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Planetary Question

todpod

todpod

Golden Member
I remember reading a long time ago that the earth and moon could be considered a dual planet system rather then a planet and satalite. The reasoning behind this was that the size/mass ratio
was alot closer with earth-moon then other planets and satalites and that the fact that the both rotate on the same axis. I don't remember were I read this but it was a fairly reliable source.
Anybody else ever here such a thing, Just wondering
 


<< the fact that the earth rotates around the moon and not the sun kind of nullifies this. >>

You, sir, are confused. The moon revolves around the earth. The earth revolves around the sun. The moon isn't nearly the size of the earth, so we can't be considered a "dual planet system;" the moon is roughly as wide as Texas.

In a case of "dual planet systems" as you call them (I can't remember the one-word, scientific name for this kind of system), both planets will not exactly follow the path around the object which they both revolve around. If you were to see the movement of both planets from above, it would almost seem like they're revolving around a non-existant object half-way between the two. And, as it is obvious, earth's moon clearly revolves around it without earth moving (much) off of it's revolutionary path around the sun.

Nik
 


<< << the fact that the earth rotates around the moon and not the sun kind of nullifies this. >>

You, sir, are confused. The moon revolves around the earth. The earth revolves around the sun. The moon isn't nearly the size of the earth, so we can't be considered a "dual planet system;" the moon is roughly as wide as Texas.

In a case of "dual planet systems" as you call them (I can't remember the one-word, scientific name for this kind of system), both planets will not exactly follow the path around the object which they both revolve around. If you were to see the movement of both planets from above, it would almost seem like they're revolving around a non-existant object half-way between the two. And, as it is obvious, earth's moon clearly revolves around it without earth moving (much) off of it's revolutionary path around the sun.

Nik >>


Ditto
 
The moon is approx 1/6 the size of earth, a much closer ratio then any other system in the solar system. The earth rotates on its axis and the moon rotates around the earth and the earth rotates on its axis,
which is the central point that everything is rotating around, so they both rotate around a central point. The only other poosible exception is the pluto-charon system assuming pluto is still a planet. Later todd
 
The moon, Earth's only natural satellite, is large as moons go. It is fifth in diameter among planetary satellites, more than two-thirds as large as Mercury, and more than three times the diameter of the largest asteroid. It is, in fact, over one-fourth the size of the earth, with a diameter of 2160 miles<!--#end intro--> (3476 kilometers
 
ACTUALLY....

todpod, you're right. I have read the same information that you have come across. The earth-moon system rotates around a focal point a few thousand kilometers beyond the surface of the earth along the axis between the earth and moon. It is around this point that the earth-moon system rotates around the sun.
 
Every planet rotates. Duh. To say that the earth and moon are a "dual planet system" simply because they both rotate, is moronic. They're not. Look it up. Planets do not rotate around other objects. They revolve.

Nik
 
I have been unable to find the info i have been looking for to clarify my arguement. But the point is that the earth-moon system is unique in our solar system and that based on those differances and the simialrities of the earth and moon could be considered a duel planet system. t
 
Considering that most of these "dual planet systems" in other galaxies and solar systems consist of planets that are virtually the same volume, we have further evidence that the earth/moon combination isn't one.

Nik
 
FFM, you're missing todpod's original point, which is valid. The moon is of a sufficient mass and proximity to the Earth that the fulcrum point upon which we orbit around the sun is NOT the center of the Earth, but rather a point close to the Earth but between the Earth and the moon. If you read some of the older astronomy texts they do refer to our planet and satellite as a "dual system". It was my error to use the word rotate in place of revolution. The Earth obviously revolves around the sun. That's not what the discussion here is about. todpod is correct that the Earth and moon revolve around a common point acentric from the Earth's core as we progress around the sun.
 


<< In a case of "dual planet systems" as you call them (I can't remember the one-word, scientific name for this kind of system) >>

iirc, it's binary-planets. much like binary-star systems (two stars revolving around one another). correct?
 


<<

<< In a case of "dual planet systems" as you call them (I can't remember the one-word, scientific name for this kind of system) >>

iirc, it's binary-planets. much like binary-star systems (two stars revolving around one another). correct? >>

w0ot.

Scores:
BrunoPuntzJones=1
me=0



Yes, I realize what the discussion is. I like to argue. 😉 😛 j/k. I understand the point and why that is happening. But I think considering earth/moon a binary planet would be stretching it too far.
 
Come on, people... the moon is 26 earth-lengths away from the earth (forgot the actual distance). A few thousand miles off of the surface of the planet isn't really anything at all.

Nik
 
Yeah I mean i pretty sure larger planets like venus rotate around the sun on a focal point away from it's center... even if it's just a few centimeters, or just milimeters, so who is to decide what can be and what can't be a binary system?? I would say the focal point would have to be somewhere in open space between both "planets", not somewhere inside the planets surface.
 
The Earth and Moon revolve about their common center of mass, which is indeed below the earth's surface. For all you ET fans... it has been speculated that the Moon was necessary for the development of life. The gravitational force of the moon creates the tides, and served a kind of a big blender. Life outside our would world be much rarer, if true. Interesting hypothesis.
 
<puts his smartass cap on>

When two objects get in each other's field of gravity they rotate around mutual center of mass. For objects like Earth and Moon, when mass of one is much bigger than the mass of the second, that center happens to be very close to the center of the bigger object. Thus, it appears as if second object (Moon) is rotating around the first object (Earth). However, in reality both object are rotating around common center of mass, which can be mathematically calculated.

<takes the cap off>


Now hand me some beer.
 
I'm confused...



<< the moon is roughly as wide as Texas. >>




<< The moon is approx 1/6 the size of earth >>




<< over one-fourth the size of the earth >>

 
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