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Old 11-14-2017, 09:43 AM   #251
AlexanderHowl
 
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Default Re: Lucy's Choice: Let's make Lucifer Parallels!

An impact against the near side though could cause a massive ecological disaster as hundreds or thousands of projectiles with an average radius of 100 m could rain down upon the Earth.
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Old 11-14-2017, 10:04 AM   #252
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Default Re: Lucy's Choice: Let's make Lucifer Parallels!

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I still wonder about that dinosaur killer rock hitting the moon. What are the best/ worst cases? I doubt Luna's orbit would shift enough to be worrisome, but how bad would the shrapnel be to Earth?
Best case- nothing happens. Ploompf- new crater.
Worst case- armageddon on Earth. Millions of tons of rocky debris falls into Earth's atmosphere, over a couple decade timescale, causing catastrophic impacts and severe atmospheric heating. Might need something bigger than the Chixculub meteor though to get that effect.
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Old 11-14-2017, 01:12 PM   #253
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Default Re: Lucy's Choice: Let's make Lucifer Parallels!

Just rough estimates here, one 100-ton rock that could hit the Earth at dangerous velocities, if it instead hit the moon, would probably have much less than 50% efficiency at dropping moon rocks on Earth at dangerous velocities.

That's not to say that it's a bad approach; a lunar debris storm after a, say, Ceres-sized object strikes the moon would result in a very interesting world exactly because it is one with a heavy rain of smaller impacts. Plus the moon would be glowing orange, so that would be cool too.
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Old 11-14-2017, 01:29 PM   #254
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Default Re: Lucy's Choice: Let's make Lucifer Parallels!

Dinosaur hunting for the seriously hardcore cross time hunter.

I suppose an angular hit on the moon while the rock is inbound to Sol would be the worst case. Trading in the slug hit of the original dino killer for a spray of shotgun pellets. I guess it would all come down to details of the impact after all.
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Old 11-14-2017, 01:35 PM   #255
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Default Re: Lucy's Choice: Let's make Lucifer Parallels!

Again it depends on how bad it has to be to be a Lucifer.
Even a relatively localized disaster could destroy say the burgeoning populations of humanity in Mesopotamia, dropping everyone back into the stone age. "Better" still if it causes just enough of climate change as to negate any other starting agricultural pockets.
I suppose it really depends on the TL of the locals as to how bad things must be to be really really bad.

Or it could go full on Cowboy Bepop inhospitable Earth from Moon debris.
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Old 11-14-2017, 01:40 PM   #256
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Default Re: Lucy's Choice: Let's make Lucifer Parallels!

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Dinosaur hunting for the seriously hardcore cross time hunter.

I suppose an angular hit on the moon while the rock is inbound to Sol would be the worst case. Trading in the slug hit of the original dino killer for a spray of shotgun pellets. I guess it would all come down to details of the impact after all.
Imagine finding such a world but seeing as how 66 million years is a long time... virtually all the non-avian dinosaurs still died out for other reasons.
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Old 11-14-2017, 01:50 PM   #257
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Default Re: Lucy's Choice: Let's make Lucifer Parallels!

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Calculating the effects of a near Lunar miss on a passing space rock years out still strikes me as tricky. That there would or would not be an effect, yes, but not being able to plot the exact effect until it gets closer sounds more realistic.

Having a near Lunar miss happen and then realizing the new course of the object impacts Earth some years in the future is quite doable.
If a moon-sized extra-solar asteroid first came into solar system, would the pull of the sun be enough to pull it into an orbit around the sun (even if an erratic, parabolic orbit)? And if so, could the orbit even be calculated?


Perhaps there is a near-miss, relatively, not moon-near but close. It goes by, spotted and noted by Earth astronomers, but by the time it was figured to go near Earth, it was known that it wasn't going to hit the Earth (or the moon). So just a weird astronomical event.

But then the body gets into an orbit around the sun, and threatens a 'second pass' that might hit the Earth (or the moon). Now people are worried. And even if it misses the Earth/moon, could come back again & again until its hits it.



Quote:
Originally Posted by Jasonft View Post
I still wonder about that dinosaur killer rock hitting the moon. What are the best/ worst cases? I doubt Luna's orbit would shift enough to be worrisome, but how bad would the shrapnel be to Earth?
There's a great 2015 book by Neil Stephenson, Seveneves, which starts with some small but really hard & fast object (dubbed "The Agent") shooting straight through the moon, breaking it up into a few pieces that become a few more, and a few more, until the remains become debris that fall on Earth, leaving it uninhabitable for 5,000 years.
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Old 11-14-2017, 01:55 PM   #258
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Default Re: Lucy's Choice: Let's make Lucifer Parallels!

That totally depends on how fast it enters our system. Below the escape velocity of the sun and it will stay. If it's faster like the recently discovered extrasolar rock, then nope. It's just visiting.

http://www.syfy.com/syfywire/breakin...ote-not-aliens

In case anyone's missed this awesome discovery.
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Old 11-14-2017, 02:28 PM   #259
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Default Re: Lucy's Choice: Let's make Lucifer Parallels!

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That totally depends on how fast it enters our system. Below the escape velocity of the sun and it will stay. If it's faster like the recently discovered extrasolar rock, then nope. It's just visiting.

http://www.syfy.com/syfywire/breakin...ote-not-aliens

In case anyone's missed this awesome discovery.
That is an awesome story - in The Economist, they said the asteroid should be named 'Rama', after Rendezvous with Rama. It's what made me think of long-term asteroid threat.

If an extrasolar asteroid is moving slow enough to get captured by the sun, its subsequent orbit would still be highly erratic, right? Not just parabolic like a comet, but still swinging this way and that thanks to the initial extrasolar momentum, before 'settling down'.

I'm just wondering if such an asteroid could immediately settle into an Earth-grazing orbit (even one that is slightly erratic enough to eventually hit the Earth), or if it might not have different loops initially, only going near Earth once (if at all).
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Old 11-14-2017, 03:59 PM   #260
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Default Re: Lucy's Choice: Let's make Lucifer Parallels!

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If an extrasolar asteroid is moving slow enough to get captured by the sun, its subsequent orbit would still be highly erratic, right? Not just parabolic like a comet, but still swinging this way and that thanks to the initial extrasolar momentum, before 'settling down'.
There is no settling down. Things are in ballistic orbits and orbits don't change unless something changes them. So you need a close pass to a larger object. That is a rare event
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