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What Are Alien Megastructures?

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Channel: Fraser Cain
Categories: Astronomy   |   Physics   |   Science  
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Did scientists find a giant alien structure around KIC 8462852? Probably not, but if they did, what would these structures look like?
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Team: Fraser Cain - @fcain
Jason Harmer - @jasoncharmer
Susie Murph - @susiemmurph
Brian Koberlein - @briankoberlein
Chad Weber -
Kevin Gill - @kevinmgill

Created by: Fraser Cain and Jason Harmer

Edited by: Chad Weber

Music: Left Spine Down - “X-Ray”

In the summer of 2015, astronomers announced a strange new discovery from NASA’s planet hunting Kepler space observatory. Some object was blocking out about 22% of the light from its parent star: KIC 8462852.

Even the largest planet in the Solar System, Jupiter, would only block out 1% of a star’s light, so something much larger must be doing this.

But what?

Astronomers proposed a few ideas: a cloud of comets, or a maybe the debris from a recently destroyed planet. But another idea was put on the table: an alien megastructure.

Now keep in mind, aliens are way down in the list of possibilities here. It’s almost certainly, for sure, probably not aliens. Seriously, every other possibility is a zillion times more likely than aliens. But there’s a remote, non-zero chance that it’s aliens, and their alien megastructures.

Are you having trouble imagining what an alien megastructure might look like, and why it would exist? No problem, join the club.

All we’re doing is extrapolating from our current demand and growth for energy to its logical conclusion.

Imagine the future of humanity. We use more energy now than we did in the past. And in the future, we’ll want even more energy. Eventually we’ll use up all the energy on Earth, then we’ll figure out how to use up all the energy flowing out of the Sun. After that, we’ll use up all the energy in the entire Milky Way.

Finally, we’ll use up all the energy within every single galaxy that we can get our hands on.

And to do this, we’re going to want to build megastructures. Aliens will call them alien megastructures.

So what kind of megastructures will we build to extract all the energy from the Sun?

Imagine you encased the entire Sun in a rigid sphere; this the concept of a Dyson Sphere, first described by Freeman Dyson back in the 1960s. In fact, if you dismantled every single planet, moon, comet and asteroid in the Solar System, you could build a shell around the Sun about half a meter thick.
It would have an interior living space of about 600 million times what we currently have on Earth. And if you set the whole sphere turning, the people at the equator would experience Earthlike gravity from the centripetal force pushing them outward.

This actually isn’t a great idea. You’d have to be pretty close to the equator to experience any gravity, and the forces on the whole sphere would try to tear it apart. There are no materials that we could imagine that could hold a structure like that together.

A more realistic concept is a Dyson Swarm, where you build a single solar power collection satellite. And then use its energy to manufacture more of these things until there’s a cloud of them orbiting the Sun, and you’ve got your greedy hands on every single stray photon.

Seen from afar, a cloud of these satellites would block the light from the Sun as they swept past, and make astronomers wonder if they’re seeing an alien megastructure.

But for a powerful alien civilization with the ability to dismantle a Solar System, this is just the first step.

The next megastructure is a Shkadov Thruster. This is a reflective half shell that’s put in place beside a star. Light pressure from the star pushes outward, holding the shell in place, and gravity from the shell pulls the star towards it. Over billions of years, a civilization could reorganize all the stars in their galaxy into a more useful configuration.

Any galaxy that isn’t already moving away faster than the speed of light could be raw materials for a powerful civilization looking to get at every joule of energy.

So what do you think is causing KIC 846852 to dim? Which theory do you like the best? Tell us your thoughts in the comments below.

In our next episode, we talk about planetary rings. Where do they come from, and what would Earth look like with rings of its own?

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