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In my misconceptions articles I intentionally don't correct grammatical
mistakes. I do this
first because most grammatical mistakes don't produce science
misconceptions. If an "error" doesn't cause confusion and misconception,
then it's usually not an error worth discussing. And many educational
involve simplifications which nitpickers could attack as "errors", for
example the idea that atoms are like solar systems. But if such "errors"
do promote understanding, but don't create nearly-incurable
misconceptions, then they aren't errors of consequence. But second... Many years ago I realized that if we hide misconceptions
found in books, we cannot learn from them. DON'T TRUST MY WEBPAGES, and
please trust textbooks even less. Don't trust ANY authority 100%. Trust
them in proportion to how good a job they've done in the past, but always
maintain your distrust. But if we can't trust authoritative sources, what
then? WHAT THEN?
Exactly. That's the point.
First stop trusting authority... then cast about for another option.
What is that option? I'm not going to say. EVERYONE MUST FIGURE IT OUT
THEMSELVES. That's the whole point in refusing to trust authority. But
I'll give a hint. When reading any textbook,compare it with what you
already know in order to look for contradictions. You'll find lots Also
look for self-contradictions, fuzzy areas, egoism, politics, and hypocrisy.
Authors are very human, and textbooks contain these problems. The good
ones will reveal them intentionally, the bad ones will hide them and
attempt to be a "Voice of God Above." So go learn about their authors,
or at least make plenty of
dark speculations. Critical thinking requires loads and loads of criticism
and stiff refusal to accept what you're being taught.
(That's why critical thinking is not taught in K-12. Students who
distrust and question their teachers require applause, but try to find a
school system which doesn't punish such things.)
In my misconceptions articles I intentionally don't correct grammatical mistakes. I do this first because most grammatical mistakes don't produce science misconceptions. If an "error" doesn't cause confusion and misconception, then it's usually not an error worth discussing. And many educational techniques involve simplifications which nitpickers could attack as "errors", for example the idea that atoms are like solar systems. But if such "errors" do promote understanding, but don't create nearly-incurable misconceptions, then they aren't errors of consequence.
But second... Many years ago I realized that if we hide misconceptions found in books, we cannot learn from them. DON'T TRUST MY WEBPAGES, and please trust textbooks even less. Don't trust ANY authority 100%. Trust them in proportion to how good a job they've done in the past, but always maintain your distrust. But if we can't trust authoritative sources, what then? WHAT THEN?
Exactly. That's the point.
First stop trusting authority... then cast about for another option. What is that option? I'm not going to say. EVERYONE MUST FIGURE IT OUT THEMSELVES. That's the whole point in refusing to trust authority. But I'll give a hint. When reading any textbook,compare it with what you already know in order to look for contradictions. You'll find lots Also look for self-contradictions, fuzzy areas, egoism, politics, and hypocrisy. Authors are very human, and textbooks contain these problems. The good ones will reveal them intentionally, the bad ones will hide them and attempt to be a "Voice of God Above." So go learn about their authors, or at least make plenty of dark speculations. Critical thinking requires loads and loads of criticism and stiff refusal to accept what you're being taught.
(That's why critical thinking is not taught in K-12. Students who distrust and question their teachers require applause, but try to find a school system which doesn't punish such things.)> What rules of English or mathematics provide for a number less than
I too have a large nitpicking side, one which wants to make errors vanish everywhere. But if (for example) the K-6 textbooks were all repaired, then they'd look like the "Voice of God," and the public would unwisely start trusting them as authorities. In other words, the sad state of K-6 textbooks is a goldmine for true learning, and for teaching the skill of Thinking.> Mis-using the plural so, is sloppy mathematics and indicative of
> intellectual laziness.
Or it's a dastardly plot crafted intentionally in years past!
But you're right. I *am* intellectually lazy. Rather than go and fix my grammar, I'd insteadcome up with a huge tortuous explanation for why the errors should stay. And about projecting a facade of superior accuracy: instead I follow the lead of physicist R. Feynman, who delighted in preserving his Heavy Bronx Accent. Those who take facades seriously will learn a lesson when they meet a famous nobel laureate physicist who sounds like a NYC taxi driver. And those few who practice going past the surface are rewarded when the surface does not match what's hidden within.
Bill Beaty <billbatxxxxeskimo.com>
Seattle, USA - Wednesday, December 29, 2004 at 12:35:51 (PST)
Grade school and even high school science books "prove" the contents of air to have 20% oxygen by placing a burning candle in a plate full of water and putting a glass atop it. Soon the candle burns itself out and water rises inside it. They say "behold, for the candle burned the oxygen, and since water rose at 20% of the glass height, it means there's 20% oxygen in the air, because that gas is gone from the air!"
Unfortunately, it's the wrong explanation. As oxygen burns, the volume occupied by the oxygen does not just vanish, it is instead replaced by equal amounts of carbon dioxyde.
The reason that the water rises in the glass is that the candle HEATS the air in the glass, and some of it escapes from under the glass, thus explaning the bubbling you see in the water as the candle burns. When the candle burns itself out, the air still trapped inside cools down and contracts again, syphoning in a certain volume of water to make up for lost volume.
This would explain why the water rises suddenly AFTER the candle burns itself out, instead of rising steadily from the instead the glass is placed atop the candle. The 20% volume occupied in the glass by water is not a direct reflection of oxygen contents in air, merely a concidental amount.
It's been a pet crusade of mine to see scientists and mathematicians follow ALL the rules that apply to their discipline. The problem is identified with classical clarity by; "You want a value between 0.1 farad and 0.5 farads." to be found in your "Lemon Battery" article. What rules of English or mathematics provide for a number less than unity or one to be assigned a plural form? It is equivalent to expressing the term "half a loaf of bread" or "a half-loaf of bread" as "half a loaves of bread" or "a half-loaves of bread". Properly the farads should be expressed as "0.1 farad and 0.5 farad". Conversion of the terms to fractions illustrates the point; One-tenth farad and one-half farad. There is no question of the plural being used in either of these cases. Mis-using the plural so, is sloppy mathematics and indicative of intellectual laziness.
Warren Glover <thextropiansatoptusnetcom.au>
Sydney, NSW AUSTRALIA - Tuesday, December 28, 2004 at 15:25:27 (PST)
I tried to write you before but i still don't see an answer in decomment book. So here is my entry again: There is an error about weightlessness in the text you wrote about gravity (http://www.amasci.com/miscon/miscon4.html#grav)
The first part of the article is correct but at the end you mix up "weight" with "gravity".
"You shouldn't say that astronauts are "weightless," because if you do, then anyone and anything that is falling would also be "weightless." When you jump out of an airplane, do you bcome weightless? And if you drop a book, does gravity stop affecting it; should you say it becomes weightless? If so, then why does it fall? If "weight" is the force which pulls objects towards the Earth, then this force is still there even when objects fall."
Gravity is the force of the earth pulling you down (it is the force between masses according to Newton's law Fg=G (M1 M2)/sqr(R)) When you're standing on the ground you don't fall because the ground pushes back to your feet. When there is no acceleration (up or down) this normal Force is just as big as the gravitational force thus the result on your body is zero (F=m x a; F=0 -> a=0).
According to Newtons third Law all Forcescome in pairs with the same size and opposite directions. (F action = - F reaction) Your weight is the Force opposite to and of the same size as the normal force hence: without acceleration in vertical direction your weight has the same size and direction as the gravitational force BUT THEY ARE NOT THE SAME!
When you are on a scale in an elevator the scale measures your weight. When elevator is standing still your weight is the same as the gravity. When the elevator is accelerating upwards your weight increases (the net force (F normal - F gravity) on your body accelerates your body upwards as well). When the elevator accelerates downwards your weight decreases (the net force (F gravity - F normal) on your body accelerates your body downwards as well). When the elevator falls down i.e. accelerates down with 9,8 m/(sxs) you fall along with the elevator. The net force on your body is then formed only by gravitation. The normal force on your body bcomes zero hence your weight is zero but the gravity is not!
I hope I wrote down something you can understand because I don't write in English very often.
Why is the water in the Carribean more blue than the water in the Atlantic Ocean in New England. [ I've heard two reasons for this. For one thing, Carribean water near the shore has white sand sea bottom, while cold northern waters tend to have olive drab algae-covered bottoms. (If you hold white paper behind your cup of dyed fluid, the color looks far brighter.) Second: warm ocean water is full of viruses, and they keep the population of single-cell organisms down. In other words, warm tropical waters are nearly transparent, while cold northern waters are full of suspended algae and bacteria. -billb]
white river jct, vt USA - Wednesday, November 24, 2004 at 16:31:22 (PST)
Dear Mr. Beaty: I wonder if you couldcomment a little on my post at
Hi Bill thanks for a good, clear informative site. I have many misconceptions about science, most of which you have calrified. Studying "baffled" by Keith Waterhouse and logged onto your site to help me out. Thanks for your help. From Josie 3 Nov 04
Josie Beamish <EDCJBEA1atlivjm.ac.uk>
Liverpool, England - Wednesday, November 03, 2004 at 13:13:03 (PST)
if i say i'm going to create low pressure on top of a wing to make the high pressure that is above the low pressure above the wing, and make the high pressurecome down, is saying the same thing as creating low pressure above the wing to make the wing go up. by expirement i have found that there is high pressure above the low pressure above the wing. this pressure is eqal and opposite the high pressure under the wing. since it is equal and opposite the net effect is no lift because of pressure differences via, Bernoulli principle. i once believed planes flew because of pressure differences above and below the wings. i now know planes fly because of momentun transfer between a fluid and a solid. exactly how this takes place i don't yet understand. i realy wished i did. mike
mike g <mdgenereauxatyahoocom>
Las Vegas, NV USA - Tuesday, November 02, 2004 at 16:47:25 (PST)
As you state, IR does't heat things because it is a form of heat. Likewise it doesn't heat particularly well because it is a 'very bright' light. Heat is the vibration of molecules. Some frequencies interact with specific molecules better than others. Consequently, one should consider the frequency as well as the intensity.
Roger Thompson <thompsrcathotmailcom>
Alvin, TX USA - Tuesday, October 26, 2004 at 13:39:33 (PDT)
Great to see so many false science assertions debunked - epecially the air balloon which has annoyed me for years.
Here is another which appears in many science books and is slavishly taught by teachers but is just plain wrong.
The demonstration is to float a candle on water and then cover it with a jam jar. The water pulls up inside the jam jar as the volume of gas around the candle decreases so this is given as proof that the candle is using up the oxygen in the air. I have even seen it used to measure the proportion of Oxygen in air.
Firstly a candle gives off (almost*) as much CO2 as it uses Oxygen so the volume should not change. Secondly, the observant will notice that the water does not rise until after the candle has gone out. What actually happens is that the heat of the candle expands the air which for a few seconds bubbles out of the jam jar - generally unnoticed. Then the flame expires due to lack of Oxygen and the water rises as the air in the jar cools and contracts. (I try to avoid saying the air is 'sucked in' for fear of getting into more controversy about air pressure and sucking vacuums - but I digress!)
In my years as a science teacher (Biology!) I have seen many staff and a good few books misunderstand this simple demo. Please feel free to add it to your website.
*As a humble Biologist my chemistry is a bit rusty but I recall that Carbohydrates when burned give off as much CO2 as they use up O2 (Respiratory Quotient = CO2/O2 = 1). Fats give off less CO2, (RQ = 0.7). I don't know the position with Candle Wax but beingorganic and not unlike Fat it may be that it has an RQ of less than 1. If this is the case it might be possible to conduct this experiment in a sealed chamber so that no gas escaped during the expansion phase and the gas volumes could becompared before and after the experiment when the gases had returned to room temperature. This would at perhaps show that some gas had been consumed but this is a long way from the amateurish demonstration which forms the basis of many students learning!
Excellent website...it is good to souind off against the bad science which abounds. If one more child tells me that they are going to put volts through a wire... !
Freddy Janse wrote: > Hello William, > > Thank you for answering my mail! > > The error on weightlessness is in indeed the text you wrote about gravity > (http://amasci.com/miscon/miscon4.html#grav) > The first part of the article is correct but at the end you mix up "weight" > with "gravity". > > You wrote: > "You shouldn't say that astronauts are "weightless," because if you do, then > anyone and anything that is falling would also be "weightless." When you > jump out of an airplane, do you bcome weightless? And if you drop a book, > does gravity stop affecting it; should you say it bcomes weightless? If so, > then why does it fall? If "weight" is the force which pulls objects towards > the Earth, then this force is still there even when objects fall."Actually the situation is similar to the one with the term "electricity." There is no single right answer because there are multiple conflicting definitions of the the "weight" in physics texts.
You're no doubt aware that some authorities define weight as mass, and they
measure weight in units of pounds or KG! This usage is so widespread, and
takes place at such high levels of society that we can't simply declare it
to be wrong. That never works. And besides, if the people who say that
weight is mass are in the majority, they could even declare us to be
wrong, and force us to capitulate because of our minority status. Heh!
Arguments about "weight" versus "gravity" bring up issues identical to
the "weight" versus "mass" problem.
I've seen several contradictory definitions in textbooks. For example,
I've seen "Gravity" defined as a field rather than a force, while the
attraction force created by gravity is then called "weight." (Note that
if gravity is a field, then it cannot be a force, since "fields" can exist
in empty space with no forces present. Forces only arise when a mass is
present within the gravity field.)
As you said, there are TWO force-pairs here: first, the purely gravitational
net-force existing between all the atoms in the Earth and all the atoms in the
object in question. And if the object is not falling freely, there is a second
force-pair between this object and the surface upon which it rests. This
second force-pair is electrostatic (caused by strained chemical bonds in the
object and in the floor,) and this force vanishes when the object falls freely.
Physics teachers say this:
"Weight" is what scales measure... but this statement doesn't separate the downwards gravitational force from the downwards force against the floor. In other words, if the scales are not at rest but accelerate vertically, do they still measure the object's weight? If the whole floor is accelerating, are the scales measuring the real weight, or should we stat that this acceleration produce measurement inaccuracy?)
You no doubt can find websites which support your definition. Here are some
which support the opposite one, where your "gravity" is called "weight:"
http://scienceworld.wolfram.com/physics/Weight.htmlWhy does an object fall? According to the above sources, we should say that objects fall because of their weight; their weight-force pulls them towards the Earth, and their weight is determined by mg alone and does not change if the object happens to accelerate vertically or fall freely. On the other hand, according to your definition of "weight," an object's weight depends on its acceleration, and the reason it falls towards the Earth is NOT because of its weight, since its weight entirely disappears during free fall.
Here's one page that discusses the issue, and the author states the truth:
the word "weight" has two conflicting definitions:
Here's another page which notes the conflict, but then tries to choose a
"single right answer":
USA - Friday, October 08, 2004 at 14:14:49 (PDT)
Maybe your readers can respond to this: Of recent interest to
government and scientists (at least here in Australia) is the contribution
to greenhouse of methane production by impolite bovines. I've long
believed that burning fossil fuel contributes to greenhouse because it
releases carbon that has long been trapped, but burning wood does not
contribute (in anything other than a short term) because the carbon in the
wood is still in the biosphere, thus not trapped. In the same way, eating
grass and breathing out CO2 doesn't add to the carbon load in the
atmosphere because the CO2 is reabsorbed by new plant growth. The methane
issue bothers me though - doesn't it fit into the same category as
breathing out CO2? Sure, methane isn't CO2, but in the atmosphere
(especially the more energetic layers of the atmosphere) wouldn't it
simply react with atmospheric oxygen to the more chemically stable state
of water and CO2 - with the CO2 simply being reabsorbed in new plant
growth? So, is the scientific desire to develop cows with better manners
just another furphy?|
Alan Whyborn <alan.whybornateq.edu.au>
Hervey Bay, Qld Australia - Thursday, October 07, 2004 at 02:47:53 (PDT)
I wrote you acomment about weightlessness and gravity because there are some errors on your site concerning these subjects. Thecomment was written in june but it is still not placed at the site. Was thecomment lost or don't you read thecomments any more? Please let me know something!!
Freddy Janse <F.Janseatdr-knip.nl>
Helmond, netherlands - Saturday, October 02, 2004 at 02:48:25 (PDT)
"In truth, n/(small number) equals a large number, and n/0 is not a number, it's infinity."
Sorry for mycomplaint but although it's a fact that
If your statement was correct simple algebraric rules would break since it would follow that
0 x infinity = n for any value of n and so all numbers are equal.
Actually n/0 is undefined for all n
Should I start a mathematics misconceptions page?
By the way thanks for your contributions to good science. It seems to me that pure maths is easy, but reality is infinitelycomplex (or at least it tends to be.)
I Love your site and have spent far too much time enjoying it. Re: the ice skate piece. I checked the "Bad Chemistry" article on ice skating to and found that there seems to be a basic misunderstanding about skates. I don't doubt that the slipperiness of ice is due to the thin molecular layer of water at the surface, but it's important to know that a skate blade is neither flat in length nor width. From front to rear skates have a radius (I think of about six feet) One can feel the rocking when you stand on skates. Also the blade itself is hollow ground so that at any given time the skater's weight is concentrated on fairly small knife edges; a much smaller surface area than the simple calculations of length times width of the blade. I bet the PSI is pretty high. It'd be neat if someone morecompetent than I could do the math. I'm glad to contribute my nitpicking. Keep up the fine work. Bob
Bob Havira <robert.haviraatwmich.edu>
Portage, MI USA - Wednesday, September 29, 2004 at 07:08:26 (PDT)
Is it true that the sun rises exactly in the east and sets exactly in the west every day?
Boston, MA USA - Monday, September 20, 2004 at 16:14:20 (PDT)
hey there, i'm so glad i found this page. i'm a student that doesn't idolise pop stars and actresses.. but people like you -- for challenging ideas that everyone just readily accepts, for daring to be different and seeking the truth. but i would like to know the answer for the question posed by this man on 4th Feb 2004, about the hindenburg disaster and iron oxide and aluminium powder being extremely flammable, hence causing the airship to go up in flames. could you tell me more bout that?
Yi Lin <chonyilinathotmailcom>
singapore - Saturday, September 18, 2004 at 12:44:21 (PDT)
some interesting ideas, some of which sound good and plausible, but doesnt seem to explain some observations that i have concerning what makes flight possible.
- balsa rubber band planes, while the wing is flat, it is curved, and the
distance across the top isnt the same as that of the bottom. traced with a
finger, it cant go though the wing to follow the shortest path, it must
follow across the top to get to the trailing edge, unlike the case at the
bottom, where your finger can go straight to the trailing edge from the
leading edge.paper aircraft wings glide, not generating lift, because it
traps/resist the downward motion of the body, like an inefficient
parachute. (flying squirel as example)everything else that is designed and
manufactured to fly from r/c aircraft,the wright flyer and on to the space
shuttle has been built with a leading edge thicker that that of the
trailing edge, and/or some degree of curvature for its wing.from a design
standpoint wouldnt it be easier to design a flat wing for all aircraft?
there must be some reason as to why designers havent done so from the
1900s on to now.and that reason must be insufficent lift production.
-thicker,more curved airfoils = more lift. yes fighters have really thin
,symetrical wings, and mustcompensate by having a higher takeoff speed to
generate the necessary lift for takeoff. and they can fly upside dwn, but
as mentioned in an usaf airshow manual (which for the life of me i cant
find now) which describes the procedures/maneuvers for the pilots, they
have to "apply needed backpressure" to "maintain a level attitude".
meaning he/she uses the rear elevators to push/pull the nose of the
aircraft up, thereby recreating a positve angle of attack for the leading
edge of the wing.
- the effect of icing on an aircraft wings leading edge iscompletely
ignored. something important must take place at the very front that the
accumulation of ice deprives from an wing in flight that severly
diminishes the amount of lift availible.(remember thecommercial airliner
that crashed after takeoff into the potomac river some years ago?that was
blamed on wing icing, something every pilot training textbook warns
strongly against).if lift is solely the result of air impacting the bottom
of the wing and whatever "magic" occurs over the top of the wing from air
circulation, this passenger jet wouldnt have gone down.
-the bottom of the wing of the cessna 152 that i used for pilot training
was indeed flat, and the top highly curved and thick, meaning high lift
and relatively slow takeoff speed
-from various observatons of a/c taking off, from passenger jets here at
RDU, to C-141's and c-130s at pope AFB, to u-2s at kadena AB, as an
aircraft reaches takeoff speed, and not before this speed, nothing
happens, then at takeoff speed, you see the wing tips bend upward as the
wing finally develops enough lift to ovecome its own weight, then enough
lift for the rest of the plane and its cargo, then the aircraft rotates
upward and lifts off.
this site puts alot of things into perspective.
Anna Masala <blog.funnyjunkcom/blogs/Express/>
Danville, Il USA - Sunday, September 05, 2004 at 12:58:06 (PDT)
You are so right about the lens. i mean if the light from the images were flipped OUTSIDE the lens, then i would see it right side up, AND upside down if i moved the lens closer towards me and farther away! very true!
Danville, Il USA - Sunday, September 05, 2004 at 12:56:58 (PDT)
I just wrote an email to our state Department of Ed because on their site they have a model astronomy lesson that states:
"Show how the
moon orbits the Earth and how sometimes the Earth is between the sun and
moon, casting a shadow on it. This may be seen as the phases of the
A great site
vandi mugu guyman <vandiwaleatyahoocom>
ac, md USA - Monday, August 23, 2004 at 02:59:10 (PDT)
I am not a scientist. I'm a musician and a mom. I found your site because I was doing a science experiment with my son where we made a coil spin with a magnet and a battery. Our first attempt was not succesful because we had not made the coil well. I started wondering why the wires had to be in a coil. I didn't find the answer to that question but I did learn a lot from your site which helped me understand "electricity" better.
I have a couple of questions. Please remember I am not a scientist! I'm sorry if I sound really ignorant.:
1) If a "bulb doesn't change electrons or extract stored energy from a battery," how does a battery get used up?
2) You mention that a "filled freightcar" analogy doesn't work for electrical energy any more than for sound waves. I've never been able tocompletely understand the concept of sound waves. Would an analogy of a bucket brigade work for sound waves? The air particles would then pass the sound vibrations from one to the next so that it reaches the ear at the speed of sound.
3) Why do the wires have to be in a coil to generate electricity?
I read about your site on a homeschool loop. This is yet ANOTHER reason why we homeschool. However, please take the time to check your links - a number don't go anywhere (disappointing). Nevertheless, it's a great site. Keep up the good work!
Rochester, NY USA - Tuesday, July 13, 2004 at 19:42:06 (PDT)
Your statement of Newton's third law of motion is not accurate. The law states "When a force acts on one body, an equal and opposite force acts on another body". This emphasizes the fact that there are two bodies involved.
Mungai Kihanya <mkihanyaatyahoocom>
Nairobi, Nairobi KENYA - Friday, June 04, 2004 at 00:39:57 (PDT)
I love your site! It's SO great! I am learning to be a Gr10-12 Science teacher and there are so many misconceptions to ovecome, but how? Your site is a saviour. Thank you very much! I shall let the others know .....
Laura Tew <lauraatyoungtewcom>
Johannesburg, South Africa - Friday, May 28, 2004 at 09:04:19 (PDT)
Found your site when searching for something quite else on the web. Isn't serendipity wonderful!
Intrigued by your discussion of the
density of air and the balloons on the balance. When I was about 12,
science teacher did two experiments to measure the density of air (instead
of acomparison balance, he used a very sensitive electronic balance from
the chemistry lab): One using a glass bottle and a vacuum pump, which
gave a density close to thecommonly quoted figure, and one using a large
plastic bottle which was crushed to expel the air, and which naturally
enough gave a density far too low. Only recently did I realise what
caused the discrepancy!
You mention the impossibility of using the
balance experiment under water to measure the density of water. I suggest
either (1) an empty balloon and a balloon full of air, and measure the
negative effective weight, or (2) a rigid bottle of water and an identical
bottle of air, measure the reduction in effective weight.
With regard to the Wing function, it occurs to me that although Bernoulli's equation does relate pressure change and fluid velocity, he never implied that increased velocity would couse reduced pressure. He only stated that they must coincide. Any specific volume of a fluid will only accelerate (change velocity) if the pressure on one side is different than that on the other. i.e. a pressure difference will cause a velocity change. I cant see any reason to assume that a velocity change could cause a pressure change, and because the opposite is true, I think it's rather unlikely. How could a velocity change be acheaved in a steady state flow gas system, without a pressure difference causing it in the first place?
I would state that all lift is a result of reaction only. If a wing accelerates air down, then the wing is pushed up. The resulting pressure changes above and below a wing are due to it accelerating the air mass. These pressure differences are the cause of the air increasing or decreasing it's velocity (As Bernoulli describes). Therfore the Bernoulli effect does not cause lift or play any part in its generation. The velocity differences are caused as the result of the pressure differences, which are the result of the lift generated.
On the point of upper wing lift Vs lower surface lift... There is pressure all over the wing surface. All the pressure is positive. There is no such thing as a negative pressure. The pressure above is less than the pressure below. Therfore the pushing force from below is more than the pushing from above. Lift is the difference between the two forces. Discussion about one Vs the other are not meaningful, as both are pushing against the wing surface and only the difference between them is lift.
Excuse me but I'm not bedazzled by your alternate explainations for things. [Yay! A thinker! Argumentative types who aren't simply rigidly prejudiced seem rare. -billb] Sure you've cleared up some mistakes but, as I am taking a grain of salt with some of your corrections I find that some of them are very hard to swallow. I've seen things like a potato battery actually working on a lightbulb... Maybe there was a capacitor involved but I don't recall there being one, I remember being amazed seeing it, so it's not something I orget too easily... [I'd love to find out about that. I built some of these batteries and tested voltage, series impedance, output vs. time, etc. I've never been able to light even the world's most sensitive bulb. PS, Someone said that some television science show (perhaps Bill Nye The Science Guy? I don't know...) performed this experiment, but since he couldn't get it to work, he cheated and used a hidden power supply. If such dishonesty actually happened, then perhaps this is the potato-battery you're remembering. -billb] and another thing... About your Zero gravity in space one... sure it makes sense about falling in the orbit of the planet, that is how orbit is achieved afterall.. but what about a shuttle that has escaped orbital velocity and is now drifting to the moon or mars... when does your correction bcome wrong? Because so long as the thrust is no longer pushing the shuttle it can obtain weightlessness, although it is not falling towards anything in particular. How can you explain that? [As long as a spaceship is in free fall, the ship and crew fall together and seem weightless. It doesn't matter whether the ship is in orbit around Earth, or is in a Transfer Orbit around two or more planets. To experience gravity-weight, the ship would have to rest upon a tower connected to a planet (or connected to several planets.) In order to experience zero gravity, the ship could rest on the top of a tower midway between earth and moon, with the location altered a bit so the attraction of the sun and other planets and the Milky Way galaxy was nulled out. THAT would be "zero gravity." But if a ship is not resting on a planet or on a plant(s) based tower, then the ship is in free-fall and the crew will seem weightless. -billb]
I do take this with a grain of salt and I appreciate you trying to correct
things... but like butchering Newton's third law is just not right.
[ Heh. Well, Newton wrote in Latin. The english
translation depends on the preferences of the translator. The common
translation is simply common, but that doesn't mean it's authoritive. If
we take the
latin for "an acting-upon" to mean Force rather than Action, then Newton's
3rd law comes out differently. But if we don't dare change what he said,
then we'd better be teaching the original latin. -billb] Sure
Newton's law may be better worded another way, but that's the way he
worded it and it DOES make sense, so long as you don't take it the WRONG
way. It may not be good to re-word it for people and then tell us that
your way is the way it SHOULD be worded... That's like re-writing Mozart
and saying that your symphony is more correct than his original.
Science should simply be taken less literally and if you're confused about something, either rely on quantum physics or test it out yourself. Quantum physics would tell us to keep all possibilities open until they have been extinguished. "IF a cat is put inside a box, the cat is both alive and dead until you can prove otherwise."
Taking ANYONE'S word for something is what we do as an act of faith. But really, who's to say anyone else is more correct than any other given person? I consider these "misconceptions" to be theories that **I** have yet to prove.
I am a Physics teacher at Akins High School in Austin Tx. Thanks for all of the interesting info about bad physics. I preach to my kids daily about the misconceptions that are made in Physics texts......sadly to say I have made a few as well. I have decided to create a project for my kids based of off your observations. I will let you know ho itcomes out.
Brad Milam <bmilamataustin.isd.tenet.edu>
austin, tx USA - Thursday, April 08, 2004 at 08:28:21 (PDT)
Re: How wings work.
Aircraft stay in the air because they accelerate enough air downwards to balance their weight. This is easily seen in helicopters, and even more so in VTOL aircraft. In fact it is easy to calculate the jet efflux of a Harrier (AV8A) and see that it matches the aircraft weight. This is accelerating the air from stationary to vertically downwards. Multiplying the air mass involved in each second by the exhaust speed gives the same numbers as multiply the aircraft weight by the acceleration due to gravity.
When flying horizontally the forces must also balance but the wing moves a much greater mass each second to a lower resulting vertical speed.
The bounelli effect works (where it exists) by producing a low pressure area above the wing. Air above that 'falls' into that causing it to add to the total mass being accelerated vertically. Thus a wing shape is more efficient than a symmetrical wing because it 'captures' a greater volume as it passes through the air.
Another aspect of flying is that it must also satisfy Boyle's laws of gas volume and pressure.
An aircraft's weight is ultimately supported by the ground. If we take an area of say one square mile then the weight of air above that is roughly 25 million tons at 14.7 lbs/sqin. If a 747 of 250 tons flies into that square then the total above that square bcomes 25,000,250 tons and the average pressure must increase to 14.700147 lbs/sqin. The only ways that the pressure between the aircraft and the ground can increase is if the temperature increases or if the amount of air is greater (Boyle). Thus it can be seen that the aircraft maintains this pressure by pumping air from above and around it into the space between it and the ground in order to produce sufficient increase in pressure to support its weight.
Of course air isn't an ideal gas and so the transfer of pressure differences is not instantaneous.
i amcompleting my pgce and as part of the university course we have to look at childrens misconceptions in science, focusing on particular topics. i am focusing on the misconceptions of mass and gravity. do you know any useful references?
uk - Tuesday, March 16, 2004 at 03:31:40 (PST)
Hi William, love your site. I have some questions that I hope you can answer: I've read your article "IN A SIMPLE CIRCUIT, WHERE DOES THE ENERGY FLOW?" Now! The earth has both a magnetic field and force fields (most likely created by the sun) Do you think one cancompare the earth and the sun to an electric circuit? Also in a molecyle there is a magnetic field and a force field. Do you think every molecule contain the potential for electric energy? And finally... do you know what it is, that makes the electrons spin (What kind of energy is that? Maybe Electrical?) I hope very much that you will find the time to (try to) answer my questions. Sincerely Nicolas
Nicolas Alstrup <nicolasalstrupatkabelnettet.dk>
Copenhagen, Denmark - Friday, March 12, 2004 at 04:53:12 (PST)
I am floored that in a mere hour of reading a few of your articles, I finally understand capacitors to a much greater degree. To continue with your explaination, it may be worth mentioning what the impact on the current/voltage is when the capacitor is storing energy (not charging!). Does it impede the electrical flow until it hascompletely stored it's energy? In my mind, I don't see it impacting it because you stated the same amount of positive goes on one plate as negative flows out from the other creating a difference between them. Does my question make sense? [ Yep. When charging, the capacitor acts like a resistor. The same charge flows "through," but there is a "friction" effect. And when discharging, the capacitor acts like a battery or like a negative friction which forces charges forwards rather than rubbing on them and slowing down the whole "belt" made of charges. Don't orget to think in terms of drive belts inside wires, belts with friction which slows down the whole belt, or with drive wheels which pump the belt into increasing velocity. -billb] Also, using your description, how do electrons continue to flow once the capacitor has reached capacitance? The "rubber plate" cannot continue to bend forever storing unlimited energy! [Right! But if you charge a typical capacitor to millions of volts, the "rubber plate" only deflects slightly. If we could sweep all the free electrons out of one plate and drop them into the other one, the force between the plates would be immense (like millions of tons), and the repulsion between the metal atoms would also be immense, causing the metal to bcome a gas. In real-world capacitors, the capacitor would short out from overvoltage before that "rubber plate" could be deflected more than a tiny amount. This fits in with the fact that electric current in wires is a very slow oozing motion. It takes many minutes of high current before an electron would move visibly forward along a wire. -billb] Can that explaination be worked into your iron sphere example? I've feel like I have 2/3 of the story and want the rest ;)
Thank you for saving me from my textbooks. Your thought process reminds me of R. Feynman and you are clearly influence by him as well. ;)
Dear friends, The "principle of equivalence" of the Geeneral Theory of Relativity is wrong! (see,www.tsolkas.gr), link:GALILEO and EINSTEIN are wrong! Thanks
Christos A. Tsolkas <tsolkas1atotenet.gr>
Agrinion, GREECE - Sunday, March 07, 2004 at 03:16:23 (PST)
Regarding air weight and balloons: Another problem worth mentioning. If you inflate a balloon with human breath andcompare its weight to an uniflated one, you are likely to be unknowingly influenced by all the water that is exhaled by humans which condenses right away and being condensed, doesn't really count as "air".
Another question: Would a single lemon electrochemical cell produce enough
current to deflect a standardcompass if bell wire is wrapped around the
[ I don't know, you'd have to try it. It probably
requires many, many turns of wire, so try some #30 gauge electromagnet
wire to start. -billb]
I am a former science teacher, UT student, and homeschooler. While looking for science books for my son, I found an error in the book _Bouncing_Science:_No_Sweat_Projects_ by Jess Brallier, A edition, ISBN 0-448-44088-1. It mentions that momentum is mass _plus_ speed, including the underlining of the word "plus." It is stated 3 times on two facing pages. I sent an email to the publisher, Planet Dexter, about it, but no response, yet.
Pam Crouch <jasonpamatswbell.net>
Pflugerville, TX USA - Tuesday, February 17, 2004 at 19:51:05 (PST)
Somewhere around here you note that science doesn't always base itself on or define itself by the scientific method. Yet it must be defined by something in order to categorize it in such a way so that it distinguishes itself from non-science. I think a good definition for "science" may be: logical analysis applies to observations/detected phenomena. The rest is methodology to establish accuracy.
[ Just search on "what is science?" and you'll find that the topic is hotly debated among the professionals. As far as I know, all the simple definitions have counterexamples which render them incorrect (being either fields of science which lie outside the definition, or non-science fields which fit the definition.) Beware of the classic mistake: definining Physics as proper science, then pretending that other fields of science are poor stepchildren of physics. Here's acommon definition: Science is whatever professional scientists agree that it is. -billb]
Benjamin Mayefsky <benji9877ataolcom>
Brooklyn , NY USA - Tuesday, February 10, 2004 at 20:11:52 (PST)
Airfoils by the reaction model - Some interesting points here, but I feelcompelled to disagree on one of them:
From an earlier post: "1. If the trailing edge of the airfoil does not deflect the air downwards, then the airfoil does not create a lifting force." - not (quite) true. Yes, the airfoil (as a whole) must have a net effect of deflecting air downward, but the trailing edge is not always the instrument of this deflection. It's quitecommon for the trailing edge of straight-across or 'plank' flying wings to be tilted up quite steeply, to bring the coefficient of moment to zero. This prevents the wing diving (as these aircraft have no tail section or delta). Even sharper trailing edge uptilts are used to produce negative coefficient of moment, which allow reverse-delta wings to remain stable. When flying, the angle of attack (of the whole wing) is clearly not large enough to turn the uptilt of the trailing edge into a downtilt. Of course, the camber and thickness of these airfoils are quite large near the front, allowing them to produce decent lift - only a fraction of what the same front section would if the trailing edge were level or tilted down, but a lot more than none. The point is of course that is is the net effect of the wing that matters, not any particular part (the 'trailing edge' theory has been somewhat overstated by you and others).
["Trailing edge theory" is overstated because it's a
central part of simplified "
circulation theory" appearing in introductory
The simplifed theory requires that there be no
detachment of flowing air from the surface, and that the trailing edge of
the wing be infinitely sharp. In that case the trailing edge
determines the location of the rear "stagnation point", which determines
the circulation, which entirely determines the lifting force. The leading edge
generates lift of course, but only because the trailing edge tells it to
do so, and the leading edge shape is totally irrelevant as long as no
stall occurs. But real wings don't have razor-sharp trailing edges, and
real wings are always partially in "stall," so the simplified theory is
only an approximation. -billb]
PPS As this is a moderated list, would it not make sense to add the
comments to the relevant pages?
Text books, and politics drive me nuts. Take the hiendenburg disaster. No chemist or anyone else in the universe has ever seen hydrogen burn with a bright red orange flame. Yet there in a modern chemistry book they show the airship on fire. No other hydrogen airships of that day ever burned that way. The hindenburg was painted with a coat of iron oxide for strength and aluminum powder for reflecting qualities. Iron oxide and aluminum powder is a thermit mix for thermit welding. It is also a rocket fuel. People of the day knew heads would roll if the disaster were blamed on the skin. Why do scientist still believe hydrogen to be to dangerous to use in airships? What about gloabal warming? Can science prove it. Is it fact or politics. I believe it politics. Scientist often follow politics.
Mike Genereaux <mdgenereauxatmsncom>
Las Vegas, NV USA - Wednesday, February 04, 2004 at 12:41:00 (PST)
I thought you site has lots of good information. Do you know anything about misconceptions children hold about animals? I am doing this as a topic for an elementary science class. Any information you have would be very helpful!
Shannon Osask <srosaskatsasktel.net>
Moose Jaw, Saskatchewan Canada - Thursday, January 22, 2004 at 15:49:04 (PST)
Hi Bill, Regarding the following page andcomment re gravity in space.
Your site states that a person 300 miles up on a ladder will weigh 15
percent less than on earth. The example given states that the 115 pound
person will weigh 100 pounds. This is incorrect. If we apply a
mathematical calculation we see that 15 percent of the total original
weight is (.15x115) or 17.25 pounds. To find the weight after gravity has
lesser effect on it we simply subtract our answer from the total. In
short, a person weighing 115 pounds on earth would weigh 97.75 pounds at
the top of the 300 mile ladder.