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Would it be a bigger surprise if Planet 9 existed, or if Planet 9 doesn't exist? This isn't my field of study, but as I understand there's a good amount of indi

Would it be a bigger surprise if Planet 9 existed, or if Planet 9 doesn't exist? This isn't my field of study, but as I understand there's a good amount of indirect evidence for a Planet 9... and still no direct proof. Assuming we're searching in the right areas, if a scan of the first 80% didn't reveal it, it seems unlikely (but of course not impossible) that we'll find it in the last 20%.

pmcf 3y ago
“Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's long way down the road to the chemist's, but that's just peanuts to space.”
- iszomer 3y ago
  "Don't Panic."
- 14 3y ago
  I like to tell people how big space is just by describing how fast voyager 1 is moving and how long it will take to reach 1 light year of travel. Voyager 1 launched back in the 70's and is traveling around 38,210 mph. Even at that speed it will take another approximate 18,500 years for it to reach it's first light year traveled. The closest star is about 4.2 light years away so at it's current speed it would take about 75,000 years for it to reach Alpha Centauri.The more you start getting into the numbers and things like how many light years across the milky way is and how far to the next galaxy and how many galaxies their are you start to see the universe is unimaginably large. I don't think one could fully grasp it's size. Amazing
halfcat 3y ago
There’s a difference between completing 80% of the work, and ruling out 80% of the options. We could rule out 80% of the options and still have 99% of the work yet to be completed. Like if we’re looking for a bacteria on the land surface of the earth, and we rule out 80% of the options, that leaves us with searching an area the size of Africa for a microscopic life form.
- medstrom 3y ago
  Doesn't change the fact that whatever probability you previously assigned to finding Planet 9, it should be one fifth of that now. (Sort of. Not so drastic if you have strong reasons to think there is a Planet 9)
  - seeknotfind 3y ago
    The suggestion is maybe part of the sky is easier to survey, so it was completed cheaply, even though that part wasn't the most likely part. I don't know which way it is, but it's an interesting question, and that's what OP is getting at for understanding the relevant probabilities instead of the relevant area.
vikingerik 3y ago
Existing would be the bigger surprise. We've ruled out anything of Earth's mass out to distances of 100 AU and Jupiter's mass to 1000 AU, since those would be visible to telescopic searches and have measurable gravitational effects on known objects that we don't see from observation. It's almost certain that there's nothing that would meet the "clearing the neighborhood" definition of a planet. At most there would be more dwarf planets on the size order of Pluto and Eris and Quaoar, which are common, but those are each comparatively tiny, like 0.2% of Earth's mass. The article says "78% of places have been searched"... but that's a really weirdly imprecise way of saying that. What are "places" here? Like, the sphere out to 100 AU is 78% of the volume out to 120 AU... but that makes no sense, the possible locations go out to 1000 AU or more. There are indeed lots of claims of some evidence for another planet existing... but all those claims are different with no consensus, and it's largely fairly specious proposals trying to get some funding.
- sparrowInHand 3y ago
  Eh, we ruled that out - within our observable time-frame, but we do not know about exotic, long-term orbits. Like a 50.000 year elipse out into the ort cloud and back in.

pmcf 3y ago

“Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's long way down the road to the chemist's, but that's just peanuts to space.”

iszomer 3y ago
"Don't Panic."
14 3y ago
I like to tell people how big space is just by describing how fast voyager 1 is moving and how long it will take to reach 1 light year of travel. Voyager 1 launched back in the 70's and is traveling around 38,210 mph. Even at that speed it will take another approximate 18,500 years for it to reach it's first light year traveled. The closest star is about 4.2 light years away so at it's current speed it would take about 75,000 years for it to reach Alpha Centauri.The more you start getting into the numbers and things like how many light years across the milky way is and how far to the next galaxy and how many galaxies their are you start to see the universe is unimaginably large. I don't think one could fully grasp it's size. Amazing

halfcat 3y ago

There’s a difference between completing 80% of the work, and ruling out 80% of the options. We could rule out 80% of the options and still have 99% of the work yet to be completed. Like if we’re looking for a bacteria on the land surface of the earth, and we rule out 80% of the options, that leaves us with searching an area the size of Africa for a microscopic life form.

medstrom 3y ago
Doesn't change the fact that whatever probability you previously assigned to finding Planet 9, it should be one fifth of that now. (Sort of. Not so drastic if you have strong reasons to think there is a Planet 9)
- seeknotfind 3y ago
  The suggestion is maybe part of the sky is easier to survey, so it was completed cheaply, even though that part wasn't the most likely part. I don't know which way it is, but it's an interesting question, and that's what OP is getting at for understanding the relevant probabilities instead of the relevant area.

vikingerik 3y ago

Existing would be the bigger surprise. We've ruled out anything of Earth's mass out to distances of 100 AU and Jupiter's mass to 1000 AU, since those would be visible to telescopic searches and have measurable gravitational effects on known objects that we don't see from observation. It's almost certain that there's nothing that would meet the "clearing the neighborhood" definition of a planet. At most there would be more dwarf planets on the size order of Pluto and Eris and Quaoar, which are common, but those are each comparatively tiny, like 0.2% of Earth's mass. The article says "78% of places have been searched"... but that's a really weirdly imprecise way of saying that. What are "places" here? Like, the sphere out to 100 AU is 78% of the volume out to 120 AU... but that makes no sense, the possible locations go out to 1000 AU or more. There are indeed lots of claims of some evidence for another planet existing... but all those claims are different with no consensus, and it's largely fairly specious proposals trying to get some funding.

sparrowInHand 3y ago
Eh, we ruled that out - within our observable time-frame, but we do not know about exotic, long-term orbits. Like a 50.000 year elipse out into the ort cloud and back in.