# Possibility of undiscovered planet hiding behind the sun? **URL:** \ **Category:** Factual Questions\ **Created:** [February 19, 2008, 11:19pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317 "2008-02-19T23:19:28Z")\ **Posts on this page:** 19\ **Page:** 2
**Author:** ![nd\_n8](https://avatars.discourse-cdn.com/v4/letter/n/439d5e/32.png) [@nd\_n8](https://boards.straightdope.com/u/nd_n8)\ **Post date:** [February 20, 2008, 12:19pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/21 "2008-02-20T12:19:09Z")
[QUOTE=Otto] Any movie _period_ would be better with Gamera. [/QUOTE] Gamera would have definitely improved any or all of the Mel Gibson historical epics (or any other Mel Gibson movie for that matter). ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [February 20, 2008, 12:48pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/22 "2008-02-20T12:48:32Z")
[QUOTE=Santo Rugger] I thought Lagrange points were only for a third object that had negligible mass compared to the other two masses? [/QUOTE] You’re right. ---
**Author:** ![asterion](https://avatars.discourse-cdn.com/v4/letter/a/4da419/32.png) [@asterion](https://boards.straightdope.com/u/asterion)\ **Post date:** [February 20, 2008, 3:39pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/23 "2008-02-20T15:39:35Z")
[QUOTE=nd\_n8] Gamera would have definitely improved any or all of the Mel Gibson historical epics (or any other Mel Gibson movie for that matter). [/QUOTE] “Two kaiju enter! One kaiju leaves! Two kaiju enter! One kaiju leaves!” ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 20, 2008, 3:42pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/24 "2008-02-20T15:42:54Z")
[QUOTE=Randy Seltzer] I don’t get it: what’s wrong with the question besides betraying ignorance of planetary physics and sci fi pop culture? [/quote] I don’t get it either, it was a reasonable question. And while an actual _planet_ would be easily detectable through its gravitational effect on other planets, a small asteroid may not be so easy to detect. I’m not sure if we’ve actually mounted an astronomical telescope on an interplanetary probe and pointed it there. I think the only argument against it is that it’s not a stable orbit, and it would be incredibly unlikely that an asteroid just happened to get into that position and remained there for the past century or two. ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [February 20, 2008, 3:45pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/25 "2008-02-20T15:45:30Z")
[QUOTE=Santo Rugger] I thought Lagrange points were only for a third object that had negligible mass compared to the other two masses? [/QUOTE] They are. To really figure out what would happen if you had a counter-Earth, you’d need some sort of celestial mechanics computer simulation. If you have three objects interacting gravitationally, and one of them has a negligible mass compared to the other two, you have an example of the restricted three-body problem. That’s a lot easier to deal with than the full three-body problem. The full three-body problem is insoluble, so that’s why we need simulations. ---
**Author:** ![Scuba\_Ben](https://avatars.discourse-cdn.com/v4/letter/s/278dde/32.png) [@Scuba\_Ben](https://boards.straightdope.com/u/Scuba_Ben)\ **Post date:** [February 20, 2008, 3:59pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/26 "2008-02-20T15:59:16Z")
[QUOTE=Qadgop the Mercotan] I recall that this was the premise for a movie too, and I’m not talking about a “Gor” movie. I even remember a scene from the movie, where a satellite suddenly rotated upwards to show a planet with land and seas. Anybody remember the name of that movie? If not, I may have to query in CS! [/QUOTE] MST3K: The theatrical version screened _This Island Earth_ which also featured a Counter-Earth. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [February 20, 2008, 9:20pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/27 "2008-02-20T21:20:18Z")
[QUOTE=Anne Neville] They are. To really figure out what would happen if you had a counter-Earth, you’d need some sort of celestial mechanics computer simulation. If you have three objects interacting gravitationally, and one of them has a negligible mass compared to the other two, you have an example of the restricted three-body problem. That’s a lot easier to deal with than the full three-body problem. The full three-body problem is insoluble, so that’s why we need simulations. [/QUOTE] Pedantic correction: the general three-body problem (where all masses are non-negligible) is insoluble but there are specific cases of bodies with M1\>\>M2=M3 and M1=M2=M3 (and more generally M1=M2=…=Mn as in a Klemperer rosette) which do have explicit solutions. However, such solutions would require some very specific starting conditions for initial stability, and are readily perturbed and unstable for any reasonable periods of time, so we would not expect to find them in nature or in any system which is not artificially stabilized. It is also worth noting that while the current orbit of the Earth has an eccentricity of only about 0.0167; while this is pretty close to being a circle, there would still be points at which Earth would lead or lad Htrae; probably not enough to see directly observe the other planet, but sufficient that other orbital perturbations (drag of the Moon, attraction of Jupiter) would eventually pull it out of synch. The orbits of Earth and Htrae would precess and over the long term (tens of millions of years) there is even the possibility that they might collide, or at least get close enough to disrupt one another’s orbit. Stranger ---
**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\ **Post date:** [February 20, 2008, 9:24pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/28 "2008-02-20T21:24:47Z")
Dr. Who’s “The Tenth Planet” episode also talked about a counter Earth (it was originally where the cybermen came from). It’s a very old SF trope. ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [February 20, 2008, 9:25pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/29 "2008-02-20T21:25:26Z")
[QUOTE=Randy Seltzer] I don’t get it: what’s wrong with the question besides betraying ignorance of planetary physics and sci fi pop culture? It’s not like I actually believe such a planet to be there; I was just wondering why we know it’s not. Of course, now that I’ve been pointed towards previous threads on the subject (and a fascinating article about lagrange points), I can educate myself. [/QUOTE] I’m sorry, **Randy** , it’s just that I view you as a pretty intelligent guy, able to quiz the basics of this out for yourself. 🙂 So I wondered if the question weren’t more of a way to get a discussion going on the concept as you recalled it from movie/literature… ---
**Author:** ![garygnu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garygnu/32/2924_2.png) [@garygnu](https://boards.straightdope.com/u/garygnu)\ **Post date:** [February 20, 2008, 10:07pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/30 "2008-02-20T22:07:27Z")
[QUOTE=Scuba\_Ben] MST3K: The theatrical version screened _This Island Earth_ which also featured a Counter-Earth. [/QUOTE] Metaluna, the other planet in _This Island Earth_ is not a Counter-Earth, it’s extrasolar. **CalMeacham** can probably give more details. ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [February 21, 2008, 12:14am UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/31 "2008-02-21T00:14:34Z")
[QUOTE=garygnu] Metaluna, the other planet in _This Island Earth_ is not a Counter-Earth, it’s extrasolar. **CalMeacham** can probably give more details. [/QUOTE] [OT]My Luna cat has a new nickname now- Metaluna.[/OT] ---
**Author:** ![Petey](https://avatars.discourse-cdn.com/v4/letter/p/f1d935/32.png) [@Petey](https://boards.straightdope.com/u/Petey)\ **Post date:** [February 21, 2008, 2:31pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/32 "2008-02-21T14:31:58Z")
[QUOTE=Scuba\_Ben] MST3K: The theatrical version screened _This Island Earth_ which also featured a Counter-Earth. [/QUOTE] It was Episode 305 - _Stranded in Space_ that had a Counter-Earth. ---
**Author:** ![Bill\_Door](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)\ **Post date:** [February 21, 2008, 2:40pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/33 "2008-02-21T14:40:56Z")
[QUOTE=Otto] Any movie _period_ would be better with Gamera. [/QUOTE] Gamera is to movies as bacon is to food. ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [February 21, 2008, 3:59pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/34 "2008-02-21T15:59:02Z")
[QUOTE=Bill Door] Gamera is to movies as bacon is to food. [/QUOTE] [Homer] Mmmm, bacon-flavored Gamera [/Homer] ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 21, 2008, 8:23pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/35 "2008-02-21T20:23:06Z")
> [@](#): > > I thought Lagrange points were only for a third object that had negligible mass compared to the other two masses? To be perfectly precise, the Lagrange solutions require that M1 \>\> M2 \>\> M3. If any two of the masses are comparable to each other, you can get qualitatively similar solutions, but which differ numerically from the Lagrange points. I only learned this fact myself the hard way, when I had a problem on my comprehensive exams concerning a planet in a binary star system (M1 = M2 \>\> M3). I set up some trancendental equations, and was all set to show that they were solved by theta = 60 degrees, only to discover that lo, they weren’t. Closer to the original topic, if you did try to put a mass on the opposite side of the Sun, it’d end up in a horseshoe orbit, like that of the asteroid [2002 AA[sub]29[/sub]](http://en.wikipedia.org/wiki/2002_AA29). It moves a slightly closer (and thus slightly faster) orbit than Earth, until it gets close enough that it almost laps us, and then is moved outward into a larger (and thus slightly slower) orbit by perturbation from Earth’s gravity. 95 years later, when it’s almost fallen behind one lap, the Earth’s gravity pulls it back in to a smaller orbit, and the cycle repeats. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [February 21, 2008, 8:42pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/36 "2008-02-21T20:42:32Z")
[QUOTE=malkavia] EXACTLY THIS. How weird. [/QUOTE] What are you, a realtor or something? ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [February 21, 2008, 11:37pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/37 "2008-02-21T23:37:32Z")
[QUOTE=Otto] Any movie _period_ would be better with Gamera. [/QUOTE] A few of my favorites improved: _Round Midnight_ “You’re Gamera! You’re too good for this sh!t.” _The Conversation_ “Gamera’d kill us if he had the chance.” _Hard Eight_ a.k.a. _Sydney_ “Gamera f&cked me, and now he’s gonna pay me what he owes me!” _All the President’s Men_ “The whole thing was a Gamera operation.” Yeah, I guess you’re right. ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [February 21, 2008, 11:44pm UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/38 "2008-02-21T23:44:18Z")
Now, when I read a fortune cookie fortune, I can see myself adding, “with Gamera” at the end. 😃 You will find good fortune … with Gamera. ---
**Author:** ![jackdavinci](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackdavinci/32/3259_2.png) [@jackdavinci](https://boards.straightdope.com/u/jackdavinci)\ **Post date:** [February 22, 2008, 12:00am UTC](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317/39 "2008-02-22T00:00:54Z")
I believe the last two season of Lexx involved a counter-Earth. [Previous page](https://boards.straightdope.com/t/possibility-of-undiscovered-planet-hiding-behind-the-sun/438317.md?page=1)