Thanks, everyone, for your patience. What a summer it has been! I think I'm back on my feet now, so let's catch up on our space studies. If you've been following the lessons in the sidebar--congrats! Hope you get a little refresher on those things we missed.
Doppler Effect. Lesson 6.4 here: http://www2.jpl.nasa.gov/basics/bsf6-4.php
I have to admit, I always have a hard time wrapping my head around this one, and the little pulse graphics don't help me. I prefer to visualize it as a wave--like a slinky, for example. If you hold one end still and move the other in an even up-and-down pattern, you get a wave of a certain length and frequency. Now move one end away from the other, but don't change the rhythm of the up-and-down motion. Your frequency stays the same, but the wavelengths are longer. The difference in the wavelengths is your Doppler shift.
Paul Hewitt explains it very well--and he's funny, too.
We hear Doppler shifts all the time--the most common example is in how a train whistle or a siren sounds higher when approaching and lower when moving away.
Doppler shifts are great for telling position and distance--or how fast you are speeding down the highway. Come back tomorrow, and I'll tell you a funny story involving Doppler shift, my father, and my husband. For now, let's move on.
Reflection of Radio Waves: Lesson 6.5 here: http://www2.jpl.nasa.gov/basics/bsf6-5.php
This is a pretty basic lesson, and a phenomenon we are all familiar with, although I didn't know about the skipping phenomenon with x-rays. What the lesson doesn't tell you, either, is how x-ray astronomy is giving us a whole new look at the universe.
Refraction: Lesson 6.6 here: http://www2.jpl.nasa.gov/basics/bsf6-6.php
Again, this is a common phenomenon on earth, but it's cool to see how it's being used in space exploration. I wonder if that's how tricorders are supposed to work when analyzing atmosphere, etc? (I'll need to check out The Physics of Star Trek, if I can find it in my husband's library.)
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