What to do when your instructor is wrong?

[jtbell]

A couple kids even asked why light doesn't weigh anything.

I can imagine why that question would make the instructor freak out, especially if he/she has visited PF and seen some of our threads about photons and invariant versus relativistic mass.

More seriously, I don't know what it's like in your state, but in my state, and specifically at the college where I work, students can get certified to teach middle-school science after taking two semesters of intro biology, one semester of intro chemistry, one semester of intro physics (algeba-based), and one earth-science course. Plus a bunch of education courses, of course. You shouldn't expect a great depth of science knowledge from them (I'm sure there are shining exceptions, of course.)

 

[Sankaku]

It was a bit of a smartass answer, but handling smartass answers without screaming is a pretty basic part of classroom management.

This is exactly what I was going to say. Not every school-teacher has enough knowledge to answer technical questions, but they all should have the skills to manage the question.

For the OP, as has been said before, do your best to raise questions at the time. Some of my best professors were prone to mistakes at the chalkboard. I find that a correction phrased as a polite question is received much better than one that is done with aggression.

 

[Chemicist]

I tried making a correction to his equation, after class and privately.

Apparently as far as the EQUATION that was supposedly wrong goes, the place I got my information from was wrong. Although his other mistakes still stand.

 

[mathwonk]

Making mistakes does not matter. Leaving them unquestioned does matter. A great way to learn is to ask about every single thing you disagree with, no matter who may be mistaken.

This is not a competition, to always be right. The idea is to make it a collaboration, trying to discuss together and learn. If you see things you disagree with and do not bring them up for discussion, it is you who is making the biggest mistake.

 

[Moonbear]

In the UK, at least, your physics teacher might be a biology graduate, and mass-energy equivalence is not something biology graduates are expected to know much about...

http://www.guardian.co.uk/science/blog/2010/dec/13/physics-teachers-shortage

"the subject is far too often being taught by "non-specialists", teachers who are usually qualified in chemistry or biology. Many of these teachers have not studied physics beyond GCSE and some even actively dislike physics."

I want to smack around the people who decided to drop the physics requirement for a biology degree. Though, conservation of mass AND energy was taught to me back in high school chemistry...or perhaps sooner. It makes perfect sense to discuss it when covering chemical bonds and energy released from breaking the bonds (such as the flash bulb example...though today I'm surprised students still know what a flash bulb is). Anyway, physics is needed to understand a lot of biology. I know I really struggle having to lecture about lenses or membrane potential or blood pressure changes with vessel diameter and changing velocity when my students haven't had any physics.

 

[chill_factor]

I did this with one of my teachers.

He said that in a closed system like a flashbulb, the weight of the bulb didn't change after the chemical reaction. I raised my hand and told him that the flashbulb was a little bit lighter after the flash because of the light that escapes. He said no, that light didn't weigh anything. I then said that the light had an equivalent mass by E=mc^2 so that was the mass that was lost.

He started screaming at the top of his lungs that light didn't weigh anything. I just calmly told him he was wrong. The principal took over the science class after that for about a month.

I suggest talking to him when the rest of the class isn't around.

you are wrong. the change in mass is unmeasurable. chemical reactions do not result in mass change only mass redistribution. if it cannot be measured it does not exist. you want to be a smartass and say that the 10^-19 joules or so is actually going to influence the mass of the system?

this is why relativity should be left for grad school, it only confuses people including me, and it is not useful in the design of new devices.

 

[genericusrnme]

this is why relativity should be left for grad school, it only confuses people including me, and it is not useful in the design of new devices.

I support this 100%!

Relativity and quantum mechanics shouldn't even be brought up in those intro high school/first year physics textbooks unless they include full derivations (which would be beyond a first years skills), most of the analogies and/or equations they just pump out at you are either very easy to take out of context or very oversimplified. It does more harm than good imo.

 

[chill_factor]

quantum should still be brought up imo because it is the core of all chemistry. you can't do chemistry without knowing what an electron is it just doesn't happen.

relativity on the other hand is not useful for 99.9999999999% things that happen right here on earth.

 

[Jorriss]

quantum should still be brought up imo because it is the core of all chemistry. you can't do chemistry without knowing what an electron is it just doesn't happen.

relativity on the other hand is not useful for 99.9999999999% things that happen right here on earth.

I think relativity is better to bring up because it is very easy to build intuition for special relativity as opposed to quantum. The arguments for relativity are very clear compared to quantum.

And relativity is not something most people will use regularly but it has its uses, even to us chemistry people. Outside of physical, its not uncommon for relativistic effects to be noticeable in, say, gold compounds or as a partial explanation for lanthanide contraction.

 

[DaveC426913]

relativity on the other hand is not useful for 99.9999999999% things that happen right here on earth.

Well, considering a large fraction of world's population owns a cellphone that has a GPS tracker in it, your numbers are way off.

While we don't necessarily have to know how it works, you can rest assured the tracker in your phone has to know - quite often over the course of a day - or it would not work.

 

[chill_factor]

Well, considering a large fraction of world's population owns a cellphone that has a GPS tracker in it, your numbers are way off.

While we don't necessarily have to know how it works, you can rest assured the tracker in your phone has to know - quite often over the course of a day - or it would not work.

GPS and other satellite navigation systems can be replaced by a network of radio beacons. Its not irreplacible technology and its just 1 niche application. I can go on and on about the applications of quantum physics but we already know that.

Jorris:

Relativity has niche uses in chemistry and materials science for sure, like you said, for gold, lanthanide contraction and even the liquidity of mercury. However, we cannot MANIPULATE relativity the way we can manipulate quantum effects, so while its nice to have, its just purely theoretical science and not applicable outside, like you and dave mentioned, niche fields.

On the other hand I really think people should know what an electron is and why it behaves the way it does, before touching chemistry. without quantum mechanics, chemistry would just be statistical mechanics, thermo, empirical chemical kinetics and maybe some heat/mass transfer.

i also believe the math for quantum, at the level needed for even advanced chemistry and materials science, is far easier than even a basic understanding of relativity.

 

[DaveC426913]

GPS and other satellite navigation systems can be replaced by a network of radio beacons. Its not irreplacible technology...

What does "replacing" have to do with anything? You said it was not useful in real world applications. It's quite useful.

... and its just 1 niche application.

Cellphones are niche applications?? What millennium are you in?

There are more than 4 billion cellphones in the world. That's better than 1 in 2.

10 year olds have cellphones. 10 year olds don't even have cars. Are cars a niche application?

 

[Jorriss]

Jorris:

Relativity has niche uses in chemistry and materials science for sure, like you said, for gold, lanthanide contraction and even the liquidity of mercury. However, we cannot MANIPULATE relativity the way we can manipulate quantum effects, so while its nice to have, its just purely theoretical science and not applicable outside, like you and dave mentioned, niche fields.

I'm not an inorganic chemist but I have heard good inorganic chemists need to know about special relativity as it can be a guiding factor of how to synthesize certain compounds. Rarely, but I've heard it's good to know. Not a rigorous mathematical manipulation but small corrections to MO's and such. I'm speaking outside my comfort zone here though.

Otherwise, I wouldn't say it's a chemists first weapon at attacking a problem but I think chemists should be aware of special relativity.

On the other hand I really think people should know what an electron is and why it behaves the way it does, before touching chemistry. without quantum mechanics, chemistry would just be statistical mechanics, thermo, empirical chemical kinetics and maybe some heat/mass transfer.

Well I'm not arguing quantum is less important than relativity! I just think at a lower division one can say a lot about relativity without feeling too lost or drowned in math.

Also, you must be referring to p chem. Because without quantum, most chemistry is still organic chemistry haha.

i also believe the math for quantum, at the level needed for even advanced chemistry and materials science, is far easier than even a basic understanding of relativity.

I don't know about that. I feel someone can get a really good insight into special relativity with just some calculus and algebra. I would say they can be treated on equally light mathematical footings and still not be meaningless.

 

[chill_factor]

What does "replacing" have to do with anything? You said it was not useful in real world applications. It's quite useful.

Cellphones are niche applications?? What millennium are you in?

There are more than 4 billion cellphones in the world. That's better than 1 in 2.

10 year olds have cellphones. 10 year olds don't even have cars. Are cars a niche application?

i do not believe that GPS is necessary for cell phone usage. most cell phones function fine without relativity. its just straight EM for data transmission and solid state physics for the processor hardware.

 

[chill_factor]

I'm not an inorganic chemist but I have heard good inorganic chemists need to know about special relativity as it can be a guiding factor of how to synthesize certain compounds. Rarely, but I've heard it's good to know. Not a rigorous mathematical manipulation but small corrections to MO's and such. I'm speaking outside my comfort zone here though.

Otherwise, I wouldn't say it's a chemists first weapon at attacking a problem but I think chemists should be aware of special relativity.


Well I'm not arguing quantum is less important than relativity! I just think at a lower division one can say a lot about relativity without feeling too lost or drowned in math.

Also, you must be referring to p chem. Because without quantum, most chemistry is still organic chemistry haha.


I don't know about that. I feel someone can get a really good insight into special relativity with just some calculus and algebra. I would say they can be treated on equally light mathematical footings and still not be meaningless.

well, organic chemistry needs to understand a lot about orbitals and electron transfer reactions... oh no quantum, what's an orbital, what's an electron?!

i just mean to say that relativity has very few applications and most people do not need to know it.

 

[Jorriss]

well, organic chemistry needs to understand a lot about orbitals and electron transfer reactions... oh no quantum, what's an orbital, what's an electron?!

Organic chemists don't need to know a lot about orbitals or the quantum mechanics of electron transfer. Organic chemist in practice involves zero to no quantum. Organic chemists actually still use lewis structures predominantly because they are qualitatively correct for second row elements despite being utterly wrong.

i just mean to say that relativity has very few applications and most people do not need to know it.

Most people probably won't. But you take relativity in a lower division modern physics course or in upper division classical mechanics. You don't really know what you need at that point.

 

[Fredrik]

i just mean to say that relativity has very few applications and most people do not need to know it.

You could say this about anything except maybe basic reading/writing skills.

 

[chiro]

Cmon peoples!

Everything is useful in some way or another and although there probably are practically things that are more useful than others (like reading and writing as mentioned by Fredrik), the fact is that it doesn't take away from the fact that everything is still undoubtedly useful.

Its like when I hear about Arts majors being useless, but then if you think about what you can learn by reading a few accounts of history you learn not only human behaviour (and thus psychology) but all about the things that are implied from that: this is valuable information if used in the right context.

I hear about all kinds of bashing of all kinds and at the end of the day it's just pretty much for many purposes, absolutely pointless.