8 ms·

Billion-Ton Comet May Have Missed Earth by a Few Hundred Kilometers in 1883

109 points by gnosis 14y ago

dmix 14y ago
> They point out that nobody else on the planet seems to have seen this comet passing in front of the Sun, even though the nearest observatories in those days were just a few hundred kilometers away. This is 1883 and noone else recorded seeing it? Even in all of mexico?
- Gustomaximus 14y ago
  The do say in the article about no-one seeing it; "That can be explained using parallax. If the fragments were close to Earth, parallax would have ensured that they would not have been in line with the Sun even for observers nearby. And since Mexico is at the same latitude as the Sahara, northern India and south-east Asia, it's not hard to imagine that nobody else was looking." Is this realistic? Also would the time of day matter? If the sun was low to the horizon etc.
  - lutusp 14y ago
    > The do say in the article about no-one seeing it; "That can be explained using parallax ..." > Is this realistic? No. Even today not many observatories specialize in sun observations. It's not at all surprising that only one astronomer witnessed this, and it's a stretch to suggest the explanation that the observed object was therefore very close -- there are many more plausible explanations. > Also would the time of day matter? No, not for an object silhouetted against the sun. Consider this year's Venus transit -- everyone who could see the sun at the appointed time, also could see the transit.
deleted 14y ago
[deleted]
venus 14y ago
> A sobering thought. An even more sobering thought is that even in the present day, if we detected something like that heading our way, there'd be absolutely nothing we could but sit and wait for it to arrive.
- Shank 14y ago
  This is slightly true, though notably the Torino Scale mentions that once an object is classed at level 5, governments may begin to take action to counteract such a collision before it arrives at earth, if the encounter is set to be less than a decade away. http://en.wikipedia.org/wiki/Torino_Scale http://en.wikipedia.org/wiki/Torino_Scale Edit: NASA's JPL maintains the Sentry Risk Table, which tracks all objects that may impact the Earth, with various data points about said objects. http://neo.jpl.nasa.gov/risk/ http://neo.jpl.nasa.gov/risk/
  - deleted 14y ago
    [deleted]
  - gnosis 14y ago
    The time to initiate an asteroid defense project is long before a threat is even detected. There needs to be time for technology development, deployment, and testing. Tackling an extinction-level event is not something we want to scramble for at the last possible minute, using untried technology.
    - bad_user 14y ago
      Research in this area should have happened since yesterday, but deployment and testing? The probability of something big hitting us is really low, coupled with the fact that we can see it coming since all objects in space are visible. Miss-calculating a trajectory could indeed happen and we may not notice it if it's coming from the direction of our sun, but the probability of that is even lower. So why would you spend tons of natural resources, time and money for a machinery of dealing with a problem that we may not have in the next 100,000 years? And what should that machinery do in the meantime? Personally, I think our world has to solve bigger and more imminent problems that can lead to extinction too ... hunger, disease, overpopulation, economic recessions, natural resources running out, global warming, the destruction of the only habitat we know that can sustain life, nuclear wars and the list of things that can happen in the next 400 years can probably go on. Heck, we came closer to extinction during the Cold War than we ever ever did from a comet passing by and the only thing saving us was the few reasonable men in charge, but we may not get so lucky next time.
temphn 14y ago
No photographic evidence. No corresponding accounts. No raw data. Bonilla published his account of this event in a French journal called L'Astronomie in 1886. Unable to account for the phenomenon, the editor of the journal suggested, rather incredulously, that it must have been caused by birds, insects or dust passing front of the Bonilla's telescope. As the saying goes: when you hear hoof-steps, think horses, not zebras.
- mistercow 14y ago
  Yeah the prior probability of "fragmenting comet within 8000 km of Earth" seems kind of a lot lower than that of "dust in front of the telescope".
  - quarterto 14y ago
    http://rationalwiki.org/wiki/Improbable_things_happen http://rationalwiki.org/wiki/Improbable_things_happen
    - mistercow 14y ago
      That's a silly argument. Yes, improbable things happen, but our beliefs should be informed by whatever hypothesis is assigned the highest probability. The difficulty that a hypothesis with very low prior probability (like this one) has is that in order for it to reach a level of probability necessary to compete with the more mundane explanations like dust or birds, it is going to have to be backed by very strong evidence. This is the Bayesian expression of "extraordinary claims require extraordinary evidence". The hypothesis needs to make some predictions that are exceptionally unlikely given those mundane hypotheses. Unfortunately, it's difficult to see what predictions those might be. The authors of the paper don't give any, and their primary "evidence" for the hypothesis - that nobody else saw the object - is actually more likely given the birds/dust hypothesis than the comet hypothesis. So yes, there's a tiny possibility that this could have been a comet, but if so, it's hard so imagine that it could ever be elevated to the point of a hypothesis that we should even take seriously, much less one that we should believe.
- 14y ago
mchouza 14y ago
A more skeptical analysis by Phil Plait: http://blogs.discovermagazine.com/badastronomy/2011/10/17/did-a-fragmenting-comet-nearly-hit-the-earth-in-1883-color-me-very-skeptical/ http://blogs.discovermagazine.com/badastronomy/2011/10/17/di...
- ChuckMcM 14y ago
  Was going to add this one as well. A comet of that size, that close, would have raised questions in other places. The point that we didn't have nearly the observational capacity a couple of hundred years ago that we have today is well made, we certainly might have dodged a bullet, we have seen two comments hit the bigger planets (Jupiter and Saturn) but we only noticed because we were looking. So I share the skepticism that this was a Comet in 1883 but I don't doubt for a moment comets have come that close to the planet.
  - jacquesm 14y ago
    They got a lot closer than that in recent times, but not quite as massive: http://en.wikipedia.org/wiki/Tunguska_event http://en.wikipedia.org/wiki/Tunguska_event In the long run cometary impact is pretty much a certainty and close passes are a lot more likely than impact. So even if this particular observation is probably attributable to something else there is a good chance that something like it did happen at another point in time in the last 2,000 years or so. http://en.wikipedia.org/wiki/Chicxulub_crater http://en.wikipedia.org/wiki/Chicxulub_crater was 65M years ago, http://en.wikipedia.org/wiki/Sudbury_Basin http://en.wikipedia.org/wiki/Sudbury_Basin 1.9B years ago, http://en.wikipedia.org/wiki/Vredefort_crater http://en.wikipedia.org/wiki/Vredefort_crater 2B years and so on. The http://www.passc.net/EarthImpactDatabase/index.html http://www.passc.net/EarthImpactDatabase/index.html Earth Impact Database holds currently 183 recorded impacts over a period of about 2.4 billion years. 2400M / 183 gives a probability of 7.6x10-8, but that's for impacts, and near misses don't leave any evidence other than people that happened to be looking in that direction. The question then is how many near misses before you get a 'hit', probably a fairly large number depending on how you classify a near miss. Anything closer than the earth moon orbit would be fine with me as a 'near miss' (according to George Carlin an accident is a near miss, but never mind that). The exposed target of the earth-moon bounded sphere is substantially larger (~2000 times or so?) and would increase the chance of a near miss from the impact figure to about 0.000167 for any given year, or about once every 6,000 years. And the base figure here is craters that we know about, which means they're likely on the land, that misses 2/3rd of the planet. I'm sceptical about this but I would not rule it out entirely.
TimJRobinson 14y ago
I'm confused as to why this is coming up now, did they find some new evidence or residual rock from this comet? If not how do they now know that it was actually a comet and not simply a mistake on the astronomers part as they previously thought it was?
- lutusp 14y ago
  > ... how do they now know that it was actually a comet and not simply a mistake on the astronomers part as they previously thought it was? They don't. The linked article assumes the veracity of the original account, it doesn't introduce anything new.
polarcuke 14y ago
Well if this is true I guess there is one more thing for us to be thankful for today!
- Geee 14y ago
  It doesn't matter because we wouldn't be here thinking about it. On the other hand, the extinction event would have been a gold mine for the future archaeologists that would have evolved on Earth in the next 100 million years.
  - monochromatic 14y ago
    You're right, let's NOT be thankful that we're still here.
    - Geee 14y ago
      What do you mean? You can't be subjectively thankful of something that you wouldn't otherwise exist to be the subject of. However, I'm thankful that everyone else is here, including you.
      - monochromatic 14y ago
        > You can't be subjectively thankful of something that you wouldn't otherwise exist to be the subject of. Sure you can. You couldn't be disappointed if things had gone the other way, but you can certainly be thankful to have dodged a bullet.
lutusp 14y ago
A quote: "They point out that nobody else on the planet seems to have seen this comet passing in front of the Sun, even though the nearest observatories in those days were just a few hundred kilometers away. That can be explained using parallax." It can also be explained by the simple fact that (a) not many observatories specialize in observing the sun even now, and (b) the observation may only have lasted a few hours (as with this year's Venus transit). Remember Occam's razor -- the simplest explanation is to be preferred.
pgsandstrom 14y ago
The paper in question: http://arxiv.org/ftp/arxiv/papers/1110/1110.2798.pdf http://arxiv.org/ftp/arxiv/papers/1110/1110.2798.pdf It is written in comic sans and one of the authors is using a yahoo mail. Maybe I'm just being an elitist nerd, but really...
- monochromatic 14y ago
  That does not look like Comic Sans. Maybe just some weirdness with font rendering on an iPad though...
- tolos 14y ago
  Hector Javier Durand-Manterola is the author with the yahoo address. It looks like he did work at Universidad Nacional Autónoma de México (UNAM), where the other two authors are from, at one point [1]. He's authored a few other astronomy papers at arxiv [2] even though he doesn't seem to be in the database. Perhaps he has retired from academic life. [1] http://www.researchgate.net/profile/Hector_Durand-Manterola/ http://www.researchgate.net/profile/Hector_Durand-Manterola/ [2] https://www.google.com/#q=site:arxiv.org+hdurand_manterola%40yahoo.com https://www.google.com/#q=site:arxiv.org+hdurand_manterola%4...
VMG 14y ago
Anthropic principle? If it had hit we wouldn't be talking about it.
apaprocki 14y ago
The link to the original L'Astronomie journal article, which contains a diagram and photograph is here: http://books.google.com/books?id=Vt1NAAAAMAAJ&pg=PA347#v=onepage&q&f=false http://books.google.com/books?id=Vt1NAAAAMAAJ&pg=PA347#v... "PASSAGE SUR LE DISQUE SOLAIRE" p. 347, L'Astronomie Vol. IV Transcript (French) https://gist.github.com/4136038 https://gist.github.com/4136038 Transcript (English, Google Translated) https://gist.github.com/4136045 https://gist.github.com/4136045 Also, it appears there are letters to the journal regarding the original article in the subsequent Vol. V, which can be viewed here: http://hdl.handle.net/2027/mdp.39015069401779?urlappend=%3Bseq=80 http://hdl.handle.net/2027/mdp.39015069401779?urlappend=%3Bs...
losethos 14y ago
seeing Estonia fires vices uncertain recollection hear Revenue purchased proclaim blamest beholds Lebanon balancings lust fearful suffer intermit treasure-house equally scratch apparent donations causing formed confute each Here shatter stripped Circensian steal imperfection merely neither honesty puppies strengthenest Drunkard ensnaring unconsciously confession perchance trembled -such service Substance remembered scattered doting tax-deductible causes grassy saving kick_back happen contracted emotion intenseness Newsletters remembers re-create thread dutiful intermitted imprinted expects Robert pile studied gladness wild darkly reposeth merry_christmas Ten contemplating asked Send eagerly fervent repose
SpikeDad 14y ago
Is there a remedial school for headline writers? Naturally it missed the Earth or we wouldn't be here. Perhaps the headline writer meant - "Billion-Ton commet MISSED Earth by perhaps a few hundred kilometers in 1883". To quote George Carlin - "It's not a near miss. A collision is a near miss. It's a near HIT!"

109 points by gnosis 14y ago

dmix 14y ago

> They point out that nobody else on the planet seems to have seen this comet passing in front of the Sun, even though the nearest observatories in those days were just a few hundred kilometers away. This is 1883 and noone else recorded seeing it? Even in all of mexico?

Gustomaximus 14y ago
The do say in the article about no-one seeing it; "That can be explained using parallax. If the fragments were close to Earth, parallax would have ensured that they would not have been in line with the Sun even for observers nearby. And since Mexico is at the same latitude as the Sahara, northern India and south-east Asia, it's not hard to imagine that nobody else was looking." Is this realistic? Also would the time of day matter? If the sun was low to the horizon etc.
- lutusp 14y ago
  > The do say in the article about no-one seeing it; "That can be explained using parallax ..." > Is this realistic? No. Even today not many observatories specialize in sun observations. It's not at all surprising that only one astronomer witnessed this, and it's a stretch to suggest the explanation that the observed object was therefore very close -- there are many more plausible explanations. > Also would the time of day matter? No, not for an object silhouetted against the sun. Consider this year's Venus transit -- everyone who could see the sun at the appointed time, also could see the transit.

deleted 14y ago

[deleted]

venus 14y ago

> A sobering thought. An even more sobering thought is that even in the present day, if we detected something like that heading our way, there'd be absolutely nothing we could but sit and wait for it to arrive.

Shank 14y ago
This is slightly true, though notably the Torino Scale mentions that once an object is classed at level 5, governments may begin to take action to counteract such a collision before it arrives at earth, if the encounter is set to be less than a decade away. http://en.wikipedia.org/wiki/Torino_Scale http://en.wikipedia.org/wiki/Torino_Scale Edit: NASA's JPL maintains the Sentry Risk Table, which tracks all objects that may impact the Earth, with various data points about said objects. http://neo.jpl.nasa.gov/risk/ http://neo.jpl.nasa.gov/risk/
- deleted 14y ago
  [deleted]
- gnosis 14y ago
  The time to initiate an asteroid defense project is long before a threat is even detected. There needs to be time for technology development, deployment, and testing. Tackling an extinction-level event is not something we want to scramble for at the last possible minute, using untried technology.
  - bad_user 14y ago
    Research in this area should have happened since yesterday, but deployment and testing? The probability of something big hitting us is really low, coupled with the fact that we can see it coming since all objects in space are visible. Miss-calculating a trajectory could indeed happen and we may not notice it if it's coming from the direction of our sun, but the probability of that is even lower. So why would you spend tons of natural resources, time and money for a machinery of dealing with a problem that we may not have in the next 100,000 years? And what should that machinery do in the meantime? Personally, I think our world has to solve bigger and more imminent problems that can lead to extinction too ... hunger, disease, overpopulation, economic recessions, natural resources running out, global warming, the destruction of the only habitat we know that can sustain life, nuclear wars and the list of things that can happen in the next 400 years can probably go on. Heck, we came closer to extinction during the Cold War than we ever ever did from a comet passing by and the only thing saving us was the few reasonable men in charge, but we may not get so lucky next time.

temphn 14y ago

No photographic evidence. No corresponding accounts. No raw data. Bonilla published his account of this event in a French journal called L'Astronomie in 1886. Unable to account for the phenomenon, the editor of the journal suggested, rather incredulously, that it must have been caused by birds, insects or dust passing front of the Bonilla's telescope. As the saying goes: when you hear hoof-steps, think horses, not zebras.

mistercow 14y ago
Yeah the prior probability of "fragmenting comet within 8000 km of Earth" seems kind of a lot lower than that of "dust in front of the telescope".
- quarterto 14y ago
  http://rationalwiki.org/wiki/Improbable_things_happen http://rationalwiki.org/wiki/Improbable_things_happen
  - mistercow 14y ago
    That's a silly argument. Yes, improbable things happen, but our beliefs should be informed by whatever hypothesis is assigned the highest probability. The difficulty that a hypothesis with very low prior probability (like this one) has is that in order for it to reach a level of probability necessary to compete with the more mundane explanations like dust or birds, it is going to have to be backed by very strong evidence. This is the Bayesian expression of "extraordinary claims require extraordinary evidence". The hypothesis needs to make some predictions that are exceptionally unlikely given those mundane hypotheses. Unfortunately, it's difficult to see what predictions those might be. The authors of the paper don't give any, and their primary "evidence" for the hypothesis - that nobody else saw the object - is actually more likely given the birds/dust hypothesis than the comet hypothesis. So yes, there's a tiny possibility that this could have been a comet, but if so, it's hard so imagine that it could ever be elevated to the point of a hypothesis that we should even take seriously, much less one that we should believe.
14y ago

mchouza 14y ago

A more skeptical analysis by Phil Plait: http://blogs.discovermagazine.com/badastronomy/2011/10/17/did-a-fragmenting-comet-nearly-hit-the-earth-in-1883-color-me-very-skeptical/ http://blogs.discovermagazine.com/badastronomy/2011/10/17/di...

ChuckMcM 14y ago
Was going to add this one as well. A comet of that size, that close, would have raised questions in other places. The point that we didn't have nearly the observational capacity a couple of hundred years ago that we have today is well made, we certainly might have dodged a bullet, we have seen two comments hit the bigger planets (Jupiter and Saturn) but we only noticed because we were looking. So I share the skepticism that this was a Comet in 1883 but I don't doubt for a moment comets have come that close to the planet.
- jacquesm 14y ago
  They got a lot closer than that in recent times, but not quite as massive: http://en.wikipedia.org/wiki/Tunguska_event http://en.wikipedia.org/wiki/Tunguska_event In the long run cometary impact is pretty much a certainty and close passes are a lot more likely than impact. So even if this particular observation is probably attributable to something else there is a good chance that something like it did happen at another point in time in the last 2,000 years or so. http://en.wikipedia.org/wiki/Chicxulub_crater http://en.wikipedia.org/wiki/Chicxulub_crater was 65M years ago, http://en.wikipedia.org/wiki/Sudbury_Basin http://en.wikipedia.org/wiki/Sudbury_Basin 1.9B years ago, http://en.wikipedia.org/wiki/Vredefort_crater http://en.wikipedia.org/wiki/Vredefort_crater 2B years and so on. The http://www.passc.net/EarthImpactDatabase/index.html http://www.passc.net/EarthImpactDatabase/index.html Earth Impact Database holds currently 183 recorded impacts over a period of about 2.4 billion years. 2400M / 183 gives a probability of 7.6x10-8, but that's for impacts, and near misses don't leave any evidence other than people that happened to be looking in that direction. The question then is how many near misses before you get a 'hit', probably a fairly large number depending on how you classify a near miss. Anything closer than the earth moon orbit would be fine with me as a 'near miss' (according to George Carlin an accident is a near miss, but never mind that). The exposed target of the earth-moon bounded sphere is substantially larger (~2000 times or so?) and would increase the chance of a near miss from the impact figure to about 0.000167 for any given year, or about once every 6,000 years. And the base figure here is craters that we know about, which means they're likely on the land, that misses 2/3rd of the planet. I'm sceptical about this but I would not rule it out entirely.

TimJRobinson 14y ago

I'm confused as to why this is coming up now, did they find some new evidence or residual rock from this comet? If not how do they now know that it was actually a comet and not simply a mistake on the astronomers part as they previously thought it was?

lutusp 14y ago
> ... how do they now know that it was actually a comet and not simply a mistake on the astronomers part as they previously thought it was? They don't. The linked article assumes the veracity of the original account, it doesn't introduce anything new.

polarcuke 14y ago

Well if this is true I guess there is one more thing for us to be thankful for today!

Geee 14y ago
It doesn't matter because we wouldn't be here thinking about it. On the other hand, the extinction event would have been a gold mine for the future archaeologists that would have evolved on Earth in the next 100 million years.
- monochromatic 14y ago
  You're right, let's NOT be thankful that we're still here.
  - Geee 14y ago
    What do you mean? You can't be subjectively thankful of something that you wouldn't otherwise exist to be the subject of. However, I'm thankful that everyone else is here, including you.
    - monochromatic 14y ago
      > You can't be subjectively thankful of something that you wouldn't otherwise exist to be the subject of. Sure you can. You couldn't be disappointed if things had gone the other way, but you can certainly be thankful to have dodged a bullet.

lutusp 14y ago

A quote: "They point out that nobody else on the planet seems to have seen this comet passing in front of the Sun, even though the nearest observatories in those days were just a few hundred kilometers away. That can be explained using parallax." It can also be explained by the simple fact that (a) not many observatories specialize in observing the sun even now, and (b) the observation may only have lasted a few hours (as with this year's Venus transit). Remember Occam's razor -- the simplest explanation is to be preferred.

pgsandstrom 14y ago

The paper in question: http://arxiv.org/ftp/arxiv/papers/1110/1110.2798.pdf http://arxiv.org/ftp/arxiv/papers/1110/1110.2798.pdf It is written in comic sans and one of the authors is using a yahoo mail. Maybe I'm just being an elitist nerd, but really...

monochromatic 14y ago
That does not look like Comic Sans. Maybe just some weirdness with font rendering on an iPad though...
tolos 14y ago
Hector Javier Durand-Manterola is the author with the yahoo address. It looks like he did work at Universidad Nacional Autónoma de México (UNAM), where the other two authors are from, at one point [1]. He's authored a few other astronomy papers at arxiv [2] even though he doesn't seem to be in the database. Perhaps he has retired from academic life. [1] http://www.researchgate.net/profile/Hector_Durand-Manterola/ http://www.researchgate.net/profile/Hector_Durand-Manterola/ [2] https://www.google.com/#q=site:arxiv.org+hdurand_manterola%40yahoo.com https://www.google.com/#q=site:arxiv.org+hdurand_manterola%4...

VMG 14y ago

Anthropic principle? If it had hit we wouldn't be talking about it.

apaprocki 14y ago

The link to the original L'Astronomie journal article, which contains a diagram and photograph is here: http://books.google.com/books?id=Vt1NAAAAMAAJ&pg=PA347#v=onepage&q&f=false http://books.google.com/books?id=Vt1NAAAAMAAJ&pg=PA347#v... "PASSAGE SUR LE DISQUE SOLAIRE" p. 347, L'Astronomie Vol. IV Transcript (French) https://gist.github.com/4136038 https://gist.github.com/4136038 Transcript (English, Google Translated) https://gist.github.com/4136045 https://gist.github.com/4136045 Also, it appears there are letters to the journal regarding the original article in the subsequent Vol. V, which can be viewed here: http://hdl.handle.net/2027/mdp.39015069401779?urlappend=%3Bseq=80 http://hdl.handle.net/2027/mdp.39015069401779?urlappend=%3Bs...

losethos 14y ago

seeing Estonia fires vices uncertain recollection hear Revenue purchased proclaim blamest beholds Lebanon balancings lust fearful suffer intermit treasure-house equally scratch apparent donations causing formed confute each Here shatter stripped Circensian steal imperfection merely neither honesty puppies strengthenest Drunkard ensnaring unconsciously confession perchance trembled -such service Substance remembered scattered doting tax-deductible causes grassy saving kick_back happen contracted emotion intenseness Newsletters remembers re-create thread dutiful intermitted imprinted expects Robert pile studied gladness wild darkly reposeth merry_christmas Ten contemplating asked Send eagerly fervent repose

SpikeDad 14y ago

Is there a remedial school for headline writers? Naturally it missed the Earth or we wouldn't be here. Perhaps the headline writer meant - "Billion-Ton commet MISSED Earth by perhaps a few hundred kilometers in 1883". To quote George Carlin - "It's not a near miss. A collision is a near miss. It's a near HIT!"