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

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

#21

Post by rizzom5000 »

lifeformed wrote: post #16
jacquesm wrote: post #15

Earlier quoted context omitted.

It's not Hollywood, it's ballistics.

With early enough detection, even a slight change in it's trajectory can make the asteroid veer off course enough to save earth.

In context, if we look at the current state of humanity; sure some of our great minds have helped some (not all) of us to live pretty nice lives here on Earth. But on the whole, we're pretty good at screwing up basic things. Non-basic things, like for example having a Mars orbiter not crash into the planet, yeah, we screw those up too.

Anyway, I thought the OPs comment was likely more facetious than anything. Only in Hollywood can we expect a perfect ending.

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

#22

Post by jacquesm »

ChuckMcM wrote: post #12
mchouza wrote: post #9

A more skeptical analysis by Phil Plait: http://blogs.discovermagazine.com/badastronomy/2011/10/17/di...

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 skeptici…

They got a lot closer than that in recent times, but not quite as massive:

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 was 65M years ago, http://en.wikipedia.org/wiki/Sudbury_Basin 1.9B years ago, http://en.wikipedia.org/wiki/Vredefort_crater 2B years and so on. The 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.

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

#23

Post by gnosis »

jacquesm wrote: post #22
ChuckMcM wrote: post #12

Earlier quoted context omitted.

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 skeptici…

They got a lot closer than that in recent times, but not quite as massive: 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…

Also see:

http://www.youtube.com/watch?v=zc4HL_-VT2Y

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

#24

Post by jacquesm »

lifeformed wrote: post #16
jacquesm wrote: post #15

Earlier quoted context omitted.

It's not Hollywood, it's ballistics.

With early enough detection, even a slight change in it's trajectory can make the asteroid veer off course enough to save earth.

The critical figures here are what the relative speeds are, when the asteroid/comet is detected, what it is made of and how masssive it is.

After you've figured all those out the stage is set and you get a menu:

  - party like it's 2012

  - attempt to deflect it 

  - brace for impact and deal with the aftermath
Any attempt to deflect it has a large degree of uncertainty, including the trouble of getting humanity to pull in one direction for any length of time.

You'd have to develop the vehicle (and the fuel expenses to get the right velocity / direction are going to be terrible, they may be beyond current tech to make a manoeuvre like that, imagine meeting an oncoming bullet by matching speeds and direction where the bullet can come from any direction and you're sitting on a spinning ball), a plan to deflect the mass (by then you'll have burned up a lot of your time budget) and so on.

Maybe, for very small values of maybe.

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

#25

Post by gnosis »

Shank wrote: post #7
venus wrote: post #5

> 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.

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 Edit: NASA's JPL maintains the Sentry Risk Table, which tracks all objects that may impact the Earth, with various data…

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.

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

#26

Post by rizzom5000 »

AlexMennen wrote: post #20
rizzom5000 wrote: post #18

Earlier quoted context omitted.

When faced with impending doom, optimism and pessimism are both equally fine sentiments. The caveat is that only one of them accurately reflects reality, not that it matters at that point. I also suppose that industriousness would be helpful for taking one's mind away from the reality of that impending doom. But hell, nukes to deflect a comet? Sure, we may as well try it -- but I only suggest doing this if we are 100…

If there is a significant chance that a comet will hit and destroy us, it makes sense to do everything we can to prevent it from doing so. Given the stakes, .1% chance should be more than enough for us to take it seriously. It does not seem plausible that we could harm ourselves much by nuking a comet that wasn't going to hit us anyway.

It does seem plausible that we could in fact harm ourselves by attempting to launch a nuclear device out of Earth's orbit. We do have a record of failed launches, several of them recent. Once the nuclear device is out of orbit however, I agree that the harm it can do to us is negligible.

Edit: Also, it just occurred to me the possibility of deflecting a comet (which was never in our path) into our path, instead of away from it, which is really great material for a Hollywood comedy.

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

#27

Post by danso »

temphn wrote: post #6

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 ze…

I had never heard that saying before but I fear I will use it much too often in the future

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

#28

Post by AlexMennen »

rizzom5000 wrote: post #26
AlexMennen wrote: post #20

Earlier quoted context omitted.

If there is a significant chance that a comet will hit and destroy us, it makes sense to do everything we can to prevent it from doing so. Given the stakes, .1% chance should be more than enough for us to take it seriously. It does not seem plausible that we could harm ourselves much by nuking a comet that wasn't going to hit us anyway.

It does seem plausible that we could in fact harm ourselves by attempting to launch a nuclear device out of Earth's orbit. We do have a record of failed launches, several of them recent. Once the nuclear device is out of orbit however, I agree that the harm it can do to us is negligible. Edit: Also, it just occurred to me the possibility of deflecting a comet (which was never in our path) into our path, instead of aw…

Good point, but the chances of a failed launch are fairly small, and the damage from accidentally detonating a large nuke on the Earth's surface, while bad, would be small compared to human extinction.

If we are sufficiently uncertain about the comet's path, we might accidentally deflect it towards us. Obviously, if this is just as likely as deflecting it away from us, it would not be worthwhile to try. But most likely we would be able to reduce the probability of a catastrophic impact even after taking into account the possibility of such an error.

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

#29

Post by StuieK »

venus wrote: post #5

> 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.

Here is a very early draft of a list of options I've been working on for deflecting asteroids.

http://slant.co/topics/what-is-the-best-way-to-stop-an-aster...

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

#30

Post by ars »

danso wrote: post #27
temphn wrote: post #6

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 ze…

I had never heard that saying before but I fear I will use it much too often in the future

It's from this: http://en.wikipedia.org/wiki/Zebra_%28medicine%29
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