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Binary planet?
The "Seasons on Gas Giant Moons" thread got me wondering... would a
"binary" system of earth-like planets be possible? And what would happen once any civilizations on the two planets got evidence of each other's existence? Just an odd thought while bored at work... |
#2
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Binary planet?
Good afternoon,
Hail, Bob Martin! We who are about to post salute you. The "Seasons on Gas Giant Moons" thread got me wondering... would a "binary" system of earth-like planets be possible? And what would happen once any civilizations on the two planets got evidence of each other's existence? Just an odd thought while bored at work... While I didn't read that particular thread, I'll still take a crack at this one... No. Under the assumption that these planets are near a star, the tidal forces of two Earth-sized planets close enough to orbit about a common center of mass would pretty much ruin their "Earth-like" nature. Take care, cb -- Christopher A. Bohn ____________|____________ http://www.cse.ohio-state.edu/~bohn/ ' ** ** " (o) " ** ** ' "The commanders of armies are more to be pitied than one would think. Without listening to them, all the world denounces them, the newspapers ridicule them, and yet, of the thousands who condemn them, there is not one that could command even the smallest unit." - Frederick the Great |
#3
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Binary planet?
Engr Bohn wrote:
Good afternoon, Hail, Bob Martin! We who are about to post salute you. The "Seasons on Gas Giant Moons" thread got me wondering... would a "binary" system of earth-like planets be possible? And what would happen once any civilizations on the two planets got evidence of each other's existence? Just an odd thought while bored at work... It would be extremely unlikely that the two civilizations would evolve at the same time. Most likely one of the two worlds would develop the capability to visit the other before the other worlds develops the capability to build a wheel. In the extremely unlikely scenario where both worlds would have a means of communicating with the other (by radio for instance) before any of the worlds would have the capability to visit the other, I think that they would have great collaboration while learning what the other world knows. This great collaboration would make them friendly to one another before they meet. That would probably make a much softer and friendlier encounter than Europeans meet Americans in 16th century or French and English meet Vikings in 9th century or most any civilization encounter on Earth. While I didn't read that particular thread, I'll still take a crack at this one... No. Under the assumption that these planets are near a star, the tidal forces of two Earth-sized planets close enough to orbit about a common center of mass would pretty much ruin their "Earth-like" nature. Why? Alain Fournier |
#4
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Binary planet?
Good evening,
Hail, Alain Fournier! We who are about to post salute you. Engr Bohn wrote: Good afternoon, Hail, Bob Martin! We who are about to post salute you. The "Seasons on Gas Giant Moons" thread got me wondering... would a "binary" system of earth-like planets be possible? And what would happen once any civilizations on the two planets got evidence of each other's existence? Just an odd thought while bored at work... [...] While I didn't read that particular thread, I'll still take a crack at this one... No. Under the assumption that these planets are near a star, the tidal forces of two Earth-sized planets close enough to orbit about a common center of mass would pretty much ruin their "Earth-like" nature. Why? Well, okay -- I *should* have said "I doubt it". That is, I was making a WAG since I didn't have numbers in front of me. I can do (a little) better now... Assuming the planets each have one Earth mass and are 1 AU from a star with the Sun's mass, then using the "sphere of influence" fiction, the planets should be no farther apart than 900,000 km. Let's call the two planets Dirt and Soil. In addition to assuming Dirt and Soil each have the same mass as Earth, we'll also assume they have about the same radius as Earth. This being the case, and if Dirt and Soil are at the threshold of 900,000 km, the gravitational acceleration Dirt would have on the near side of Soil is about 0.500 mm/s^2; on the far side of Soil, about 0.486 mm/s^2 For comparison, the gravity due to the Moon on the near side of Earth: 0.0344 mm/s^2; the far side of Earth: 0.0321 mm/s^2. Here's where I run out of numbers. But the accelerations that Dirt imposes on Soil (and vice-versa) is a full order of magnitude greater than the Moon has on Earth. I expect this would have a significant effect on the mantles and tectonic plates, and it would have a decided effect on the oceans and atmospheres. Take care, cb -- Christopher A. Bohn ____________|____________ http://www.cse.ohio-state.edu/~bohn/ ' ** ** " (o) " ** ** ' "The commanders of armies are more to be pitied than one would think. Without listening to them, all the world denounces them, the newspapers ridicule them, and yet, of the thousands who condemn them, there is not one that could command even the smallest unit." - Frederick the Great |
#5
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Binary planet?
Imagine what an incentive to science it would be to have a large
planet hanging in your sky! But you wouldn't need to wait for radio to achieve communication. Seems to me, a heliograph would do fine. Cheers -- Martha Adams |
#6
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Binary planet?
Martha H Adams wrote:
Imagine what an incentive to science it would be to have a large planet hanging in your sky! But you wouldn't need to wait for radio to achieve communication. Seems to me, a heliograph would do fine. I'm not sure what you call a heliograph. I speak french and in french a "héliographe" is something used to measure the length of sunshine time. From the context, and the greek origins of the word I will assume you are referring to a device sending signals by reflecting sunlight. It would be possible to do so. But you would have to build something really huge or assume that the receiving end has telescopes and know where to look. If you know that there is someone listening at the other end you could go that way. But I never heard about any Earthling trying to signal the inhabitants of the moon that way. I don't really see why inhabitants of the twin planets would view their co-twin planet differently than humans viewed the moon until about 200 years ago. Today we know that the moon is very different from Earth but about 200 years ago the moon was a mysterious place. And as far as I know, nobody built a device to communicate with the moon just in case there would of been someone listening on that mysterious place. By the time you have the technology to detect life and civilization on the other planet, then many means of communication become available. Alain Fournier |
#7
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Binary planet?
Engr Bohn wrote:
Good evening, Hail, Alain Fournier! We who are about to post salute you. Engr Bohn wrote: Good afternoon, Hail, Bob Martin! We who are about to post salute you. The "Seasons on Gas Giant Moons" thread got me wondering... would a "binary" system of earth-like planets be possible? And what would happen once any civilizations on the two planets got evidence of each other's existence? Just an odd thought while bored at work... [...] While I didn't read that particular thread, I'll still take a crack at this one... No. Under the assumption that these planets are near a star, the tidal forces of two Earth-sized planets close enough to orbit about a common center of mass would pretty much ruin their "Earth-like" nature. Why? Well, okay -- I *should* have said "I doubt it". That is, I was making a WAG since I didn't have numbers in front of me. I can do (a little) better now... Assuming the planets each have one Earth mass and are 1 AU from a star with the Sun's mass, then using the "sphere of influence" fiction, the planets should be no farther apart than 900,000 km. Let's call the two planets Dirt and Soil. In addition to assuming Dirt and Soil each have the same mass as Earth, we'll also assume they have about the same radius as Earth. This being the case, and if Dirt and Soil are at the threshold of 900,000 km, the gravitational acceleration Dirt would have on the near side of Soil is about 0.500 mm/s^2; on the far side of Soil, about 0.486 mm/s^2 For comparison, the gravity due to the Moon on the near side of Earth: 0.0344 mm/s^2; the far side of Earth: 0.0321 mm/s^2. Here's where I run out of numbers. But the accelerations that Dirt imposes on Soil (and vice-versa) is a full order of magnitude greater than the Moon has on Earth. I expect this would have a significant effect on the mantles and tectonic plates, and it would have a decided effect on the oceans and atmospheres. Yes much bigger tides and probably much more volcanoes and a few other differences. But I don't think that would make the planets uninhabitable. But I must say that my knowledge in that field is rather limited. I never lived anywhere but on this planet and I don't know anyone from an extraterrestrial civilization so I don't really know what are the necessary conditions for a planet to be able to sustain a civilization. Alain Fournier |
#8
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Binary planet?
Alain Fournier wrote:
I'm not sure what you call a heliograph. I speak french and in french a "héliographe" is something used to measure the length of sunshine time. From the context, and the greek origins of the word I will assume you are referring to a device sending signals by reflecting sunlight. That's it exactly; armies used them to communicate prior to telegraphy and radio http://myweb.cableone.net/kd7aoi/homebrew.htm It would be possible to do so. But you would have to build something really huge or assume that the receiving end has telescopes and know where to look. If you know that there is someone listening at the other end you could go that way. But I never heard about any Earthling trying to signal the inhabitants of the moon that way. There were plans to contact other planets via earth-based signs and signals proposed in the past; there is an article about some of the ideas he http://seti.org/seti/our_projects/in.../messages.html I don't really see why inhabitants of the twin planets would view their co-twin planet differently than humans viewed the moon until about 200 years ago. Today we know that the moon is very different from Earth but about 200 years ago the moon was a mysterious place. And as far as I know, nobody built a device to communicate with the moon just in case there would of been someone listening on that mysterious place. One difference would be that moving clouds would be visible on the other planet, and it wouldn't take much imagination to realize what they were. And the lights of major cities would also be visible through even primitive telescopes if it possessed a technological civilization that built cities. Pat |
#9
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Binary planet?
Alain Fournier wrote
Yes much bigger tides and probably much more volcanoes and a few other differences. But I don't think that would make the planets uninhabitable. Bigger ocean and body tides mean more tidal breaking of rotation, thus one or both planets will likely become tidally locked to the other. I.e., there will be near and far sides. IIRC, there was one, maybe more science fiction stories in the 1950s or so that had this premise. Civilization evolved on a continent on the far side of one planet. Boy, did they get a surprise when the first Magellan-equivalent sailed! |
#10
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Binary planet?
Pat Flannery wrote:
Alain Fournier wrote: It would be possible to do so. But you would have to build something really huge or assume that the receiving end has telescopes and know where to look. If you know that there is someone listening at the other end you could go that way. But I never heard about any Earthling trying to signal the inhabitants of the moon that way. There were plans to contact other planets via earth-based signs and signals proposed in the past; there is an article about some of the ideas he http://seti.org/seti/our_projects/in.../messages.html Interesting article. But those were just plans. Never implemented because as I said you need something really huge. One difference would be that moving clouds would be visible on the other planet, and it wouldn't take much imagination to realize what they were. Yes clouds would help the imagination. But I think that many people in a period of a few millennia before 1800 knew that the moon was a place where one could walk but didn't know that the moon didn't have an atmosphere. Many of those people probably thought that there might be people living on the moon. They didn't try to communicate with the moonlings because it was too difficult. And the lights of major cities would also be visible through even primitive telescopes if it possessed a technological civilization that built cities. Once you have major cities with serious lighting, communication becomes much easier. Here on Earth the time between the first electrified major cities and the famous stroll of Neil Armstrong was just a few decades. If those few decades happen at the same time on both of the twin worlds then yes very interesting things can happen. But I think that it is extremely unlikely that the two worlds would evolve at the same rate for a few billion years and be both at the same evolutionary stage to a precision of a few decades. Nonetheless, even if it is very unlikely it is fun to imagine what would happen in such an interesting case. Maybe we will live to see something similar. Imagine if SETI makes contact with a world at about our evolutionary stage. Not very likely, but it would be very interesting. Of course finding a world with life at a different evolutionary stage would be also be interesting. But in such a case information flow would essentially be one way. I think that would make it less thrilling. Alain Fournier |
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