For Science!
Astronomer Reveals The Truth Behind Civilization: Beyond Earth's Exoplanets

CJ Miozzi | 4 Sep 2014 04:00
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How Beyond Earth stays true to science

Beyond Earth won't simply include random tilesets that are named after actual exoplanets - the developers want to get as close as possible to reality.

"I know that the design team has been really excited about including exoplanet map packs," said Dr. Kane. "They want to include more of these exoplanet discoveries, and my goal will be to make these as real-to-life as possible."

Now, what does Dr. Kane mean by "real-to-life?" It's all about realistic extrapolation of limited data. For example, one thing we know about these exoplanets is their distance from their star, so a planet that is near the inner edge of its planet's habitable zone may be a baked desert world, while one on the outer edge may be more of an icy world.

"Of course, there is a certain point at which you're forced to take poetic license, such as if you want to describe the surface in any detail at all," said Dr. Kane. "But we want to try to make sure those cases where we do try to imagine what the surface is like are driven by what we do know and make that extrapolation as realistic as we can."

Apart from the distance to their star, there are other things we know about exoplanets that can help the Beyond Earth developers integrate these worlds into the game. The techniques that we have for detecting exoplanets allow us to learn some basic things about them, and by combining the data from different techniques, we can make inferences about a planet's nature. Specifically, one method reveals a planet's mass, while another reveals its size, and together, these tell you the planet's average density. "That's when we can really start talking about characterizing these planets," said Dr. Kane, "because once you have the mean density, you can start to think about what the interior looks like. For example, if it's extremely dense, you imagine it has a very iron-rich core, or you can also think about how thick its atmosphere might be once you know the surface gravity."

Will Beyond Earth run out of habitable exoplanets to include?

One concern about grounding a game in reality is the limitations that imposes. For instance, Civilization can only include so many ancient civilizations - eventually, there's no ground left to cover. How long will it take Beyond Earth to run out of exoplanets?

"...the last thing you want to do is travel the great distance between stars, go to a planet which is the size of the Earth, but then find that it has a surface much like Venus."

Currently, Dr. Kane's website is tracking the orbits of 1457 exoplanets, 51 of which are in the habitable zone. If Firaxis has only covered six of those so far, it seems we're good for at least another eight exoplanet packs. But keep in mind that Beyond Earth takes place 200 years in the future - that's a lot of time to discover new exoplanets. Just how many may we discover by then? I turned the question to our astronomer.

"I absolutely love this question," said Dr. Kane. "Let me start out by saying that the field of exoplanets over the past two decades has progressed so quickly and changed so radically that almost all predictions we made in 1995 about where we would be in 2005 were wrong."

If 10 year predictions could be so far off, what hope do we have for accurately predicting the situation in 20 times that time span? Still, Dr. Kane was up for the challenge and began to lay out the facts. "We've figured out that there are far more smaller planets than their are larger planets," he said. "That means there's lots and lots of terrestrial planets out there (like Earth and Venus, as opposed to gas giants like Saturn and Neptune) - and that's great." When considering habitability, terrestrial planets are what we're looking for. "The other thing that we're concluding is that all stars have planets - that planets are a natural consequence of star formation. What this means is that every single star has terrestrial planets, and many of them probably have a terrestrial planet in the habitable zone. We just need to find them."

Working under the assumption that habitable planets are bountiful in our universe, the question then becomes: how many can we find in the next 200 years? "I would put the answer in the hundreds of thousands - at least," said Dr. Kane. Looks like Firaxis can sit easy - Beyond Earth essentially has no limit to the number of worlds it can allow players to colonize while remaining in the realm of possibility. But the news is even better for humanity.

"Given the rate that we've seen technology progress over the past 10-20 years in being able to find exoplanets," said Dr. Kane, "200 years from now, not only are we going to have found at least hundreds of thousands of exoplanets around the nearest stars to the Earth, we'll have been able to take images of the planets, identify which have suitable atmospheres, and know exactly which to colonize without any guesswork involved. Because the last thing you want to do is travel the great distance between stars, go to a planet which is the size of the Earth, but then find that it has a surface much like Venus. That would be very disappointing, to say the least."

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