A comet's journey to the center of the earth

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andykhang
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A comet's journey to the center of the earth

Postby andykhang » Thu Sep 08, 2016 6:32 pm UTC

Supposedly you open a portal, big enough for an asteroid to go through, directly to the center of the earth.You know what up, so what would happen with a 1km in diameter? How about 10,100?

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Re: A comet's journey to the center of the earth

Postby gmalivuk » Thu Sep 08, 2016 7:31 pm UTC

I assume you last sentence should have a space after the comma, meaning "10 or 100"? Because a 10,100km body is somewhat too big to be called a comet.
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Re: A comet's journey to the center of the earth

Postby doogly » Thu Sep 08, 2016 7:40 pm UTC

And if you are opening portals you probably want the fictional subforum. Which really should just be an entirely different forum, so that my eyes do not light up when I see a new post in Science only to be crestfallen when it is just silly.
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Re: A comet's journey to the center of the earth

Postby gmalivuk » Thu Sep 08, 2016 7:56 pm UTC

Yeah, that's a valid point. Moved.
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doogly
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Re: A comet's journey to the center of the earth

Postby doogly » Thu Sep 08, 2016 8:09 pm UTC

But also to answer the question, the earth pushes the comet back through the portal and the open portal starts sucking out the core, and eventually the whole thing implodes. Unless you specifically want a one way portal. Then it explodes. Gonna plode though, pretty sure. Unless it is a special carving-out type portal. Then the comet takes the core's space, and everything is awkward for a while but it should heat up soon enough, but there are probably earthquakes and shit.
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SDK
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Re: A comet's journey to the center of the earth

Postby SDK » Thu Sep 08, 2016 8:31 pm UTC

andykhang wrote:Supposedly you open a portal, big enough for an asteroid to go through, directly to the center of the earth.You know what up, so what would happen with a 1km in diameter? How about 10? 100?

Depends on a lot of things. Are you conserving the comet's momentum, or is that 1 km chunk appearing stationary relative to the Earth's motion? I assume this portal is one-way, but how is the comet overcoming the immense pressure at the center of the Earth to get there in the first place? Are you basically just asking for a force calculation to know how much the Earth gets shaken up by the impact?

I'm going to assume it's the last one, so let's pick a random comet... Halley's Comet? 11 km in diameter, weighing 2.2×1014 kg, moving 70.56 km/s at its fastest. E=0.5mv2 gives us 5.5x1023 J of energy. That's about equivalent to the Chicxulub Impact that killed the dinosaurs. Something in the neighbourhood of a magnitude 13 earthquake (well above the holy-shit-that's-huge type of quake). If that hit the Earth's surface, obviously terrible things would happen. But the center of the Earth? Hard to say what we're in for in that case. Magnitude 5 and higher quakes can cause serious damage, but it's not at all clear that large earthquakes will cause quakes in other regions, even when the quakes are very large. It's possible that one large earthquake can trigger others across the globe, but that's often hours after the fact, something scientists don't really understand at this point. The mechanics of what goes on in the mantle is fuzzily understood at best, let alone what happens in the core. With that much energy input it's hard to imagine nothing happening, but exactly what would happen is difficult to say.

Oh, you want bigger? Okay. 100 km in diameter assuming the same density as Halley gives us 1.65×1017 kg to play with instead. Same speed results in 4x1026 J. Still not sure what's going to happen, but multiplying a devastating impact by a thousand can't be good. I can only assume we'd all be dead. Still a million times too small to overcome Earth's gravitational binding energy though, so Earth (the rock) survives at least. I love happy endings.
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