What If The Moon Was As Big As Venus?

[SaxonViolence]

Just for a moment imagine that instead of the Moon, we substituted the planet Venus.

 

Let's move the orbit back far enough that the gravitational pull from Venus is the same as we now experience from the Moon.

 

#1} How could such an unusual configuration come about? It would have to be a highly unlikely chain of events—but not completely impossible.

 

So lets extrapolate from there.

 

#2} My orbital mechanics aren't that good, but if we move the planets further apart (anyone know exactly how far?) so that Venus exerts precisely the same pull on us as the Moon does today, wouldn't the Orbital period then be the same—approximately 28 Days?

 

#3} Would the Earth tend to become tidally locked to Venus—and vice versa—so that the two planets forever had the same face toward each other?

 

#4} Let us assume that the planets do become tidally locked. That would give Earth a 28 "Day" long Day.

 

What is our best guess what the Earth's climate would be like if we had 14 days of sun followed by 14 days of night?

 

Alright, I'm not so much thinking of the Earth and Venus, but a hypothetical solar system men might conceivably visit someday with the freakishly unusual occurrence of two habitable worlds orbiting each other.

 

I just don't know, but I'd think that the long cold night would be more problematic for life than a baking day. Anyway that the Atmosphere could be tweaked a bit towards warmer/more habitable conditions?

 

#5} Lets assume that "Venus" has approximately the same fraction of water covered surface and about the same albedo as the Earth—at a distance where we felt the same gravity from Venus as we now feel from the Moon—just how large and bright would "Venus" appear?

 

How much surface detail would Earth based telescopes—particularly early telescopes—reveal about the surface of the companion World?

 

Anyone that has insight into this, please comment.

 

{In an alternate history with a habitable Venus no more than 4 or 5 million miles away—do you think we'd have colonized "Venus" yet? To what degree?}

 

Thanks.

 

 

Saxon Violence

[sanctus]

I think this bbc documentary replies to most of your questions (although it also spends some time on what if the moon was closer or further):

http://www.youtube.com/watch?v=spZ-jXzEDd4&feature=kp

[Cyberia]

I got "This video does not exist".

 

To try and answer the questions:

 

1. It is unlikely that two planets about the same size would become such companions. Moons are either caught or as we believe with our Moon, made. But it is not impossible that two so similar bodies could orbit each other though the chances of that orbit being stable for billions of years and the bodies not drifting apart or towards each other are close to impossible, without being so.

 

2. Two points. The Earth and Moon orbit each other, but because of the Earth's much larger mass, the centre of orbit is close to the Earth. With two bodies of about equal mass, it would be about halfway between the two. With a much larger orbit, the bodies would take longer to go around each other (or rather the common point), having a much longer distance to go.

 

3. The Moon is tidally lockerd with the Earth because it is so small (and close) by comparison. While there would possibly be some slowing of rotation, the planets would have to be dangerously close and so moving very fast to stand any chance of being tidally locked. I would be more interested in what would happen to the oceans as in tides.

 

4. Common sense says that a 14 day long "day" and a 14 day long "night" would mean more heating and cooling of planetary surfaces so we would have hotter days and cooler nights. But we have regions near the poles where they have months long days and months long nights without catastrophe so....?

 

5. Venus would now be quite some distance from us but even primitive telescopes would reveal land masses, bodies of water and clouds. More modern telescopes would reveal an inhabited Venus as in lights of large communities at night, and later spreading cities.

 

I wonder what the religions would have made of such a world, calling it heaven or hell, and later what they would think of the people who might live there? Certainly it would have been a cause to spend lots on space travel and we would decades ago have landed there. If the people there did not land here first.

 

Colonizing a livable planet, even just 4-5 million miles away is a massive outlay. If uninhabited, we would have bases there, but they would be few at present.