of a non-aviator! An aircraft, or an airman inside of one, may experience forces significantly greater than one G, even without inverted flight. For example, take a look at load factor. When we get quantitative about this, there is no way you can know what high G loading feels like, let alone how it affects your spatial awareness, until you do it; but you can run some simple trigonometry to see how very easily we can experience ±2G in a normal aircraft operation.

For perspective, consider this. I know a lot of guys who ride motorbikes or drive fast sports cars. I have heard them boast about "pulling lateral Gs" on closed racetracks. They always do this in a land vehicle. It always piques my interest to hear their boisterous claims of heavy forces and "slamming" in their seats.

One of the aircrafts I fly is certificated in the aerobatic category and it has an accelerometer that goes up to +12G. Once in a while, I bring a boisterous character up for a ride, and subject them to, let's say, +1.5 G in a moderate or a steep turn. This kind of maneuver shuts up most mere mortals. At -0.5G, many will lose their stomach contents. At +3.0 G, most passengers can no longer figure out which direction to turn their heads to look out the windows (and their heads are three times heavier, which makes pulling them out from between their knees a real challenge of physical and mental strength). At +3.0G, our flight club requires us to wear parachutes. This is, roughly speaking, the boundary between "normal" operation and the entry into "aerobatic" category operations (per interpretation of Federal regulation). (14 CFR 91.303 and 91.307 specify other regulatory requirements related to parachutes and aerobatic flight; conservative interpretation of such rules is often a good idea).

The magnitudes of force that you are familiar with, and the magnitudes of force that aviators normally experience, are quite different. Aviators cannot rely on pure intuition or sensory perception. An aircraft in instrument meteorological conditions, in heavy turbulence, may very well be so disorienting that an aviator can not tell which direction is up, even if the wings are level. You don't have to take my word for it: this is the probable cause listed on many accident investigation reports. If you wish to read about Mr. Kennedy Jr.'s incident, there is a full report available at no cost, on www.ntsb.gov in the aviation accidents database.

Nimur (talk) 15:48, 1 June 2015 (UTC)

Well worth reading, thanks Nim. For anyone that couldn't be bothered, the accident number is NYC99MA17, enter it in the appropriate field in the NTSB status section as stated above. Ironmungy (talk) 08:05, 2 June 2015 (UTC)

Thanks. The above answers are getting technical and "over my head". I am trying to find a "common sense" answer that makes sense to me. (Not necessarily a very scientific answer. If that makes sense.) So, let me re-phrase my question. Let's say that I am sitting in my car, right-side-up. I feel fine. Now, let's say that I am strapped into my seat-belt in my car. And the car is hoisted and inverted, so now I am upside-down. I would certainly "feel" that I am upside-down (either with or without any visual cues around me). I would feel my body pulling down toward the ground, through gravity. And I would feel the seat-belt "holding me up" or suspending me (or otherwise I would fall out of my seat). I would feel the pressure of the seat-belt against my body (shoulders, stomach, etc.). So, why is this not the case with the pilot in the airplane? And, if I was not 100% upside-down, let's say that I am "tilted to the left" (or to the right) by some large degree. I would still feel that. I would feel like I am slipping out of my seat, and that the seat-belt is "holding me in". So, why is this not the case with the pilot in the airplane? Thanks. Joseph A. Spadaro (talk) 16:03, 1 June 2015 (UTC)

You are imagining steady state. Imagine, instead of being hoisted, that you are instead jostling around a lot, and you feel forces from the jostling around, and then the vehicle moves abruptly and quite fast (like a roller coaster or a merri-go-round). Perhaps you feel a spinning effect (like you've closed your eyes on the merri-go-round). When you hop off, you may still feel dizzy - perhaps you have the optical illusion that the ground is spinning, and you are standing still, and whirling at the same time.

Now, hop off the merri-go-round, and keep your eyes closed (to simulate having no visibility of the outside world, due to clouds). Can you walk in a straight line? If you can, you've successfully navigated on one single plane, but you're cheating - because you don't have to even worry about up and down, as long as your feet are on the ground.

Medically speaking, your inner ear has adapted and believes it is still spinning. This is only the most common one (!) of the many different sensory illusions and errors that your inner ear, and your entire sensory system, can undergo.

Nimur (talk) 16:11, 1 June 2015 (UTC)

If you still saw a view that made you think the inverted car was in the correct orientation, then you probably wouldn't think you were upside down. Instead, you would wonder why the seat belt was cutting into your shoulders and why the blood was rushing to your head. This might also be true if there was no view outside, just darkness. The way our perceptions work is that your brain starts with an assumption of how things are, and then tries to match perceptions to that. Changing the underlying assumption can be difficult. A similar example I've had is when stopped at a light, when trucks on either side of me started edging forward at the same speed. This made me feel like I was slipping backwards, so I pushed the brake pedal down as hard as I could to try to stop. StuRat (talk) 16:14, 1 June 2015 (UTC)

Indeed. "Wrong" visual cues - like a road at night or a weirdly-shaped cloud - or water waves or clouds moving in the wind - can really mess up the aviator. These are real effects: if you click on the link to Aeromedical Factors that I posted above, those are actually textbook examples of what you should not depend on. Out in rural California (and many other rural areas), there are a lot of places where the horizon has no light at all, and many aviators have fatally rolled the airplane to level the wings with the nearest slanted road angle. Street lights on long, straight desert roads look very straight and flat: like artificial grape flavor, the fake sensory input seems better than the real one! This ends badly. Nimur (talk) 16:23, 1 June 2015 (UTC)

OK, thanks. Let's forget the pilot for a moment. (Since he is busy and distracted and doing important tasks.) I am just a passenger in a plane. (So, I am not busy or distracted or preoccupied with anything. I am just sitting there.) The plane is flying completely upside-down (for whatever reason). All of the window shades are drawn, so I have no visual cues of the outside world. You mean to tell me that – as a passenger strapped into my seat by a seat-belt – I would not realize that I am upside-down? Joseph A. Spadaro (talk) 20:00, 1 June 2015 (UTC)

You might not be able to reliably know whether you are upside down. If I asked you, the passenger, to point toward the ground, you might point in the wrong direction. Perhaps you would point towards the correct half-sphere, but that's not really close enough, accurate enough, or reliable enough to ensure positive control of the aircraft. What is worse, though, is that if you used this sensation to control the aircraft, and the result was that the aircraft continued to fly in an unstable or constantly-changing attitude, the plane may pitch, roll, stall, or spin; and this will subject you to increasingly accelerating forces. As time progresses, the degree to which your sensory information is incorrect will increase. Nimur (talk) 20:25, 1 June 2015 (UTC)

It might help if you watch what a spin looks like. For example, watch this video: Super Decathlon spin. See how the aircraft can point in any direction! You might be confused because you're thinking only of two cases: straight-and-level, and straight and level while inverted. As you can see in this video, the aircraft is climbing towards the "up" - as evidenced by the bright blue sky above... and then all of a sudden, the ground slides in from the left (as the aircraft stalls, the wing drops, and the pilot intentionally enters an aerodynamic spin). Aviators have to be aware of all combinations of all three dimensions. The ground can be in any possible direction - not just above your head or below your feet. The aircraft's attitude/orientation does not have to align with its trajectory - especially in uncoordinated flight, or during a stall or a spin. Now imagine that you cannot see which direction from which the ground will approach, because you are in the clouds. Which direction would you steer - rather, how would you manipulate the controls and the engine -to recover? Nimur (talk) 20:42, 1 June 2015 (UTC)

Let's try to explain this concisely, because a complicated explanation isn't necessary.

In the vomit comet, passengers are weightless and can float around, because the aircraft is accelerating toward the ground at the same rate as the acceleration of gravity. Could you tell which way is up and which way is down? Clearly not--being weightless means you don't feel any gravity (even though it exists), and without feeling gravity, how can you tell which way is up?

Now let's imagine 2 scenarios. In scenario 1, an aircraft is rightside-up and accelerating toward the ground slightly faster than the vomit comet. This means passengers feel a force pulling them toward the ceiling. In scenario 2, an aircraft is upside-down and accelerating toward the ground slightly slower than the vomit comet. This means passengers feel a force pulling them toward the ceiling, since the "ceiling" is in the opposite direction as in scenario 1. How can you, as a passenger, tell the difference between scenarios 1 and 2? In both, you feel a force pulling you toward the ceiling. --Bowlhover (talk) 06:26, 2 June 2015 (UTC)

Huh? In an airplane, the passengers don't become weightless. Joseph A. Spadaro (talk) 04:01, 2 June 2015 (UTC)

That is why I specifically mentioned, and link to, the vomit comet. People do become weightless on the vomit comet, as you can see from the images in that article. --Bowlhover (talk) 06:26, 2 June 2015 (UTC)

Correct. And that is why I am confused. On the vomit comet, people (apparently) do become weightless. On a regular airplane, as a regular airplane passenger, people do not become weightless. So, why were you comparing the two (completely different) scenarios as if they were analogous? Joseph A. Spadaro (talk) 15:35, 2 June 2015 (UTC)

What you call a "regular airplane" is an airliner: a large jet flown by an Airline Transport Pilot, operating under very strict regulations and company policies. These large aircraft are massive - they have a lot of inertia - and they are engineered and operated for the utmost stability.

Small general aviation aircraft typically fly in accordance with different rules and regulations. They are engineered to be light and maneuverable. They frequently maneuver for navigation and traffic avoidance, and to avoid weather, in ways that large commercial airliners do not. These type of aircraft operations have more in common with NASA's "vomit comet" than they do with airline transport: even down the to applicable regulations! (Well, at least that was the case when the aircrafts were operated by NASA. As of 2014, Zero Gravity Corporation has privatized this service and operates as a Part 121 operation, just like a commercial airline... I can rail against the regulatory implications of the privatization and commercialization of aerospace research at some other time. At present, the "Vomit Comet" is an airline for regulatory purposes, which means, among other things, that its maneuvers and operations and its safety margins are more rigorously constrained than those of a small GA airplane!)

A small aircraft can easily achieve 0G for short durations. In severe turbulence, the crew and passengers may oscillate between positive and negative G and each time they cross the 0 point, they will actually, really, seriously experience a moment of weightlessness. Nimur (talk) 15:49, 2 June 2015 (UTC)

@Nimur: So, for all practical purposes ... you are saying that the JFK small plane is more comparable to the vomit comet, than it is to a regular passenger airliner. Right? Joseph A. Spadaro (talk) 15:00, 3 June 2015 (UTC)

Let me express my intended meaning more precisely. You are probably familiar with commercial airlines; but the "ride" and "feel" of a commercial airline is not a good comparison to the "ride" and "feel" of a small general aviation airplane. Most Saratoga pilots do not fly zero-G parabolas; the Piper Saratoga is a "normal category" aircraft. However, even during normal operation, maneuvers in such small planes can feel more dramatic. Weather effects are more pronounced. Unlike large jet operations, most general aviation occurs in the troposphere, as opposed to the stratosphere, "above the weather." GA planes have a lot more wobbles.

So, when we compare operations, we can find lots of similarities and differences. My point is that your experience on a jet liner is not a great reference-point, because those planes are huge, stable, and flown incredibly conservatively. Nimur (talk) 16:25, 3 June 2015 (UTC)

@Nimur: OK. Thanks. Great. Excellent points. I was indeed basing all of my frame of reference on big, commercial airliners. I never stopped to think about the differences between the large commercial airliners and the small Kennedy-type of Saratoga plane. Indeed, there must be many differences. And the "ride" would be quite different. I just never thought of that detail. I just hear the word "plane" and my mind immediately clumped them all into the same category, without really thinking it through. Thanks for the detailed explanation. Joseph A. Spadaro (talk) 22:36, 3 June 2015 (UTC)

Just out of curiosity Nim, you seem like an experienced aviator of some sort. The accident report for John Juniors ill-fated flight states "The noninstrument-rated pilot obtained weather forecasts for a cross-country flight, which indicated visual flight rules (VFR) conditions with clear skies and visibilities that varied between 4 to 10 miles along his intended route. The pilot then departed on a dark night." In your opinion, if he was IFR rated, do you think there would have been far less chance of the accident occurring at all ? Or would have made it no problems even ?

I don't think my opinions belong on Wikipedia, as tempting as it is for me to offer them. I would prefer to provide factual references. A great website is FAA Safety: Safer Skies Through Education. Read it often.

Perhaps this accident was caused by bad luck. The Airplane Flying Handbook does not contain any mention of "luck" or "chance," but it has an entire chapter on decision-making. And a brochure. And an Advisory Circular. And another entire chapter in the PHAK.

Aviators can not plea-bargain their way out of bad situations when the weather sours or the equipment malfunctions by appealing to "luck" or "fairness." They must be prepared to deal with bad luck and incredibly improbable chances. Extra training, including an IFR rating, is one among the many tools the aviator may draw from to prepare for adverse situations. And, as the Pilot's Handbook of Aeronautical Knowledge says, sometimes the best way to reduce risk is to simply choose not to fly.

Many experienced aviators make good decisions and still end up as a scorch mark in the desert or splash down as fish food. Aviation is an inherently risky activity.

Nimur (talk) 06:26, 3 June 2015 (UTC)

Indeed, it is risky, even being in a fast jet during peacetime (let alone war) with an ejection seat is no guarantee of safe egress and survival. As you inferred, looking back in hindsight, the most prudent decision seems to be to have delayed the flight until the next day. Thanks for the links! Ironmungy (talk) 09:15, 3 June 2015 (UTC)

Thanks, all. Quite an interesting and informative discussion. Thank you! Joseph A. Spadaro (talk) 15:04, 3 June 2015 (UTC)

Soil mech

In soil mechanics, how do you know when to use the submerged unit weight and when to use saturated unit weight when calculating earth pressure? — Preceding unsigned comment added by 194.66.246.51 (talk) 13:51, 1 June 2015 (UTC)

Can you re-freeze food after it has thawed out in the refrigerator?

Say that I have frozen food in the freezer (maybe hamburgers or steak or whatever). I want to defrost it, so I place it in the refrigerator for a day or so. Then, the next day, I decide that I want to eat something else (and not the hamburger meat or the steak that I had defrosted). So, can I place the now-defrosted meat back into the freezer, to have it frozen again? Or should I not do that? I looked this up on the Internet with a Google search. Some people say "absolutely not, it's dangerous and can lead to food poisoning and salmonella". Some people say "it's perfectly fine and people do it all the time". So, I am not sure what to believe? 2602:252:D13:6D70:9DA1:666F:A7B5:2BD3 (talk) 15:55, 1 June 2015 (UTC)

It is safe to refreeze thawed meats, though the freezing-thawing-freezing process may degrade the quality of the meat, affecting it's palatability. The caveat is that the thawed meat should have never been allowed to enter the "danger zone" for food-safety purposes, that is meats should not be thawed in an environment where they are allowed to get above 4 degrees C (40 degrees F). If they have been thawed above that temperature, the meat should not be refrozen, as any pathogens that may have colonized the food at the unsafe temperature may not be eliminated by the refreezing process. --Jayron32 16:16, 1 June 2015 (UTC)

Just to clarify, if you left it about 4 degrees C: The refreezing does not make the food unsafe. It just doesn't reset the clock, that's all. If your choice is refreezing or leaving it in the fridge for an extra week, for sure refreeze. The freezer stops the clock, it doesn't reset it. Ariel. (talk) 17:38, 1 June 2015 (UTC)

Thanks. So am I correct to assume that the average refrigerator is set to a temperature that avoids the "danger zone"? 2602:252:D13:6D70:D2C:6172:6309:7E8 (talk) 20:10, 1 June 2015 (UTC)

Technically it's more delay than avoid. But in the typical way the word "danger zone" is used to refer to food: yes, the refrigerator avoids it. Ariel. (talk) 20:33, 1 June 2015 (UTC)

And if it's been thawed but below 40°F for long, then there will be some bacterial growth. The total time it's been in the fridge needs to be considered, before the first freezing, between freezings, and after the last freezing. The problem is that once it's been in the freezer for a month, you may completely forget about it already having been refrigerated for a fair amount of time, and not figure that in. Of course, if you use common sense, and throw out anything that looks or smells bad, and cook any meat thoroughly, then you will minimize the risk.

Suggestion: The usual reason for thawing and refreezing is that it was frozen in too large of a batch to use at once. Just subdivide food into smaller batches before you freeze it, to avoid this problem. Another reason for refreezing is if the frozen food thaws on the way home from the grocery store. Packing all the frozen food together, surrounded by refrigerator temperature food, in a cooler or thermal bag, can help prevents this.

Also note that some foods, like bread, are actually damaged by the freeze/thaw process directly, rather than by bacteria (parts of bread become stale or soggy). Fruit and some veggies will tend to become mushy, due to breaking of cell walls. This is OK if you use them in dishes where mushy is expected, like a stew or maybe berries with ice cream. But, if you need firm veggies or fruit, you want to avoid refreezing (and flash freezing is really needed to keep them crisp during the first freeze). StuRat (talk) 16:29, 1 June 2015 (UTC)

Thanks. The issue was simply that I planned to eat the food the next day. When the next day rolled around, my plans changed. So, I realized that I would not be eating the defrosted meat that day. (And I was not sure as to when exactly I would ever get to it.) So, I wanted to just throw it back in the freezer. As opposed to letting it sit in the refrigerator for who-knows-how-long. 2602:252:D13:6D70:D2C:6172:6309:7E8 (talk) 20:08, 1 June 2015 (UTC)

Yes, put it back in the freezer. Doing so will preserve it longer than leaving it in the fridge. Ariel. (talk) 20:33, 1 June 2015 (UTC)

And you can repeat this several times? Or only once? 2602:252:D13:6D70:CCFE:173D:7A3:CC25 (talk) 21:49, 4 June 2015 (UTC)

Paper v Plastic v Reusable cups

I wonder if there has been any updates to Martin Hocking's research about the relative energy uses of these three things? Or if there are studies that suggest his conclusions are wrong or outdated? My cursory googling primarily yields results comparing plastic to paper, or finds conclusory sites demanding we all have reusable mugs. The research seems pretty damning to me--who uses reusable mugs enough and cleans them efficiently enough to justify their use? But I'd like to see if there is any other research before I imperiously respond to people about my paper Starbucks cup. Thanks! ÷seresin 23:55, 1 June 2015 (UTC)

I found this, which also considers CO₂ and hand washing and uses more modern figures on dishwasher efficiency. It says that hand washing is much more efficient than using a dishwashing appliance (contradicting the PDF you linked). It points out that the break-even point is very sensitive to the assumptions. It still doesn't consider any costs other than energy or CO₂, such as other pollutants produced in manufacturing, the problem of plastic litter, or the fact that styrene is classified as a possible human carcinogen (though so is coffee). -- BenRG (talk) 18:03, 2 June 2015 (UTC)