Thread: Another Earth In Our Solar System.

Let me first of all categorically state that I fully understand that no such planet exists in our solar system. I am fully aware that there is only one earth in our solar system.

However, let us hypothesize - say I was writing a brief science fiction novel whereby an identical planet to Earth populated with about 10 billion humans appeared in our solar system by some freak "accident" (it does not matter how, just that it happened).

Now, in what orbit/position would this Alter-Earth have to be in, in order to not negatively affect the state of our own planet (e.g. not cause devastating earthquakes, tsunamis) and not devastate the entire harmony of the solar system.

Would it have to be in the position of the so-called "Gor" Earth (i.e. "Counter-Earth")?

Cheers in advance.

Originally Posted by AHeinrich

Let me first of all categorically state that I fully understand that no such planet exists in our solar system. I am fully aware that there is only one earth in our solar system.

However, let us hypothesize - say I was writing a brief science fiction novel whereby an identical planet to Earth populated with about 10 billion humans appeared in our solar system by some freak "accident" (it does not matter how, just that it happened).

Now, in what orbit/position would this Alter-Earth have to be in, in order to not negatively affect the state of our own planet (e.g. not cause devastating earthquakes, tsunamis) and not devastate the entire harmony of the solar system.

Would it have to be in the position of the so-called "Gor" Earth (i.e. "Counter-Earth")?

Cheers in advance.

That is an interesting idea. I'm not sure there is any possibility that a new world could appear in our solar system without disrupting the existing planetary orbits. But I have read a SciFi plot that had a duplicate Earth in the same orbit as our Earth, but on the opposite side of the sun. As far as I know this scenario has never been seen before in any of the new systems we have discovered. But it would be very interesting if it did exist.

Well, if the sun reflects back what we see then is there another side to the sun?

Originally Posted by andythomasthekey

Well, if the sun reflects back what we see then is there another side to the sun?

Yes, and if there were another Earth sized planet there we would see the effects of it, and we don't. Plus, I believe we have launched satellites to watch the other side of the sun, to give us more warning of potential problems coming our way.

For the stories sake could we imagine there are no satellites might make for a more interesting story if we can't cheat to see it..

Originally Posted by andythomasthekey

For the stories sake could we imagine there are no satellites might make for a more interesting story if we can't cheat to see it..

True, but what about gravity? It would have an effect we would notice. For the sake of an interesting SF plot, I could ignore that fact to enjoy the story. But I would still know the reality of our situation.

Ahem, hows this for a pop then..

Old man travelling through the desert stumbles across two men arguing about the shape of the planet..

Old man " hey guys what's the problem here?"

Angry man A. "this guy here (angry man B.) thinks the world is round" sniggering to him self.

Old man "well he is right, what are you laughing for?"

Angry man A "Don't be daft, how can you be so sure of what you say?"

Old man "Well there is this thing called gravity which keeps us down, it pulls us down like an apple falling off a tree."

Angry, but listening man A says "how does this prove we live on a round planet?"

The old man pulls a balloon from his pocket that he conveniently had, blew it up and began to rub it on his fleece that he loved to wear in the desert. Holding the balloon up with one hand he says "this balloon is earth and this cornflake is a person." Then held the corn flake near to the underside of the balloon and watched as the the cornflake was sucked up toward the balloon and remained.

Old man "this is gravity and it is this that shows me the planet is round!"

Hows about that for a story filler!

Originally Posted by andythomasthekey

For the stories sake could we imagine there are no satellites might make for a more interesting story if we can't cheat to see it..

The problem is that the counter-orbit orbit is not stable. A planet there will drift out of position. Also, we would not have to see it to know that it was there, its gravitational effect on the other planets would be easily noticeable.

Originally Posted by Janus

Originally Posted by andythomasthekey

For the stories sake could we imagine there are no satellites might make for a more interesting story if we can't cheat to see it..

The problem is that the counter-orbit orbit is not stable. A planet there will drift out of position. Also, we would not have to see it to know that it was there, its gravitational effect on the other planets would be easily noticeable.

I'm pretty sure it never happens, however I'm not clear why the orbit could not be stable. Would you or someone else please explain it, so if this topic ever comes up again I'll know more about it?

I could point you to the wiki about it..

Lagrangian point - Wikipedia, the free encyclopedia

Originally Posted by SpeedFreek

I could point you to the wiki about it..

Lagrangian point - Wikipedia, the free encyclopedia

Thanks Speed, that was a good explanation for our solar system. But would it be possible in just a two equal sized planets system with a very close to a circular orbit? Just thinking there might be a situation where it might be possible.

Originally Posted by Bad Robot

But would it be possible in just a two equal sized planets system with a very close to a circular orbit? Just thinking there might be a situation where it might be possible.

A system of just two equal sized planets with a close to circular orbit - the two planets would orbit around a common barycentre.

Originally Posted by SpeedFreek

Originally Posted by Bad Robot

But would it be possible in just a two equal sized planets system with a very close to a circular orbit? Just thinking there might be a situation where it might be possible.

A system of just two equal sized planets with a close to circular orbit - the two planets would orbit around a common barycentre.

I did mean in orbit around a sun, not just each other.

Originally Posted by Bad Robot

I did mean in orbit around a sun, not just each other.

Sorry, I should have guessed you meant that!

That would be a highly unlikely configuration to occur naturally, and if you made it artificially, how long could it last before the gravity of the nearest system to it had an effect on it?

Originally Posted by SpeedFreek

Originally Posted by Bad Robot

I did mean in orbit around a sun, not just each other.

Sorry, I should have guessed you meant that!

That would be a highly unlikely configuration to occur naturally, and if you made it artificially, how long could it last before the gravity of the nearest system to it had an effect on it?

I couldn't even make a guess, but was thinking maybe long enough for life to develop on both worlds. Anyway, that's the fun way of thinking about it.

Does the "second Earth" have to be a planet? It is quite possible to build a space habitat capable of supporting 10 billion people with only a tiny fraction of the Earth's mass. Such a habitat would have much less influence on the orbits of the known planets than an actual earth-like planet.

Originally Posted by danhanegan

Does the "second Earth" have to be a planet? It is quite possible to build a space habitat capable of supporting 10 billion people with only a tiny fraction of the Earth's mass. Such a habitat would have much less influence on the orbits of the known planets than an actual earth-like planet.

Yes, I believe what you said could be possible. However, that's not what the OP wanted to talk about.

What about tidal effects of the two planets on each other?

Just a guess here but if somehow a second earth mass body could be inserted into earth orbit opposit earth I would think it could be stable in the fairly short term say a couple hundred years. Longer than that I would begin to get nervous.