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Thread: Question about an earth-like planet

  1. #1 Question about an earth-like planet 
    Forum Freshman Gritty's Avatar
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    Hey team,

    As we're all (hopefully) aware, there is no other planet very similar to earth in our solar system but it is reasonable to assume that in the daunting vastness of space, there may be some out there. My question is whether it is possible to have two very similar planets in one system. I suppose the frequency of lovely cloudy blue specs in the cosmos are very low anyway, and hoping to find two orbiting one star may well be ridiculous, but I'd like to know whether it is possible IN THEORY, regardless of the odds

    Would two planets occupying the Goldilocks zone end up just "competing" for the niche? I imagine if they had similar orbit distances they would be likely to collide, and if their distances were different enough from each other, then one might be missing out on that luxury zone and end up not qualifying for what we would call earth-like.

    I ask because I've been entertaining in my head a little fantasy about humans finding an earth-like planet in their own solar system and rushing to colonize and domesticate it around the late 21st century. I may be silly, but I'd like to keep my fantasies at least feasible, and although fantastic, not impossible. Could anybody shed any light on whether I'm being totally ridiculous or not? If a planet was orbiting a bit further away from the sun than us (without colliding) would it be too far away for liquid water (even just on the equator) or is my knowledge of temperature and distance in space rather lacking?

    Thanks in advance for anybody willing to share in my silly speculations! Have a great day.


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  3. #2  
    Time Lord
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    A slightly different atmosphere could support reasonable temperatures at different orbits. Both Venus and Mars have been speculative targets for such basic "terraforming".

    You wouldn't likely see a blue-water planet until it had free oxygen, generated by something like our early cyanobacteria. Their oxygen poop rusted all the iron out of our seas, leaving them the colour we all love.


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  4. #3  
    Forum Masters Degree Implicate Order's Avatar
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    Quote Originally Posted by Gritty View Post

    I ask because I've been entertaining in my head a little fantasy about humans finding an earth-like planet in their own solar system and rushing to colonize and domesticate it around the late 21st century. I may be silly, but I'd like to keep my fantasies at least feasible, and although fantastic, not impossible. Could anybody shed any light on whether I'm being totally ridiculous or not? If a planet was orbiting a bit further away from the sun than us (without colliding) would it be too far away for liquid water (even just on the equator) or is my knowledge of temperature and distance in space rather lacking? Thanks in advance for anybody willing to share in my silly speculations! Have a great day.
    Keep writing that story. There is ample opportunity to support life attributed to local variations (conditions) on a planet even if it does not specifically lie in the goldilocks zone. The goldilocks zone is more a generalised statement relating to a region around a sun that allows for the ubiquitous availability of liquid water which therefore by default includes the need for a suitable temperature and atmospheric pressure for this to occur. Don't forget however within this zone that you need to take account of a planet of sufficient gravitation to retain an O2 rich atmosphere without putting undue gravitational stress on our physiology and structure. Also make sure you don't poison us to death with too much methane and watch out for runaway global warming in thick atmospheres. You could have a wide goldilocks zone around a sun to support two planets that are habitable........but you are also not restricted to this zone if you can ingeniously think of local conditions that can replace these principles yet allow for habitation. For example, go geothermal away from the sun or go subterranean closer to the sun. :-))

    PS More ideas here.http://en.wikipedia.org/wiki/Circumstellar_habitable_zone

    P
    PS When you find this habitable planet of yours can you let me know. I need a change of scene./tic
    Last edited by Implicate Order; January 9th, 2014 at 07:09 AM.
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  5. #4  
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    I should expand on the problem of free oxygen, which you'll need for a plant + animal ecology. The problem is that iron is going to soak up oxygen faster than any life can produce it, until the last bit of iron is spent. When you consider the amount of rusty rock in our crust, plus the even greater volume churned into the mantle, this is going to take some time...
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  6. #5  
    Forum Bachelors Degree GoldenRatio's Avatar
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    Its entirly possible. Like pong said both venus & mars are within the goldilock zone, the problem is the atmosphere. Venus has way too much which makes it a super greenhouse and thus far too much heat. Mars has way too little thus too cold (not to mention not enough pressure for liquid water or breathable air)

    A planet like earth could even have a different moon that could support life. binary planets exist even with out solar system (pluto-charon) earth is almost a binary planet with our moon.

    I do not know if 2 planets could share the same orbital path around the host star. For instance if earth had a twin orbiting around the sun directly on the other side, we would never see it because the sun would always be in the way. Unsure if something like this is possible, however for fictional story writing its a great way to go.
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  7. #6  
    Forum Masters Degree Implicate Order's Avatar
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    Quote Originally Posted by GoldenRatio View Post

    I do not know if 2 planets could share the same orbital path around the host star. For instance if earth had a twin orbiting around the sun directly on the other side, we would never see it because the sun would always be in the way. Unsure if something like this is possible, however for fictional story writing its a great way to go.
    Shouldn't you have given a spoiler alert or something. That probably has just ruined his story. :-))
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  8. #7  
    Genius Duck Moderator Dywyddyr's Avatar
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    Quote Originally Posted by Gritty View Post
    Would two planets occupying the Goldilocks zone end up just "competing" for the niche? I imagine if they had similar orbit distances they would be likely to collide, and if their distances were different enough from each other, then one might be missing out on that luxury zone and end up not qualifying for what we would call earth-like.
    Don't explain it.
    That way you can leave it open for a follow-up: is it natural? Did aliens put it there?
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  9. #8  
    Forum Freshman Gritty's Avatar
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    Thanks for the responses. It's a great reaction to get from my first proper thread here! Very encouraging.

    Unfortunately this isn't for a proper story though. It's purely for my mental musings and drawings! Call me a stickler, but I wasn't comfortable committing more brain time to it without slightly verifying its scientific grounds! I'm going to allow myself the luxury afforded by Dywyddyr's conclusion and keep doodling away to my heart's (brain's) content knowing that yes, it MAY be possible within the laws of nature. But how? Well that can just be added to that horrifically long list of unanswered questions in science. Or I could go down the Prometheus route and half explain it with a twisty mess of an idea. Apologies to anybody that does completely understand that film. I mean no offence. Cheers.
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  10. #9  
    Universal Mind John Galt's Avatar
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    I think it is not only possible, but quite likely. By that I do not mean commonplace, but even if there is only a .1% chance of it occurring, that still means millions of instances in this galaxy alone. If Venus were just a small distance further away from the sun, it is probable that it would be more Earthlike. The same applies with Mars: if has been Earth sized it would have retained a magnetic field and an atmosphere. But keep in mind that being in the Goldilocks zone does not mean that life will develop, only that if it does develop it could be sustained over billions of years.
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  11. #10  
    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by GoldenRatio View Post

    I do not know if 2 planets could share the same orbital path around the host star. For instance if earth had a twin orbiting around the sun directly on the other side, we would never see it because the sun would always be in the way. Unsure if something like this is possible, however for fictional story writing its a great way to go.
    They've already made a movie a long time ago based on that idea. Unfortunately, such an arrangement is not stable. Eventually, due to the various gravitational tug of the other planets, they will drift out of that perfect alignment, when they do so, they'll just continue to drift further out of position. (Also, even if the orbits were stable, the planet would not remain hidden from us. Its gravity would have an effect on the other planets, and their behavior would tell us that an object with the mass of the Earth was on the other side of the Sun.)

    However, this does set up another interesting type of orbit. As the planet's drift, one will start to catch up with the other in their orbit. At some point their gravity will start to measurable pull on each other. The trailing planet will be pulled forward and the leading planet will be pulled back.

    By being pulled forward, the trailing planet is lifted into a higher orbit and by being pulled backward the leading planet is dropped into a lower one. Higher orbits are slower and lower orbits are faster.

    What ends up happening is that the trailing planet starts to lose ground on the leading planet and begins to fall behind. Eventually, the leading planet in its faster orbit will start to "lap" the trailing planet. IOW, it will become the trailing planet, and the whole process starts up again with the planets swapped in position.

    This type of orbit is sometimes called a "horseshoe" orbit" (because from the reference of one of the planets the other planet's orbit is somewhat horseshoe shaped. )

    If you are on one of these planets, You will see the other planet seem to approach from one direction recede again then approach from the other direction and recede again. Long spans of time will pass between the close approaches of the other planet (more than a century or two).

    This could set up an interesting idea for a story. What if you had two such planets, in the habitable zone. What would a culture make of this regular but infrequent visitor, which could get as large as, say, 1/10 the size of the our Moon?

    What if they eventually colonize it? How would it effect trade when the short and easy route between the two happen decades apart?

    This of course assumes that even the horseshoe orbit is stable over the long run, but for the sake of a good story, I think that this is something that can be assumed.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  12. #11  
    Forum Freshman Gritty's Avatar
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    Janus, thanks for the comprehensive response. I think I'll have to re-read that mechanism a few times to get my head around it! I love the idea of how those moments of relatively easy transport would affect the relationship between the two.
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  13. #12  
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    They've already made a movie a long time ago based on that idea.
    Doppelgänger (1969 film) - Wikipedia, the free encyclopedia

    wasn't very good from memory.
    Sometimes it is better not knowing than having an answer that may be wrong.
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  14. #13  
    Forum Bachelors Degree GoldenRatio's Avatar
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    Also, keep in mind a habitat zone is a sphere radiating out from the sun, not a flat plane. You could have a planet orbiting around the equator (as our planets do)(transverse) or a planet could orbit pole to pole. as long as they do not collide, a transverse & say a sagittal or a coronal plane or even all 3 could orbit the host star although that will get a bit crowded. Not impossible, but improbable due to collision risk.

    You could go the route of a binary star system if they are far enough apart to each have a habital zone. if jupiter was just a bit bigger it would be a brown dwarf and just up from that (about 80 jupiter masses) you hit red dwarf which is enough for a small habitual zone.
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  15. #14  
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    if you find a sistem that has 2 suns, it is far more likely for life to evolve upon such a planet, also of course water is one of the main things to look out for
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  16. #15  
    Forum Bachelors Degree GoldenRatio's Avatar
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    if the sun's are far enough apart. binary stars are quite common in the cosmos. However i believe (could be wrong) that most binary stars orbit each other very closely, like sol-mercury or sol-venus closeness. A planet would need to orbit around both of them, not in-between which removes the effectiveness of having 2 suns.

    Then again there is also the issues of actual orbits. singular stars are easy with orbits.

    2 stars, you might have a planet orbiting just 1, both, or doing a lil figure 8 between em. things can get weird when you try to factor in 2 gravity wells.
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  17. #16  
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    Quote Originally Posted by GoldenRatio View Post
    2 stars, you might have a planet orbiting just 1, both, or doing a lil figure 8 between em. things can get weird when you try to factor in 2 gravity wells.
    Yup. For that reason the odds of finding planets are lower. If you're gambling for an earth-like planet, two stars are not better than one.
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