Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

What would happen if an artificial force made the moon to stay at a perpetual opposition from the sun?

Assume that the artificial force necessary is possible, and capable of making the moon stay at sun's opposition and keep from being dragged towards the planet by the gravity.

this question was inspired by another of my questions: Planet in which satellite(moon) and star(sun) appear together once a year

share|improve this question
3  
This is unphysical. The Earth and Moon would be attracted to each other and would collide. If you invoke magic and used this artificial force to stop their attraction then you can use that magic to pick what else happens too. –  Brandon Enright May 29 '13 at 0:32
    
@BrandonEnright I don't see I that would have to be magic, I am not a physicist, but for all I know it could simple be really potent rockets that would do it. If I am wrong, and was explained it, would be as helpful as explaining what I asked. Sometimes being wrong teaches more than being right. –  Philipi Willemann May 29 '13 at 3:21
2  
@BrandonEnright One could argue that placing the Moon at the Sun-Earth L2 Lagrangian point would be physical. Granted, Sun, Earth and Moon would all have to be perfectly spherical, the only bodies in the universe, the Moon has to be placed at the exact L2 for this configuration to remain stable (not to mention be made of styrofoam to be 'massless' but still visible from that distance), but this would at least not have to invoke magic. –  Rody Oldenhuis May 29 '13 at 4:24
    
You could pose the question a different way by considering a smaller planet to that of the Earth, but one that exhibits tidal locking with the parent star. –  Killercam May 29 '13 at 12:17
add comment

closed as off topic by David Z May 29 '13 at 3:17

Questions on Physics Stack Exchange are expected to relate to physics within the scope defined by the community. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about reopening questions here.If this question can be reworded to fit the rules in the help center, please edit the question.

1 Answer

This question was already answered in your other question by Crazy Buddy. You can either change the mass of the planet or distance away from the planet to make the period equal to one year. Now, position the moon behind the planet. As the planet revolves around the sun, the moon will revolve around the planet, and will be in perpetual opposition.

$$v_{moon}=\sqrt{\frac{GM_{planet}}{r}}$$ $$T_{moon}=\frac{2\pi r}{v_{moon}}$$ Disclaimer: These equations are for uniform circular motion.

Set $T_{moon}=1yr$ and you get a relationship between $M_{planet}$ and $r$. Choose a suitable mass for your planet and solve for the distance to the moon.

share|improve this answer
    
Yes, that answer the other question, but on this I was thinking on the effects on the planet, like would this change the way tides behave. English is not my native language so I am not very good at expressing my self in it. –  Philipi Willemann May 29 '13 at 3:15
    
@PhilipiWillemann: You can imagine a lot of things. But, the way you express it to your fellow members is what makes the question popular and encourage'able or uninteresting and misleading. –  Waffle's Crazy Peanut May 29 '13 at 3:45
add comment

Not the answer you're looking for? Browse other questions tagged or ask your own question.