Earth's Twin Planet: Can It Stay Behind the Sun?

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In summary, the conversation discusses the possibility of a twin planet opposite the Earth and the factors that would affect its position. It also mentions the instability of the L3 Lagrange point and the role of GAIA satellite in astrometry. The conversation also touches on the discovery of non-Newtonian effects on Mercury's orbit and Neptune in the 19th century and the interest in physics and cosmology sparked by popular media such as the TV show Cosmos.
  • #1
Johnnyallen
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I was watching a really bad Japanese sci-fi movie in which the writers employed a frequent plot device. The Earth had a twin planet opposite the sun which made it undetectable to earthlings.
This, of course, would be possible if the Earth's orbit was a perfect circle, which it isn't. It is, of course, elliptical.
Question: Given that the Earth's speed in it's orbit varies according to its distance from the sun, would a planet opposite the Earth always maintain its position behind the sun?
 
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  • #2
In the ideal case that the Sun's gravitation was completely dominant and the eccentricities and radii were the same and their perihelion positions were on opposite sides of the Sun, yes. Now, any perturbations to this (such as the influence from other bodies in the solar system) would accumulate over time and break this situation, not to mention that you could discover the opposite planet using spacecraft .
 
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  • #3
Thanks for the quick reply.
I'm new to this forum and am looking forward to future discussions, etc.
I didn't mention the obvious about discovering the planet with satellites or spacecraft because this was a very bad Japanese movie from the 60's
 
  • #4
Johnnyallen said:
a very bad Japanese movie from the 60's
Well it might not have been as bad as you think considering that western sci fi movies at the time were concentrating on super heroes with magical powers.
 
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  • #5
Johnnyallen said:
...
This, of course, would be possible if the Earth's orbit was a perfect circle, which it isn't. It is, of course, elliptical...

I do not think circular orbits matter. Could be an extremely elliptical orbit, like a comet. Just has to be perfectly opposite.

You can hang out at 5 Lagrange points. Only L3 is on the far side of the sun.

There is also an asteroid called 3753 cruithne which has a 1 year orbit around the sun.
 
  • #6
stefan r said:
I do not think circular orbits matter. Could be an extremely elliptical orbit, like a comet. Just has to be perfectly opposite.

You can hang out at 5 Lagrange points. Only L3 is on the far side of the sun.

There is also an asteroid called 3753 cruithne which has a 1 year orbit around the sun.
The problem with the L3 point is that it is unstable. The slightest drift from that perfect balance point and the combined gravity of the sun and Earth will tend pull it even further out of position. This is unlike the L5 and L4 points, where a slightly dislodged object will tend drift back into place.
 
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  • #7
rootone said:
Well it might not have been as bad as you think considering that western sci fi movies at the time were concentrating on super heroes with magical powers.
Not to labor the point but Hollywood produced some sci fi clunkers in the 50's excluding the classic Plan 9 From outer Space.
 
  • #8
Johnnyallen said:
Not to labor the point but Hollywood produced some sci fi clunkers in the 50's excluding the classic Plan 9 From outer Space.
A trip to the moon dates to 1902.
 
  • #9
stefan r said:
A trip to the moon dates to 1902.
Very interesting, though somehow I got a psychedelic 60's impression of it.
 
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  • #10
Back on the OP: The Earth's Twin's gravity will also perturb the orbits of the inner planets. My guess is that, even as early as the 19th Century, people would have easily been able to deduce its presence from them.

This is the same story as the discovery of non-Newtonian effects on Mercury's orbit and of Neptune itself, both of which were indeed detected in the 19th C (though people didn't know what to make of Mercury's orbital anomalies at the time). However, I don't have the numbers for an Earth's Twin.
 
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  • #11
Janus said:
The problem with the L3 point is that it is unstable. The slightest drift from that perfect balance point and the combined gravity of the sun and Earth will tend pull it even further out of position. This is unlike the L5 and L4 points, where a slightly dislodged object will tend drift back into place.
Briefly, I don't have a degree in Physics. I credit Carl Sagan's Cosmos for igniting my interest in it and Cosmology. Your reference to Lagrange points got me to look it up. I had heard something about them, but that's about it.
The material I read mentions the GAIA satellite at L2. I had heard of GAIA but not exactly what it does.
I subscribe to a YouTube channel Space Time. Those guys are awesome. Their short lectures are captivating although a little hard to follow sometimes. And sometimes the material is a little over my head.
Gabe's series on General Relativity is, as promised, mind blowing.
I recently watched one on GAIA'S contribution to Astrometry. Wow is about all I can say.
BTW, thanks for your reply.
 
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  • #12
Johnnyallen said:
Briefly, I don't have a degree in Physics. I credit Carl Sagan's Cosmos for igniting my interest in it and Cosmology. Your reference to Lagrange points got me to look it up. I had heard something about them, but that's about it.
The material I read mentions the GAIA satellite at L2. I had heard of GAIA but not exactly what it does.
I subscribe to a YouTube channel Space Time. Those guys are awesome. Their short lectures are captivating although a little hard to follow sometimes. And sometimes the material is a little over my head.
Gabe's series on General Relativity is, as promised, mind blowing.
I recently watched one on GAIA'S contribution to Astrometry. Wow is about all I can say.
BTW, thanks for your reply.
Gaia is in a (gravitationally) unstable Lagrange point. It is actively stabilized by non-gravitational means. Like being on the top of a hill, gravity works against staying there, but it's a lot easier to keep yourself in place there, with small forces, than to keep yourself in place on the side of hill, where you need much larger ones.
 
  • #13
JMz said:
Gaia is in a (gravitationally) unstable Lagrange point. It is actively stabilized by non-gravitational means. Like being on the top of a hill, gravity works against staying there, but it's a lot easier to keep yourself in place there, with small forces, than to keep yourself in place on the side of hill, where you need much larger ones.
I had to do some reading up on Lagrange points. So GAIA is at L2 and is in a, for lack of a better phrase, lock step orbit with the Earth opposite the sun. Was it Newton that attributed the inverse square law to Keppler's planetary motions, so wouldn't GAIA's orbital speed be slower than the Earth's or is the Earth's mass (General Relativity) dragging the satellite along with it?
 
  • #14
Johnnyallen said:
I had to do some reading up on Lagrange points. So GAIA is at L2 and is in a, for lack of a better phrase, lock step orbit with the Earth opposite the sun. Was it Newton that attributed the inverse square law to Keppler's planetary motions, so wouldn't GAIA's orbital speed be slower than the Earth's or is the Earth's mass (General Relativity) dragging the satellite along with it?

GAIA or any satelite place at L2 is orbiting both the Sun and the Earth. It has a 365 day orbit. Both 365 days around Earth and 365 days around the sun.

For L2 the orbital speed is higher than Earth's orbital speed. For L1 the orbital speed around the sun is lower. Compare to the moon which is sometimes orbiting the sun faster (full moon), sometimes orbiting slower (new moon) and sometimes about the same (quarter). You are also orbiting the sun faster at midnight than you are during lunch. It is not breaking Kepler's laws.

Yes Newton did the inverse square.
 
  • #15
stefan r said:
GAIA or any satelite place at L2 is orbiting both the Sun and the Earth. It has a 365 day orbit. Both 365 days around Earth and 365 days around the sun.

For L2 the orbital speed is higher than Earth's orbital speed. For L1 the orbital speed around the sun is lower. Compare to the moon which is sometimes orbiting the sun faster (full moon), sometimes orbiting slower (new moon) and sometimes about the same (quarter). You are also orbiting the sun faster at midnight than you are during lunch. It is not breaking Kepler's laws.

Yes Newton did the inverse square.
Thanks for describing GAIA's orbit. I was confused. The material that I read about Lagrange points had a graphic of the points with a little picture of GAIA at L2. But after double checking the material, it shows an orbital path for GAIA around L2 which I really kinda overlooked.
With what you describe and what the graphic shows, it is making sense now.
 
  • #16
stefan r said:
GAIA or any satelite place at L2 is orbiting both the Sun and the Earth. It has a 365 day orbit. Both 365 days around Earth and 365 days around the sun.

For L2 the orbital speed is higher than Earth's orbital speed. For L1 the orbital speed around the sun is lower. Compare to the moon which is sometimes orbiting the sun faster (full moon), sometimes orbiting slower (new moon) and sometimes about the same (quarter). You are also orbiting the sun faster at midnight than you are during lunch. It is not breaking Kepler's laws.

Yes Newton did the inverse square.
Thanks for describing GAIA's orbit. I was confused. The material that I read about Lagrange points had a graphic of the points with a little picture of GAIA at L2. But after double checking the material, it shows an orbital path for GAIA around L2 which I really kinda overlooked.
With what you describe and what the graphic shows, it is making sense now.
 
  • #17
Johnnyallen said:
is the Earth's mass (General Relativity) dragging the satellite along with it?
This is Newtonian gravity: no need for Einstein (which was good for Lagrange, since he didn't know about GR ;-).
Johnnyallen said:
orbital path for GAIA around L2
Yes, this is the "balancing on top of the hill" part: The satellite would spiral away from L2, slowly at first, were it not for active stabilization. Slowly is the key for stabilization, and it's generally available only at the 5 Lagrangian points.
 
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  • #18
Johnnyallen said:
I was watching a really bad Japanese sci-fi movie in which the writers employed a frequent plot device. The Earth had a twin planet opposite the sun which made it undetectable to earthlings.
This, of course, would be possible if the Earth's orbit was a perfect circle, which it isn't. It is, of course, elliptical.
Question: Given that the Earth's speed in it's orbit varies according to its distance from the sun, would a planet opposite the Earth always maintain its position behind the sun?

What movie was that? Googling it, I couldn't find it. :/
Some times ago, I watched a movie called "Another Earth", in which a "copy" of the Earth was discovered.
Then, there is "Melancholia" (by von Trier - one the worst directors ever ?:)), in which a planet from nowhere is going to collide with Earth.
 
  • #19
Mr Wolf said:
What movie was that? Googling it, I couldn't find it. :/
Some times ago, I watched a movie called "Another Earth", in which a "copy" of the Earth was discovered.
Then, there is "Melancholia" (by von Trier - one the worst directors ever ?:)), in which a planet from nowhere is going to collide with Earth.

Saw both of those movies, Another Earth I thought was pretty good as a low budget venture, interesting story. Melancholia was just plain strange..
 
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  • #20
Mr Wolf said:
What movie was that? Googling it, I couldn't find it. :/
Some times ago, I watched a movie called "Another Earth", in which a "copy" of the Earth was discovered.
Then, there is "Melancholia" (by von Trier - one the worst directors ever ?:)), in which a planet from nowhere is going to collide with Earth.
The movie was called Gorath. The gist was that a red hot planet was heading to collide with the Earth. All the plot descriptions that I found don't allude to it as being a twin planet.
One of those extra off-air networks called Comet TV showed it. They rerun a lot of stuff, so according to their website, it will be shown at 12 PM ET on May 29. I'll be sure to watch it again.
 
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  • #21
Glenstr said:
Saw both of those movies, Another Earth I thought was pretty good as a low budget venture, interesting story. Melancholia was just plain strange..
The movie was called Gorath. The gist was that a red hot planet was heading to collide with the Earth. All the plot descriptions that I found don't allude to it as being a twin planet.
One of those extra off-air networks called Comet TV showed it. They rerun a lot of stuff, so according to their website, it will be shown at 12 PM ET on May 29. I'll be sure to watch it again.

BTW I'm new to this forum. I copied and pasted this from a reply to another person because I don't know if you'll get an alert.
Also, what does quote do?
 
  • #22
Glenstr said:
Saw both of those movies, Another Earth I thought was pretty good as a low budget venture, interesting story. Melancholia was just plain strange..
I stand corrected, The movie was not Gorath but Warning From Space.
 
  • #23
Johnnyallen said:
Warning From Space.
"Spacemen Appear in Tokyo!" seems to be close to the correct translation
 
  • #24
This thread has become a movie review, not Science. Move to general discussion SF section.
 

1. What is Earth's twin planet?

Earth's twin planet is a hypothetical planet that is similar in size, composition, and distance from its star as Earth. It is often referred to as a "twin" because it shares many similarities with Earth.

2. Can Earth's twin planet stay behind the sun?

No, it is not possible for Earth's twin planet to stay behind the sun. The orbit of a planet is determined by its distance from the sun and its velocity. Due to the laws of gravity, the planet would eventually be pulled closer to the sun or flung out into space.

3. Is there evidence of Earth's twin planet existing?

At this time, there is no concrete evidence of Earth's twin planet existing. However, astronomers continue to discover new exoplanets that share similarities with Earth, giving hope that a twin planet may exist somewhere in the universe.

4. What would it mean if Earth's twin planet was discovered?

If scientists were to discover Earth's twin planet, it would have significant implications for our understanding of the universe and the possibility of extraterrestrial life. It could also provide insights into the formation and evolution of planets.

5. How do scientists search for Earth's twin planet?

Scientists use various methods to search for Earth's twin planet, such as transit photometry, radial velocity, and direct imaging. These techniques involve observing changes in a star's light, tracking its gravitational pull, and capturing images of distant planets, respectively.

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