I've finally read it. Very infotaining. I know you've been obsessed with this rock for a while. I knew about its anomalous aspect ratio, but not the other things. How rare is local standard of rest in itself?
That part is pretty unclear to me. Loeb seems to make a case that it would be quite unlikely to occur by chance, and his critics have not, from what I can tell, disputed that meaningfully, but I'm wary to index on it too much.
Maybe I missed it in the post or comments, but is there any value in looking at the characteristics of our own human produced space trash as a minor baseline for the kind of calculations you propose?
Does the 'space-trash-definition' mandate that space trash has to be that which escapes our planetary orbit (not so much trash I would think) or our solar system (little to none?).
[I am not a specialist] Your post led me to learn that "space-trash" or "space junk" or more formally "space debris" includes defunct satellites, rocket stages, mission-related debris, and fragments from collisions or breakups of spacecraft. Even tiny particles like paint flecks are considered space debris and human-produced space junk, and while primarily concentrated in near-Earth orbit, some _could_ theoretically reach interstellar space over very long timescales. Avi Loeb's term "Empty Trash Bag Objects" (ETBOs) {https://avi-loeb.medium.com/interstellar-empty-trash-bag-objects-80528ca13fad} specifically addresses how human debris in Earth's orbit might be pushed away from the Sun by solar radiation pressure, potentially venturing out of our solar system - much like an empty trash bag blown down the street could end up on another continent. While the vast majority of space junk stays in Earth's vicinity, the possibility of some human-made debris eventually reaching interstellar space exists, albeit over extremely long durations. So, could the characteristics of these small objects be useful in your baseline calculations?
I think this really needs a reference to the expected number of interstellar objects produced by natural phenomena. Without knowing a rough order of magnitude number it's very difficult to know what prior we should pick for trash vs. rock. I would suspect there are quite a lot of interstellar rocks, so an alien civilization capable of rivaling their amount with trash would be galactic scale.
Ya, there were several components of the puzzle that I didn't get the chance to go as deep as I would've liked on in this post, and that was one of them.
I think now that we've observed 2 interstellar objects (and perhaps 2 much, much smaller ones that hit the Earth), it's possible to infer the density of these objects:
However, that's not particularly useful... what we want is a prior estimate from BEFORE we observed 'Oumuamua, derived from first principles on solar system formation.
I'll have to look for sources on those, but to my understanding, physicists very much did not expect to see an interstellar object of the size of 'Oumuamua as soon as we did upon PAN-STARRS going online, which implies that we had either
1) under-estimated the density of natural objects
2) there's space trash
In my opinion, this is somewhat weak evidence in support of a technosignature origin.
This showed up in my back-of-the-napkin bayesian calculator bs estimate as "99%" agreement with technosignature (basically, it's completely expected if we think that space trash is likely to be out there) but only 66% agreement with natural origin (only slightly surprising). I think someone like Avi Loeb would give this a much lower probability, but I was trying to be somewhat conservative.
"Assuming that other planetary systems resemble the Solar System, PanSTARRS should not have discovered any interstellar rock in the first place. In a paper published a decade ago, we predicted an abundance of interstellar asteroids that is smaller by many (2-8) orders of magnitude than needed to explain the discovery of `Oumuamua as a member of a random population of objects. In other words, the population of interstellar objects is far greater than expected. Each star in the Milky-Way needs to eject 1015 such objects during its lifetime to account for the inferred population, much more than anticipated based on the Solar System. Thus, the nurseries of `Oumuamua-like objects must be different from the familiar ones."
and FWIW, the fact that we observed a second, less weird (although still fairly puzzling) object a couple years after, is a /stronger/ update AGAINST the technosignature theory in my BOTN math!
> "99%" agreement with technosignature (basically, it's completely expected if we think that space trash is likely to be out there
Only if we expect the civilization to be very large! And a civ that large would likely be visible in other ways. (Or if they're trying to hide, it would be easy to hide their trash as well.)
I mean, my intuition here was to treat that line as:
"does the fact that we found an object at all in the timespan we were looking agree with our prior on the density of objects", and by definition, technosignature has to be higher than natural there
On the other hand, if we hadn't seen any object at all, that would be a slight Bayesian update towards natural origin of the first object we do see.
Also, for example, if the prior on density of interstellar objects had been orders of magnitude HIGHER than what we actually found, then I guess you'd say that finding an object was still in 99% agreement with natural origin. This is a little counter-intuitive but obviously you can't update towards "this is suspicious that we found something" if you actually expect to be finding MORE objects.
I don't agree with this, because for example, the estimate that physicists had come up with (from our own solar system) before seeing any objects was many orders of magnitude lower.
I, for one, welcome our high aspect ratio overlords.
I thought this was going to be about https://boardgamegeek.com/boardgame/418059/seti-search-for-extraterrestrial-intelligence which does feature ʻOumuamua
oh that's cool, I've never heard of that board game!
I've finally read it. Very infotaining. I know you've been obsessed with this rock for a while. I knew about its anomalous aspect ratio, but not the other things. How rare is local standard of rest in itself?
That part is pretty unclear to me. Loeb seems to make a case that it would be quite unlikely to occur by chance, and his critics have not, from what I can tell, disputed that meaningfully, but I'm wary to index on it too much.
Maybe I missed it in the post or comments, but is there any value in looking at the characteristics of our own human produced space trash as a minor baseline for the kind of calculations you propose?
Does the 'space-trash-definition' mandate that space trash has to be that which escapes our planetary orbit (not so much trash I would think) or our solar system (little to none?).
[I am not a specialist] Your post led me to learn that "space-trash" or "space junk" or more formally "space debris" includes defunct satellites, rocket stages, mission-related debris, and fragments from collisions or breakups of spacecraft. Even tiny particles like paint flecks are considered space debris and human-produced space junk, and while primarily concentrated in near-Earth orbit, some _could_ theoretically reach interstellar space over very long timescales. Avi Loeb's term "Empty Trash Bag Objects" (ETBOs) {https://avi-loeb.medium.com/interstellar-empty-trash-bag-objects-80528ca13fad} specifically addresses how human debris in Earth's orbit might be pushed away from the Sun by solar radiation pressure, potentially venturing out of our solar system - much like an empty trash bag blown down the street could end up on another continent. While the vast majority of space junk stays in Earth's vicinity, the possibility of some human-made debris eventually reaching interstellar space exists, albeit over extremely long durations. So, could the characteristics of these small objects be useful in your baseline calculations?
I think this really needs a reference to the expected number of interstellar objects produced by natural phenomena. Without knowing a rough order of magnitude number it's very difficult to know what prior we should pick for trash vs. rock. I would suspect there are quite a lot of interstellar rocks, so an alien civilization capable of rivaling their amount with trash would be galactic scale.
Ya, there were several components of the puzzle that I didn't get the chance to go as deep as I would've liked on in this post, and that was one of them.
I think now that we've observed 2 interstellar objects (and perhaps 2 much, much smaller ones that hit the Earth), it's possible to infer the density of these objects:
https://lweb.cfa.harvard.edu/~loeb/EL.pdf
However, that's not particularly useful... what we want is a prior estimate from BEFORE we observed 'Oumuamua, derived from first principles on solar system formation.
I'll have to look for sources on those, but to my understanding, physicists very much did not expect to see an interstellar object of the size of 'Oumuamua as soon as we did upon PAN-STARRS going online, which implies that we had either
1) under-estimated the density of natural objects
2) there's space trash
In my opinion, this is somewhat weak evidence in support of a technosignature origin.
This showed up in my back-of-the-napkin bayesian calculator bs estimate as "99%" agreement with technosignature (basically, it's completely expected if we think that space trash is likely to be out there) but only 66% agreement with natural origin (only slightly surprising). I think someone like Avi Loeb would give this a much lower probability, but I was trying to be somewhat conservative.
Couple relevant links:
https://iopscience.iop.org/article/10.1088/0004-637X/704/1/733/pdf
https://iopscience.iop.org/article/10.3847/2041-8213/aaae67/pdf
In his words:
"Assuming that other planetary systems resemble the Solar System, PanSTARRS should not have discovered any interstellar rock in the first place. In a paper published a decade ago, we predicted an abundance of interstellar asteroids that is smaller by many (2-8) orders of magnitude than needed to explain the discovery of `Oumuamua as a member of a random population of objects. In other words, the population of interstellar objects is far greater than expected. Each star in the Milky-Way needs to eject 1015 such objects during its lifetime to account for the inferred population, much more than anticipated based on the Solar System. Thus, the nurseries of `Oumuamua-like objects must be different from the familiar ones."
and FWIW, the fact that we observed a second, less weird (although still fairly puzzling) object a couple years after, is a /stronger/ update AGAINST the technosignature theory in my BOTN math!
> "99%" agreement with technosignature (basically, it's completely expected if we think that space trash is likely to be out there
Only if we expect the civilization to be very large! And a civ that large would likely be visible in other ways. (Or if they're trying to hide, it would be easy to hide their trash as well.)
I mean, my intuition here was to treat that line as:
"does the fact that we found an object at all in the timespan we were looking agree with our prior on the density of objects", and by definition, technosignature has to be higher than natural there
On the other hand, if we hadn't seen any object at all, that would be a slight Bayesian update towards natural origin of the first object we do see.
Also, for example, if the prior on density of interstellar objects had been orders of magnitude HIGHER than what we actually found, then I guess you'd say that finding an object was still in 99% agreement with natural origin. This is a little counter-intuitive but obviously you can't update towards "this is suspicious that we found something" if you actually expect to be finding MORE objects.
"Hmm, 1015 is a pretty low number in astronomical terms, it seems completely plausible that a star system could eject that many objects."
"...Ah, I think Substack is converting superscript into normal text."
I don't agree with this, because for example, the estimate that physicists had come up with (from our own solar system) before seeing any objects was many orders of magnitude lower.
Physicists believed that our solar system had ejected less than ten objects in its entire lifetime?
oh wait I misunderstood, disregard XD