Kaidan Alenko (![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png)
not_a_whiner) wrote in ![[community profile]](https://www.dreamwidth.org/img/silk/identity/community.png)
fandomhigh2013-09-27 01:28 pm
not_a_whiner) wrote in fandomhigh2013-09-27 01:28 pm
Entry tags:
Space!, Friday
"Today, we're going to be talking about atmosphere," Kaidan said. Appropriately, the screen behind him displayed a slowly spinning globe. "Not every planet has one. In fact, the circumstances have to be just right for a planet to assemble its own atmosphere. So we're lucky Earth got one, because without it, things would've looked pretty bleak for the possibility of our ancestors' bacterial ancestors to, uh, come to life at all."
He pointed at the globe. "That little shield of gasses is what keeps us from burning up, brings us rain, brings us oxygen. 'Course, it wasn't always that way. The first atmosphere our planet had was probably closer to the make-up of Jupiter than the one we've got now. It definitely didn't have any oxygen in it. Rain fell and became an ocean - the two processes tied into each other. The water being there meant life started to evolve. We got algae. And algae, being plants, started to photosynthesize carbon dioxide into oxygen."
The globe behind him shifted colors as he spoke, simulating the processes in question. "That happened about 2.7 billion years ago. But we weren't done yet. See, it took plate tectonics to really shake things up. Because the continents kept moving, carbon dioxide wound up being stored underground. The free oxygen levels went up, carbon dioxide went down-- and we wound up with our current atmosphere of 78% nitrogen, 21% oxygen, 1% water vapor."
He cleared his throat. "We tend to divide up our atmosphere into a couple of parts," he said. "At the very top lies the ionosphere. That's the part of the atmosphere that connects ions to atoms - a process called ionizing. It also captures photons from the sun and reflects radio waves, which makes a lot of modern communications work. Below that is the mesosphere. It's a cold place, about mins 143 degrees celsius. It rests between fifty and a hundred kilometers up. The mesosphere fries up most of the meteors that try to hit Earth."
"Below that is the stratosphere, which also holds the ozone layer. The ozone layer absorbs ultraviolet radiation. In this time, people are really worried about the damage certain products inflict on this ozone layer. Look it up." Okay. "Contrary to what goes on on our end of the planet, the stratosphere is colder at the bottom than it is at the top. It starts at about ten kilometers above us. Which means that if you're getting on a plane, chances are you're going to wind up flying in the stratosphere. It's also the highest part of the sky where life can survive."
"And finally," he finished, "there's the troposphere. The troposphere is what we're in right now. It's the place weather takes place in, it's got a lot of water vapor hanging around. There's a buffer between it and the stratosphere called the tropopause."
He pointed at the globe. "That little shield of gasses is what keeps us from burning up, brings us rain, brings us oxygen. 'Course, it wasn't always that way. The first atmosphere our planet had was probably closer to the make-up of Jupiter than the one we've got now. It definitely didn't have any oxygen in it. Rain fell and became an ocean - the two processes tied into each other. The water being there meant life started to evolve. We got algae. And algae, being plants, started to photosynthesize carbon dioxide into oxygen."
The globe behind him shifted colors as he spoke, simulating the processes in question. "That happened about 2.7 billion years ago. But we weren't done yet. See, it took plate tectonics to really shake things up. Because the continents kept moving, carbon dioxide wound up being stored underground. The free oxygen levels went up, carbon dioxide went down-- and we wound up with our current atmosphere of 78% nitrogen, 21% oxygen, 1% water vapor."
He cleared his throat. "We tend to divide up our atmosphere into a couple of parts," he said. "At the very top lies the ionosphere. That's the part of the atmosphere that connects ions to atoms - a process called ionizing. It also captures photons from the sun and reflects radio waves, which makes a lot of modern communications work. Below that is the mesosphere. It's a cold place, about mins 143 degrees celsius. It rests between fifty and a hundred kilometers up. The mesosphere fries up most of the meteors that try to hit Earth."
"Below that is the stratosphere, which also holds the ozone layer. The ozone layer absorbs ultraviolet radiation. In this time, people are really worried about the damage certain products inflict on this ozone layer. Look it up." Okay. "Contrary to what goes on on our end of the planet, the stratosphere is colder at the bottom than it is at the top. It starts at about ten kilometers above us. Which means that if you're getting on a plane, chances are you're going to wind up flying in the stratosphere. It's also the highest part of the sky where life can survive."
"And finally," he finished, "there's the troposphere. The troposphere is what we're in right now. It's the place weather takes place in, it's got a lot of water vapor hanging around. There's a buffer between it and the stratosphere called the tropopause."