I wonder what would happen if you turned noclip back off in the exact moment the asteroid passes through the center of the Earth.
The proverbial Earth-Shattering Kaboom?
I don’t know. The Earth is very big, the nucleus and the mantle are viscous, perhaps the energy would dissipate as heat? Perhaps the Earth would shatter? Ring like a bell? Let’s assume a Chicxulub sized asteroid that happens to hit the center of the Earth and that can magically be noclip’d on and off remotely.
Armageddon.
if the object suddenly materializes where there is already another object, wouldn’t that result on two atoms occupying the same space? That being impossible I guess the result would depend on how the universe suddenly reacts to that impossibility, if it interprets it as a collision I guess the Earth could abide, but if makes all the existing atoms move away to avoid superposition the Earth would probably shatter, or at least the earthquakes would destroy civilization.
The ultimate telefrag.
At least it isn’t Deep Impact.
Though @Frodo’s scenario sounds more like Timecop.
Ha, my exact thought. (Timecop)
This is interesting. If something like this were to happen, atoms wouldn’t collide. Being mostly empty space, I imagine they would overlap. The big question is what happens with this overlap. Would the various nuculid be close enough to trigger the Strong Nuclear force, resulting in a giant asteroid sized atom in the middle of the Earth, which would be incredibly unstable. Or would the Electromagnetic Force have a stronger effect and all the atoms bounce off each other?
This is the ultimate “What If?” question. Quick someone alert Randall Monroe!
All those protons and neutrons compacted - I thinking a gigantic fission “experience”. It won’t go well. 
Atomic nuclei are vastly smaller than the atoms themselves, roughly a trillionth of the volume, and in ordinary matter, even at the center of the Earth, the atoms themselves occupy a small fraction of the bulk volume. So I think that magically overlapping two pieces of ordinary matter is unlikely to end up with very many nuclei overlapping.
“What If?” questions seldom do.
The nuclei would still be a large distance apart – most of the atom’s size is the electron cloud.
I think you’d just get a realignment of atoms into a denser structure, but the “instantaneous” part of the scenario means there’s no actual science behind it so you can make up whatever you want.
But as far as the atoms finding some way to arrange themselves assuming a reasonable timescale, I don’t think it’s that big a problem. If my googling is accurate, a typical asteroid has a density of 2-4 g/cm3. The Earth’s core is about 13 g/cm3, so the result would be a 15-30% increase in density. Compare that to Jupiter, which has a density of 20-25 g/cm3.
The problems are going to be the kinetic energy suddenly added to the core, and that the current density of the core is in balance with the pressure. If the density is suddenly increased while the pressure stays constant, will that rupture something, similar to an overfilled balloon?
I’m guessing you meant fusion, not fission. But we’re many orders of magnitude below the density needed for fusion of compounds like iron and nickel.
I was thinking fusion followed immediately by fission.
Nope, fission. Same as U235/U238 undergoing decay. The immense sudden split, perhaps not an atomic bomb, but a potent fizzle. It’s all imaginary though. I’m certainly NOT doing the math
Fission isn’t going to happen because nuclei are being packed tightly. Atoms aren’t like a rock that shatters when it gets smashed.
I don’t think the Earth is in for a good time if this happens, but nuclear fission isn’t one of the things we need to worry about.
Yep, that is what would interest me.
In physics, the kinetic energy of an object is proportional to its mass, so, indeed, it will not have much energy left. Also, a material that sparse is just going to disintegrate, unlike a chunk of iron.
Matter, like electrons, indeed cannot be squeezed to the same place because of the Pauli exclusion principle, so if you try to squeeze them together there will be an increasingly high resisting pressure.
My WAG is the asteroid suddenly appearing in the core would have no discernible effects whatsoever. How big is this asteroid? A very large one like Chicxulub (10 km)? So the result is a very tiny particle (a few millionths of one percent of the Earth’s volume) deep within the Earth is suddenly a few percent denser than it was before. There will be a little burp as the matter adjusts, but it will be damped by the enormous pressure of all the gazillion tons of overlying rock and have no effect on the surface. At that depth the material is not a friable solid and can’t “shatter”; it acts more like a liquid.
The effect of the added kinetic energy on the Earth’s orbit will be the same as if it had hit the surface in the normal manner; that is, no measurable effect.