Author Archives: Mark P

Twinkle, twinkle, city lights

Posted on by

We can see the city lights from our front door.

They twinkle.

The video doesn’t really capture very well what the eye sees. I think the twinkling is more pronounced on cold, clear nights. That’s when there is a lot of variation in the air temperature, which can cause twinkling at the air moves around. Windy nights might be good as well, but we haven’t had a windy night without rain and fog, so the lights haven’t been visible then.

I have read that stars twinkle but that planets do not, unless they are visible near the horizon. The reason is that stars are point-sources, while planets are not. The light from a star appears to twinkle because of atmospheric refraction of the light. The refraction would be constant and the light would be steady if the air were still, but the atmosphere is constantly in motion, so the light from the stars has to travel through a medium whose density constantly varies along its path. Planets are actually discs. You can see that with a telescope, but even without a telescope the width tends to suppress the effect of refraction.

This site explains the twinkling by saying that a star’s light follows a zig-zag path, but that’s not exactly accurate. If you stand next to someone and look up at the night sky, you can both see the same star, but the light that falls on your eyes follows a slightly different path from the light that falls on your friend’s eyes. When the light going to your eyes is refracted away from its path, you end up not seeing that light. However, light that was following a different path is refracted into your eyes, so it looks like it comes from a slightly different location. That makes the star seem to move very slightly in the sky, which we see as twinkling.

When I look out at the city lights, the smaller lights twinkle while the bigger, brighter lights don’t. In this case, the small lights are like stars, and the bigger lights are like planets. None of them are point sources, so you might think they wouldn’t twinkle, but their light is passing through the densest and (often) most turbulent part of the atmosphere, which is enough to make them twinkle.

The old, blue Dodge

Posted on by

Back in 1995 I ordered a brand-new 1996 Dodge Ram 2500 with a Cummins turbodiesel engine. I had gone though a 1984 Datsun pickup and a 1987 Ford and had decided that I wanted a real truck. It was the first year of Dodge’s “big-rig” look truck style, the one that Dodge and now Ram has used ever since. I sat down with the salesman at the dealership and went though everything I wanted. He nodded and said yes until I said I wanted a manual transmission. That stopped him. Not many people wanted a manual. But I wanted every little big of mileage I could get, and the manual did a better job than the automatic in those days.

Almost immediately after I took delivery, I drove the truck down to Mexico with my friend Tom, who is fluent in Spanish. We went beyond the frontier, deep into the parts of Mexico that most tourists don’t go. We stayed in motels that had gated courtyards, like an old castle keep. We went to department stores with no English speakers anywhere except us. We ate food cooked on wood-fired grills. Tom took a picture of me and the truck somewhere in Mexico.

Both of us were younger in those days.

Most people who buy pickup trucks use them as everyday transportation, just a very big, inefficient car. It was my only vehicle for a while, but it got reasonable mileage for something that big, around 20 mpg. But I also used it as a truck. It was in pretty constant use as a truck while I built my first house, where Leah and I lived before we moved to our current house. That diesel engine was loud. When I visited my friends Errol and Cookie near Atlanta, they said they could hear me coming from a couple of blocks away (that might have been an exaggeration). Errol said it sounded like the garbage truck coming. Here is a photo I took of the truck, my father, and one of my Dobermans.

Those are the footing forms I built for the house. The forms themselves were a major construction project. I had to step them down around 20 feet from the highest corner of the garage to the lowest back corner.

When I bought the truck I was living in Alabama, where I worked. When I moved back to Rome in around 1999, I decided I needed something a little smaller and more fuel efficient, so I got a VW diesel. That got 50 mpg. I kept the truck because the house construction went on for a long time. I eventually got another truck in 2003, and rather than trade the old blue Dodge, I sold it to my brother, Henry.

Henry drove the truck from 2003 until he died last April. He used it down in southern Mississippi when he worked for Presbyterian Disaster Assistance, helping people rebuild their homes after Katrina, when just about everybody else had forgotten about the hurricane victims. The truck got worn and dented, inside and out. It needed various bits and pieces, some of which were no longer available new. Through everything, it just kept trucking’.

When Henry died, his older son Thomas took the truck. Thomas lived in Atlanta at the time, but moved to Dallas a few months ago. We hadn’t heard from him since he moved, so we were glad to get a text Saturday. Unfortunately, it was not good news. Someone had stolen the Dodge, and it had not been found.

It’s so old it has very little value, except for the Cummins turbodiesel engine. That apparently has a fairly high value. But maybe it wasn’t stolen for that reason. Maybe it was just someone off on a joy ride. Maybe it will show up. Maybe it won’t be dismantled, wrecked or burned. I hope so.

If a leaf falls in the forest

Posted on by

When I take the dogs for their long morning walk, I usually drift off into thought. I can walk hundreds of yards without remembering anything about the actual walk. On one of our walks recently I suddenly realized there was a fairly loud noise coming from the woods. I stopped and looked, and then I realized it was the sound of leaves falling off the trees. I couldn’t believe at first that it was just leaves. I tried to get a video so you can hear the sound, but it may be hard to hear. I saved the video in two formats. Maybe one will be better than the other. I can’t really see the leaves in either of these.

If you can’t hear the leaves falling, here is a shut of some leaves and moss that I though was nice.

Phone vs old camera

Posted on by

I always have my iPhone with me, so when I walk the dogs, that’s what I use to take photographs. However, its lens is a wide angle. That means sometimes I can’t get the picture I want. I rummaged around and found my old Canon SD790 IS, which was introduced in March 2008. That makes it more than 10 years old, an antique in the digital camera world. But, it is small, and it has image stabilization, so I thought I would give it a try. On Saturday, I took some comparison photos with it and my iPhone. I enhanced the Canon images a little, but not the iPhone’s.

This is a nice maple with red leaves. First the Canon, then the iPhone.

The iPhone image has more vibrant colors right out of the phone, and it looks more like what I see when I look at the scene. Notice the yellows. I’m not positive that the actual scene looked quite like the iPhone image, but I prefer it to the Canon.

Next was a yellow maple, Canon first, then phone.

The iPhone, again, has more vibrant colors. The Canon image seems especially muddy up in the top, right-hand corner.

Next, Canon first, then phone.

Again, the iPhone image has “nicer” colors.

Saturday was a cloudy day, and the colors were muted. It’s possible the Canon images are a more accurate representation of the scenes as they actually were; I’m not positive. I can say, though, that I prefer the iPhone images over the Canon images.

There is a setting within the Canon’s menu system that allows setting a “vivid color” mode. I plan to select that and try some more comparisons. I would really like to start using the little Canon again because the lens allows a little more flexibility in framing images. I’ll try that when I can.

And town disappeared

Posted on by

A few days ago Leah got up earlier than me — thanks, Mollie — and saw that most of the rest of the world had disappeared beneath a blanket of fog. She shot a bunch of pictures, and this is one.

The long ridge on the right is Mount Alto.

We often see spots of fog in the morning, here and there, mainly collecting in the lower parts of the up-and-down terrain below the mountain. This is called valley fog. It’s caused by radiative cooling of the air near the surface which then flows downhill into the valleys, where it collects. If it’s cold enough, water vapor condenses to form fog. So, it’s really a type of radiation fog.

This morning, however, the fog was everywhere, not just in the valleys.

This view is directly towards downtown Rome. The tower is a telephone company antenna.

I can’t see the top the City Clock, which stands on what used to be Neely Hill and is now called Clock Tower Hill, but it was just peeking through the fog. The stacks and cooling towers of Georgia Power’s coal-fired generating plant is barely visible on the horizon.

This fog is radiation fog. We had a cool, clear night with conditions just right for fog formation. We also sometimes see a sort of reverse advection fog. Advection fog is usually considered to be the type of fog that forms when warm, moist air moves over a cool surface, causing water vapor to condense and form fog. In our cases, however, it is cool air moving over the warm rivers, causing moisture evaporating from the river to condense as fog in the cool night air. This is usually called steam fog.

We often talk about fog “lifting” as the sun rises. As the sun rises, it tends to warm the ground, which causes the air just above to get warmer and the fog to evaporate. As the air gets warmer, the bottom layer of the fog retreats upwards until all the fog dissipates. If the fog is thick enough, it can keep the surface from warming because not enough sunlight can penetrate. People on the West Coast are probably more familiar with that kind of thick fog that we are here in the Southeast.

This was a welcome change for us. For a couple of weeks we, up here on the mountain, were the ones in the fog. For the people down below, we were up in the clouds.