How Many Earth Like Planets..............

[All Seeing Eye]

............. Could Orbit Our Sun At The Same Orbital Distance?

What I mean is, if an advanced alien race (or perhaps future Humans) had the ability to locate Earth like planets (same mass, composition, atmosphere, size etc) and place them in the habitable zone around our star in the same orbit as the Earth and have their orbital speed the same as Earth how many Earth like planets could share our orbit around the sun??

My main reason for wondering about this is because I was thinking about how a Xenophobic alien race might attempt to stay isolated from the rest of the universe but find a way to expand it's population without needing to leave the confines of its solar system. So I realised that perhaps if they are advanced enough they could bring planets actually INTO their solar system and have them share the same orbit as their homeworld.

I'm sure there will be some of you who will say that the planets would not need to even be in the same orbit etc but for the sake of argument let's say they are going to put the planets in the same orbit. How many planets could fit in Earths solar orbit?

Let's look at it from a purely Science Fiction point of view. Anyone who's watched the Sci Fi show Andromeda will be aware of the Magog World Ship. Well that world ship is pretty crazy but from a Sci Fi perspective it makes interesting TV. Let's look at it as if this is going to be part of a future upcoming Sci Fi TV show and a Xenophobic race has placed multiple planets around it's parent star in the fashion described.

So using Earth and our Sun as the example Solar system etc how many Earth like worlds could share Earths orbit around our Sun?

 

[TheMasterOfOrion]

I read a paper that once said a max of 5, but it involved a really large goldilocks zone. A very luminous star, and some very complicted orbits involving a GasGiant with a Moons and smaller planets follwing the Trojanpoint orbits, that's 3 covered. Then one planet in the inner part of the habitable zone and one in the outer part. To say the least it seemed more like science fiction than science plausible

I wasn't up to speed on the math but I'm sure some other egghead busted this theory

 

[All Seeing Eye]

wow, judging by the vast length of Earths orbit and small size of our planet I'd have assumed a much larger number than 5.

It's pretty funny that you should be the first to post, when I was thinking about Xenophobic races the Orions from the game Master Of Orion sprang to mind.

 

[Christopher]

Sharing exactly the same orbit? In the long term, only one as a rule. There's a reason why each orbit has only one planet in it. No orbit is completely invariant; there are always slight perturbations from the gravity of other bodies, tiny changes in speed. Eventually, any two bodies sharing the same orbit will converge and collide, or else the larger one will eject the smaller one or capture it into orbit.

I suppose a double planet, like the Earth and Luna only more equal in size, might be possible. Essentially both bodies would be orbiting a common center of mass, which in turn would be orbiting the primary star.

As for the Trojan-orbit scenario proposed above, it's conceivable, but highly unlikely. The L4 and L5 Trojan points are basically stable, but not completely so. It's believed that there used to be a Mars-sized protoplanet in Earth's L4 point, but then it collided with Earth and the blown-off detritus formed Luna. If a Trojan planet could survive the early, turbulent phase of planet formation and still be there once things settled down, it could probably remain stable for billions of years afterward, but that's a really big if, especially considering that Jovians tend to migrate during that phase (which is a leading cause of the turbulence).

More broadly, as The Master of Orion hinted, the odds of a star's habitable zone being wide enough to contain two or even three planets in different, adjacent orbits are far higher. The Sun's habitable zone is nearly wide enough to encompass Venus and Mars, so a bigger star with a wider CHZ could fit two or three planets in it.

 

[Meredith]

You can make far more space colonies than you can build and/or movie planets. You could put habitats at any place within the Habitable zone or even outside of it. You just need bigger mirrors for the ones past Mars's orbit. I think with enough colonies you could easily house several trillion humans in relative suburban/rural style space habitats in our solar system.

 

[T'Girl]

I'm going to say six, each sixty degrees apart in a single orbit. Something like the moon and the third, forth and fifth lagrange positions, but with two more bodies, all six worlds equidistant from each other and the sun.

 

[Christopher]

^That might be quasistable in the short term, maybe as some massive work of cosmic engineering, but it would never happen naturally for the reasons I discussed above -- sooner or later, bodies sharing the same orbit converge on one another, because perturbations make it impossible for them to maintain exactly the same orbital velocity as one another forever.

 

[Alpha_Geek]

Go read some Larry Niven and pay attention to the Pupetteers, particularly regarding Klemperer Rosettes.

Unfortunately, they are unstable so the answer is "One." unless you have some method to keep the whole shebang aligned.

 

[Christopher]

^Way ahead of you on reading Niven. Decades ahead.

 

[Verteron]

If you're capable of the kind of cosmic engineering that would be required to move planets between solar systems, why would you even need them inside the habitable zone of a particular star system?

Surely your civilisation would be capable of the kind of megascale engineering required to build light reflectors to gather and channel extra light at a planet like Mars (too far away from the Sun) or block light from Venus (too close to the Sun) or heat the moons of Jupiter and increase their mass by crashing asteroids at them until their gravity is more comfortable?

Indeed, why would such an advanced civilisation even live on planets when there are
other far better options available per mass if you're looking to build living space and harness the star's energy?

 

[Christopher]

^To show off? Sometimes civilizations just like to demonstrate their power over nature. That's why China built the monstrous and highly dangerous Three Gorges Dam rather than going the more sensible route of building multiple smaller dams. They wanted a monument to the power of the state.

 

[Alpha_Geek]

^Way ahead of you on reading Niven. Decades ahead.

Nah, I was reading lots of it when it was new.

 

[Alpha_Geek]

Obvioulsy what is needed here is a large circular track wherein the planets can roll at a greater than orbital velocity. This negates the instability of the rosette, keeps them on the track due to centripedal force, and is a project of such magnitude that the OP will be pleased with the concept.

 

[Lindley]

So long as you don't mind a large swath of the planet getting crushed every night, sure.

 

[Christopher]

^Way ahead of you on reading Niven. Decades ahead.

Nah, I was reading lots of it when it was new.

Sorry, ambiguous phrasing. The phrase "way ahead of you" generally means "I'm acting way ahead of your suggestion," so I meant to say I read Niven's works decades before you suggested it yesterday, not before you actually read them.

 

[Alpha_Geek]

Sorry, ambiguous phrasing. The phrase "way ahead of you" generally means "I'm acting way ahead of your suggestion," so I meant to say I read Niven's works decades before you suggested it yesterday, not before you actually read them.

Ooooh, ok!
Just finished World of Ptavvs for the umpteenth time.

 

[Verteron]

^To show off? Sometimes civilizations just like to demonstrate their power over nature. That's why China built the monstrous and highly dangerous Three Gorges Dam rather than going the more sensible route of building multiple smaller dams. They wanted a monument to the power of the state.

Heh heh... perhaps.

One would hope that such behaviours might've been eliminated by the time a society reached that level of advancement, but one never knows, I suppose!

Maybe a society rich enough in science and technology to perform such megascale engineering projects might also consider them as a strange form of artistic endeavour... a sculpture in the cosmos itself...

 

[Lindley]

^To show off? Sometimes civilizations just like to demonstrate their power over nature. That's why China built the monstrous and highly dangerous Three Gorges Dam rather than going the more sensible route of building multiple smaller dams. They wanted a monument to the power of the state.

You mean they didn't build the Three Gorges Dam to provide power to every city on this continent and increase the chances of the host city generating a Great Engineer?

Damn you, Sid Meier....

 

[Myasishchev]

If you wanted multiple Earthlike bodies all roughly the same distance from the sun, and had limitless energy to move planets around already, could you not move a Jupiter-mass gas giant into a 1AU orbit and then orbit the Earthlike "planets" around it? Seems like you could fit at least four.

Or is this a cheating answer?

 

[Christopher]

I don't think you could fit four habitable moons around the Jovian, since the closer-in ones would be subject to radiation and tidal stresses that could render them inhospitable. Also, if the moons are big enough to be called Earthlike, then in the tight confines of a Jovian moon system they'd exert significant seismic stresses on one another. Space their orbits far enough apart to avoid that and the outer ones might be too far out to avoid getting perturbed out of orbit by neighboring planets' gravity. Not to mention that the outer moons would be moving several million kilometers in and out from the primary star as they orbited the Jovian, which could keep them from having a stable temperature. Maybe life could evolve to survive such periodic temperature swings, but the conditions could hardly be called Earthlike except in the broadest sense.