This is how I felt at the end of the day today.

**Physical Science**: Today we continued working on SI prefixed, and doing unit conversions. I teach kids to set them up as ratios. Kind of like this.

It comes about from reading parts of Aron’s book on teaching Physics. Ratio reasoning is a great skill for students to develop. It really comes into play when analyzing data. Being able to break down complex sets of units and figure out the meaning of them (say like when making a graph) can be really useful.

For the freshmen though, its more about making the measurement stuff in lab easier. We can measure stuff in centimeters and grams, and then convert it over to SI units later. So we’re working on that. Tomorrow we will look at the first assignments in trying it out.

**Chemistry:** We discussed the homework from yesterday, dealing with density, mass, and volume. Everything went really well. Especially since this was the first time that they encountered how awesome developing models really is. Since we created a mass-volume graph and analyzed it, plus developed the line equation into a nice general equation, they had two ways to solve many of the problems.

A graphical model (no math), or a mathematical model (for those not big on visual learning.)

It makes me wonder why anyone would ever stand in front of a class and say, “This is density, this is its definition, and this is the equation. Go solve some problems.” It might seem like a crazy thing to spend a week developing the idea of mass, another with volume, and then a week on density. However, the depth of learning, not just on those topics, but also data analysis, multiple problem solving methods and the options presented, I would never go back to the “Sage on the Stage” days.

**Physics of Light**: Holy cats, we finally finished up looking at light intensity! Actually, I don’t mind, because none of the time was wasted. Students spent most of the hour working on lab write ups and problem solving some intensity stuff that we will talk about tomorrow.

I however went on a bit of a spiral after this question:

“What is the difference between a laser pen and a laser pointer?”

I showed them a laser pointer (shorter) and a laser pen (longer). I looked at one which is red and the other green. Then I thought to myself, “what would happen if I crossed the laser beams?”

So I got out the disco fog, apologized that I was turning out the lights on everyone, and started playing around. This is what we got:

It’s yellow! Why? I’m not talking about it. My kids thought it was awesome too.

Ss: “Can we learn why that happened?”

Me: “I think we can figure it out someday.”