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Interrogating Light

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Other than purely theoretical astronomy, all astronomy depends on some kind of light (electromagnetic wave).

Among ancients the most they could do was determine the position of stars accurately and relate their position to the rotation of the earth.

Today, one of the most valuable instruments for really getting information about the star itself,  is the spectroscope.

How broad the spectral lines are, any shift in their position and the patterns of emission and absorption lines all tell us about the star.

To get practical experience in how valuable this is, I had the youth group of the Spokane Astronomical Society build spectroscopes using the Mac and Cheese boxes common in 2002.  We also had access to some grating material from my employer at the time.  The only  other supplies needed were some thick black paper and some black photographer’s tape for the slit and grating ends of the box.

I created a worksheet which used the grating equation to figure out what angle the spectrum would appear at relative to the slit on the other side of the box.  To test the results of our computations, we held a red laser (633nm)  one mac-&-cheese-box-length away from a white board and marked where the light fell.  Then we passed it through the grating onto a white board and marked where that light fell. Then we measured the distance between the two.

The design looked like this:

 

spectro1

I created several light sources to see the different spectra possible and provided this chart to classify what gasses were in those sources.

spectrum

 

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Gravity Waves

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I was thrilled to hear the announcement that gravity waves had been detected by scientists at the LIGO telescope in Washington.

When I lived in Spokane, Washington I was active with the Spokane Astronomical Society where I made a number of presentations about several exotic theories.

Among these was the presentation I gave on INTERFEROMETRY which preceded a field trip by members of the youth group I had been tutoring.  At the time of our visit in 2003, LIGO was still in its first engineering runs and only had hopes of what was discovered in September 2015.

Among the tools I used to teach the students was a laser interferometer I built using a laser pointer.