Astronomy class lecture with Phil Plait(Assuming Phil Plait, a popular American Astronaut teaches a guest lecture to a class filled with amateur astrophysicists).
Good morning star-gazers! I hope your day is as illuminating as ever. Astronomy is a science for the big hearted. For the curious. Space isn't that different from a murky pond. You feel your way through a murky pond and in the similar fashion you try to catch a glimpse of electromagnetic radiations to observe space. Let's begin today's class before your enthusiasm fades away.
The sunlight that is now slowly creeping inside from that window is an electromagnetic spectrum from a star 150 million kilometres across. And the visible spectrum, I.e..; the part of light spectrum that helps us see, has only about 300-700 nanometers of wavelength. This tiny wavelength range snatches away from us many beautiful sights. As a light wave moves further away from its source, its wavelength gets streched. When the wavelength goes well beyond or below the visible spectrum, the source is invisible to the naked eye. But that is where spectroscopy comes in. We monkeys did pretty well with our huge telescopes. But as our curiosity got bigger, we needed advanced ways to map difficult distances. This is how spectroscopy is useful in practice.
Kepler observes Earth-like planets, right? And to find a suitable rock among tremendously brilliant trillions of stars is practically impossible. That is why astronomers rely on the "transit". Let me pick up my phone and switch the flash light for you. Done. Now you can see this piece of tape I've got in my hand. When I pass this piece of tape against the flash, you don't see the tape. But you would see one thing. For few moments the intensity of the flash drops. That is what we astronomers measure. We pinpoint our spectroscopes towards a star. And when a planetary body crosses the star, there's a measurable drop in the star's intensity. Such a simple and effective solution ,right? We then filter the transit data to find a planet that matches the size of our Earth. Transits literally tells us everything we need to know about a distant object. I wish to cover more on this when I discuss "Doppler effect" with you.
Let's break the class for today. See you all tomorrow.
(Entry for the Lecture competition).