The Search For Dyson Spheres Has Begun

[katmai]

Kekekeke Zerg rush?

[Ed Anger]

I really need to sleep with one of my students.

[katmai]

Don't break a leg!

[Eddie Teach]

I really need to sleep with one of my students.

Have a particular one in mind?

[CountDeMoney]

I really need to sleep with one of my students.

Do you think he'd mind?

[Ed Anger]

I really need to sleep with one of my students.

Have a particular one in mind?

Yep.

[jimmy olsen]

I figured the only place you'd meet a skinny Korean chick would be in the poor Korean countryside.

Oh wait, Timmay says the poor Korean countryside doesn't exist anymore.  The entire southern half of the peninsula is apparently now paved with fiber optics cabling, and everybody earns a living playing MMORPGs.

95% of Korean women 20-35 are skinny. Societal pressure to be thin here is immense. They do walk a ton, but even so, I wouldn't be surprised if a huge fraction have some kind of eating disorder.

[jimmy olsen]

Luddites! 

http://www.forbes.com/sites/alexknapp/2012/04/03/destroying-mercury-to-build-a-dyson-sphere-is-a-bad-idea/

Destroying Mercury To Build A Dyson Sphere Is A Bad Idea

Futurist George Dvorsky has penned an article in which he proposes building a Dyson Sphere around the Sun by basically destroying Mercury and using it for parts. A Dyson sphere, for those who missed the Star Trek: The Next Generation episode where Scotty came back, is a theoretical construct whereby a hollow sphere is built in orbit around the Sun (with the Earth inside), and the sphere collects virtually100% of the energy coming from the Sun, providing a limitless source of energy.

Now, Dvorsky isn't proposing a "classic" Dyson sphere that's one huge construct. Instead, he proposes a "swarm" of solar collectors placed in various orbits to capture the Sun's energy. Based on the work of Stuart Armstrong, he's broken this project into 5 steps.



    1. Get energy
    2. Mine Mercury
    3. Get materials into orbit
    4. Make solar collectors
    5. Extract energy

Let's put aside the fact this isn't something that we can start now and build in four decades, as Dvorsky claims.  It's relatively self-evident that this technology required to basically destroy Mercury and collect materials to build a first stage Dyson sphere doesn't exist yet.  But lets assume that it does. From there we have to question, does it make sense to destroy Mercury to build a Dyson Sphere? The math says no.

I emailed Astronomer Phil Plait about this project, who told me in no uncertain terms that the project doesn't make sense.

"Dismantling Mercury, just to start, will take 2 x 10^30 Joules, or an amount of energy 100 billion times the US annual energy consumption," he said. "[Dvorsky] kinda glosses over that point. And how long until his solar collectors gather that much energy back, and we're in the black?"

I did the math to figure that out.  Dvorsky's assumption is that the first stage of the Dyson Sphere will consist of one square kilometer, with the solar collectors operating at about 1/3 efficiency – meaning that 1/3 of the energy it collects from the Sun can be turned into useful work.

At one AU – which is the distance of the orbit of the Earth, the Sun emits 1.4 x 10^3 J/sec per square meter. That's 1.4 x 10^9 J/sec per square kilometer. At one-third efficiency, that's 4.67 x 10^8 J/sec for the entire Dyson sphere. That sounds like a lot, right? But here's the thing – if you work it out, it will take 4.28 x 10^28 seconds for the solar collectors to obtain the energy needed to dismantle Mercury.

That's about 120 trillion years.

Of course, that's only the first stage. Going simply by the numbers that Dvorsky provides, without critique or comment, the Dyson sphere would eventually encompass 6.9 x 10^13 square kilometers. Which means that if we assume that we're capable of transmitting the energy from the collectors to Earth at 100% efficiency (no power loss) and even if we assume that we don't use any energy at all except what we need to dismantle Mercury (unlikely), it would still take 174 years to gather the amount of energy needed to dismantle Mercury.

Which begs the question – if we're capable of generating the amount of energy right now that would take a Dyson Sphere 174 years to recover, why would we need to build a Dyson Sphere in the first place?

Of course, since we're not capable of producing that much energy right now, and it would take a Dyson Sphere over a century to gather the energy needed to build a Dyson Sphere, I'm comfortable with saying that this project isn't practical, or even possible.

Update: I've written a follow-up piece with some more thoughts on the impracticality of this proposal, which you can read here.

Update 2: Thanks to those in the comments for explaining why the energy payback timeline is irrelevant in a "bootstrapping" scenario.  I get it now, and you're right.  If you build it a little bit at a time, the human initial energy cost can be small, because you then collect solar energy to mine Mercury to build more solar collectors to gather energy to mine Mercury.  So you're right – my critique of the energy payback timeframe with respect to the amount of energy it takes to dismantle Mercury for the initial phase of construction doesn't matter, because the amount of energy needed to send the initial robots to Mercury is the whole of the human energy investment.

That said, the amount of energy it takes to dismantle Mercury doesn't change no matter how you do it, so that's still going to be a fundamental constraint on the speed with which a Dyson sphere can be built. Which means we're talking centuries at minimum, because the solar collectors can only collect so much energy.  Then moving the Dyson swarm out to 1 AU is going to be an ENORMOUS energy sink, and in that case I think an energy payback timeframe matters a great deal, though right now I'm not sure what that timeframe is.

[Eddie Teach]

Cue for Seedy or Ide to ask to crash on your couch.

[Darth Wagtaros]

1. Get Energy
2. Destroy Mercury
3. ????
4. Profit

[Maximus]

Luddites! 

http://www.forbes.com/sites/alexknapp/2012/04/03/destroying-mercury-to-build-a-dyson-sphere-is-a-bad-idea/

The real issue is that humans aren't capable of the kind of long-term planning and follow-through to accomplish this.

[garbon]

Why is Phil Plait using the current US annual energy consumption as a comparison for this future scenario? Perhaps that amount of energy will be child's play once we're at a stage where we can easily destroy planets.