Quantum to Classical: A Reflection

[physicsisphirst]

quantum --> classical

i'm new and this is my first post so i hope this is the most appropriate forum for this thread.

i had an uncomfortable time with quantum mechanics because i had been brought up on classical physics. i wondered at that time whether it would have been nicer if we learned quantum first or even along side classical.

admittedly, it would not be possible to do a particularly mathematical treatment, but just the idea that there is another way to look at the world might be a good thing. i recall being very upset upon learning that electrons don't really orbit the nucleus the same way planets orbit the sun - rather like being told that really wasn't a santa claus!

i don't know how well i have handled the latter, but i'd be curious to know what people think about getting into quantum mechanics earlier :)

 

[Vodka]

my physics teacher liked to have fun razzing the people in our class who didn't get it. he say they should free themselves from their horribly wrong Newtonian view of the world, then gently reminded us our final marks rest with him

conceptualizing theoretical physics has always been easy for me, but when it comes to quantizing it [er...bad word. doing the math, rather] i have more difficulty. i find it a fun mind exercise to think of the world in a quantum manner...throw some de broglie wavelengths here and there, imagine that I'm just seeing huge lumps of quarks walking around, thinking of light as quanta of energy, wondering when the next particle is going to pop into existence...its fun ^_^ until i have to do the math [b(] haha

i didn't do well either with the santa clause bit too

 

[Gara]

"electrons don't really orbit the nucleus"

OMG THEY DONT!?

my life has been a lie!

*runs off sobbing*

 

[ZapperZ]

Originally posted by physicsisphirst
i'm new and this is my first post so i hope this is the most appropriate forum for this thread.

i had an uncomfortable time with quantum mechanics because i had been brought up on classical physics. i wondered at that time whether it would have been nicer if we learned quantum first or even along side classical.

admittedly, it would not be possible to do a particularly mathematical treatment, but just the idea that there is another way to look at the world might be a good thing. i recall being very upset upon learning that electrons don't really orbit the nucleus the same way planets orbit the sun - rather like being told that really wasn't a santa claus!

i don't know how well i have handled the latter, but i'd be curious to know what people think about getting into quantum mechanics earlier :)

What you proposed is a good idea - at first. It certainly is something that has been discussed by physics educators on whether QM should be brought in earlier in a student's education. There are however several major setbacks to this.

1. It is difficult to illustrate QM effects, whereas classical mechanics examples are abundant. So teaching QM at an early stage would require students to accept these effect "by faith", rather than having clear demonstrations of them that they can see everyday. As an experimentalist, I do not particularly like this approach.

2. Without understanding classical mechanics first, the Schrödinger equation/QM Hamiltonian would seem to appear out of nowhere. Things like this are seldom very good in the teaching and understanding of physics.

3. Our measurements and concepts are still classical. We impose onto the quantum world our classical ideas of position, momentum, energy, etc... which are things we know, understand, and can measure that are all classical. It certainly is a possible reason why all these concepts appear "weird" in the QM world - they have vague, maybe even non-applicable concepts in such a world.

4. Without knowing classical mechanics first, you would never appreciate how different, unusual, and revolutionary QM is. You will also not know why it was needed in the first place, since you would not have already seen where classical mechanics break down.

I think in many schools there are some sort of an intro to modern physics course aimed at maybe sophomore students. This serves primarily as an appetizer before they take the "real" QM classes, so it lacks in-depth details, but are quite good in giving a brief survey of what's to come. So there are certainly opportunities for students to get to see QM rather early in their academic program. Hopefully, when they do get to those more detailed courses, they won't be that weirded out.

Zz.

 

[russ_watters]

Originally posted by Gara
"electrons don't really orbit the nucleus"

OMG THEY DONT!?

my life has been a lie!

*runs off sobbing*

Its easiest for the people who just memorize and accept whatever a teacher tells them. I, however (and likely most of the people in this forum), am the type who wants to know and understand everything. Though I don't remember the exact issues, I do remember several things in high school calculus and science I had trouble with because I refused to just accept them without an explanation of why.

 

[physicsisphirst]

Originally posted by ZapperZ
What you proposed is a good idea - at first. It certainly is something that has been discussed by physics educators on whether QM should be brought in earlier in a student's education. There are however several major setbacks to this.
Zz.

thank you Zz
your detailed explanations are much appreciated and will prove to be helpful.

 

[Gara]

i acually heard about the non orbit thing ages ago, but so far as yet i have not found any url about it. so could someone point me in the right direction?

 

[physicsisphirst]

Originally posted by Gara
i acually heard about the non orbit thing ages ago, but so far as yet i have not found any url about it. so could someone point me in the right direction?

this looks good gara:

http://csep10.phys.utk.edu/astr162/lect/light/bohr.html
then follow the more realistic discussion of what atomic orbitals look like in quantum mechanics link to atoms in a box - nice animations!

here's another that ties ideas together nicely (the whole site is excellent in fact):
http://hyperphysics.phy-astr.gsu.edu/hbase/bohrcn.html

it's not so bad ... they just don't orbit the way we were told and the pain goes away after a few decades I've found :D

in friendship,
prad