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Traab
2014-05-07, 03:20 PM
Just left the death star thread in media when an odd notion hit. Lets say the death stars super weapon hit earth. Instead of shattering it into an asteroid field, it literally punched a clean hole through the middle of the planet and out the other side. What effect would that have on the planet? For fun try and describe the effects if say, it completely obliterates the inner core, it punctures the inner core, or it manages to miss the inner core on its straight line in one end and out the other.

Eldan
2014-05-07, 03:50 PM
I'm not a physicist, but I imagine the end result would be that Earth would settle down into a smaller sphere. The hole would almost certainly collapse, though I don't know how quickly or violently. Probably massive volcanoes and earthquakes.

Max™
2014-05-07, 05:23 PM
Be a heck of a gun to core a planet without moving the pieces to infinity. A starbreaker might do something like that, but the sides of the tunnel shouldn't hold up too long, though I want to say it would "zip" itself back up from the outside in, as gravity is pulling the very center sections outward as much as inward.

shawnhcorey
2014-05-07, 06:23 PM
Assuming the hole was created very quickly, most of the material from the hole would blast back to the cannon. You had better have good shields on the Death Star.

As material fell into the hole, the crust would break into ever-widening circles around the hole until it is broke into many small pieces, say 100 km to 1,000 km in size. About this time, a large jet of material would be forced out of both holes. For the next several years, the Earth would shake like Jello until the vibrations finally damped down.

Life would be very difficult. Aside from the earthquakes and volcanoes, there would be debris falling back from space. And that doesn't account of all the various toxic gases released from underground.

Traab
2014-05-07, 09:03 PM
Could the planet actually recover from something like that though? I mean, I would assume losing the inner core of our planet would kind of ruin our day. But even with the other options at the very least the new massive craters on both sides of the planet would dramatically effect the environment, ignoring the likely multiple year long shroud covering the sky from all the debris, but once the proverbial dust settles, would the planet still be capable of sustaining life? It might even depend on where it hits. For example, how much of our oceans would we lose if the death star hit dead center in one? Would any land mass around the impact site even survive the likely crumbling effect of the hole filling in? Of course, that depends on how big of a hole we are talking about. If the initial blast hit in say, kansas, I wonder if america would become a nation separated by a massive pit stretching across the entire landmass.

Ravens_cry
2014-05-07, 10:12 PM
The Planet? Yes. Planets are tough nuts to crack (http://qntm.org/destroy). Life existing after would be a different story.

Tebryn
2014-05-07, 11:50 PM
Something that seems to have been missed is...what would happen with the atmosphere? A super hot blast of energy, strong enough to core a planet, couldn't leave the Ozone Layer in that good a state right?

Ravens_cry
2014-05-08, 12:06 AM
Something that seems to have been missed is...what would happen with the atmosphere? A super hot blast of energy, strong enough to core a planet, couldn't leave the Ozone Layer in that good a state right?
I think that's the least of your worries.:smalltongue:

Eldan
2014-05-08, 01:46 AM
What about the magnetic field? How much would a hole through the core impact that? Any ideas?

factotum
2014-05-08, 02:00 AM
If this hole is big enough to completely obliterate the core, then the planet is pretty much destroyed--we'd be talking a hole around 3500 miles across, and with the planet's diameter a bit short of 8000 miles, that's a pretty darned big hole! If the hole is only a few miles across then it would collapse almost instantly. Probably wouldn't completely obliterate the planet, but the energy release would almost certainly kill everyone and everything on the surface. Either way, I don't think the effects on the magnetic field would be a big factor in anyone's lives after that point. :smallsmile:

Jimorian
2014-05-08, 02:12 AM
A lot depends on exactly how much material was "removed". Setting aside direct damage as the result of that material vaporizing and escaping, creating a sudden cylindrical hole through the earth would release tremendous amounts of gravitational potential energy as the planet tried to reestablish a solid spherical shape that represented the new total mass.

Make the hole large enough, and the resulting collapse will essentially melt and liquify the entire crust again. It's very unlikely that the hole would last very long. At planetary scales, everything is "liquid", as even the so-called solid crust is barely stiff enough to support variances from a perfect sphere of .2% (8 miles up or down from sea level over a radius of ~4000 miles.

Later, I may try to work out the energy release based on a variety of hole diameters.

Traab
2014-05-08, 10:26 AM
If this hole is big enough to completely obliterate the core, then the planet is pretty much destroyed--we'd be talking a hole around 3500 miles across, and with the planet's diameter a bit short of 8000 miles, that's a pretty darned big hole! If the hole is only a few miles across then it would collapse almost instantly. Probably wouldn't completely obliterate the planet, but the energy release would almost certainly kill everyone and everything on the surface. Either way, I don't think the effects on the magnetic field would be a big factor in anyone's lives after that point. :smallsmile:

Ah, see, I didnt realize the inner core was THAT huge, I knew it would make a very very large hole, but that pretty much turns earth into a donut.

Frozen_Feet
2014-05-08, 10:46 AM
One way to look at it would be to count how much material you'd have to remove. Earth's diameter is 12756 kilometers, so punching even a fairly small hole (around a meter, f. ex.) all the way through would require obliterating a cylinderic iron object of immense size and weight. That in turn requires helluvalot of energy. The waste heat alone would schorch the surface and boil away the atmosphere.

shawnhcorey
2014-05-08, 11:20 AM
One way to look at it would be to count how much material you'd have to remove. Earth's diameter is 12756 kilometers, so punching even a fairly small hole (around a meter, f. ex.) all the way through would require obliterating a cylinderic iron object of immense size and weight. That in turn requires helluvalot of energy. The waste heat alone would schorch the surface and boil away the atmosphere.

Don't forget the blowback. All that material would come out of the hole at high speed, straight back to the laser.

Kato
2014-05-08, 11:51 AM
Don't forget the blowback. All that material would come out of the hole at high speed, straight back to the laser.

Sorry, but.. why? :smallconfused: I guess it depends on what evacuation mechanism we imagine... If we talk abut "we cook us some magma and get massive amounts of gaseous rock" I guess there'd be quite a bit of backfiring, yeah, but otherwise... would that even happen or would the pressure of the laser direct the flow out the other side? I honestly don't know.


Factotum's right, I wasn't aware the (outer) core was so huge. But I guess even a hole the size of the inner core would have pretty drastic effects on earth... If we talk about any clean shot through earth I'd wager it depends a lot on how large it is. As Frozen noted, a hole of 1m diameter (or radius, whatever in this case) would likely just collapse within a given time.

Magnetic field I think is pretty simple: It is widely accepted our magnetic field is created by our core, so no core, no magnetic field. Well, haven't used a compass in forever anyway. ( Before someone chops in on it: I think there are quite a few scientists of the opinion loss of the magnetic field wouldn't result in instantly burning us all with cosmic radiation, as is often proclaimed... it's happened often in the past and life survived. One theory from what I recall is our atmosphere interacting with the radiation creating its own shielding equilibrium... something. I forgot what exactly the mechanism was sorry )

shawnhcorey
2014-05-08, 12:31 PM
Sorry, but.. why?

All that material has to go somewhere, even if it's a gas. If you punch the hole thru quickly, there's going to be a very large, very dense blowback. If you don't do it quickly, the magma will continuously refill the hole.

ChristianSt
2014-05-08, 12:57 PM
The first thing I thought while reading the question was: "Mh, I'm pretty sure I haven't seen that scenario on xkcd: what if? (http://what-if.xkcd.com/)".

I don't know how Randall Munroe selects his topics, but I think it would be a fun enough question, so you could try to submit that question and get some nice pictures along the way :smallwink:

Jay R
2014-05-08, 02:00 PM
Just left the death star thread in media when an odd notion hit. Lets say the death stars super weapon hit earth. Instead of shattering it into an asteroid field, it literally punched a clean hole through the middle of the planet and out the other side. What effect would that have on the planet? For fun try and describe the effects if say, it completely obliterates the inner core, it punctures the inner core, or it manages to miss the inner core on its straight line in one end and out the other.

An actual physical or energy attack would shatter the planet, not core it. Your question assumes a change in physical laws, and therefore cannot be answered by application of those laws.

shawnhcorey
2014-05-08, 02:15 PM
An actual physical or energy attack would shatter the planet, not core it. Your question assumes a change in physical laws, and therefore cannot be answered by application of those laws.

In order to shatter the planet, it would have to turn the insides into very hot gas, which would push the surface outward. That would take a lot more energy than simply drilling a hole thru it.

Max™
2014-05-08, 09:04 PM
From what I've read due to links in a recent What If? the amount of material removed from some of the largest open pit mines would be enough to drill at least a narrow tunnel through the planet.

The question of where the material goes is why I mentioned starbreakers, for those who never read any of the Xeelee stories, it's a focused beam of gravity waves, one of the first depictions was a delicate handgun with multiple settings, the low ones produce synchrotron radiation, the race which found it had been afraid to try the higher ones. Later in a panic they fired it on the highest setting at and through a stolen Xeelee Nightfighter which had arrived back in their system a little too close to their star for comfort (that's what my Avatar is, btw) and accidentally triggered a massive stellar eruption which took out their planet.

One of the stories describes a cylindrical crater with vertical walls on what was a colony moon around Jupiter or Saturn, forget which one.

Stands to reason that if you could make the material "fall" in the direction of the beam you could punch a core out and send it out the far side... though keeping the rest of the material around the impact point from following it is another matter.

Nice representation of the crust/mantle/outer/inner core scales:
http://discovermagazine.com/~/media/Images/Issues/2013/Jan-Feb/earths%20layers.jpg

Tebryn
2014-05-08, 09:15 PM
I think that's the least of your worries.:smalltongue:

Well, part of the question was how would life handle it I thought. That matters I'd say.

Knaight
2014-05-08, 09:58 PM
An actual physical or energy attack would shatter the planet, not core it. Your question assumes a change in physical laws, and therefore cannot be answered by application of those laws.

The question is about the aftermath. The getting there is nonsense, but if it is already in that state it can be handled with physical laws just fine.

Jay R
2014-05-08, 11:14 PM
In order to shatter the planet, it would have to turn the insides into very hot gas, which would push the surface outward. That would take a lot more energy than simply drilling a hole thru it.

Simply untrue.

Take a rock and a hammer. Is it easier to shatter the rock, or to drill a hole through it?

Then look at the Moon. Did the asteroid that created the Tycho crater (http://upload.wikimedia.org/wikipedia/commons/e/e1/FullMoon2010.jpg) start a hole through the moon, or leave long stress rays way beyond the crater?

Then look at every astronomical body we've ever seen. Do we have any evidence at all for a possible hole drilled through one?

Astral Avenger
2014-05-09, 12:24 AM
Simply untrue.

Take a rock and a hammer. Is it easier to shatter the rock, or to drill a hole through it?

Then look at the Moon. Did the asteroid that created the Tycho crater (http://upload.wikimedia.org/wikipedia/commons/e/e1/FullMoon2010.jpg) start a hole through the moon, or leave long stress rays way beyond the crater?

Then look at every astronomical body we've ever seen. Do we have any evidence at all for a possible hole drilled through one?

OTOH, people have pointed out that a hole through a planet/celestial body would collapse in on itself very quickly or make the entire thing go boom into a nebula or rocky, dusty cloud. Either way, we see a lot of nebulas and dusty clouds out there, and we also see a lot of very beat up planets out there.

Tebryn
2014-05-09, 12:25 AM
Simply untrue.

Take a rock and a hammer. Is it easier to shatter the rock, or to drill a hole through it?

Then look at the Moon. Did the asteroid that created the Tycho crater (http://upload.wikimedia.org/wikipedia/commons/e/e1/FullMoon2010.jpg) start a hole through the moon, or leave long stress rays way beyond the crater?

Then look at every astronomical body we've ever seen. Do we have any evidence at all for a possible hole drilled through one?

I've never seen the after-effects of a DEW on a planetary body. I can't think that it would behave the same way as a giant asteroid however. Could be wrong though.

factotum
2014-05-09, 01:59 AM
Ah, see, I didnt realize the inner core was THAT huge, I knew it would make a very very large hole, but that pretty much turns earth into a donut.

To clarify: that's the inner core *and* outer core. The Earth's magnetic field is generated by liquid movements in the outer core (the inner core is completely solid), so to seriously disrupt it you'd have to take both out.

Mind you, the inner core is still a good 900 miles across, which is still a significant enough fraction of the planet's diameter that the collapse of the remnants would certainly kill us all and destroy everything we've built.

Kato
2014-05-09, 04:02 AM
To clarify: that's the inner core *and* outer core. The Earth's magnetic field is generated by liquid movements in the outer core (the inner core is completely solid), so to seriously disrupt it you'd have to take both out.
That's still at best a very likely theory.. I'm always intrigued with what certainty people claim to know about the make-up of the inside of our planet when we really mostly have to infer stuff from the little we know about it's surface. (Obviously not saying it's false, but taking it as die-hard facts...)


Mind you, the inner core is still a good 900 miles across, which is still a significant enough fraction of the planet's diameter that the collapse of the remnants would certainly kill us all and destroy everything we've built.
Oh, factotum, you old pessimist, there_s a decent chance a few of us might survive for a while and a few buildings could remain intact long enough for us to hide from the amounts of falling debris and live out their lives until the atmosphere collapses... which I guess it would do rather fast, I'll admit.

factotum
2014-05-09, 07:11 AM
That's still at best a very likely theory.. I'm always intrigued with what certainty people claim to know about the make-up of the inside of our planet when we really mostly have to infer stuff from the little we know about it's surface. (Obviously not saying it's false, but taking it as die-hard facts...)

We know a lot more about it than that. They monitor the reflections of seismic waves travelling through the body of the planet and can see the discontinuities between different zones--that's how they know how big the inner and outer cores are, and their approximate densities.

Comissar
2014-05-09, 07:27 AM
Not sure how relevant this What-if xkcd (http://what-if.xkcd.com/20/) is, specifically the bit where the meteor is given the speed of the oh-my-god particle. The OP made me think of it, though.

shawnhcorey
2014-05-09, 07:55 AM
Simply untrue.

Take a rock and a hammer. Is it easier to shatter the rock, or to drill a hole through it?

Then look at the Moon. Did the asteroid that created the Tycho crater (http://upload.wikimedia.org/wikipedia/commons/e/e1/FullMoon2010.jpg) start a hole through the moon, or leave long stress rays way beyond the crater?

Then look at every astronomical body we've ever seen. Do we have any evidence at all for a possible hole drilled through one?

You are forget the crust (that's the solid part) is only about 50 km thick. Most of the drilling would be thru the mantle, which is liquid, and the outer core, which is also liquid, before you get to the solid inner core. Everything under the crust is very hot and under extreme pressure. As soon as you punch a hole into one layer, it would instantly turn to vapour and be expelled out of the hole. And this would interfere with the laser beam and possibly damage the laser itself. Unless your laser is powerful enough to punch thru quickly, you would have to vaporize almost all of the mantle and outer core before you can start on the inner core.

And the inner core is solid only because of the pressure. Drill a hole down to it, and it too would instantly become a vapour.


To clarify: that's the inner core *and* outer core. The Earth's magnetic field is generated by liquid movements in the outer core (the inner core is completely solid), so to seriously disrupt it you'd have to take both out.

Mind you, the inner core is still a good 900 miles across, which is still a significant enough fraction of the planet's diameter that the collapse of the remnants would certainly kill us all and destroy everything we've built.

The crust is about 50 km thick, the mantle about 2900 km, the outer core 2250 km, and the inner core 1300 km.

factotum
2014-05-09, 12:59 PM
Most of the drilling would be thru the mantle, which is liquid, and the outer core, which is also liquid, before you get to the solid inner core.

Actually, the mantle is mostly in a state described as "plastic", as I recall--the pressure and temperature allow it to flow a certain amount over geological timescales, but it's certainly not liquid in the same way that lava released on the surface is.

shawnhcorey
2014-05-09, 01:15 PM
Actually, the mantle is mostly in a state described as "plastic", as I recall--the pressure and temperature allow it to flow a certain amount over geological timescales, but it's certainly not liquid in the same way that lava released on the surface is.

All of this (https://en.wikipedia.org/wiki/2011_T%C5%8Dhoku_earthquake_and_tsunami#Geophysica l_effects) happened in 6 minutes. The mantle is under tremendous pressure and can respond quickly to changes in pressure. Plastic does not describe it.

Max™
2014-05-09, 02:03 PM
That's still at best a very likely theory.. I'm always intrigued with what certainty people claim to know about the make-up of the inside of our planet when we really mostly have to infer stuff from the little we know about it's surface. (Obviously not saying it's false, but taking it as die-hard facts...)
Theory doesn't mean "guess", it means "sound explanation with confirmed predictive power", and it isn't a guess that the planet interior has these properties.

http://www.surveying.org/home.htm

This is an overlay on google maps of the geoids produced by various gravity surveys.

Combining data from gravity surveys and seismic data with magnetic surveys we can produce very detailed pictures of the interior of the planet.

By comparing known behavior of sound wave propagation through various materials we can determine what the composition of the interior must be, as there aren't other options available to explain certain combinations of known properties with observations.

Taken together we can very safely say that while there are still surprises related to say, the exact chemical properties or proportion of various elements, and there are still new and interesting types of crystal formations and phase changes to explore in the interior, but we can be very confident that at depth x there is a transition from crust to mantle and at depth y there is another transition from mantle to outer core and at depth z there is another transition from outer to inner core. We can determine the temperature and density of the materials present, we can tell how much pressure they must be under, and we can tell what these materials must be to surprisingly accurate levels.

Looking at the surface can tell us a lot, studying volcanic activity and lava can tell us more, but that is far from the limit of our capabilities with regard to studying the interior of the planet.


Oh, factotum, you old pessimist, there_s a decent chance a few of us might survive for a while and a few buildings could remain intact long enough for us to hide from the amounts of falling debris and live out their lives until the atmosphere collapses... which I guess it would do rather fast, I'll admit.
Atmosphere collapse?

There would be an injection of HUGE amounts of heat and vaporized rock into the atmosphere, it would expand and the pressure would increase dramatically, as would the temperature.

The sun probably wouldn't be visible from the surface any longer, though that would be the least of our worries, a nuclear winter would be welcome compared to the whole "trying to breathe vaporized rocks" problem.

factotum
2014-05-10, 02:09 AM
All of this (https://en.wikipedia.org/wiki/2011_T%C5%8Dhoku_earthquake_and_tsunami#Geophysica l_effects) happened in 6 minutes. The mantle is under tremendous pressure and can respond quickly to changes in pressure. Plastic does not describe it.

Er, earthquakes are nothing to do with the mantle--they're due to faults in the crust buckling or shifting. In this case, the fault in question was in the subduction zone where the Pacific plate slides under the Eurasian one. The crust effectively floats on top of a liquid layer at the top of the mantle, but that liquid layer is itself quite thin--almost all of the mantle is in a near-solid state as I mentioned above.

shawnhcorey
2014-05-10, 07:53 AM
Er, earthquakes are nothing to do with the mantle--they're due to faults in the crust buckling or shifting. In this case, the fault in question was in the subduction zone where the Pacific plate slides under the Eurasian one. The crust effectively floats on top of a liquid layer at the top of the mantle, but that liquid layer is itself quite thin--almost all of the mantle is in a near-solid state as I mentioned above.

So, when the coast of Japan subsided, it collapsed into an air pocket under it. There was no mantle holding it up because the mantle does not move during an earthquake.

Sorry, I don't belief there was an air pocket that big.

factotum
2014-05-10, 09:25 AM
So, when the coast of Japan subsided, it collapsed into an air pocket under it. There was no mantle holding it up because the mantle does not move during an earthquake.

Sorry, I don't belief there was an air pocket that big.

Are you deliberately ignoring half my comment because it doesn't support your argument? I said that there is a thin liquid layer at the top of the mantle that the crust floats on. That's where the crustal plates disappear to at subduction zones. That does not make the *entire* 2000-odd mile thickness of the mantle liquid.

shawnhcorey
2014-05-10, 09:52 AM
Are you deliberately ignoring half my comment because it doesn't support your argument? I said that there is a thin liquid layer at the top of the mantle that the crust floats on. That's where the crustal plates disappear to at subduction zones. That does not make the *entire* 2000-odd mile thickness of the mantle liquid.

So, there is a tiny layer on top, a few meters thick, where the pressure and temperature is the least, that acts as liquid but the rest, where the pressures and temperatures are higher, are not? The complete inverse of thermodynamics (https://en.wikipedia.org/wiki/Triple_point)?

Tirunedeth
2014-05-10, 10:04 AM
So, when the coast of Japan subsided, it collapsed into an air pocket under it. There was no mantle holding it up because the mantle does not move during an earthquake.

Sorry, I don't belief there was an air pocket that big.

There is enough play in the crust itself to account for the 0.5 to 1 meter subsidences observed in Japan. Before the earthquake, the crust was under stress, and so was larger than it would be at equilibrium. After the quake, the crust returned to a state closer to equilibrium, resulting in the observed subsidences (at least, in part; settling of surface materials triggered by the quake can cause additional subsidence).


Are you deliberately ignoring half my comment because it doesn't support your argument? I said that there is a thin liquid layer at the top of the mantle that the crust floats on. That's where the crustal plates disappear to at subduction zones. That does not make the *entire* 2000-odd mile thickness of the mantle liquid.

Actually, the entire mantle is solid, as evidenced by its ability to conduct S-waves. There is a layer at the boundary between the mantle and the crust which is about 100 times less viscous than the mantle at large, but that still puts it about a billion times more viscous than solid lead at room temperature (and about on par with glass (http://www.cmog.org/article/does-glass-flow), interestingly enough).


So, there is a tiny layer on top, a few meters thick, where the pressure and temperature is the least, that acts as liquid but the rest, where the pressures and temperatures are higher, are not? The complete inverse of thermodynamics (https://en.wikipedia.org/wiki/Triple_point)?

Increasing pressure on a liquid can cause it to become a solid, as shown in the chart on the very page you linked to. In principle, with the correct gradients of pressure and temperature, you could get a transition form solid to liquid and then back to solid. While this doesn't happen in the Earth's mantle, it does happen deeper, in the outer and inner core.

Jimorian
2014-05-10, 10:07 AM
So, there is a tiny layer on top, a few meters thick, where the pressure and temperature is the least, that acts as liquid but the rest, where the pressures and temperatures are higher, are not? The complete inverse of thermodynamics (https://en.wikipedia.org/wiki/Triple_point)?

I believe the reason for that is a combination of contaminants from the crust plus lighter elements oozing up from the mantle, so it's effectively not the same material, so would have different properties. As said upstream, this isn't wild guesswork on geologists' part, but is the kind of thing fairly easily measured with a variety of techniques.

Kato
2014-05-10, 11:46 AM
We know a lot more about it than that. They monitor the reflections of seismic waves travelling through the body of the planet and can see the discontinuities between different zones--that's how they know how big the inner and outer cores are, and their approximate densities.


Theory doesn't mean "guess", it means "sound explanation with confirmed predictive power", and it isn't a guess that the planet interior has these properties.

[...]

By comparing known behavior of sound wave propagation through various materials we can determine what the composition of the interior must be, as there aren't other options available to explain certain combinations of known properties with observations.

Eh, I didn't intend to sound like some conspiracist or anything and I'm actually very willing to belief generations of geologists haven't done their best to figure out what the interior of our planet looks like. It just happens I have sometimes a hard time believing how reliable some stuff is, especially in regards to "must be so and so" just because nobody came up with another suitable idea, and the interior of planets or other things you really have a hard time seeing is among those. Dang, I'm doing it again, sorry :smallredface:
(Also, last time I checked I thought the geo dynamo theory for the magnetic field was still a bit more unclear but I guess I was a bit behind on that front)


Atmosphere collapse?

There would be an injection of HUGE amounts of heat and vaporized rock into the atmosphere, it would expand and the pressure would increase dramatically, as would the temperature.

Hm, I reasoned such a massive loss of material would result in a drastic reduce in gravity and thus atmosphere. Again, totally willing to concede my point.


So, there is a tiny layer on top, a few meters thick, where the pressure and temperature is the least, that acts as liquid but the rest, where the pressures and temperatures are higher, are not? The complete inverse of thermodynamics (https://en.wikipedia.org/wiki/Triple_point)?
Huh? :smallconfused: Higher pressure almost always leads to more solid states (I can only think of a few cases were water screws with that right about now) so except for the minor-ish pressure gradient, why wouldn't the surface of the mantle be more liquid? (Yeah, yeah, "more liquid is a stupid expression)

shawnhcorey
2014-05-10, 01:14 PM
Huh? :smallconfused: Higher pressure almost always leads to more solid states (I can only think of a few cases were water screws with that right about now) so except for the minor-ish pressure gradient, why wouldn't the surface of the mantle be more liquid? (Yeah, yeah, "more liquid is a stupid expression)

It's a question of what happens if some of the pressure is reduced, as in an earthquake, or totally removed, as in drilling down to it.

And I do believe the expression is more fluid. :)

Max™
2014-05-10, 06:12 PM
Eh, I didn't intend to sound like some conspiracist or anything and I'm actually very willing to belief generations of geologists haven't done their best to figure out what the interior of our planet looks like. It just happens I have sometimes a hard time believing how reliable some stuff is, especially in regards to "must be so and so" just because nobody came up with another suitable idea, and the interior of planets or other things you really have a hard time seeing is among those. Dang, I'm doing it again, sorry :smallredface:
(Also, last time I checked I thought the geo dynamo theory for the magnetic field was still a bit more unclear but I guess I was a bit behind on that front)
Belief is nasty stuff, there are lots of ideas which were suitable, but there are also lots of lines of information which only fit certain ideas.

After combining properties which fit say, seismic mapping, with observations of lava flow, magnetic properties, gravity mapping, and so forth, there aren't many possible explanations left.

Unfortunately one of those possible explanations is always "everything we know about everything is completely wrong and the universe is made of farts and pixie dust", but we discount that as it offers no useful insight, particularly when placed aside models that do explain many things.

We can look at the inside of the sun with seismic and gravity mapping, we are getting to the point that neutrino flux measurements should be providing useful mapping options before long.

Science is the process by which we take what we can see and compare it with what we can measure so we can try to explain both in a way that tells us something new.

The models which remain are those which do all of that in a more elegant and broadly useful manner than the others did.


Huh? :smallconfused: Higher pressure almost always leads to more solid states (I can only think of a few cases were water screws with that right about now) so except for the minor-ish pressure gradient, why wouldn't the surface of the mantle be more liquid? (Yeah, yeah, "more liquid is a stupid expression)
More liquid isn't such a bad term, but higher pressure is only part of the state inside a planet.

There are parts of Jupiter where there should be metallic hydrogen, normally you NEVER see metallic hydrogen outside of extremely high temperatures and pressures.

Then you get helium where the liquid states persist down to absolute zero and you need higher pressures to produce a solid, which can then be compressed a ridiculous amount because helium laughs at things like behaving normally, make sure you seal the top of the container holding your extra liquid helium though, it kinda climbs out if you get it in the superfluid realm, which has such weird behavior we had to invent a type of second and third sound to describe it.

https://en.wikipedia.org/wiki/Second_sound
https://en.wikipedia.org/wiki/Third_sound

Now suffice to say, the temperatures and pressures involved with those aren't going to give the same responses as a big lump of iron/silicon/oxygen like the one we'rd sitting on now.

If you're interested in learning a bit more about how we worked out these transitions: https://en.wikipedia.org/wiki/Mohorovi%C4%8Di%C4%87_discontinuity is a fascinating starting point.

ericgrau
2014-05-10, 11:31 PM
I don't think anything would survive outside of a few select bacteria. Even those that sought shelter would have to deal with the drastic change in the atmosphere, temperature and pressure. I don't think even a space suit could handle it because it wouldn't have a way to keep cool enough among all that heat.

You'd need a pressure sealed bunker with air conditioning with extreme energy usage. Which means your bunker needs a generator with a massive amount of fuel. And your own oxygen supply or some rather sophisticated and, again, energy intensive air scrubbers. It might be easier and cheaper to survive in orbit. If there was no warning of the attack, everyone would certainly die.

The temperature changes, especially with the difference close to and away from the blast zone, would also cause storms far beyond what the planet has ever seen before. Super hurricane force winds far beyond any known disaster would become the daily norm.


We take for granted the thousands of degrees of heat all around. And a super pure and calm atmosphere compared to pretty much any other planet in the solar system. With a tightly regulated temperature. The 10 or 20 degrees that annoy us are a drop in the bucket compared to how easily it could be -300 one day and 1500 the next, along with the resulting winds.

gomipile
2014-05-12, 07:31 PM
Don't forget the blowback. All that material would come out of the hole at high speed, straight back to the laser.

Initially. The laser travels in a straighter line, but the blowback is affected more by gravity and inertial effects because atoms and electrons have mass. Those inertial effects add up, so if the laser is a reasonable distance away, it probably wouldn't get hit by any or much of the blowback. The difference between a ballistic geodesic and a light speed geodesic over a distance is considerable.

shawnhcorey
2014-05-12, 08:18 PM
Initially. The laser travels in a straighter line, but the blowback is affected more by gravity and inertial effects because atoms and electrons have mass. Those inertial effects add up, so if the laser is a reasonable distance away, it probably wouldn't get hit by any or much of the blowback. The difference between a ballistic geodesic and a light speed geodesic over a distance is considerable.

The hole would be drilled along the line of the laser. Assuming they are drilling straight in because it would be the quickest way to the core, the blowback would be straight up, no curves.

gomipile
2014-05-12, 09:01 PM
The hole would be drilled along the line of the laser. Assuming they are drilling straight in because it would be the quickest way to the core, the blowback would be straight up, no curves.

Only if the planet doesn't rotate at all and is in an otherwise homogeneous universe with nothing in it but the planet and the laser-producing device.

In a real universe where the planet and the laser device are in different inertial reference frames and the planet is spinning, by the time the blowback reaches the "death star"'s orbital track, there will be a significant distance between the blowback and the "death star" if the "death star" is at a reasonable distance (say, geosynchronous orbit or further.)

AgentPaper
2014-05-14, 10:51 AM
Depends a lot on how wide the hole is. If it's just a few feet wide, the hole will be stable in the upper crust, and collapse instantly in the lower crust. The further down you go, the faster the hole will collapse, and depending on how close the magma is to the surface, you might get a small eruption, but most likely the magma is going to be too far down to rise high enough before it runs out of pressure.

If the hole is larger, a volcano becomes more and more likely, and also potentially much larger. I don't know what the exact numbers would be, but eventually you'd have a hold large enough (maybe a dozen feet?) that could allow the molten iron from the outer core to rise to the surface before the mantle closed completely, creating a volcano larger than any we've ever seen. All life would be destroyed, though the planet itself would barely even notice.

If you increase the size of the hole even more, and hit the core, then depending on how you hit it, you could destabilize it and cause the entire core to wobble like an unbalanced gyroscope. This movement probably wouldn't translate to the surface much, but it would push on the outer core quite violently, causing every volcano on earth to erupt. Which might be pretty cool to watch, if we weren't all dead already from the massive eruption that happened just before it.

Of course, all of this assumes that the death star somehow creates the hole in the earth instantly, and without imparting any extra energy to the planet itself, as if it simply teleported all that matter away rather than shooting it with a laser. If you shot the earth with a laser powerful enough to bore a 1-foot wide tunnel through the earth, quickly enough to do it before the tunnel collapsed upon itself, you'd probably just end up vaporizing half the planet and destroying it anyways.

Icewraith
2014-05-15, 07:17 PM
As you increase pressure and temperature on solids, you get more and more exotic types of solid. Think Diamonds.

The portion of deep-earth geophysics research I participated in during my undergrad was determining the high and low temperature behavior of certain -ites.

I concur with the anti-death star laser people. A laser wouldn't do it. Maybe if you got a long, ultrahard material built like an enormous armor penetrating shaped charge up to a high enough speed against a large enough planet that somehow didn't have an extremely hot interior from the gravitational pressure and was maybe made out of the large scale equivalent of safety glass (brittle and fails locally but not necessarily globally, or not immediately) you could think about something like that happening instead of just shattering the planet.

gomipile
2014-05-16, 03:00 AM
As you increase pressure and temperature on solids, you get more and more exotic types of solid. Think Diamonds.

The portion of deep-earth geophysics research I participated in during my undergrad was determining the high and low temperature behavior of certain -ites.

I concur with the anti-death star laser people. A laser wouldn't do it. Maybe if you got a long, ultrahard material built like an enormous armor penetrating shaped charge up to a high enough speed against a large enough planet that somehow didn't have an extremely hot interior from the gravitational pressure and was maybe made out of the large scale equivalent of safety glass (brittle and fails locally but not necessarily globally, or not immediately) you could think about something like that happening instead of just shattering the planet.

Or something like an earth-diameter length+ "apple corer" made out of a piece of metal protected by a Larry Niven style stasis field. Move it fast enough that it would take instruments to notice it as it passed through the earth, and you might get the desired effect.

Max™
2014-05-16, 04:37 AM
Could "Forge of God" it.

Drop a neutronium pancake (spin stabilized) into the planet from one side, drop an anti-neutronium pancake from the other side.

When they meet the pancake shapes should be turned into rods by the explosion, and ideally the energy would be channeled back out through the holes made as they fell through the planet.

It would only work if you could keep neutron star matter stable without the massive gravity well of said neutron star, and it wouldn't really notice the matter in the way. The anti-pancake would build up a sheath of plasma, as the only thing dense enough to actually trigger a full annihilation would be the other pancake.

Icewraith
2014-05-16, 04:07 PM
Or something like an earth-diameter length+ "apple corer" made out of a piece of metal protected by a Larry Niven style stasis field. Move it fast enough that it would take instruments to notice it as it passed through the earth, and you might get the desired effect.

If planets weren't problematic spherical shapes, but something a bit more prone to brittle failure along one axis, you'd have a much easier time literally blowing holes in one.

Incidentally, if you were going to try the experiment, you should therefore be trying to blow a hole through a planet's rotational axis rather than through its equator, which is what people are far more likely to think of given how it looked in the movie.

Any planet (with a land-dwelling populace) with icecaps you'd want to be shooting thorugh the poles anyways, so even if the planet stays mostly intact anything that survives the heat from the blast, the nuclear winter and debris fallout, and the subsequent tectonic events has to deal with a hundred meter+ sea rise on top of flooding and tsunamis generated by the local topography rearranging itself.

I think.

Wardog
2014-06-07, 05:36 PM
So, there is a tiny layer on top, a few meters thick, where the pressure and temperature is the least, that acts as liquid but the rest, where the pressures and temperatures are higher, are not? The complete inverse of thermodynamics (https://en.wikipedia.org/wiki/Triple_point)?

A few points:
The "crust" and "mantle" are defined by chemical composition.
The "lithosphere" and "asthenosphere" are defined by structural properties.

The lithosphere (crust + top of the mantle) is rigid and brittle.
The asthenosphere (upper-middle of the mantle) is ductile.

The solidity of the crust and mantle depend on temperature, pressure, and composition. In general, none of it is liquid. Melting occurs when parts of the crust or mantle get moved so that their temperature, pressure, or composition change. E.g. if deep manttle is droght to the surface, its heat is still high enough, and pressure now low enough for it to melt. Or at subduction zones, water and other material from the surface gets brought down, thereby changing the composition and causing melting. (According to this wikipedia article (https://en.wikipedia.org/wiki/Subduction#General_description) it is specifically due to the water reducing the pressure enough for melting to occur, although I had been taught it was due to the lowered melting point of the resulting mixture).