Analemma On My Wall

A prism of high quality glass sits in a south window above our mantle. It is part of a surplus optical instrument from WW-II. The window crank gives a sense of its 2″x1″x1″ size.


When the Sun is low in the sky during late fall and winter, light through the prism casts a large full spectrum on the wall on the opposite side of the house. This is a closeup of the spectrum. It is always a delight to see the colors move slowly across the wall during the middle part of a sunny day.


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NASA Twins Study | Early Results Reported

Astronaut twins Mark and Scott Kelly participated in a study conducted by ten researchers on the effects of long duration space flight. Scott was aboard the International Space Station for 340 days while Mark remained on Earth. Scott returned to Earth 1 March 2016. For details about his return, read this previous post.

Ten researchers reported preliminary results on 23 Jan 2017 in Galveston TX of their comparative studies of the twins. The NASA issued statement is here. I’ll attempt to summarize eight of their findings below.

Credit: NASA

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Ceiling Lights | Incandescent | CFL | LED

Our home has many can-light ceiling fixtures. We replaced the original incandescent bulbs with CFL in many of them and noticed some cost savings on our electric bill for several years. More recently we added some LED style.

Bulb costs, duration of use, and total cost of use are some of the quantities tabulated in the chart below from wikipedia. I don’t know how recent are the values. But, they illustrate the cost savings with LED. With LED costs coming down, the savings is improving.

The main problem with an incandescent bulb is that about 75% of the energy needed to operate it is wasted as heat energy to the surroundings. Only about 25% goes toward making light energy. The CFL and LED bulbs convert a much greater fraction of their operating energy into light energy. As a result, they need less electrical energy to produce the same light output as an incandescent.


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Scanned Images | More Examples

Previously, I presented images of leaves using a flatbed scanner set to reflection and transmission modes for comparison. See those here. This post includes scans of a variety of common objects. My favorite is the back of the Lincoln penny with him sitting in the monument. Images are viewable in larger size. Each image square is barely more than 2.1 cm (0.83″) on a side.


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Autumn Leaves | Scanned Images

Fellow bloggers Steve and Steve often include beautiful close-up photos of leaves in their posts. They inspired me to try imaging leaves in a different way. I decided to use a flatbed scanner. During a recent walk, I picked up three examples that were colorful and still in good shape. I got a pin oak, maple, and ornamental pear and headed home.

First up on the scanner was the oak leaf. I placed it face down on the glass and set the resolution to a high value of 800 dpi. I wanted to get lots of detail in the scanned image.


Pin oak | 800 dpi | Reflection setting

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Moon’s Far Side | Tycho Crater | Apollo 15

Far Side of the Moon

This image of the Moon is probably not familiar to you. It is the Moon’s far side. Only 24 people have seen it with their own eyes and not as an image. They are the Apollo astronauts. Click on this image for a detailed and closeup view.


NASA | Goddard | Arizona State University


Because the moon is tidally locked (meaning the same side always faces Earth), it was not until 1959 that the far side was first imaged by the Soviet Luna 3 spacecraft. Russian names are common for prominent far side features, such as Mare Moscoviense. The widespread smooth maria on the nearside that we see do not appear much on the far side. It is a very different world from what we see from Earth.

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Gravity | How It Behaves

There are two astronauts somewhere in space, 3 meters apart, and not moving relative to each other. Astronaut Lucy has a total mass of 100 kg including her suit. Astronaut Ricky has a total mass of 140 kg including his suit. Question 1 – Is there a physical attractive force between them? Question 2 – What are the variables which affect the strength of that force? Question 3 – How large is that force? Those questions will be answered in this post.


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