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Astro Sciences, Friday
Friday, October 5th, 2012 06:25 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
not_a_whiner"Today we're going to start edging away from astronomy a little, into physics," Kaidan said. He was standing in the classroom in front of the holographic board again, which was currently displaying a small round object emitting some kind of waves. "We'll be having a test on everything we've done these past few weeks after the break, by the way, so make sure to check your notes."
Ahem.
"You might have found last week that it can be hard to determine how far away a star is," he said. "It's even harder to tell whether a star or an object might be moving, because how could you measure that...? Well, for that, we've got the, uh, the Doppler effect."
He pointed at the board. "Originally discovered by Christian Andreas Doppler in 1845, the Doppler effect dictates the changing wavelength of forces around a moving object. For forces using waves, such as sound, it is both determined by the movement of the object and the movement of the observer." He glanced back towards the class. "Basically, the length of the waves get shorter upon approach, and longer the further the object goes away from you. How does that work into astronomy? Well, light is a wave."
The waves emitted by the object on the board helpfully shifted color.
"Basically, the longer the wavelength of light, the redder something gets." He was... trying to keep this simple. Hoped it was working. "The shorter it is, the bluer it gets. So objects moving towards us become noticably bluer - that's called a blueshift - while objects moving away undergo a redshift. Of course, we can't actually see the colors unless an object is moving at a relativistic speed - but we'll get to relativity next week."
He cleared his throat. "But we can measure it," he said. "For example, we can tell the Andromeda galaxy is moving towards us. Perhaps more importantly, though, this is how we first started to catch on to the idea that the galaxy is still expanding - because the universe around us at large is redshifting. If you want to know more about that-- here's some handouts."
It'd be useful for the test was all he was saying.
"But today I want you all to participate in an experiment," he said. "Push your tables to the sides of the room, please."
He put several large tennis balls on the desk, one for every two students. "Each one of these has a siren inside of it," he said. "Now everyone takes one of these sound pressure level meters--" he pointed at the other devices on the desk. "Roll the balls around the room. Measure the pitch as it moves towards you or away from you. Write down your findings." Beat. "If you get done with that early-- there's an applet you can try, too."
Ahem.
"You might have found last week that it can be hard to determine how far away a star is," he said. "It's even harder to tell whether a star or an object might be moving, because how could you measure that...? Well, for that, we've got the, uh, the Doppler effect."
He pointed at the board. "Originally discovered by Christian Andreas Doppler in 1845, the Doppler effect dictates the changing wavelength of forces around a moving object. For forces using waves, such as sound, it is both determined by the movement of the object and the movement of the observer." He glanced back towards the class. "Basically, the length of the waves get shorter upon approach, and longer the further the object goes away from you. How does that work into astronomy? Well, light is a wave."
The waves emitted by the object on the board helpfully shifted color.
"Basically, the longer the wavelength of light, the redder something gets." He was... trying to keep this simple. Hoped it was working. "The shorter it is, the bluer it gets. So objects moving towards us become noticably bluer - that's called a blueshift - while objects moving away undergo a redshift. Of course, we can't actually see the colors unless an object is moving at a relativistic speed - but we'll get to relativity next week."
He cleared his throat. "But we can measure it," he said. "For example, we can tell the Andromeda galaxy is moving towards us. Perhaps more importantly, though, this is how we first started to catch on to the idea that the galaxy is still expanding - because the universe around us at large is redshifting. If you want to know more about that-- here's some handouts."
It'd be useful for the test was all he was saying.
"But today I want you all to participate in an experiment," he said. "Push your tables to the sides of the room, please."
He put several large tennis balls on the desk, one for every two students. "Each one of these has a siren inside of it," he said. "Now everyone takes one of these sound pressure level meters--" he pointed at the other devices on the desk. "Roll the balls around the room. Measure the pitch as it moves towards you or away from you. Write down your findings." Beat. "If you get done with that early-- there's an applet you can try, too."
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