A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » Space Science Misc
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Binary planet?



 
 
Thread Tools Display Modes
  #1  
Old April 27th 04, 07:39 PM
Bob Martin
external usenet poster
 
Posts: n/a
Default 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  
Old April 27th 04, 08:03 PM
Engr Bohn
external usenet poster
 
Posts: n/a
Default 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  
Old April 27th 04, 10:51 PM
Alain Fournier
external usenet poster
 
Posts: n/a
Default 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  
Old April 28th 04, 03:55 PM
Engr Bohn
external usenet poster
 
Posts: n/a
Default 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  
Old April 28th 04, 04:04 PM
Martha H Adams
external usenet poster
 
Posts: n/a
Default 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  
Old April 29th 04, 01:23 AM
Alain Fournier
external usenet poster
 
Posts: n/a
Default 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  
Old April 29th 04, 01:36 AM
Alain Fournier
external usenet poster
 
Posts: n/a
Default 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  
Old April 29th 04, 05:51 AM
Pat Flannery
external usenet poster
 
Posts: n/a
Default 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  
Old April 29th 04, 06:18 PM
Allen Thomson
external usenet poster
 
Posts: n/a
Default 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  
Old April 30th 04, 02:59 AM
Alain Fournier
external usenet poster
 
Posts: n/a
Default 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

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
If gravity is required, what are the planets in the SolarSystem? quilty Space Science Misc 11 April 23rd 04 04:59 PM


All times are GMT +1. The time now is 02:15 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.