Fandom High School

Kaidan's wasn't the first class to do this, but he thought it was a sane choice anyway.

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"Today, we're going to dive into history and talk about humanity's first baby steps into space exploration," Kaidan said.

He paused. "Well... sort of. We're going to be talking about Mars. Now, in my time, it's been home to a large science compound for a long time. We found information there... archives, buried by a civilization that died long before we got there. But it took us a long time to find it."

"The first people who tried to land on Mars were the Russians. This was in the days of the Space Race, two giant Earth nations battling it out over who could get the furthest in space." He smiled briefly. "They sent a bunch of probes towards Mars in the 60s. None of them made it there. Some burned up in orbit, some they lost contact with halfway in. The Americans soon joined them in trying, but it was the Russians who successfully landed the Mars 2 probe on the planet. Well... crash landed. But the first soft landing wasn't far behind - Mars 3 touched rock a couple of days later, and managed to transmit data for all of fourteen seconds."

He whistled. "Kind of impressive," he said, "At the time."

He sort of even meant that. "It was the American Mariner 4 that managed to grab the first images of Mars in 1965. It was the first time anyone on Earth had seen the surface of another planet. Later photographs showed that there might've been water on Mars at least once in the past. They kept working at it, and in 1975 it was the American Viking landers that touched ground and managed to stay functioning. We got even more evidence that there used to be water on Mars. But there was only so much they could do. It wouldn't be until 1997 that we actually put something up there that could move around - the Sojourner rover."

He displayed a picture on the holographic screen.

"We kept looking. We kept gathering data. And last year - local time - NASA put another rover on that planet. This time, its mission was to check and make sure Mars had really been habitable at some point." Beat. "Just to save you the excitement - yeah, it was."

He called up holographic screens above everyone's desks. "I could tell you about that," he said, "But I'm not sure how much my future checks out for all of you. Besides... this might be an interesting moment to learn something about the history of space exploration. There's a sim that lets you drive the Curiosity rover. I want you to go through it today."

"We talked about what was necessary for life last week," Kaidan said. He gestured at a large hologram of... well, it was Sur'Kesh, actually. "Well, according to the scientists of this era, number one with a dot is water. You don't get life without it. According to some estimates, one in five solar systems should have a planet that can support life."

He cleared his throat. "That's not taking the water factor into account," he said. "We're talking about Earth-like planets here. Planets in the right temperature zone. Hotter than that, and water evaporates. Colder than that, it freezes. Each solar system has a kind of... sweet spot, depending on the size and strength of its star, where life could hypothetically be possible. 'Course, not all of them have planets there."

His mouth quirked briefly. "So no," he said. "Unlike what some Earth philosophers would've liked to think in this time-- we're not special."

He handed a stack of handouts to Mercy, instructing her to give one to each student.

"We're all going to design a planet today," he said. A holographic interface appeared over each student's desk. "I want you all to team up. Each team designs one habitable and one uninhabitable planet."

"Interstellar travel," Kaidan began, "Has long since been something that fascinates us. Uh, in my time, we've found a way around them, through the mass relays-- but before that happened, we spent a lot of time trying to figure out how it could work."

"The big problem is that space is big. Really big," he continued, wryly. He pointed at the holographic image of the galaxy behind him. "This is just our galaxy. It's over a hundred thousand lightyears in diameter. A lightyear is the distance light travels in a year, meaning six trillion miles. Try finding a car that can cover that distance in less than a few thousand human lifetimes. Hell, the star closest to us - Alpha Centauri - is still 4.2421 lightyears away from us. Think about that one for a minute."

"So we had to start looking at the question: how can we go fast enough to make the trip worth it?" he asked. "Turns out, that's another problem. If we hit lightspeed - which would still mean it'd take us over four thousand years just to get to the nearest star - we run into a couple of questions. The first problem physicists thought of has been proven to be untrue, but let's consider it anyway: time dilation. They thought that the closer we got to lightspeed, the more time would get compacted for the moving object. So... you go somewhere at light speed, it might be twenty days for you and a year for everybody outside of your vessel."

He shrugged. "Turns out the difference isn't as radical as we originally thought," he said, "But we didn't figure that one out until we figured out the second problem, which is how do we get a ship to go that fast to begin with? To reach those kinds of speeds, you need an incredible amount of energy, an amount we first thought was basically infinite just to get to the speed of light." He looked thoughtful. "Of course, in my time, we discovered element zero, which has certain qualities that help us bend laws that we used to think were absolute," he said. "But most of you - all of you, maybe - don't have that yet. So... let's conduct some research today. What's the fastest object that's been created in your time and universe? What theories do people have about being able to go faster that you think are feasible?"

"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."

The classroom was the same as it had been last week: normal, with the only tweak being the holographic blackboard at the front of the class. It was showing a three-dimensional image of the Sol system right now; Kaidan had stepped to the side to make it more visible.

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