Previously, I shared a post about a conversation with my son about the rising sun viewed at different latitudes. During that conversation, we also discussed how the length of our shadow varied over the course of a year. In winter at noon in the northern hemisphere, when the sun is low in the sky, our shadows are cast long to the north. In summer, our shadows are shorter due to the higher angle of the sun in the sky.
Imagine a plane extending through the earth at the equator. Extend that equatorial plane out into space. Between late March and late September, the sun appears above that plane. It reaches its highest extent in late June at the summer solstice. The sun appears at the elevation of the plane on the equinoxes in late March and late September. It appears at its farthest extent below the equatorial plane in late December at the winter solstice. The farthest north and south of the equatorial plane reached by the sun is 23.5˚.
Melanie and I live about 42˚ north of the equator. In the summer months, the sunlight direction is above the equatorial plane several degrees. Our short shadows are cast to the north at noon. In the winter months, the sunlight direction is below the equatorial plane. Our shadows are cast longer to the north. The blue man in this figure is not to scale, but illustrates the concept of casting of shadows.
We climbed the 245 steps to the top of the Inca ruins at Ollantaytambo in Peru and reached the Temple del Sol. It was noon with the sun high overhead. Someone looked up and noticed an ice ring encircling the sun. I had to capture this photo.
I grew up and continue to live at about 40-42˚ north latitude in the center of the U.S. The sun has never been directly overhead. But now, at noon about 13˚ south latitude, the sun was nearly straight up. I looked down to my feet and saw something I’d never seen before. My shadow was directly below me. That was fun to see.
I enjoy trying to capture passes of the Space Station over my location. Sometimes it passes in front of the Sun. That happened today at 2:20:30 local time. Here is how the Sun looked before passage. Notice the two sunspots at the right. It is in a period of quiet sunspot activity now.
There are two videos of the transit of the ISS. This first one is in real time. At about the 4 second mark, it crosses across the lower left part of the Sun. Don’t blink or you will miss it. The second video is slowed to 10% real time. The actual speed of ISS is about 5 mi/sec (8 km/sec).
It will help to adjust the quality to 1090 or 720 using the gear icon down by the YouTube label.
Melanie showed me an image in an arts and crafts book where Henri Matisse style cutouts were put on the back of a denim jacket. I immediately thought that would look good on my old jacket. Instead of Matisse, I planned to use the traditional astronomical symbols for the Sun, Moon, and planets. Some online research located a set of symbols and a source of iron-on fabric patches in a color set I liked that coordinated with denim. I am very pleased with the final result. I can’t wait to wear it on a cool day and have someone ask “What does that say on your jacket?”
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Moon and Sun
In case you didn’t notice, the predicted end of the world on 19 Nov 2017 did not happen. I don’t expect it to happen any time soon. I don’t normally make bold predictions about anything. There was one exception in 1974 in the Nixon administration. I successfully predicted he would resign. I think I was lucky.
If you are a believer in the end times prophesies, you may scoff at my prediction. That’s ok. I will give 10 reasons why I think I’m right. Mine are based on science. Join me below the glowing solar firestorm of death and destruction for the reasons we can feel the end is NOT near.
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The sun’s output in the visible spectrum peaks around yellow. Our eyes are most sensitive to that part of the visible spectrum. The sun also radiates in a broad range of other wavelengths invisible to our eyes. Each comes from dynamics taking place on the surface and in the atmosphere of the sun.
I’ve written about NASA’s Solar Dynamics Observatory (SDO) earlier in a previous post. SDO observes and images the sun several times a minute at ten different wavelengths to give a more complete picture of the activity at and near the surface. A description of those wavelengths is available here. I used the images from the SDO site to render this image of the sun at those ten wavelengths. The yellow center represents the sun’s surface. Each ring of color is at a higher altitude and temperature in the atmosphere of the sun.
Original images used from: NASA/GSFC/Solar Dynamics Observatory
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The first time I viewed a total solar eclipse was in 1999. We traveled to London, took the trains to Edinburgh, Glasgow, then Oban. Rode the ferry to the island of Barra for a few days. We came back to London and then to Dover for a couple of days. We boarded the high speed train to Paris. It went through the Chunnel and emerged in France going 185 mph. Another train from Paris got us to Stuttgart Germany in time for the total eclipse.
You need to have proper eye protection leading up to and following the total eclipse on August 21 in the United States. During the minute or two of totality, it is ok to view without eye protection. But, not before or after. Inexpensive viewers are available from many sources. Talk to a person from your local astronomy club. They will be happy to help.