Common Misconceptions within Physics and Astronomy

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Whitebluur
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Common Misconceptions within Physics and Astronomy

Postby Whitebluur » Thu Jan 19, 2012 12:16 am UTC

Misconceptions within science are a growing topic among educators and professionals. What are the misconceptions? Where do they come from? When are they learned? Two common misconceptions are the ideas that stars do indeed twinkle or that black holes are giant vacuum cleaners in space, sucking everything up! Almost anyone who takes an intro Astronomy course could tell you why these statements are untrue...

I am working on a project, not school related, and would like to invite any who are willing to share any misconception they have come across in their travels. I would like to focus on Astronomy and Physics because that is what I do, but if you feel the urge to share something else please feel free to do so.

ONWARD!

EDIT: I should have been clearer about what I am doing. I already have a large list at my disposal, http://www.physics.umaine.edu/ncomins/miscon.htm , and I am trying to lengthen it. Also these would misconceptions a layperson would have or maybe a high school student.

Edit the second: I had a thought, which was my first problem... I want to include misconceptions that you once had, in the realm of physics and astronomy, before you became your enlightned and highly educated selves.
Last edited by Whitebluur on Sat Jan 28, 2012 5:38 pm UTC, edited 3 times in total.

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Re: Misconceptions within Physics and Astronomy

Postby mfb » Thu Jan 19, 2012 5:43 pm UTC


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Re: Misconceptions within Physics and Astronomy

Postby Sagekilla » Thu Jan 19, 2012 5:49 pm UTC

mfb wrote:Something like Wikipedia:List_of_common_misconceptions?


I love reading the lists on Wikipedia. That's one of my favorites.
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Re: Misconceptions within Physics and Astronomy

Postby eSOANEM » Thu Jan 19, 2012 6:50 pm UTC

One that's not on the wikipedia list is that objects like being "at rest" (whatever that means) and therefore that, in an ideal test area, a pushed trolley will stop. Of course, most people with this misconception (who I've encountered at least) have been taught that this is due to friction and that in a truly idealised test area it will go forever but their intuition reveals that they still hold the misconception.
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Re: Misconceptions within Physics and Astronomy

Postby Sagekilla » Thu Jan 19, 2012 7:29 pm UTC

eSOANEM wrote:One that's not on the wikipedia list is that objects like being "at rest" (whatever that means) and therefore that, in an ideal test area, a pushed trolley will stop. Of course, most people with this misconception (who I've encountered at least) have been taught that this is due to friction and that in a truly idealised test area it will go forever but their intuition reveals that they still hold the misconception.


There's a misconception right there. It's not that objects "like being at rest," it's that objects stay at rest unless they're acted on by an external force.
Right idea, just worded strangely.

I'd say it's best summarized by saying that momentum is constant, unless a force is applied. When a force is applied, momentum (therefore velocity) changes.


Unfortunately, as you say, very few people realize that in Real Life, there are almost always forces acting on things.
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Re: Misconceptions within Physics and Astronomy

Postby mfb » Fri Jan 20, 2012 1:34 pm UTC

Well, eSOANEM is right with the misconception: Watch any science fiction series with spaceships, and it is likely that the spaceships in the series have to use thrust to move, not only to accelerate. Oh, that reminds me of another list, this time specialized on rockets and space travel.

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Re: Misconceptions within Physics and Astronomy

Postby gmalivuk » Fri Jan 20, 2012 2:35 pm UTC

eSOANEM wrote:One that's not on the wikipedia list is that objects like being "at rest" (whatever that means) and therefore that, in an ideal test area, a pushed trolley will stop.
For the question of why people have some of these misconceptions, this one is easy: For 100%* of human history, 100%* of objects known to in motion later come to rest. So that one is very possibly hardwired in the way our brains think about movement.

* Within three significant figures.
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Re: Misconceptions within Physics and Astronomy

Postby Fire Brns » Fri Jan 20, 2012 3:13 pm UTC

The atomic model.
Helping a kid with homework on valence electrons. Then I ask him what an atom looks like? He draws the intersecting ovals and a nucleus.
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Re: Misconceptions within Physics and Astronomy

Postby idobox » Fri Jan 20, 2012 5:01 pm UTC

gmalivuk wrote:
eSOANEM wrote:One that's not on the wikipedia list is that objects like being "at rest" (whatever that means) and therefore that, in an ideal test area, a pushed trolley will stop.
For the question of why people have some of these misconceptions, this one is easy: For 100%* of human history, 100%* of objects known to in motion later come to rest. So that one is very possibly hardwired in the way our brains think about movement.

* Within three significant figures.

I'm pretty sure it isn't hard wired, just not something people find themselves.
I don't remember being especially shocked or troubled by learning that, or having any difficulty handling the concept. Stuff like convergent series or quantum mechanics was(is) much harder to integrate.
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Re: Misconceptions within Physics and Astronomy

Postby Steax » Fri Jan 20, 2012 6:23 pm UTC

The next time I see someone say "oh how wonderful the creator must be, to hide such colorful things in the cosmos" at a non-visible-light spectrum image, I'm going to whack them with a microwave.
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Re: Misconceptions within Physics and Astronomy

Postby eSOANEM » Fri Jan 20, 2012 10:46 pm UTC

idobox wrote:convergent series


Speaking of convergent series:

This one doesn't really count much because I'm sure it's not very common and requires a certain amount of education before it can be formed and then requires very little more to remove; but I remember that when I first learnt about convergent series, the example given was the sum of the binary fractions being 1, from this one data point I extrapolated that any infinite series whose terms converged to zero would have a converging sum. Of course, when I tried it with the harmonic series that went out the window.
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Re: Misconceptions within Physics and Astronomy

Postby chenille » Sat Jan 21, 2012 1:17 am UTC

Just as a note, a few of the misconceptions on your list seem questionable:
  • It's true that Alpha Centauri isn't the closest star, but that's less because something is closer than that it isn't a single star; Proxima Centauri is part of it.
  • Last I had heard astronomers were still debating whether Mizar and Alcor are a true binary. They definitely share proper motion, so it comes down to distance, and current estimates aren't enough to say definitely one way or the other.
  • The solar system isn't in one of the main spiral arms, but the region the solar system is in could fairly be considered a minor one. Different people call it the Orion-Cygnus arm and Orion-Cygnus spur.
  • Planetary orbits don't cross if you leave out Pluto (so even if you don't, it can be more semantics than misconception).
  • Likewise, whether mass changes with speed is semantics. In a lot of books it means "relativistic mass", which changes, but it seems like most particle physicists mean "invariant mass" and just call the changing thing kinetic energy.
  • The combination of all colors is black, or a good approximation of it, if you're mixing pigments instead of light.
  • All electrons in an atom are identical in a very real sense; they have different places, spins, and energies, but it's important for quantum mechanics that there's no inherent way to distinguish them if they change those.
Anyways, all the common misconceptions I can think of are covered. Some unusual ones I'd heard is that the distance to stars in our galaxy has to do with redshift; that Uranus, being closer than Neptune, is a larger planet; and that asteroids are generally single solid objects, if those help any.

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Re: Misconceptions within Physics and Astronomy

Postby Steax » Sat Jan 21, 2012 2:09 am UTC

chenille wrote:[list][*]It's true that Alpha Centauri isn't the closest star, but that's less because something is closer than that it isn't a single star; Proxima Centauri is part of it.


Not exactly; "Alpha Centauri" is a binary star system which appear visually as a single point to the naked eye from Earth, composed of A and B. Proxima isn't visible to the naked eye, so we can't consider it part of "Alpha Centauri" if we define that as "the point of light seen from Earth". It's also not clear if it's a triple star system or not, so that side of the definition isn't definitive.
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Re: Misconceptions within Physics and Astronomy

Postby jmorgan3 » Sat Jan 21, 2012 4:45 am UTC

Misconceptions about airfoils, in order of increasing sophistication:

  • Airfoils produce lift by Bernoulli's equation because the air has to travel faster over the top of the wing to cover the larger distance in the same time
  • Airfoil lift has nothing to do with the Bernoulli equation
  • Airfoil lift production is split between Bernoulli effects and momentum conservation effects
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Re: Misconceptions within Physics and Astronomy

Postby eSOANEM » Sat Jan 21, 2012 1:18 pm UTC

jmorgan3 wrote:Misconceptions about airfoils, in order of increasing sophistication:

  • Airfoils produce lift by Bernoulli's equation because the air has to travel faster over the top of the wing to cover the larger distance in the same time
  • Airfoil lift has nothing to do with the Bernoulli equation
  • Airfoil lift production is split between Bernoulli effects and momentum conservation effects


I got asked how an aerofoil works in my university interview. Having not actually done much reading up on the theory, it was quite a hard question but I'm quite pleased that I managed to work through each of these in about 5 minutes.
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Re: Misconceptions within Physics and Astronomy

Postby Whitebluur » Sat Jan 21, 2012 4:19 pm UTC

Thank you for your replys thus far! Everything and anything will be helpful. Plus, i think it is a very interesting topic for discussion!

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Re: Misconceptions within Physics and Astronomy

Postby Whitebluur » Sat Jan 21, 2012 5:35 pm UTC

chenille wrote:Just as a note, a few of the misconceptions on your list seem questionable


Are you saying that it is questionable whether or not the misconceptions are true misconception?

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Re: Misconceptions within Physics and Astronomy

Postby capefeather » Sat Jan 21, 2012 9:46 pm UTC

People misinterpret various theories all the time. The average layman would probably attribute everything in modern cosmology to Einstein and MAYBE Hawking. Plus, people often fixate on certain results of a theory, thinking that that's the theory itself (E = mc^2). I once got the crazy idea of finding science videos on YouTube and I really, really regret it. Oh, and who could not forget: "Scientists discovered particles called 'neutrinos' that are faster than light! Einstein was wrong! Science is wrong!"

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Re: Misconceptions within Physics and Astronomy

Postby eSOANEM » Sat Jan 21, 2012 10:29 pm UTC

capefeather wrote:E = mc^2


I'm going to quote the fact that many people take this as a general truth as one.

That's possibly a little harsh, but it is my understanding that, nowadays, it is very rare to use "m" to refer to anything other than the invariant mass/rest mass of an object/particle in which case E only equals mc^2 for objects stationary wrt the observer which is a pretty narrow range of possible cases.
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Re: Misconceptions within Physics and Astronomy

Postby Sagekilla » Sat Jan 21, 2012 10:50 pm UTC

eSOANEM wrote:
capefeather wrote:E = mc^2


I'm going to quote the fact that many people take this as a general truth as one.

That's possibly a little harsh, but it is my understanding that, nowadays, it is very rare to use "m" to refer to anything other than the invariant mass/rest mass of an object/particle in which case E only equals mc^2 for objects stationary wrt the observer which is a pretty narrow range of possible cases.


This. m is supposed to be equal to m_rest / sqrt(1 - v^2 / c^2). IIRC, Einstein regretted using m as the "relativistic mass" in the energy-mass equivalence equation.

This sort of thing can really bite you in the ass when you try to calculate collisions of relativistic particles and you forget the Lorentz factor.
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Re: Misconceptions within Physics and Astronomy

Postby pizzazz » Sat Jan 21, 2012 11:35 pm UTC

I feel like this belongs here.
http://www.cracked.com/article_19668_6- ... ysics.html

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Re: Misconceptions within Physics and Astronomy

Postby mfb » Sun Jan 22, 2012 1:25 pm UTC

The article itself is a misconception.

My favourite, worst parts:
However, as the heat travels from the sun's surface to the layer a few hundred miles away from its surface (known as the sun's corona), it rises to a temperature of 1,000,000 degrees Celsius.

So the author does not think that microwave ovens can be explained in science? Because "the heat would have to come from a hotter part"?

Up close, gravity gets its ass handed to it by a bond that's about as strong as worn-out Velcro. But over a distance of 234,000 miles, it acts like the chain on a mace being swung around the head of a planet-sized Viking.

This is what's known as the Higgs mass hierarchy problem.
[...]
because the closer you look at it, the more likely it is to disappear

wtf

It's called the flyby anomaly because there are multiple instances where NASA's Galileo, NEAR, Pioneer 10 and Pioneer 11 spacecraft have experienced an unexplainable increase in speed over massive distances. It's always when they're passing Earth at enough of a distance to not be affected by its gravitational pull, yet they somehow pick up speed, like some universal force is inside stepping on the accelerator.


Oh, and I would like to add two related statements as misconceptions:
"Gravitational pull has a finite range"
"The force of electric charges (on other charges) can be shielded"

While it is true that the net force from an electric charge can be reduced by putting an opposite charge next to it (or around it), that just adds another force in the opposite direction.

#3. The Law of Conservation of Energy? More of a Suggestion, Really

... and the whole point then is conservation of information (which is still an open question, unlike the article suggests), not of energy.

Quantum Zeno effect with uranium decays? Really?

And the whole neutrino stuff... well. Measurement errors can happen. They are bad, but they have a non-zero probability for each measurement. And there are a lot of measurements around.

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Re: Misconceptions within Physics and Astronomy

Postby Steax » Sun Jan 22, 2012 1:30 pm UTC

Well... it's Cracked. They do bring up some okay things, but looks like they Did Not Do The Research.

/giggles

It would appear most of that article comes from outdated material.
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Re: Misconceptions within Physics and Astronomy

Postby Whitebluur » Sun Jan 22, 2012 5:41 pm UTC

This is becoming very interesting! Thank you all for posting! I am going to sit back and simply observe what you all come up with for misconception and the general discussion. It is very interesting indeed!

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Re: Misconceptions within Physics and Astronomy

Postby Gagundathar The Inexplicable » Sun Jan 22, 2012 7:18 pm UTC

Gosh, I am just going to read the list from Wiki for a while.
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Re: Misconceptions within Physics and Astronomy

Postby krogoth » Mon Jan 23, 2012 3:03 am UTC

You're still wrong about the closest star. It's called Sol, though you probably mean, "star closest to but outside our solar system" and if that was the understoof meaning, then I'm just a troll.
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Re: Misconceptions within Physics and Astronomy

Postby Whitebluur » Mon Jan 23, 2012 6:50 pm UTC

krogoth wrote:You're still wrong about the closest star. It's called Sol, though you probably mean, "star closest to but outside our solar system" and if that was the understoof meaning, then I'm just a troll.


It is generally understood that when someone refers too, "closest star", they are refering to extra-solar stars.

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Re: Misconceptions within Physics and Astronomy

Postby SU3SU2U1 » Tue Jan 24, 2012 7:22 am UTC

The biggest misconceptions that people (or at least people in the US) have about science/astronomy that I think we (where we means scientists, especially) need to work harder to correct are:
1. there is a shortage of trained US citizen scientists
2. most people who get phds in physics/astronomy end up working as physicists/astronomers (this could be an offshoot of 1)
3. "basic" research is the opposite of "advanced" research so we obviously should be focusing on the latter.

These misconceptions have an unfortunate tendency to come up in actual scientific policy discussion (the nsf is guilty of pushing the first of these).

As for misconceptions students have about information within science:
1. scientists follow a rigid method that involves a series of steps generating a hypothesis, testing the hypothesis, etc. I confess to believing this one until my first job in an actual lab.
2. physicists/the laws of aerodynamics "prove" that bumblebees can't fly. I hear this surprisingly often from people who should know better.

Personally, I find misconceptions about the process of science to be much more alarming than simple factual mixups. I don't care if the average highschool student knows what the closest extra solar star is, outside of the occasional trivia contest, it won't matter. Understanding the process of science, however, can be enormously helpful to anyone.

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Re: Misconceptions within Physics and Astronomy

Postby mfb » Tue Jan 24, 2012 12:59 pm UTC

Well, what you learned about the scientific working flow is something like the ideal case. Sometimes and especially in everyday scientific work, things can get more complicated.
But for the large scale, it is still a good model: You make some observations (like particle creation and decays), form a hypothesis (like the standard model), calculate predictions (like the existance of a third quark generation), test it (collide particles with high energy) and see whether the result (observed bottom- and later top-quarks) matches the prediction (it does).
Of course, the model can get adjusted as soon as new experiments show deviations from the model. Sometimes, this adjustment is even done in advance - like the 3524323+-2 models of supersymmetry hanging around and waiting for some SUSY particles in the LHC. But even then, the models can make predictions like "if particle A is found with mass a, then particles B should behave like whatever" - which can be tested.

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Re: Misconceptions within Physics and Astronomy

Postby SU3SU2U1 » Tue Jan 24, 2012 5:45 pm UTC

I'll add to the list of misconceptions:

there is a strict difference between a "law", a "theory", a "hypothesis", a "model", etc.

Well, what you learned about the scientific working flow is something like the ideal case. Sometimes and especially in everyday scientific work, things can get more complicated.
But for the large scale, it is still a good model


I don't know any scientist who conceives of their work as anything like this, and certainly no one works in this way. A better description should keep induction/testing at the core, but focus on the iterative nature of science, the importance of community feedback and validation, and the idea that science outputs models.

Your description of the standard model's development illustrates my points- its not very much how the standard model was formulated. Its a just-so story told after the fact. We want young students engaged in science and thinking like scientists not learning just-so stories to encapsulate a list of facts.

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Re: Misconceptions within Physics and Astronomy

Postby mfb » Tue Jan 24, 2012 10:41 pm UTC

If you step back and look at the development over decades (at least in particle physics), it can work this way.

>> but focus on the iterative nature of science, the importance of community feedback and validation, and the idea that science outputs models.
Iteration, feedback and models as output are the core of the description you dislike :(.


>> I don't know any scientist who conceives of their work as anything like this, and certainly no one works in this way.
"Our analysis measures X. The standard model prediction is 0, new physics model A and B predict larger values, NP model C not" is very common at experiments. It is the part "test the hypothesis".
"This analysis measured Y, which is 3 sigma (standard deviations) away from the SM. My new physics model can describe this" is not so unusal, too. In fact, for most >2sigma-effects there are more theory papers as standard deviations*. "Use the observations to make a model".

*delta A_CP, the 3.5 sigma deviation from LHCb, triggered at least 10 theory papers. No idea how many the OPERA result produced, but I am sure it is more than 10.

Edit: Added some explanations to make the post more readable.

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Re: Misconceptions within Physics and Astronomy

Postby SU3SU2U1 » Tue Jan 24, 2012 11:58 pm UTC

If you step back and look at the development over decades (at least in particle physics), it can work this way.


After the fact and over decades, you can tell any story you like to fit your narrative. Look at something like "Tao of Physics" or any of Deepak Chopra's crap. You can easily fit modern experimental discoveries over decades into an eastern mysticism/new age narrative to bilk hippies out of money.

It can be made to LOOK like science works that way, but it doesn't really. As much as I'm not a huge fan of Kuhn, one of his important insights is that there is a difference between how science is actually practiced and the "folk history" scientists tell each other.

Iteration, feedback and models as output are the core of the description you dislike


No, they aren't. I think we are talking past each other. Pick up any grade school science book (literally every book in my state approved this year for K-8 science has a diagram that looks very close to this) and you'll probably see something like this: http://tinyurl.com/6oay98q Bonus extra-terribleness for using the phrase "the hypothesis is true." No mention of peer review. We don't sit down and go after hypotheses one at a time. No mention of a model anywhere- this diagram suggests science outputs "true hypotheses."

It would be preferable to see instead, something like this: http://tinyurl.com/7fpfdw9 I have no idea who made the diagram, it was a google image result, but its much better. I'd like to see explicit mentions of a model, but tremendously better than the first diagram.

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Re: Misconceptions within Physics and Astronomy

Postby eSOANEM » Wed Jan 25, 2012 8:33 am UTC

SU3SU2U1 wrote:Bonus extra-terribleness for using the phrase "the hypothesis is true." ... this diagram suggests science outputs "true hypotheses."


I'm going to take "science outputs true hypotheses" as a misconception in its own right. This is more widespread than just physics and astronomy though, all the mark schemes for past A level (final year before uni) statistics papers I've seen have had the conclusion for a negative result on a hypothesis test as "accept H0" or "H0 is true", thankfully they seem to also accept "do not reject H0" or more caveated versions.
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Re: Misconceptions within Physics and Astronomy

Postby mfb » Wed Jan 25, 2012 10:49 am UTC


Ok, that is really bad, I agree. This one is better. It is not as detailed as your graph and does not show some of its features, however.

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Re: Misconceptions within Physics and Astronomy

Postby chenille » Thu Jan 26, 2012 2:25 am UTC

Whitebluur wrote:Are you saying that it is questionable whether or not the misconceptions are true misconception?

Yep! The examples I listed are more a matter of different definitions than an idea that's wrong, except for whether Mizar and Alcor are a true pair, which is something that still isn't certain.

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Re: Misconceptions within Physics and Astronomy

Postby Whitebluur » Thu Jan 26, 2012 3:29 am UTC

chenille wrote:
Whitebluur wrote:Are you saying that it is questionable whether or not the misconceptions are true misconception?

Yep! The examples I listed are more a matter of different definitions than an idea that's wrong, except for whether Mizar and Alcor are a true pair, which is something that still isn't certain.


But in truth, nothing is every truely certain! I appreciate your point concerning different definitions. People say that language is our greatest achivement and tool. In my experience, it only mucks up the water...

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Re: Misconceptions within Physics and Astronomy

Postby Whitebluur » Sat Jan 28, 2012 6:08 am UTC

What are some misconceptions you all used to have?

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Re: Misconceptions within Physics and Astronomy

Postby mfb » Sat Jan 28, 2012 3:20 pm UTC

Do you count the Copenhagen interpretation of quantum mechanics as misconception?
It took a while for me to realize that everything consists of particles which follow quantum mechanics - and the consequence of that.

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Re: Misconceptions within Physics and Astronomy

Postby SU3SU2U1 » Sat Jan 28, 2012 5:02 pm UTC

Do you count the Copenhagen interpretation of quantum mechanics as misconception?


Why would you? Yes, it has its problems (circularity), but it lets you actually make predictions.

I will add two misconceptions in this vein, though-
1. An "interpretation of quantum mechanics" involves leaving the axioms and definitions fixed. This is false- Von Neumann quantum mechanics is always and everywhere Copenhagen, other interpretations modify axioms and definitions.
2. Many worlds can make predictions. It can't- no one knows how to get a Born rule out of the theory. WIthout getting the Born rule, you either can't make predictions or you make wrong predictions.

See this thread for a back and forth on many worlds. viewtopic.php?f=18&t=73838

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Re: Misconceptions within Physics and Astronomy

Postby mfb » Sat Jan 28, 2012 10:03 pm UTC

SU3SU2U1 wrote:It can't- no one knows how to get a Born rule out of the theory. WIthout getting the Born rule, you either can't make predictions or you make wrong predictions.

The same is true for all interpretations. The square of the amplitude is just put in. Well... there actually IS an idea how it could be the result of deeper theory. But it is too early to tell whether that could work.

>> but it lets you actually make predictions.
As long as you define by hand what counts as "measurement" for each experiment.
And one of the predictions is that particles behave different, based on the definition of "part of the experiment" (does not cause a collapse) and "not part of it" (does cause it).


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