Fourier Analysis is a mathematical tool which can do a number of things: separate out signals from noise; help identify patterns or trends in data; filter out all unwanted data and focus on a single signal; use approximations to make generalizations; make approximations of real world signals (think electronic music); combine harmonics to get a stronger signal. That's what I'll be trying to do here!! Won't you join me with your comments?
Wednesday, July 18, 2007
The Sky at Night (1)
Guest 1, pointing to the south, "Okay, which planet is that one? I say Venus."
Guest 2, "It's not a planet, it's a star:"
Me, "Yes it's a planet, either Saturn or Jupiter."
Guest 1, "No, it's too bright, must be Venus."
Guest 3, "Oh, oh, you question the "professor"? You're gonna learn something now!"
Me (ignoring the teasing), "Okay, which planet is closer to the Sun, Venus or Earth?"
Guest 1, "Venus".
Me, "So, Venus will always be close to the Sun in the sky, either right after sundown or just before sunrise."
Guest 1, "Makes sense. So which planet is it?"
Me, "Not sure. Let me look it up." I go online to Tonight's Sky. "It's Jupiter."
Guest 2, "Are you sure it's not a star?"
Me, "It's not a star. I'll prove it to you." I get out the telescope (Meade ETX-70AT Autostar). The sun had gone down, the wind had subsided, it was clear at the moment, although not really dark. The object was just above the roof of a neighbor's house and I was able to get it in focus fairly quickly. "Take a look."
Guest 1, "Okay, I see a white dot. Why is this Jupiter?"
Me, "See the little dots on either side, along the middle of the big dot?"
Guest 1, "Yeah, there are two of them."
Me, "If you look closer, you should see 3, one is really close in. Those are some of Jupiter's moons."
Guest 2, "What are you looking at?"
Guest 1, "Yeah I see 3. Those are Jupiter's moons? How many does it have?"
Me, "Over 60 so far. But only a few are visible with a small telescope. Here, let me put in a stronger lens."
Guest 1, "Honey, come look at this. Jupiter's moons!"
Guest 3, "Told you you'd learn something!"
With the new lens we could actually see 4 moons, just like Gallileo did in 1610. All our guests and their kids got a chance to look through the telescope. And the kids brought their friends who were playing on the street. And we all talked about how amazing it was.
And it was. Though I've seen the same view many times, each time is still amazing and exciting. We were fortunate with the weather and the timing. Often you cannot see all 4 moons as they are in front of or behind the planet. Or the weather is not clear enough. Or Jupiter comes up too late or too early to make it easy to set up the scope. But we were lucky. Maybe you will be too. For the next 2 weeks or so, look a little to the south for the "first star", about 30 degrees above the horizon. With clear skies and a powerful pair of binoculars, or a small telescope, you should be able to see Jupiter and if you are lucky, one or more of its moons.