Talk:List of common misconceptions/Archive 2

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Emancipation proclamation & Black hole

The change to the Emancipation Proclamation is wrong (I know) in it’s reasoning "did not immediately free all American slaves because it took winning the civil war to bring those slaves under his authority": it did not free any slaves that were not in rebellious states: those that did not rebel and had slaves were under his authority but did not have their slaves freed by the Emancipation Proclamation. - unsigned

Yes, you are right; but I was trying to fix the idea that it was supposed to free slaves not under Union control. I'll go back and make sure both our important qualifiers are clear. WAS 4.250 (talk) 23:38, 18 November 2007 (UTC)

The change to the black hole is wrong (I think) in it’s reference to the sun (which is in sol), and is not in appropriate reference to the star itself.- unsigned

"The sun's radius" was wrong, but so was "Schwarzschild radius". I changed "sun's" to "star's". BenRG (talk) 22:40, 18 November 2007 (UTC)

I meant to write "star"; thanks for fixing that. WAS 4.250 (talk) 23:38, 18 November 2007 (UTC)

I love this article

I move to vote on a consensus that this article is awesome. —Preceding unsigned comment added by 24.167.239.71 (talk) 06:10, 5 January 2008 (UTC)

I support the statement that this article is awesome. Shadoom (talk) 09:34, 19 August 2008 (UTC)

Missing a few.

Where is Iraq? More than 50% of Americans still believe that Iraq and Saddam were some how involved in 9/11. —Preceding unsigned comment added by 74.134.164.46 (talk) 01:53, 6 January 2008 (UTC)

Ah, yeah, we'll always be missing a few. But the question I have is how true is that statement? AFAIK, It's a pretty old stat, more than a few Americans have probably figured out the lack of connection. It may be misconceived that this statement is still true! But I doubt I'll be opposed to you adding it. However, we may need to create a section for it (or maybe place it under History?

BTW, just a thought, related to the subject line. There's no "Mathematics" or "Statistics" sections either. I'm sure there's hundreds we could possibly add (and unfortunately only a few that we ought or should add). Anybody want to get their copy of Innumeracy or How to Lie with Statistics and start plugging away at this? (I may if I get free time later today). Root⁴(one) 17:00, 6 January 2008 (UTC)

What is this?!? (Physics Gravity problem)

• That all objects, irrespective of their masses, fall at the same rate in a vacuum (i.e. ignoring air resistance) is only true for masses small in comparison with the mass of the Earth. The effect of gravity depends on the sum of all masses involved, and not just on the mass of the heaviest object. In other words, a hammer dropped from a tower has a greater mass than a pebble dropped from the same tower, which means that the Earth moves towards the hammer faster than it moves towards the pebble and, relative to the surface of the Earth, the hammer will be very slightly faster. If both objects are dropped in the same place at the same time, this will not apply. Nor would it apply if the unused object was left at the base of the tower (since it would then effectively add its mass to the mass of the earth).

Who came up with this? This makes no sense to me (zero). I have removed it from the article. I insist this be explained to me before I place it back on the article. THAT, or this is badly written. One suggestion:

The effect of gravity depends on the sum of all masses involved, and not just on the mass of the heaviest object.

Who would say it did? Maybe what is meant is:

The effect of gravity depends on the sum of all forces involved, and not just on the forces of all objects interacting with the heaviest object.

But even so, I'm not sure I buy the rest of it. The force required for moving the pebble is less than that for the hammer, but F=ma still applies AFAIK, so I don't see the rest of the argument is accurate. I might can see some sort of Three-Body argument, but ??. If a pebble, the earth, and the sun are all collinear with no momentum, would the argument even apply? Or what about three earths? Somebody please explain! Thanks. Root⁴(one) 04:03, 10 January 2008 (UTC)

I was a little irked by that entry, so I partially rewrote it. I have no particular interest in seeing it put back on the list, but it's actually true. I don't think it really qualifies as a common misconception though, because the "misconception" is only wrong for unrealistically heavy objects. It's a little like saying it's a misconception that your watch still works when you're on a train, because it slows down due to special relativity. Technically it's true that the watch slows down, but the change is far smaller than matters or can be measured. In the same way, although it's very accurate to say that (air resistance aside) all objects fall at the same rate, technically, a heavier object will hit the ground sooner. It can be verified with very basic physics. I will explain it briefly, but if you don't understand, that is not grounds for insisting the entry not be reinstated (again, I won't be the one to put it back).

Here is the deal: If two massive objects are released in each other's vicinity, they accelerate toward each other; each object accelerates at a rate determined by the gravitational field it experiences, which is proportional to the mass of the other object. Theoretically, that is what happens when you drop an object: the object accelerates toward the Earth, and the Earth accelerates toward the object until they collide. Any object that someone might drop has a tiny mass in comparison with the Earth, so the acceleration of the Earth is negligible, and all objects fall at the same rate. But if you were to drop something heavy enough, it would hit the ground sooner, because the Earth would move up to meet it. As an example, if you dropped an incredibly heavy marble that had the same mass as the Earth, Earth and marble would fall toward each other, and meet exactly in the middle. A regular marble would have twice as far to fall, and would take 1.4 times as long to collide with the Earth when dropped from the same height.Rracecarr (talk) 05:35, 10 January 2008 (UTC)

It should remain in the article. The combined mass is what gives the force of gravity on both objects. If the mass of the lighter object increases, the force of gravity bulling each object towards each other increases. Since the mass of the heavier object hasn't increased, it will come at a higher acceleration. This is well known fact. Only when the mass is extremely large such that the combined mass of the objects remains vertially same do they actually fall at the same speed. This is completely seperate to time dilation in a gravity field and is very important. For example if there was another earth they would fall towards each other faster than a basketball falls toward the earth. To think that they would not would be to make gravity constant. Think about it, if you increase the mass of the earth, surely you can agree gravity increases (think about gravity of jupiter). Likewise increasing the mass of the falling object will increase the 'gravity' between the objects and it will fall faster.--Dacium (talk) 06:11, 10 January 2008 (UTC)

(dratted edit conflicts)

We commonly teach first years to treat acceleration due to gravity as a constant 9.8 metres per second (32 ft/s) one week, and then the next week tell them that the force due to gravity is the product of the masses divided by the separation squared. This ideally leads the students into a greater understanding of experimental accuracy and useful approximations. In practice, however, they all too often erroneously conclude that Newton's third law (action = reaction) is bunk. The bit about summing masses is, as {1,i,-1,-i} notes, plainly wrong. Below is proposed a hopefully more lucid explanation of this misconception. Universal gravitation and g can be cited to any intro physics text, but not really the misconception itself, I do not suppose. It might also be worth noting that anyone citing this misconception is being entirely too pedantic for their own good - anyone actually trying to calculate this would be using GR, not Newtonian gravity. Eldereft (talk) 06:48, 10 January 2008 (UTC)

Have to butt in and correct Eldereft here. The original poster was correct: the relative acceleration (that is, the rate of change of the speed with with they approach each other) of any two masses separated by a given distance depends only on the sum of the masses: a + A = G(m + M)/r². Rracecarr (talk) 16:58, 11 January 2008 (UTC)

I don't know that you're actually correcting either of us. The orignal statement of contention was "The effect of gravity depends on the sum of all masses involved". This is part of the nonsense I was refering to. But judging from the other comments, I can see your statement about the acceleration between objects (i,j) looks to be true.

It looks like we can judge that

Let ${\vec {F}}_{i}$ be the vector force acting on object i

let ${\vec {F}}_{m_{i},m_{i}}$ be the individual force acting on object i resulting from object j.

let $m_{i}$ be the mass of object i

let $a_{i}$ be the overall acceleration vector (I'd call this "the effect of gravity"). This is not the relative acceleration between objects i and j, as Rracecarr's equation works.

let $d_{i,j}$ be the distance between object i and object j

let $r_{i,j}$ be the (vector) direction of the force between individual objects i and j. (mean, forces have direction, right?)

${\vec {F}}_{1}={\vec {F}}_{m_{1},m_{2}}+{\vec {F}}_{m_{1},m_{3}}$

${\vec {F}}_{1}={\vec {r}}_{1,2}Gm_{1}m_{2}/d_{1,2}^{2}+{\vec {r}}_{1,3}Gm_{1}m_{3}/d_{1,3}^{2}$

${\vec {a}}_{1}={\vec {F}}_{1}/m_{1}=G({\vec {r}}_{1,2}m_{2}/d_{1,2}^{2}+{\vec {r}}_{1,3}m_{3}/d_{1,3}^{2})$

${\vec {a}}_{i}={\vec {F}}_{i}/m_{i}=G\sum _{j=1}^{n}[i<>j]({\vec {r}}_{i,j}m_{j}/d_{i,j}^{2})$

Judging from above, I guess you could call it a weighted vector sum, so I guess it is a sum of masses of sorts, but I'd call that an abuse of language. "Linearly determined" may be better. I don't know.

Ok, it looks like we can conclude (and all agree) that Galileo's law of gravitation is, in fact, not quite right. We could call this a misconception (Aristotle was right after all! Hee). But the difference is so slight (Google says the mass of the mass of Earth = 5.9742 × 10^24 kilograms, anybody got 10^24 kg of stuff lying around? how about 10^23? Oh come on, somebody has got to have something 1/50 the size of the earth somewhere....!)practically unmeasurable for most things of interest except those on the cosmic scale. I could buy placing something relating to these statements on the page... if we also include some statement as to what distances, what size or relative masses, etc make it the facts relevant. Rracecarr's formula a + A = G(m + M)/r² looks like a good starting point. I'll think about it. Root⁴(one) 22:33, 11 January 2008 (UTC)

Rracecarr, you edited the entry? Is that the entry at the top of this section that you edited? It looks different. Can we use that as a starting point? Thanks. Root⁴(one) 22:40, 11 January 2008 (UTC)

Here is the diff showing my (minor) edit to the entry before it was deleted. I don't know what you mean by abuse of language. But let's cut to the chase: Is there anyone here who is actually interested in seeing the entry go back in? I'm against it. Partly because you could frame an equally valid "misconception" as follows: It's not true that all masses fall at the same rate, because if you pick up a heavier mass, you effectively subtract its mass from the mass of the Earth, reducing the value of g, so that (in an inertial frame) heavier objects actually fall slower. Rracecarr (talk) 23:39, 11 January 2008 (UTC)

I won't add it for a while (not this weekend at least). I may just leave it for now. Root⁴(one) 23:55, 11 January 2008 (UTC)

• That objects falling near sea level reach the ground at the same time independent of mass (neglecting air resistance) is only approximately correct. The gravitational force between any two objects is given by Newton's law of universal gravitation, which may be set equal to each object's mass times its acceleration:

$G{\frac {m_{1}m_{2}}{r^{2}}}=m_{i}a_{i}$

for each mass $m_{i}$. While the force felt by each object depends on the product of their masses, the acceleration each mass experiences is given entirely by the other mass and the separation between the two. The movement of the Earth upwards towards their common center of mass as various objects are dropped is entirely negligible. When the distance traversed is small compared to Earth's radius, this gives a constant acceleration, g, independent of mass.

I see enough people confuse themselves by reasoning that doubling either mass doubles the force between them (true) means dropping a heavy object is like throwing a light object downwards (not so true) that I would like to see it reinstated, but only if it actually meets the bar as a common misconception. Eldereft (talk) 07:11, 10 January 2008 (UTC)

It is still true that, near the surface of the earth, all objects, irrespective of their masses, fall at the same rate (i.e. with an acceleration of g) in a vacuum relative to an inertial frame of reference. If the mass of the falling object is significant compared to the mass of the Earth then the Earth's own acceleration is not negligible and so an observer on the surface of the Earth is no longer in an inertial frame of reference. Omitting the qualification "relative to an inertial frame of reference" is not really a misconception. At most, it is an oversimplification - but then again, we are ignoring air resistance, the rotation of the Earth, the oblateness of the Earth, the Moon's gravity, local gravity anomalies, tidal forces and relativistic corrections, so there is a lot of simplification already going on. Gandalf61 (talk) 14:14, 10 January 2008 (UTC)

I originally added this and, although it is a common misconception, I'm certainly not going to make a fuss about its removal. Nevertheless, I would make the following points:

• The watch/train analogy isn't really correct - if people know about Einstein's theories, they generally know about what happens to a watch on a train. However, this misconception can be prevalent even when people are aware of the basic interactions between different masses.

• It is a fairly complicated notion to phrase in a simple way. For example, dropping both objects side-by-side would not demonstrate this effect, nor would leaving one object at the base of any hypothetical tower.

Tomandlu (talk) 15:05, 14 January 2008 (UTC)

Evolution falsifiability

"The claim that evolution is not scientific since it cannot be falsified is not true. Any number of discoveries could potentially falsify evolution - for example the discovery of a contemporary mammal fossil in ancient rock strata."

While I understand the reason for having this common Creationist saw on here, it is not handled well at all. Falsifiability is major difficulty in the philosophy of science with regards to evolution. Even Sir Karl Popper agonized over it and in the end decided that evolution just wasn't a theory itself but an overarching umbrella concept that could lead to theories and thus wasn't subject to the same issues as a strict theory. Anyway, I don't think it should be on here unless it is handled a bit better, and in this case the standard pro-Evolution sites are often very philosophically weak. Whether it is falsifiable or not, and whether that matters or not in this case, is more complicated than can just be summed up in a sentence (a lot of it depends on what you mean by "evolution"—common descent? natural selection? modern synthesis?). See, for example, Falsifiability#Evolution. I find the "find a modern fossil in the Precambrian" personally rather unconvincing (even though I believe in evolution): that's not a "test" that you can run, and there are many ways you can imagine evolution to be false without that condition ever appearing. But anyway it's not really about what I think. --24.147.86.187 (talk) 16:04, 10 January 2008 (UTC)

Actually Popper later recanted and admitted that he had made a mistake when he first said evolution was not falsifiable, as I am sure you know. We have some material on the falsifiability of evolution already in a couple of articles (Falsifiability, and Objections to evolution) as you noted.

However I am preparing a far more extensive discussion about why falsifiability is a bankrupt concept that has long been discarded in the philosophy of science, and a failed attempt to solve the demarcation problem, and has been especially worthless and misused in biology, with a checkered history.

I am compiling a list of many many more examples of falsifiability tests of evolution from the literature, with references. Evolution is clearly falsifiable, and creationism could be falsifiable, and has been falsified plenty already. However, creationists refuse to admit they are wrong they just add on more epicycles to maintain the same basic idea of the biblical literalism.

Evolution on the other hand, has been drastically revised with all its base tenets discarded several times, from Lamarckian ideas to Transmutation to Orthogenesis to Darwinian natural selection to the Modern evolutionary synthesis to the current more sophisticated understanding. However, for this short article, just a short note is appropriate; what would make it better is a cited reference.--Filll (talk) 22:59, 11 January 2008 (UTC)

Technology

BeanShell is not a Java interpreter, but rather a scripting language on its own. Janino would be a better example: it's a third-party library that can compile Java source code on the fly. If we want to get specific, all languages are interpreted by a human/machine. The term "interpeted" is used loosely in this case. IMO this point is pretty misleading and should be removed altogether.76.67.53.28 (talk) 04:02, 23 January 2008 (UTC)

Earthworms - add if you can confirm

I think it is a common misconception in the US that if you cut an earthworm in half, both halves survive and become independent worms. ike9898 (talk) 16:06, 10 January 2008 (UTC)

Maybe earthworms, which are annelids, can't do this, but planaria, which are flatworms, can. "Worm" is ambiguous. Audiosqueegee (talk) 22:27, 22 January 2008 (UTC)

10%

The commonplace statement "We only use 10% of our brain" is completely false. I don't have any citations for this off the top of my head - nothing that explicitly contradicts this statement - but it's quite clear to me, and most likely anyone else who studies the brain. Fuzzform (talk) 01:03, 31 January 2008 (UTC)

Yes this is from the first measurements of glial cells in the brain.--Filll (talk) 20:06, 7 February 2008 (UTC)

Antarctica accumulating snow

The article claims "Antarctica may even help offset rising sea level by accumulating more snow," this is untrue as Antarctica is an arid desert with almost no precipitation (which is ironically later stated in the article). --NEMT (talk) 03:19, 17 February 2008 (UTC)

You can't deny that lots of ice certainly *has* accumulated on top of the Antarctic land mass. I have no idea if Antarctica is currently accumulating more snow *now* (very slowly of course) than it is shedding as icebergs. Do you know whether rising sea levels will tilt the balance towards greater accumulation or greater loss of ice in Antarctica? --68.0.124.33 (talk) 07:21, 19 February 2008 (UTC)

light vs sound

The following bullet point has been cut out of the article, with the edit summary "This looks like complete nonsense to me":

• It is not true that a difference between light and sound is that light travels in straight lines while sound travels around corners; both waves propagate in much the same way. Instead, the difference is between ears and eyes: because human vision allows us to pinpoint the source of light entering the eye, while ears cannot accurately pinpoint the source of a sound, much more of the available information is lost when light scatters around a corner than when sound does.

I think this is trying to state that both photons and sound waves show diffraction phenomenon, which is true. Or is this controversial or disputed for some other reason? --68.0.124.33 (talk) 07:21, 19 February 2008 (UTC)

I see two problems with it. One is that it completely misses the big difference between (audible) sound and (visible) light, which is wavelength. It's the wavelength that makes light more directional than sound, not our sensory organs. The second problem is that I don't see a common misconception here. I think people mostly understand that light is a wave. Light is more directional than sound (for the ordinary English meanings of the words, not the physicist's meanings), so that can't be called a misconception. I'm not the one who made the edit, by the way. -- BenRG (talk) 12:26, 19 February 2008 (UTC)

There are lots of differences between sound and light. For example:

• sound can have a longitudinal component, but light does not.
• light has a special role in our current understanding of physics, with the speed of light being a speed limit for the universe of sorts, and appearing as a scaling and conversion factor for example
• one is a mechanical oscillation that needs a medium to travel in, while the other is an electromagnetic disturbance that can travel in a vacuum
• the wavelength argument is sort of spurious, except for the wavelengths that humans are sensitive to.
• the statement about not determining the source of the light or sound does not make any sense to me. If I stand outside and feel the sun on my skin, I know which direction it is coming from even without using my eyes. I can see the direction the sunlight is coming from as well if I use my eyes of course. If a loud sound occurs, everyone will turn towards the source of the sound if both ears are functioning. In both cases, if the waves reflect, refract and diffract sufficiently, it is no longer possible to tell the source of the waves with unaided human senses--Filll (talk) 16:29, 19 February 2008 (UTC)

Yes, I agree with Filll that there many differences between sound and light, some of them major differences. The above "nonsense" statement is (if I understand it correctly) merely saying that, while there are many differences between them in reality, many people incorrectly think there is one more difference between them.

For example, all but one of the diagrams on the Lens (optics) article show light shooting in straight lines like a bullet -- lines that turn sharp corners at glass-to-air transition surfaces. If that is the only kind of diagram one ever saw, then one might come to the misconception that light always travels in straight lines through the air or through a vacuum. Then later being confronted by evidence that photons somehow "turn" in midair (diffraction), somewhat like sound waves "turn" in midair going around a corner, would be baffling. (But not quite as baffling as the single-particle double-slit experiment, which shows single particles somehow going through 2 different slits at the same time, or Wheeler's delayed choice experiment).

I hope that makes sense. (-: Or does this sound more like a Chewbacca defense? :-) Perhaps there is a better way of re-stating the essence of this statement? --68.0.124.33 (talk) 06:28, 21 February 2008 (UTC)

I originally added the entry. I do think it is a very common misconception, but it mostly exists in people's intuition so there aren't a lot of concrete examples. BenRG is right to point out the difference in wavelength--audible sounds have wavelengths about a million times longer than visible light. That effects how far evanescent waves penetrate, and also diffraction patterns. Reflection and absorption coefficients of various materials are also of course different for light and sound (light goes through sound-proof glass, sound goes through a black curtain). But (contrary to BenRG) in the context of human perception, these differences are small compared to those caused by the different way the ears and eyes work. If the TV is on in the living room, and you're around the corner in the kitchen, you can still hear what's being said, but you can't see what's happening on the screen. People assume that's because light rays go straight and sound rays don't. That's the misconception. The sound gets to you mostly by bouncing off walls (ok, unlike the light, some makes it through the walls, and some via the evanescent wave sneaking around the corner--but MOST of it is by reflection). The light from the screen gets to you the same way (and the fraction of the sound energy reaching you is similar to the fraction of light energy). But because the information in the light depends on resolving spatial patterns on the screen, it's useless once it's just a vague flicker spread out all over the walls. Since your ears don't care where the sound is coming from, you can still understand speech even after it is similarly "spread out all over the walls".

The differences between transverse and longitudinal waves, medium vs no medium are not really relevant. As nearly perfectly nondispersive waves, both light and sound are governed by essentially the same wave equation. Rracecarr (talk) 16:16, 27 February 2008 (UTC)

Meteorology

The first point about cloud formation is either simply incorrect or very poorly expressed.

How about the claim that toilet bowls are affected by the Coriolis effect? —Preceding unsigned comment added by 75.9.52.51 (talk) 07:32, 19 February 2008 (UTC)

It is under Physics. - Eldereft ~(s)talk~ 08:03, 19 February 2008 (UTC)

Please review section on Islam

I know little about Islam and I have no interest in arguing about it, but the section on Islam obviously needs attention from someone familiar with the subject. For example, the statement "Muslim martyrs will not go to paradise and marry 72 black-eyed virgins." is clearly not encyclopedic the way it is written. This is the sort of thing that needs to be quickly fixed, or dropped. I don't feel qualified to fix it myself. ike9898 (talk) 14:52, 21 February 2008 (UTC)

The existence of heaven or any kind of afterlife is, itself, a common misconception. Whether people believe they'll receive virgins, white grapes, or nothing there is irrelevant. --NEMT (talk) 02:39, 27 February 2008 (UTC)

Don't be ridiculous. Such a thing can not be determined one way or another- I'm fairly certain that you have no personal experience which would allow you to make such a claim. The concept is such that we really cannot be certain of the existence of such a place until we have experienced it ourselves.--C.Logan (talk) 12:51, 27 February 2008 (UTC)

Please refrain from starting off-topic discussions NEMT. This page is for discussing how to improve the article, not for venting your personal beliefs. Ike, I'll have a little look around the Islam projects and see if I can find a friendly-looking editor. Skittle (talk) 15:17, 27 February 2008 (UTC)