<p>In our paper we just used Mercury because it was convenient (close, airless, low binding energy). But we did not try to optimize the Dyson sphere design at all. It turns out that one can likely construct a far more efficient sphere out of very thin aluminium foil reflectors balancing light pressure and solar gravity to stay in place. That only takes the mass of the asteroid Vesta or so. Plus, were the reflectors manufactured out in the asteroid belt one could light-sail them into close orbits with modest effort.</p>
<p>Aluminium is just one possible material. Essentially any metal works for the reflectors (the trick is to keep the mass low enough), while energy gathering subsystems could be based on semiconductors or even heat turbines - silicates and water are not uncommon in the solar system, and presumably similarly available in others. Even if the inner region has been swept clean by a Hot Jupiter, parts can be manufactured and spiralled in from the outer system.</p>
<p>So unless we expect even asteroids to be rare (a pretty implausible idea) there is likely plenty of building material. As an answer to the Fermi paradox lack of resources is not reliable enough.</p>

CC BY-SA 4.0
2020-01-10T07:56:33.853Z
I hoped for a great answer, but not from one of the paper's authors! (Kurzgesagt is clearly just a start.) Thanks for improving my understanding of your paper's context; I've learned a lot.
J.G.
CC BY-SA 4.0
2020-01-10T00:00:01.983Z
2022-08-01T17:48:05.130Z
2022-08-01T17:48:05.130Z
Anders Sandberg
<p>The Fermi paradox concerns why we don't observe evidence of alien life, such as megastructures. If we were to build a Dyson swarm, the best source material may be Mercury (<a href="https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.800.5577&amp;rep=rep1&amp;type=pdf" rel="nofollow noreferrer">Armstrong and Sandberg 2013</a>): not only is it close, with plenty of solar power for exponential disassembly, but its mineral composition is suitable. But could planets made of suitable minerals, with plenty of solar power, be rare enough to prevent most advanced civilizations building Dyson spheres, or other detectable megastructures?</p>
<p>It's a mundane solution to the Fermi paradox, but it's conceivable on my limited knowledge of exoplanets, if only because our planetary system is atypical. For example, where we have Mercury, many systems would have hot Jupiters instead (or possibly as well, if that's consistent with how most systems form). Can we begin to answer this with our current understanding of what's typical for exoplanets?</p>

<exoplanet><fermi-paradox>
Could the mineral composition of planets explain the absence of megastructures?
J.G.
# Could the mineral composition of planets explain the absence of megastructures?

(Asked by: username_0 on 2020-01-08)

The Fermi paradox concerns why we don't observe evidence of alien life, such as megastructures. If we were to build a Dyson swarm, the best source material may be Mercury ([Armstrong and username_1 2013](https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.800.5577&rep=rep1&type=pdf)): not only is it close, with plenty of solar power for exponential disassembly, but its mineral composition is suitable. But could planets made of suitable minerals, with plenty of solar power, be rare enough to prevent most advanced civilizations building Dyson spheres, or other detectable megastructures?

It's a mundane solution to the Fermi paradox, but it's conceivable on my limited knowledge of exoplanets, if only because our planetary system is atypical. For example, where we have Mercury, many systems would have hot Jupiters instead (or possibly as well, if that's consistent with how most systems form). Can we begin to answer this with our current understanding of what's typical for exoplanets?

**Tags:** exoplanet, fermi-paradox


---

## 1 answers

### Answer by username_1 on 2020-01-10. Score: 12 | Accepted answer

In our paper we just used Mercury because it was convenient (close, airless, low binding energy). But we did not try to optimize the Dyson sphere design at all. It turns out that one can likely construct a far more efficient sphere out of very thin aluminium foil reflectors balancing light pressure and solar gravity to stay in place. That only takes the mass of the asteroid Vesta or so. Plus, were the reflectors manufactured out in the asteroid belt one could light-sail them into close orbits with modest effort.

Aluminium is just one possible material. Essentially any metal works for the reflectors (the trick is to keep the mass low enough), while energy gathering subsystems could be based on semiconductors or even heat turbines - silicates and water are not uncommon in the solar system, and presumably similarly available in others. Even if the inner region has been swept clean by a Hot Jupiter, parts can be manufactured and spiralled in from the outer system.

So unless we expect even asteroids to be rare (a pretty implausible idea) there is likely plenty of building material. As an answer to the Fermi paradox lack of resources is not reliable enough.

> **Comments:**
> **username_0**: I hoped for a great answer, but not from one of the paper's authors! (Kurzgesagt is clearly just a start.) Thanks for improving my understanding of your paper's context; I've learned a lot.  

---

