The Sun in Various Wavelengths

Cross-posted from William H Calhoun

My physics curriculum has shifted in response to our new state frameworks, and one shift has been a greater emphasis on electromagnetic radiation. I've been having fun concocting new examples and demonstrations (including an "in-house" field trip to our metal fabrication shop to experience welding).

This spring my class was having a discussion about the Sun's radiation, and how so much of what it radiates is invisible to us. They wondered what it would look like if we could see the different kinds of radiation. I explained that we can create devices or sensors that detect different wavelengths of radiation, and then construct false-color images from the information gathered. Immediately I went online and hunted for something to show them. A great resource, which I have used before, is the wonderful and painstakingly-built website called Windows to the Universe. This site is a project of the National Earth Science Teachers Association.

In particular, I went to the page entitled The Multispectral Sun, and found this animated GIF:

I liked this concept a lot, and looked around for other examples. I found What's the Sun doing lately? and Compare Multispectral Sun Images, and lots of imagery, including this NASA composite image from the Solar Dynamics Observatory:

I decided to try making something of my own. My project would be a video replication of the animated GIF above, but using many more images. And I would start with the images in the NASA image above.

Here is what I wanted: a video file so playback can be controlled, a broad and representative spectrum of images, and captions with either a specific or representative wavelength indicated. I shamelessly borrowed some aspects of the animated GIF (images scaled to the same size, captions colored to match the image, images taken on the same day). Because I started with the NASA SDO chart, I needed to know what date those images were taken. A little hunting revealed July 11, 2012.

So I was off and running. I decided to stick with spectroheliograms, rather than dopplergrams or magnetograms. I searched for quite a while for solar images in various wavelengths that were taken on 7/11/12. Depending on what time and from where the image was taken, 7/10/12 images sometimes worked as well or better.

As I accumulated my images, I had to decide on wavelength units. My students didn't know about Angstroms, so I used nanometers instead. I came to realize that I could use just three units; nanometers, millimeters, and meters. Then came the laborious Photoshop work, including colorizing a couple of the images. The video was constructed and edited with Filmora. I posted the final video on YouTube.

An interesting issue is the color of the Sun as we see it. Ask anyone, what color is the Sun? Almost everyone will say "yellow," but of course it isn't, it's white, at least to our eyes. (Please don't go out now and look at the Sun - it's bad for your eyes. But if you have a chance to look at it when it's obscured by fog or clouds, you'll see.) I found many images of yellow suns with the caption "visible light." These images were either taken through a yellow filter or they were colorized yellow because of a belief people will think it should be yellow (white light, of course, does not have a specific wavelength).

When I showed the final video to my students, they loved it. But many suggested it should have music. I was telling this to one of my fellow science teachers, and she said, "I have exactly what you need!" She owns a small, portable planetarium called Star Theater Pro, and it comes with a music CD having 15 minutes of suitably cosmic-sounding music composed by Donovan Reimer. She was right, it was perfect.

Here's the final video product:



And here's a shorter animated GIF:

Here are links for downloading the most recent versions:
MP4 Video: 4 seconds per image, with audio
MP4 Video: 4 seconds per image, no audio
MP4 Video: 3 seconds per image, no audio
Animated GIF: 2 seconds per image, continuous loop

Credits:

Radio: 0.9 m, 2.0 m - BASS2000/Nançay Radioheliograph
Microwave: 17.6 mm - Siberian Solar Radio Telescope
Microwave: 52.6 mm - Nobeyama Radioheliograph
Infrared: 1083 nm - HAO/Mauna Loa Observatory CHIP
Visible: 656 nm (Hα) - Big Bear Solar Observatory
Visible: white - NASA/SDO AIA
Visible: 393 nm (CaIIK) - Langkawi National Observatory
Ultraviolet: 170 nm through X-Ray: 9.4 nm - NASA/SDO AIA
X-Ray: 5 nm, 1.9 nm - NOAA/GOES Solar X-Ray Imager

Music - Star Theater Pro/Donovan Reimer

A Story About Weather and Teaching

Cross-posted from William H Calhoun

Physics as Story

I think of physics as a kind of story. It's actually a huge collection of stories, the result of working to understand every physical phenomenon under the sun (and beyond). In the physics classroom I am therefore a storyteller, and I endeavor to help my students become better physics storytellers.

Certainly in physics there's a specialized vocabulary that can be assembled into stories, but I also think of graphs, diagrams, and even equations as kinds of story. As with any good story, there is an art and a craft to both the understanding and telling of physics stories. Physics stories just happen to be demanding in particular ways.

High school students already know how to tell many kinds of stories. I teach juniors and seniors, and they tend to tell certain kinds of stories about the events in their lives. For instance, many of them have begun driving cars, or are about to, and there is a lot of interest in and concern about driving. Some have already had scary experiences and close-calls; few have an accurate understanding of the physics of what they are doing. A natural entry point, then, is to ask them about their driving experiences. Various instructional activities give them the opportunity to refine and change their stories. If a student can tell a solid physics story, by whatever means, to whatever extent, then that student is demonstrating learned knowledge of physics.

A Worksheet as Storytelling

An instructional tool I have used for a long time is the vocabulary worksheet. You know the kind - there's a word bank, and you fill in the blanks to complete the sentences. But my worksheets have a different twist. Most of the words in the word bank are used several times. Each blank is numbered, and if a word fits the blank, it fits all the blanks with that number. This allows me to avoid writing disconnected sentences with only one or two blanks. I can write a coherent paragraph, a whole short story. Sometimes toward the end of the worksheet the sentences are mostly just blanks waiting to be filled in. The repetition of words and phrases becomes an important part of adjusting to the new vocabulary.

After everyone finishes, we read the worksheet out loud, one student per sentence. Sometimes we'll go around the room twice. If there are diagrams or equations at the bottom of the sheet, interpreting them is part of the reading. The students really enjoy the challenge, even by the end of the year after we've done two dozen or so of these. Here's one:



These worksheets can be difficult to construct. I have written an Excel spreadsheet that helps me construct them. It allows me to just write the sentences as naturally as possible, while it keeps track of the blanks and the numbering and the word bank. You can download one here. You'll need to Enable Editing, and then Enable Content. Then click on the button labeled "Help."

The Story of Weather

So what about the weather? I have a few favorite physics topics, and weather is one of them. The problem with broad topics like this in the physics classroom is that students are struggling to learn the basic concepts and tools, and weather is a really complex topic. Still, whenever there is a good opportunity, I'll try to link some aspect of weather to whatever we're working on.

The topic of heat and heat exchange is central, for instance, to weather. Before students can begin to comprehend this story, they need to master some basic ideas and vocabulary about heat. In my classes, this work tends to happen toward the end of the school year. If I have a class that seems ready, and there's a bit of time in the busy end-of-year schedule, I have a special worksheet for them.

Or rather I've been planning a special worksheet for which there keeps being not enough time to finish and use. Not enough time for the last two years. This year, because I knew I had the students who could benefit from it, I really hustled to finish this special worksheet.

I started with a simple but long vocabulary worksheet which tells the story of how the interaction between the atmosphere and the sun's radiation results in a rainstorm. The worksheet is simple because there are only six words in the word bank! But there are 20 sentences. After I finished the basic worksheet, I got the idea to use diagrams of the entire heat process that would parallel the sentences. I used diagrams from the National Weather Service's lovely tutorials on weather called JetStream. I edited the diagrams with Photoshop, and then used Adobe Acrobat Pro to assemble my worksheet.

I decided to split the page vertically and have the running vocabulary/story part on the left half and the images on the right half. I then put fill-in blanks on the diagrams which corresponded to the vocabulary. Normally my worksheets are black-and-white, but I decided to keep the images in color and to print the worksheets using a color printer. This emphasized the "special" aspect of this worksheet (and the students who got a worksheet all said "Ooooh, color!")



While the students were working on it, I looped a time-lapse video on the SmartBoard that showed a collection of rain-clouds billowing way up into the atmosphere. It was the last vocab worksheet of the year. As usual, we read it aloud once everyone finished.

Quick Electromagnetism Demo Videos

Cross-posted from William H Calhoun

One of my students this past year had a medical condition that required him to be out of school for an extended time. In situations like this, I usually aggregate all the instructional material for a unit into a single file called a Portfolio PDF. Notes, homework, worksheets, quizzes, links to simulations, photos and videos of demonstrations and activities are all in one file. The student can either print everything out, or make changes digitally within the file and send it back.

Portfolio PDF's can only be read by Adobe Acrobat, so the student must download the free Acrobat Reader if it isn't already on his or her machine (as far as I know, the Portfolio PDF cannot be opened in Android and iOS devices yet). You need Adobe Acrobat Pro to create a Portfolio PDF - if you have access to it through your workplace, check it out. Acrobat Pro is worth the investment - get a student or teacher edition with a permanent license for a one-time fee (in other words, just purchase Adobe Acrobat Pro like in the good old days when you actually bought rather than rented software).

One of the units I packaged into a Portfolio PDF is about electricity and magnetism, and in particular about the various devices that take advantage of the E-M interaction. This is a difficult unit for my students, so hands-on equipment is the instructional tool of choice. What was I to do for my distance learner with no access to these devices?

I decided to make quick little videos for him, somehow. I had already been demonstrating the devices for my students, so the devices were out and ready, and I had my explanations practiced and warmed-up. I decided to use a simple Logitech USB webcam that normally attaches to my monitor. I experimented with rigging it up in various ways and hit upon having it point straight down at a black lab tabletop. That way just my hands and the devices would be visible while my voice narrated. The webcam software kept trying to adjust for the black tabletop, over-exposing anything not black. I finally decided to leave something bright in the frame which I knew I could crop out later. This turned out to be a pretty easy way to control the exposure.

After a couple of takes, I opened the video files in my editor of choice, Filmora (again, worth the expense), and edited the video. I created a fade from black at the beginning and a fade to black at the end. I separated the audio track, and faded the audio as well. I went through the audio to get rid of unnecessary um's and ah's and other sounds. Sometimes I inserted a bit of video or audio from another take. It was pretty quick work. I exported the videos as MP4 files and uploaded them to YouTube. The videos are below.