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        riddles >> easy >> Scientific Fallacies
        
(Message started by: Sir Col on Jun 19th, 2003, 12:35pm)
Title: Scientific Fallacies
Post by Sir Col on Jun 19th, 2003, 12:35pm
Incredible as it may seem, the following statements are genuine responses from students in a KS3 (key stage 3) science exam for 13/14 year olds in England.

(i) High temperatures kill enzymes.
(ii) Leaves are broad to help them to absorb more water.
(iii) There is no atmosphere on the moon.
(iv) You use a thermometer to measure the heat of the water in a beaker.
(v) Plants get good from the soil.
(vi) We can see the moon by the light it reflects from the sun and the stars.
(vii) Snow boards are broad to spread out the pressure on the snow.
(viii) There is no gravity on the moon.
(ix) Photosynthesis converts carbon dioxide into oxygen.
(x) Freezing food preserves food by killing the bacteria in it.
(xi) The mother's blood flows through the umbillical cord to the foetus.
(xii) Stirring makes the sugar melt faster in the tea.
(xiii) Particles in a liquid are further apart than in a solid.
(xiv) CO2 turns limewater milky.

Only one statement is correct. See if you can identify the correct statement and give a reason why each of the others are wrong.
Title: Re: Scientific Fallacies
Post by NickH on Jun 19th, 2003, 1:06pm
I'll go for...

::[hide]
(i) False; enzymes aren't alive. (But right idea; they are destroyed by heat!)
(ii) False; probably a botched reference to transpiration.
(iii) False, though there is very little atmosphere, certainly when compared with the Earth.
(iv) False; it measures the temperature.
(v) True; we don't normally refer to it as food, but surely they extract some nutrients from the soil?  That's not to negate photosynthesis, of course.
(vi) Almost true; drop the stars!
(vii) False; they spread out the force, thereby reducing the pressure.
(viii) False.  Irredeemably!
(ix) False; that's only part of the reaction.
(x) False; it slows down or stops their reproduction and metabolism.
(xi) False.
(xii) False, but it does help it to dissolve faster!
(xiii) False; needs some qualifications.  For one, it should be the same substance in each case!  Even then, and even when speaking of mean distances, there are exceptions, such as water and antimony.
(xiv) True; at least for CO2!

The last one is definitely true.  I also would say (v) is true.  Is that not the case?
[/hide]::
Title: Re: Scientific Fallacies
Post by Sir Col on Jun 19th, 2003, 3:05pm
Pretty good, NickH, but it's what I'd expect from you. ;)

I agree, (v) is a little contentious in that it is wrong based on how we interpret the meaning of food. Plants make their own food (sugars), so although they absorb minerals from the soil, what they actually 'eat' is the product of photosynthesis. You're right about the reaction with carbon dioxide and limewater in (xv), but the mistake, albeit trivial, was the use of superscript.

So which one is true?
Title: Re: Scientific Fallacies
Post by NickH on Jun 19th, 2003, 3:21pm

Quote:
but the mistake, albeit trivial, was the use of superscript.

I signified that by changing the superscript to a subscript!

If you force me to select just one, I'm really not sure.  Both (iii) and (ix) seem good candidates.  Photosynthesis does convert CO2 to O2, whereas the moon does have a wisp of an atmosphere, so, out of those two, I'll pick (ix).  

I wasn't sure about (xi) at first, but I think the foetus has its own blood supply; hence babies of HIV positive mothers can be born free of the virus.

(vi) is also almost true.  In fact, is it not true that at least some of the photons that strike the retina from the moon originated in a star (other than the Sun)?  And I think I've read that the retina is sensitive enough to detect one photon, so perhaps this is true.

So, on second thoughts, I'll plump for (vi) and (ix)!
Title: Re: Scientific Fallacies
Post by Sir Col on Jun 19th, 2003, 3:54pm
I think the objection to students writing, "Photosynthesis converts carbon dioxide into oxygen," is that the sunlight converts water and carbon dioxide into sugar and oxygen. The principle process is the conversion of carbon dioxide (CO2) into sugar (C6H12O6). The oxygen produced is a by-product of the reaction and comes from both the water AND the carbon dioxide.

I suppose that technically you're right about (vi)! It wasn't the one that I was expecting, which you have, in fact, discounted. I believed that the true answer was (iii), but I have just done some research and it seems that the moon does have a minutely thin atmosphere (around one million times less dense than the Earth).
Title: Re: Scientific Fallacies
Post by NickH on Jun 19th, 2003, 4:23pm
As regards (ix), I suppose how you judge the answer depends upon the question and the context.  If the question were "What is photosynthesis?", an answer of "It converts carbon dioxide into oxygen" would clearly be inadequate.  But, as a throwaway line, it's more defensible, as it's partly true.  But I agree it's not the truth, the whole truth, and nothing but the truth.

Interesting link: bad physics (http://www.badphysics.info/)
Title: Re: Scientific Fallacies
Post by Sir Col on Jun 19th, 2003, 4:56pm
That website is hilarious! Thanks for that, NickH.  ;D

It almost inspires me to do something similar for mathematics. However, having tried teaching using conflict methods: presenting something clearly wrong so that the students can comment on the error, it never fails to amaze me how they take it seriously and often they quickly write down the new 'clever' method. For example, I might say to a class, "Hey, I found a really neat way to cancel fractions. Look, 16/64=1/4, because you can cancel the sixes!" You can guarantee that, in an exam, one of the students will write some rubbish, like 12/24=1/4; and who says that students don't pay attention in class?
Title: Re: Scientific Fallacies
Post by Icarus on Jun 19th, 2003, 6:19pm
The problem with (ix) is that it says that CO2 is converted into oxygen. At face value, this would claim that carbon is turned into oxygen as well.

To me it shows a worse understanding of what actually goes on than such statements as (iii) and (v), or (x).

Since NickH left off the explanation of this one:
(xi) The foetus's blood flows through the umbilical cord to the placenta, where it picks up oxygen and nutrients that pass through from the mother's blood. The mother's blood never reaches the foetus, and the foetus's blood never contacts the mother at any place other than the placenta. (At least, when everything is functioning like it is supposed to...)

I also choose (vi) as correct (you could also put in twice reflected light from the earth - the largest illuminator of the moon after direct sunlight - but since it is sunlight in origin, this does not make the statement incomplete). Just because the contribution from stars is negligible does not mean it isn't there. In fact is perhaps "more there" than the moon's atmosphere.
Title: Re: Scientific Fallacies
Post by THUDandBLUNDER on Jun 19th, 2003, 6:38pm

Quote:
That website is hilarious! Thanks for that, NickH.

There is also http://www.ems.psu.edu/~fraser/BadScience.html
Title: Re: Scientific Fallacies
Post by Icarus on Jun 19th, 2003, 8:04pm
Concerning Nick's link - I found a lot of his "bad science" was more of what I would call "bad interpretation" on his part!

Some examples (there are more):
1) Centrifugal force - I too once proudly proclaimed that there was no such thing as centrifugal force. But even as he admits, it does exist. It is the reaction to the centripetal force. When you go around a corner, the car presses against you (centripetal force) and you press against the car (centrifugal force). Which do you feel? Action and reaction come together - you feel both - or you feel neither, because what you actually feel is the pressure changes resulting from the forces.
The concept of centrifugal force is misused, but when someone says that they felt the centrifugal force of a turn, they are not any more or less wrong than to say they felt the centripetal force.

2) It weighs "2 kilograms". Yes, kilograms are defined first as a unit of mass not force. However, the tie-in between mass and weight-due-to-gravity is so strong, and useful, that the "kilogram weight" has also been defined, as has the "pound mass". So it is not improper to say that something weighs 2 kilograms.
He could of emphasized the need to distinguish between the concepts of mass and weight, but instead he insists that the word kilogram can only be used for mass - and this is not true.

3) "Hydrogen is lighter than air" - I found this one particularly supercillious. When no set quantities are involved, "lighter" is always used to refer to density. So yes, hydrogen is lighter than air. His demand that it refer only to mass is ridiculous.

4) "Orbiting Astronauts are weightless" - Again, his objection depends on a specific interpretation of "weight". And his definition is not the one more commonly used in scientific discussions. He intreprets weight as the resultant force of gravity on the object. It is more commonly interpreted as the "downward" component of the action-reaction pair created when the object is pressed against something else (yes, I know this is not how you see it defined - but if you look closely, this is exactly how the word is used). Therefore scientists who know what they are talking about will tell you that an object in freefall is weightless.

5) "When a car breaks suddenly, the passengers are thrown forwards." Yes, they are - with respect to the car. He admits this, but fails to realize that there is nothing wrong with this point of view! It is in no way inferior to the "with respect to the earth" point-of-view.

To me, it is he who is committing "bad physics" here. Anyone describing this situation realizes (if they give any thought to the matter at all) that the "forward throw" is with respect to the car. But he is insisting that the "correct" description is with respect to the ground. And that is completely false. Both descriptions are equally accurate.

6) In a couple of his replies he puts forth his own fallacy: that when you close a circuit, all the electrons start moving at the same time. (And he says the same thing about water in a full hose!) Would that it were true! We could break that nasty speed limit Einstein imposed! The truth of course is that the electrons, and water, start moving with a pressure wave that travels through the wire (or hose).
The question is, for the wire, which way does the pressure wave travel: + to -, or - to + ?
Title: Re: Scientific Fallacies
Post by redPEPPER on Jun 20th, 2003, 7:38am

on 06/19/03 at 20:04:50, Icarus wrote:
6) In a couple of his replies he puts forth his own fallacy: that when you close a circuit, all the electrons start moving at the same time. (And he says the same thing about water in a full hose!) Would that it were true! We could break that nasty speed limit Einstein imposed! The truth of course is that the electrons, and water, start moving with a pressure wave that travels through the wire (or hose).
The question is, for the wire, which way does the pressure wave travel: + to -, or - to + ?

Pardon my layman's ignorance in the field but, how about both?  The wave just starts from the point in the circuit that connects last, and goes in both directions?  Just like water would do.
Title: Re: Scientific Fallacies
Post by wowbagger on Jun 20th, 2003, 9:04am
Just in case anyone cares about my opinion, I'd say statement (vi) is true.


on 06/19/03 at 20:04:50, Icarus wrote:
Yes, kilograms are defined first as a unit of mass not force. However, the tie-in between mass and weight-due-to-gravity is so strong, and useful, that the "kilogram weight" has also been defined

Has it? I don't know. Of course, people are reluctant to distinguish between mass and weight in everyday life. But how different is this from the temperature/heat issue?
Oh, and why do you consider this tie-in useful?

BTW, M-W (http://www.webster.com/) defines a kilogram as "1 : the base unit of mass in the International System of Units [...]; 2 : a unit of force equal to the weight of a kilogram mass under a gravitational attraction equal to that of the earth".
So what is the gravitational attraction of the earth? I suppose there is an accepted standard. :D
Sadly, the OALD (http://www.oup.com/elt/global/products/oald/lookup/) only refers to weight! :(
Title: Re: Scientific Fallacies
Post by James Fingas on Jun 20th, 2003, 10:19am
Actually, "centrifugal force" has a meaning--even a useful one. Let's say you were inside a gravitron (woohoo!) but didn't know it. You assume the inside of the gravitron is stationary, and as you walk around it you experience a force pushing you away from the center.

Factoid: inertial transformations don't introduce fictitious forces, but non-inertial ones do.

This is exactly centrifugal force: the fictitious force necessary to explain the motion of objects under the non-inertial transformation to a rotating frame of reference. So you could solve the "wrench in space" problem (sorry no link today) by assuming the astronauts were stationary and applying a centrifugal force to the wrench.

This also applies to people being pushed forwards in the car. This forward "force" is a fictitious force necessary to explain the motion of objects under the non-inertial transformation to an accelerating frame of reference.

So centrifugal force is a completely valid conceptual tool. It's easier to think of the gravitron not rotating and introduce centrifugal force than it is to think about what we're really doing.
Title: Re: Scientific Fallacies
Post by NickH on Jun 20th, 2003, 1:07pm

Quote:
Concerning Nick's link - I found a lot of his "bad science" was more of what I would call "bad interpretation" on his part!

Icarus, I agree with your criticisms, above.  I suspect the author is trying to lay the groundwork that is necessary to understand a more sophisticated approach.  For example, I think it's important to understand Newton's laws with respect to a fixed reference frame, before introducing the concept of fictitious forces, such as centrifugal or Coriolis forces.  At least, that's the way that seemed natural to me.

Having said that, I am uncomfortable with oversimplification, and I agree that the author has gone too far in places.

I must take this chance to mention one particular piece of oversimplification that I find annoying -- on another site: fearofphysics.com.  Take a look at Two pendulums pulled back different amounts (http://www.fearofphysics.com/Pendulums/pendda.html).  The page asks you whether two identical simple pendulums, one pulled back about 10 degrees, and one about 30 degrees, will have the same period.  The page actually goes to the trouble of telling you you're wrong if you select the correct answer!  It even shows you a little movie to back up the incorrect answer.  I don't think it would have taken too much trouble to show a movie which demonstrates the true situation.  Nice link: Large amplitude pendulum (http://hyperphysics.phy-astr.gsu.edu/hbase/pendl.html)
Title: Re: Scientific Fallacies
Post by Zeke the Geke on Jun 20th, 2003, 2:23pm
Just want to add my own 2 bits about xiv:

(xiv) CO2 turns limewater milky.

Limewater is an equilibrium between calcium carbonate, water, calcium hydroxide, and carbon dioxide:

CaCO3(s) + H2O(l) <---> Ca(OH)2(aq) + CO2(aq)

Calcium carbonate is actually "sparingly soluble" (meaning that no more than 0.1 g will dissolve in 100 g of water), so small amounts of aqueous CO2 will not cause the calcium carbonate to precipitate (form a solid).  At any rate, it is not the carbon dioxide which makes the limewater milky (at least not directly), it is the presence of the calcium carbonate which has this effect.
Title: Re: Scientific Fallacies
Post by Leonid Broukhis on Jun 20th, 2003, 3:20pm
I would classify most fallacies as linguistic, not scientific. An attempt to ignore laws of the language in analysing scientific-themed statements is a futile one.

To say "A kettle boils" is as correct as to say "I drink 3 cups of tea a day". Who would make it a point to say "I drink 3 cupfuls of tea a day", raise your hand.

To say "CO2 turns limewater milky" is as correct as to say "Cutting onions makes you cry". It is a common colloquialism to say "X does Y" instead of "X triggers a chain of events causing Y". There is nothing scientifically fallacious about it.
Title: Re: Scientific Fallacies
Post by Icarus on Jun 20th, 2003, 4:02pm

on 06/20/03 at 10:19:54, James Fingas wrote:
Factoid: inertial transformations don't introduce fictitious forces, but non-inertial ones do.


Correction: In Newtonian Physics, non-inertial transformations introduce extra force terms into the equations.

I don't like refering to these extra terms as "fictitious forces". If this terminology were rigorously adhered to, gravity would have to be considered a "fictitious force"!

I suppose this something like "imaginary numbers", but in this case the terminology is not so set by centuries of use. And I think it wise to abandon it.

Under General Relativity there is no distinction between inertial and non-inertial reference frames, so there is no such thing as a "fictitious force". All such forces are considered gravitational. (This was why Einstein came up with it in the first place.)

NickH - 10o and 30o are small enough that the non-linear effects are negligible (on the same order or less than the errors introduced by the differences between the real situation and the mathematical model), so I can't fault them too much there. But they would have been better advised to mention that this supposed equality is only a small angle approximation, not the "absolute fact" they present it as.

Wowbagger: Unlike the "kilogram mass", the "kilogram weight" is not a precisely defined quantity (and neither is the "pound mass"). You don't use it when you need that level of precision. 1 kilogram-weight = 9.8 Newtons is close enough. If you need better accuracy than that, it's time to pull out the real units. (And anyone who needs better accuracy than that already knows what the real units are, and how they differ. Either that, or they are way in over their heads anyway.)

It is EXTREMELY disappointing to discover the OALD entry for kilogram. They should be ashamed !:-[
Title: Re: Scientific Fallacies
Post by Sir Col on Jun 20th, 2003, 5:34pm

on 06/20/03 at 15:20:10, Leonid Broukhis wrote:
I would classify most fallacies as linguistic, not scientific...

Leonid, the word fallacy (from the Latin, fallacia=deceit or trick) means a false or wrong notion. The point of discussion is the half-truths that people speak of in relation to science. Surely you are not happy with people thinking that, "High temperatures kill enzymes," or "Photosynthesis converts carbon dioxide into oxygen." Science (again from the Latin, scientia=knowledge) is a discipline concerned with understanding observed phenomena. To say, "Stirring makes the sugar melt faster in the tea," is understood colloquially, but is scientifically incorrect, and I would argue that colloquialisms have no place in real science.
Title: Re: Scientific Fallacies
Post by Zeke the Geke on Jun 23rd, 2003, 6:46am

on 06/20/03 at 15:20:10, Leonid Broukhis wrote:
...To say "CO2 turns limewater milky" is as correct as to say "Cutting onions makes you cry". It is a common colloquialism to say "X does Y" instead of "X triggers a chain of events causing Y". There is nothing scientifically fallacious about it.

Leonid, I'm not one to address colloquial linguistic interpretation.  I'm just a scientist.  But I think perhaps you missed my first point, which was that you CAN have CO2 in water without having any milky precipitate appear.  Therefore, the presence of CO2 is not enough to start the chain of events leading to a milky mixture.

If it is the small amount that is being argued with, we already accepted that on the Moon, an atmosphere was present, albeit a very slight one.
Title: Re: Scientific Fallacies
Post by Leonid Broukhis on Jun 23rd, 2003, 2:30pm

on 06/20/03 at 17:34:43, Sir Col wrote:
Leonid, the word fallacy (from the Latin, fallacia=deceit or trick) means a false or wrong notion. The point of discussion is the half-truths that people speak of in relation to science. Surely you are not happy with people thinking that, "High temperatures kill enzymes,"


I am as happy with it as with "Turning the car key in the ignition counterclockwise kills the engine". Something that is not alive can be killed.


Quote:
or "Photosynthesis converts carbon dioxide into oxygen."


Yes, it does. Would you argue with "In a closed system, the CO2/O2 ratio shifts toward O2 as a result of photosynthesis?"
The colloquialism means that and no more than that.
I don't think any student really meant that some alchemical transmutation was going on.

IMO, it is completely pointless to argue the fallacity of these statements without knowing the context in which they were elicited. Were they one statement answers to specific questions, or parts of one-paragraph answers? Were they parts of essays? Surely, "Photosynthesis converts carbon dioxide into oxygen." is a wrong answer to "What is photosynthesis?", but as we do not know what was the question, or even if there was any specific question, we should not be drawing any (fallacious) conclusions about the decline of the science education.


Quote:
Science (again from the Latin, scientia=knowledge) is a discipline concerned with understanding observed phenomena. To say, "Stirring makes the sugar melt faster in the tea," is understood colloquially, but is scientifically incorrect, and I would argue that colloquialisms have no place in real science.


Of course they nave not! But without giving 13-14 year-olds a course of scientific writing it is preposterous to expect them using scientific prose instead of colloquialisms, and, moreover, by themselves, these examples do not mean that the students hold these fallacious notions. That is all.
Title: Re: Scientific Fallacies
Post by Leonid Broukhis on Jun 23rd, 2003, 2:48pm

on 06/23/03 at 06:46:40, Zeke the Geke wrote:
Leonid, I'm not one to address colloquial linguistic interpretation.  I'm just a scientist.  But I think perhaps you missed my first point, which was that you CAN have CO2 in water
Who said that it was in water? By itself the statement "CO2 turns limewater milky." is completely false: of course, the CO2 in my lungs does not turn limewater in our lab milky. You see, you have taken one implied thing ("in limewater"), but conveniently decided not to take another: it's really "Adding CO2 to limewater".


Quote:
without having any milky precipitate appear.  Therefore, the presence of CO2 is not enough to start the chain of events leading to a milky mixture.


Well, you can still claim that as adding CO2 merely shifts the balance (as opposed to triggering a chain reaction), the statement is false for sufficiently small amounts of CO2.
Title: Re: Scientific Fallacies
Post by Sir Col on Jun 23rd, 2003, 4:23pm

on 06/23/03 at 14:30:10, Leonid Broukhis wrote:
But without giving 13-14 year-olds a course of scientific writing it is preposterous to expect them using scientific prose instead of colloquialisms, and, moreover, by themselves, these examples do not mean that the students hold these fallacious notions. That is all.

The tragedy is that lack of rigour has caused a desperate decline in understanding: which is, after all, the aim of science. It may appear pedantic picking up on, what in your view are minor issues, but it is the thin end of the wedge. When a child is asked to, "Explain weightlessness in space," and they say, "Astronauts float in space because it's a vacuum." Do we praise them for knowing that space is a vacuum, even though we never asked that? Do we accept their statement with the hope that they really meant in zero gravity? Or dare we challenge their statement and attempt to draw them to a better understanding? I'm not suggesting that we present to them a complex model of equilibrium of forces, but I would feel inclined to at the very least remove their misconception that gravity and vacuums are synomonous.

The context empty questions you ask about are single sentences in response to single questions and are not part of an essay or extended response. The purpose of these tests is to measure children's responses to fundamental phenomena and scientific facts. It would follow that their answers should be factual and not fallacious or ambiguous.

I am not an educator of science, rather of mathematics, but I am a firm believer that we either teach things properly or not at all. I do recognise that through a spiralling curriculum we revisit concepts and build upon and refute previous simplifications, but never do we compromise by presenting a myth.
Title: Re: Scientific Fallacies
Post by Leonid Broukhis on Jun 23rd, 2003, 5:10pm
Sir Col, it is not my intent to keep students misinformed or encourage their misconceptions lest they be offended (I am not that PC), but I refuse to clump all 14 statements as scientific fallacies of one kind. Here's the breakdown:

1. Colloquialism.
2. Wrong. I have issues with "to help them" as well as with botched reference to transpiration.
3. Misinformation or definition problem. When does the gas next to a celestial body start to constitute an atmosphere?
4. Potentially unacceptable colloquialism; on the other hand, strictly speaking, by measuring the temperature of a known amount (a beaker-ful) of a known substance (water), don't we thereby effectively measure its heat?
5. Unfair generalization.
6. Incomplete (Earth is missing).
7. Unacceptable colloquialism, because "pressure" is a scientific term with the meaning that is different from the colloquial one.
8. Blatantly false.
9. Colloquialism.
10. False.
11. False, unless integrity of the placenta is compromised.
12. Colloquialism.
13. Unfair generalisation.
14. Colloquialism.

And, of course, mixing weightlessness and vacuum is unacceptable.

So, as you can see, I'm only defending 4 out of 14 statements.
Title: Re: Scientific Fallacies
Post by wowbagger on Jun 24th, 2003, 2:42am

on 06/23/03 at 17:10:50, Leonid Broukhis wrote:
I refuse to clump all 14 statements as scientific fallacies of one kind.

I'd also say there are fundamental differences.


Quote:
3. Misinformation or definition problem. When does the gas next to a celestial body start to constitute an atmosphere?

Hm, when it's gravitationally bound? I only remember that we once calculated something like a critical g, but that was long ago in my school days.


Quote:
6. Incomplete (Earth is missing).

Now, whether the answer is incomplete - and, more importantly, whether this makes the answer wrong - depends on the question.
If it asked to enumerate all objects from which the moon receives (possibly reflected) light, then you should include the earth, along with all other planets and moons (in principle, of course). If, on the other hand, the question was "By which light can we see the moon?", it's definitely enough to say: "By the sun's."


Quote:
7. Unacceptable colloquialism, because "pressure" is a scientific term with the meaning that is different from the colloquial one.

Wouldn't this also apply to number (xii)?


Quote:
12. Colloquialism.

Interestingly, I've never heard anyone use the corresponding verb for "melt" in German in this context, it's always "dissolve".
Title: Re: Scientific Fallacies
Post by Sir Col on Jun 24th, 2003, 4:40am

on 06/24/03 at 02:42:21, wowbagger wrote:
Interestingly, I've never heard anyone use the corresponding verb for "melt" in German in this context, it's always "dissolve".

I agree, which is why we teach children precise scientific terms like: dissolve, solvent, solute, solution, melt, boil, evaporate, condense, ...


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