A Simulated Stable Planetary System with 416 Planets in the Habitable Zone | Hacker News Reader

A Simulated Stable Planetary System with 416 Planets in the Habitable Zone

nautil.us

91 pointselorant32 comments

Stable against what perturbations? What impact would a large body passing through the system have? Stable as in self-correcting (up to a limit)? What is the limit. Even long running accurate simulations of the three body problem are sensitive to perturbations...

> This system is completely stable—I double-checked with computer simulations. But nature would have a tough time forming this system.

If I understand correctly, I think the author uses "stable" to just mean a _fixed point_. The fixed point must actually be unstable to just about every possible perturbation, which justifies the second statement; if the fixed point were actually "stable" (to perturbations) then it would occur relatively easily in nature.

I'd imagine each one of the planets would have an artificial gravity generator itself able to correct for gravitational disturbances

Assuming artificial gravity generators, who needs planets?

My understanding is that you can achieve higher density with a toroidal dyson swarm (e.g., http://burtleburtle.net/bob/scifi/dyson.html ) , although this has the drawback that planet position in the habitable zone varies.

For what definition of stable? Stable in 2d? 3d? 3d + expected disturbances from solar winds, passing objects, solar flares, etc? How about the decreasing mass of the sun? Over a year? Century? Million? Billion?

The atmospheric drag on a planet could make its orbit wobble enough to cause a cascade effect through the entire system.

As soon as one planet wanders a bit too far out of line it'll smack into others going the opposite direction and the debris will take out all the others inside of a few revolutions.

Interesting, but highly risky.

I'd love to see a simulation video of the mayhem that would ensue if a moon size object passed that system.

You could argue that if you have the technology to build something like this, you have the technology to deal with perturbations.

It's not going to stay math-stable for long, but it could stay engineering-stable for millions of years.

Fun article! Thanks for posting. Geoengineering is too narrow minded. We need star system engineering!

As, by-the-by, how important are "habitable zones" to the Drake equation these days?

We have an abundance of earth-life adapted to almost any temperature conditions commonly found on earth. Doesn't this imply that the total viable is wider than what we find here?

How cold could a planet be and still have chemosynthesis?

It'd be really interesting to see some renderings of what the sky would look like from the surface of a planet in this system.

Aren't they all in the same plane - so you'd have have a few hundred visible in a narrow band across the sky. Would look pretty interesting....

I don't understand why the outer orbits are limited to the same number of planets as the inner ones. What's the story there?

Didn't do the math myself, but I guess it's the resonance. You want the inner planet's gravity to cancel the outer one's.

That looks incredibly unstable and it feels like the gravity between the rings would easily counter their opposite rotations considering the amount of planets involved. Would not want to live there, but am interested within how many days this all crashes into the sun (and what happens to the sun with that amount of planets smashing into it)

> what happens to the sun with that amount of planets smashing into it

The mass increase would be a rounding error. The Sun is more than 300,000 times more massive than the Earth. It'd be a time for somewhat spectacular fireworks and the life of the star would be somewhat shortened (by the addition of some heavy elements) but, apart from that, nobody would be able to tell there was once a very large art installation around that star.

Can someone shed light the significance of his extra terrestrial life equation:

N = R × N(Earth) × F(Life) × F(Intelligence) × F(Communication) × L

The individual components are quite straightforward. What I don't get is that it seems like breaking one problem down into several more unknown problems none of which really help. In fact, it seems a harder to know the individual frequencies than it would be to actually find any single ET life. Even if we found life, we still wouldn't have a much of a clue of the frequencies (unless, I suppose, the ET life had mapped or sampled the universe and shared that knowledge with us or gave us FTL tech -- one can dream!).

Other discussions have focused around approximation of the # of habitable planets, which makes total sense.

I guess my question is what knowledge or insight would enable us to estimate the frequency of life occurring?

My take on the Drake equation is that it gives you a way to play with numbers and break down your guesses in a rational way. The article suggests an estimate of N(Earth) so this is one step in the direction of not entirely ruling out an N<1.

How else would you estimate N?

It just seems circular to say N can be estimated by looking at the frequency of life occurring. If we knew the frequency of life occurring we'd have a lot more information than what N would tell us, wouldn't we?

Maybe I'm overthinking this, but I see the problem as akin to someone giving me an uncountably large number of boxes with each having a some chance between zero or more of them containing a treasure of immeasurable value. The value of the treasure approaches infinity, so even a near 0 chance of its existence means that it has a positive ROI. In that vein, it doesn't really matter what the odds are of finding life, it is a justifiable expenditure that will statistically pay for itself.

Unless the formula can take down to actually zero the odds of their being discoverable life it doesn't change the calculation. That is, whether the odds are 1e-1000% or 99% we should expend basically the same amount of resources to find it.

You might be able to estimate those frequencies without actually counting them on other planets. For instance, by measuring the time between when Earth became habitable and when life started. Or by comparing the number of Earth's species that never became intelligent to those that did.

It could also tell us what the consequences will be of actually making big discoveries like managing to recreate life from scratch in the lab, find it on Mars, or find life on earth opposite chirality indicating independent orign. If we do (or can't!) find those things, how much will that help us predict that we find other civilizations in the galaxy?

I don't think the infinite value argument really works. Finding aliens isn't worth sacrificing everything else for if it's extremely unlikely to succeed. We could just carry on without knowing.

The Drake Equation is a thought experiment and a toy model that, on occasion, people mistake for having deep and empirical meaning.

This would be hilarious just for the eclipse combos.

I don't know much about astronomy, but isn't the habitable zone highly dependent on the star?

Like, how big and hot it is?

I could imagine it always has the same "width" but I could imagine that the zone of a rather big and hot star has a much higher circumference and would allow for more planets.

Also, if the planets are in the same plane, wont they eclipse every now and then?

"Our moon is almost half the size of Earth" Oh really???!! What universe are you living in? The moon's radius is about 1000 Miles, Earth's about 4000. So about 1/4 the size and only about 1/80th the mass. (Yes, 1/80th, look it up).

Would it be easier to have one giant planet in the habitable zone with 416 moons?

"You can't take the sky for me" header opportunity missed.

Time to watch Firefly again!

Should be: "I Simulated a Stable Planetary System with 416 Planets in the Habitable Zone"

It's amazing to think how far a civilization would have to advance to go from "simulated" to "built" for something like this.

It's amazing to think about how far our civilization has advanced in 40 years, going from giant government projects to calculate the orbital path for a single Earth-Moon trip to having a single researcher casually calculate the gravitational interactions of 417 bodies to discover a stable configuration.

Calculating the orbital path was not the hard part of the Earth-Moon trip.

Maybe, but simulating it fast enough to make corrections on-the-fly was not trivial.

As huge as 416 Earths sounds, this is actually paltry for what's possible for a Kardashev 2 level civilization:

https://www.youtube.com/watch?v=HlmKejRSVd8

Reply on news.ycombinator.com