Spherical Bull's photostream  

I am going to be taking pictures for our GCC Physics Department web site, so in that vein here is a photo of Ms Melody Carlson, senior physics major, tending one of Shane Brower's lasers. Melody is a friend of my family's and we've known her longer than her tenure here in the department. She is the daughter of Greg and Bethann Carlson, wonderful, godly people who have spent many years as Bible treanslators in Vanuatu, in the South Pacific. The Carlsons are proving very adept at raising physicists! Their older son, Ben, is at Carnegie-Mellon studying particle physics, and Melody is a fine physics student in her own right.

It may be my incompetence, but as much as I enjoy my camera, I think I am pushing the enveliope to get soft, well-focused images in low light conditions like this. To see the laser light clearly, we shut the door, but this necessitated a 10 s exposure at ISO 200 and f/2.7. Melody was very patient with the photographer to remain motionless for 10 s! With the larger aperture, I don't have completely good focus at all depths, but I needed the extra light. And any ISO above 100 results in too much graininess. Any tips, folks, for those of you who do a lot of photography?

I haven't taken any pictures outside in the last week or two, so I decided to be boring and take a picture of my fire. Pretty pedestrian, perhaps, but then again, fire is an amazing thing. All pictures illustrate physics, but some more than most.

The color of the glowing embers suggest a blackbody temperature of about 3,000 K, I would guess (5800 degrees Fahrenheit), but there are some very hot, blue flames in the back at > 6,000 K.

I've been asked by my kids several times, what is fire? Fire is the oxidation of highly reduced organic compounds, in this case cellulose, hemicellulose, and lignins. In general, it's the same reaction that fuels your body when you eat a Big Mac, and the same reaction that combusts gasoline in your engine:

CxHy + O2 goes to CO2 + H2O

I haven't shown stoichiometry because this reaction is too general: for one, the stoichiometry depends on whether you have even or odd carbon atoms in the hydrocarbon. Second, none of the constituents of wood that I listed above is a pure hydrocarbon. Cellulose is a huge molecule that is a polymer of perhaps thousands of glucose sugar subunits, so it has oxygen atoms too. Hemicellulose contains other carbohydrate subunits, and is a smaller molecular than is cellulose. Lignin is just a mess, a few carbohydrates subunits linked to all kinds of phenolic groups. OK, this probably doesn't make sense, unless you know a little chemistry.

For now, let's just say that this stuff makes good fuel and likes to burn. And when you burn it, you get carbon dioxide and water, just like you get when your car engine burns gas. It's highly exothermic, so the reaction also gives off lots of heat. (And, if you had a sensitive enough scale, you would notice that the products, the stuff given off, has very, very slightly less mass than the reactants, the stuff that got burned, according to Einstein's great equation E = mc^2.) You need only a very tiny amount of mass loss to make a heat equivalent to what you obtain in a fire.

So at the interface of wood and air, the chemical reaction between the highly reduced fuel (the wood) and the air (which contains oxygen) releases a lot of heat. This makes everything around it glow, and of course, since heat flows from hot to cold, the extremely hot, glowing air (which is less dense) wants to rise by convection, which we see as flames.

That's my science lesson for today. Camera settings: ISO 500, f/3.2, exp 1/8 s.

I attempted another photo of Wolf Creek, looking downstream, this time at 9:36 PM on February 6th (tonight). f/4 with 30 s exposure. ISO was 400, so a bit more pixelated than I like. This photo will look better on most monitors than the one I captured last night.

It was very peaceful, and about 38 degrees, with no wind. An extraordinary night in February.

Looking downstream, towards Grove City. Settings: aperture f/3.2, ISO 200, shutter 30 s. The sky was crystal clear and the moon brilliant. Supposedly this year is the Full Snow Moon, except the weather thankfully didn't cooperate. Other tribes called it the Full Hunger Moon, for obvious reasons at this time of the year. In late February and March, though, the sugar starts flowing in the maples, which happily would break the hunger the Indians experienced during the deep winter months.

I went for a stroll this evening towards Wolf Creek, and stopped to take a few photos of the lowering Sun over the Kind's farm. It was glorious outside, reaching approximately 45 degrees. Gorgeous day for this time of the year.

We have still not received much snowfall this winter, and I am glad for it, since in the two previous years, we have been inundated by snow, probably about 70 or 80 inches worth. This year? I'd guess that we've had no more than 20. In a normal February, we might get another fifteen inches. This year? Who knows.

Can you be inundated by something that isn't in the liquid phase?

Anyway - I have been praising God for the weather, and trying to squelch my usual pessimism. After all, if the weather keeps warm, the plants will begin to bud, only to be killed by a late frost. But if that does happen, I can't do anything about it, so why not enjoy the warmer winter anyway?