5 ms·

I wonder if it could be opposite from us, on the other side of the Sun. Rotating at the same speed and hence never observable?

coffeebeqn 3y ago
All our eyes aren’t on Earths orbit
jfengel 3y ago
It couldn't be stable there for very long. It's a three body problem. If it ever existed it would have been ejected billions of years ago.
- tejtm 3y ago
  There are uncoutably many binary star systems, one (or both) being the size of a sports ball changes nothing.
  - tejtm 3y ago
    https://duckduckgo.com/?q=estimated+percentage+of+binary+star+systems&t=lm&ia=web https://duckduckgo.com/?q=estimated+percentage+of+binary+sta...
bee_rider 3y ago
It would have to be orbiting at the same distance as the Earth to have the same speed, which seems unlikely, and only gives it a fairly small amount of space to live in, so I’m sure we’ve checked there. The hypothetical planet 9 is speculated to be far from the sun, past Pluto.
mtlmtlmtlmtl 3y ago
If you mean on the opposite side, in the same orbit(in the earth-sun L3), this has been hypothesised as far back as the presocratic Greeks(https://en.wikipedia.org/wiki/Counter-Earth https://en.wikipedia.org/wiki/Counter-Earth), but we now have a lot of evidence that it isn't there. Also, planet 9 was hypothesised in order to explain the orbits of transneptunian objects, which an antiearth wouldn't do. If you mean behind the sun on a completely different orbit, well it wouldn't stay behind the sun relative to us forever, and likely would only very rarely be obscured by the sun.
andruby 3y ago
Have you seen the movie Another Earth (2011)? That’s the exact plot. It’s not realistic (space probes would have “seen” the other earth), but does make for an interesting film. https://en.m.wikipedia.org/wiki/Another_Earth https://en.m.wikipedia.org/wiki/Another_Earth
- wkat4242 3y ago
  The premise there is also that the other earth developed in exactl synchronism until they discovered each other which is much less realistic :)
  - andruby 3y ago
    If you liked the premise, I can warmly recommend Counterpart. It’s a series with JK Simmons. It’s much better imo. https://en.m.wikipedia.org/wiki/Counterpart_(TV_series) https://en.m.wikipedia.org/wiki/Counterpart_(TV_series)
    - wkat4242 3y ago
      Yes that was a great series. Though it went a bit off track in the second season with the story all over the place. I wasn't surprised they cancelled it.
chasil 3y ago
We would certainly see something that is six times the mass of the earth sharing our orbit. The wiki estimates the missing planet to be 6.3 times as massive as the Earth, could be up to 2.3 times more or −1.5 times less than this figure. "Based on earlier considerations, this hypothetical super-Earth-sized planet would have had a predicted mass of five to ten times that of the Earth, and an elongated orbit 400 to 800 times farther from the Sun than the Earth is." https://en.wikipedia.org/wiki/Planet_Nine https://en.wikipedia.org/wiki/Planet_Nine

coffeebeqn 3y ago

All our eyes aren’t on Earths orbit

jfengel 3y ago

It couldn't be stable there for very long. It's a three body problem. If it ever existed it would have been ejected billions of years ago.

tejtm 3y ago
There are uncoutably many binary star systems, one (or both) being the size of a sports ball changes nothing.
- tejtm 3y ago
  https://duckduckgo.com/?q=estimated+percentage+of+binary+star+systems&t=lm&ia=web https://duckduckgo.com/?q=estimated+percentage+of+binary+sta...

bee_rider 3y ago

It would have to be orbiting at the same distance as the Earth to have the same speed, which seems unlikely, and only gives it a fairly small amount of space to live in, so I’m sure we’ve checked there. The hypothetical planet 9 is speculated to be far from the sun, past Pluto.

mtlmtlmtlmtl 3y ago

If you mean on the opposite side, in the same orbit(in the earth-sun L3), this has been hypothesised as far back as the presocratic Greeks(https://en.wikipedia.org/wiki/Counter-Earth https://en.wikipedia.org/wiki/Counter-Earth), but we now have a lot of evidence that it isn't there. Also, planet 9 was hypothesised in order to explain the orbits of transneptunian objects, which an antiearth wouldn't do. If you mean behind the sun on a completely different orbit, well it wouldn't stay behind the sun relative to us forever, and likely would only very rarely be obscured by the sun.

andruby 3y ago

Have you seen the movie Another Earth (2011)? That’s the exact plot. It’s not realistic (space probes would have “seen” the other earth), but does make for an interesting film. https://en.m.wikipedia.org/wiki/Another_Earth https://en.m.wikipedia.org/wiki/Another_Earth

wkat4242 3y ago
The premise there is also that the other earth developed in exactl synchronism until they discovered each other which is much less realistic :)
- andruby 3y ago
  If you liked the premise, I can warmly recommend Counterpart. It’s a series with JK Simmons. It’s much better imo. https://en.m.wikipedia.org/wiki/Counterpart_(TV_series) https://en.m.wikipedia.org/wiki/Counterpart_(TV_series)
  - wkat4242 3y ago
    Yes that was a great series. Though it went a bit off track in the second season with the story all over the place. I wasn't surprised they cancelled it.

chasil 3y ago

We would certainly see something that is six times the mass of the earth sharing our orbit. The wiki estimates the missing planet to be 6.3 times as massive as the Earth, could be up to 2.3 times more or −1.5 times less than this figure. "Based on earlier considerations, this hypothetical super-Earth-sized planet would have had a predicted mass of five to ten times that of the Earth, and an elongated orbit 400 to 800 times farther from the Sun than the Earth is." https://en.wikipedia.org/wiki/Planet_Nine https://en.wikipedia.org/wiki/Planet_Nine