Monday, July 9, 2012

The original God particle: the Rutherford atom

This is a bit long-winded.
I hope at least one elementary school teacher reds this through.
Science education lives and dies by those who teach before children before they can shave.

Learning science here in Jersey is a bit like learning in catechism class--the parts all nest together neatly in strange-sounding phrases that were once attached to miraculous things, but to get through CCD (or science class), it's more than enough just to learn how the various strange-sounding phrases fit together.

YouTube teems with videos that help children learn "science."

This video has been viewed well over a million times--and I bet most times happened in schools.

Our state standards don't help much. By 8th grade, students should be able to "explain that all matter is made of atoms."

Well, what is an atom?  Turns out you really don't need to know. Oh, by 12th grade you need to know a few basic parts, but you still don't know what an atom is.

Ask someone, anyone, to draw an atom. Most will draw something, probably something like this:

If I were to draw a picture of an atom to a similar scale, say 6 inches across, on a piece of paper, this is what it would look like:

Space. Empty space.Few high school kids know this, and even fewer know why we think this. The situation is even worse among grown-ups.

My grandfather was 12 years old in 1910, old enough to read, just a few years shy of running away from home to go fight in the Great War. Electrons had been postulated just a few years earlier.

Around the same time, one of the great experiments of our time, and one that is fairly easy to grasp, was conducted by Ernest Rutherford. Remember, the concept of atoms having more than one part was still new, and atoms were viewed as a tiny blob of positive mass with electrons studded throughout (another story for another time).

Rutherford wanted to get to know a little bit more about atoms, so he (well, his underlings, anyway) shot tiny particles (the catechism says "alpha particles") through exceedingly  thin pieces of gold foil, fully expecting them to pass through slight deflections by the gold atoms. He could see where each particle ended up by using a screen that lit up when hit by particles, the same way older televisions worked.

Now what's the point?
To understand how this works, imagine shooting a rifle at a mound of loose snow: one expects some bullets to emerge from the opposite side with a slight deflection and a bit of energy loss depending on how regularly the pile is packed. One can deduce something about the internal structure of the mound if we know the difference between the initial (before it hits the pile) and final (after it emerges from the pile) trajectories of the bullet. If the mound were made of loose, powdery snow, the bullets would be deflected very little; if the bullets were deflected wildly, we might guess that there was a brick of hard material inside.
from Medium Energy Ion Scattering laboratory, Rutgers University

So what happened?

Just about every particle went right through the foil like it wasn't there. About 1 in 8000 got deflected like it hit a proverbial brick wall.

"It was almost as if you fired a fifteen-inch shell at a piece of tissue paper and it bounced back and hit you."

Ernest Rutherford
No one's seen an atom--we only see the effects of particles bent this way or that. The classic atom pictured above never existed. It's not real, it's a story. A special story, molded to fit what we know of our natural world, but still a story.

That is the nature of science, not catechism. There is no Temple of Science (despite our culture's deep religious belief that that Temple exists). We don't get to vote on it, we don't to pick and choose our results.

We do get to create better stories as we learn more about what we don't know.

I know a lot of folks got pretty excited about the God particle last week--it was like Holy Communion for the science news fetishists, no understanding required.

 The Rutherford model has long been surpassed by better models, of course--if you're looking for a permanent reality, you won't find it in science. Maybe Father Kelly can help you, though....


Kathryn J said...

Every year, I try to get this concept across to students - starting on Day 1. Sadly few can reliably demonstrate understanding that matter is mostly empty space. I am going to try art projects this year in which students must create one early atomic model and one wave-mechanical atomic model. I think it needs to be more tangible for them.

I hold a poppy seed on the tip of my finger in the middle of my classroom - that is the nucleus relative to the electron cloud. I use baseball and soccer analogies. They can't see it so they don't internalize it. The discovery of atomic structure is one of the best scientific stories ever!

doyle said...

Dear Kathryn,

I think we're asking the impossible, and I don't mean that in a cynical way. This needs to be internalized at a young age, and our culture is stuck with a 1910 model.

The more I learn about what happens at the elementary level, the more I think we should just stop pretending and limit "science" to observing, something few kids do well anyway.

If nothing else, I wish the kids came up understanding that these are, indeed, stories. Useful, true, but still myth in the finest sense of the word.

Jenny said...

The more I read from you (or from books you point me to) the more I want to completely avoid teaching science! Luckily, at first grade I can mostly allow students to observe, ask questions, test their ideas. There isn't too much I have to directly teach them in science. That stops being true by second or third grade unfortunately.

Mary Ann Reilly said...

We are mostly consumers. We understand empty space as a momentary lapse in judgment--one that can be and is quickly filled with powerful versions of Baltimore catechism that we foolishly call our own.

How can we embrace uncertainty when we're so practiced at 'the explanation'?

Doug Noon said...

I suppose the key idea here is that, as you say, "Turns out you really don't need to know." If the model serves the purpose, whatever that might be, then it's done it's job. In school, "the purpose" usually has something to do with a grade. For teachers .... well, it's in the curriculum. So it goes.

Recognizing the difference between the map and the territory is something we might want to learn for any number of reasons.

doyle said...

Dear Jenny,

I was thinking of your approach to your students when I started on this, then got tangled up in all kinds of tangential nonsense, and almost deleted it because I missed both original points--which Doug nailed in a brief response.

At the risk of sinking deeper into the muck, let me be less obtuse here:

1) The concept can be grasped by a child--atoms are almost completely empty. (Alas, "empty" itself is confusing--an empty bottle is full of air particles.)

I'm not worried about your students--you know what you don't know, a rare gift in a teacher. Somewhere along the line here in Jersey, kids are learning a bad model, which gets us to ...

2) what Doug succinctly said. It is critical that someone a child trusts gets that these are models, maps of whatever it is that whatever is.

Grasping the second part changes the way you look at the world--the transition is scary, and all of us resist it at times, and many resist it all the time.

OTOH, knowing this elevates the idea of story-telling, which is what we do. And who is a better story-teller than a gifted elementary teacher?

doyle said...

Dear Mary Ann,

We understand empty space as a momentary lapse in judgment.

I was thinking a lot about private spaces yesterday, and how they're disappearing, but that wasn't quite what I meant to say, so I deleted a bit about that. And you nailed it.

I may put up a variation of your words in class:
Embrace empty spaces.

I am tempted to combine all the comments so far in one post, and say "See? This is what I mean..."

doyle said...

Dear Doug,

We are leveling classes this year--I have been wrestling with how to start. We're essentially creating a new course.

The more I look at this, the more I think this may be the theme for next year. The more I look at it, the more I realize how confused I am myself.

I may bother you a bit more on this...

Jenny said...

Honestly, I think kids probably grasp many concepts much better than we adults do. My daughters occasionally look at me as though I'm crazy when I answer their questions about the natural world. My responses are in such conflict with their observations. I'm trying to learn to ask more questions rather than spout off. It's tough for me but I'm working on it.

Doug's point about the map and the territory is huge. I'll be mulling that some more.

doyle said...

Dear Jenny,

My responses are in such conflict with their observations.

Some days I worry that public schooling (or any formal education) does more harm than good just for this reason.

I tend to spout off, too. I've been working on it. The kids notice.