How to destroy the Earth (completely)
qntm.org
qntm.org
This particular article can't hold a candle to rec.arts.sf.science discussions of the same topic from the early 90's.
See http://www.aip.org/pnu/2008/split/871-1.html
Obviously, there is a tipping point where a black hole becomes dangerous - but it's worth remembering that gravity is the weakest of the major forces. Any physics geeks care to calculate how long it would take an Everest-sized black hole to eat the earth?
The article does mention Everest mass.
Everest volume would, of course, not be a "small" black hole at all.
Everest mass would be a very tiny black hole.
As it oscillated back and forth it's picking up momentum from the earth, which slows down the oscillation. It would end up right in the center, but not moving.
After that it will wait for the pressure of the earth to feed it mass.
[EDIT] Hmm I think I see the point. The resulting force would be proportional to the ratio (black hole mass / earth's mass). Very small indeed.
For a solid sphere, there is always force toward the center. (And the closer to the center the lower the force, reaching 0 in the middle.)
In a solid sphere there is always force, and it always points to, and is lowest, at the center.
Or more accurately oscillating back and forth in the middle, but not touching the wall.
If there was any vapor in the middle (which seems likely to me, considering it would be a perfect vacuum at pretty extreme temperatures), then the gas would eventually slow down the oscillations and it would end up exactly in the middle.
BTW, Sci fans of yesteryear were disappointed when it was discovered that Dyson Spheres and Ring Worlds gravitationally unstable...
It won't. The first time it touches (or comes near) the wall it will take what it can get, but it will never go farther than that. There is nothing that will "push" it closer to the walls.
So this means that inside the cave the black hole will just move in one direction, until it hits the wall. Then it will suck up some mass and be pulled back to the center. Then it will suck up some mass on the other side, etc.
The only way the black hole will remain in the cave is if you put it in the cave with exactly zero velocity to begin with. As soon as one atom falls into it it will start to eat up the earth.
You are missing a point.
Yes, inside the cave there is no force. But the black hole can hit the wall just once. After that it can not go any farther.
If passes thought/inside the wall it will be pulled back to the center, and the momentum exchange with the earth will slow it down (so next time it won't go as far). If it was just touching the wall, then that is as far as it can possibly go.
So once it's inside it's little cave, it's done. It can't eat anymore. (Unless of course there is no cave and the earth feeds it, but we are assuming a cave.)
You are missing three points: one is that if there is no cave, and it's oscillating through the earth, it will be pulled to the center. Two is that it looses momentum each time through the earth. And three is that once it's inside it's hollow cave it can no longer reach the wall.
> You are missing three points: one is that if there is no cave, and it's oscillating through the earth, it will be pulled to the center.
Agreed.
> Two is that it looses momentum each time through the earth.
I'm not so sure about that. Mass is added to the black hole, and perhaps this causes the total momentum to increase.
> And three is that once it's inside it's hollow cave it can no longer reach the wall.
If it is stopped inside the cave. But there is no force to stop it.
Imagine a tiny black hole arriving on earth. It grabs some mass. The black hole is moving, but the mass it ate is not. So rather than free falling, it looses momentum. As it falls through the earth it keeps doing that.
So it will not rebound back up to the top at the same height it fell. It will be lower. The second time through the same thing will happen.
Each time it oscillates it will get lower and lower.
Next. Say the black hole is a bit bigger. And it eats some mass on one side of the earth - now there is an imbalance. There is more mass on the other side. So the forces will cause it to slow down more than it otherwise would.
When it finally settles down enough to make a cave, it will "swing" as much as it can. But each swing can not be any higher than the one before. Over time, with random atoms falling into the cave it, it will come to rest at the exact center.
There is no force on the black hole, so if it moved at all it would crash into the wall. Only when it actually ate some of the wall would it turn around. So each swing would eat more and more.
But with a bit of thought, it occurs to me that the iron at the center of the earth is only 'sold' dues to the intense pressure it is under (360 gigapascals). Relieve the pressure and you've got molten iron (at 5,700 degrees K).
http://en.wikipedia.org/wiki/Inner_core#Temperature
A Sunday wikipedia-ing...
The physics is different down deep, as we've found to our chagrin in other circumstance...
I never realized that.
... Can I have one as a pet?
1) we are here
2) that we're savages who have nuclear weapons and who are perfectly willing to use them on each other.
3) we're going to develop interstellar spacecraft
I think many civilizations worthy of the name would want to bomb us before we get out of Earth's gravity well en masse.
They are definitely scalable, but they are certainly no Dr. Device
In that vein I'd like to say that killing all life currently within 6500 kilometers of the Earth's center of mass is, in some ways, harder than simply destroying the Earth.
Take for instance the humble Water Bear they range from microscopic to a millimeter in size and can survive being frozen to within a degree of 0k and have survived 10 days in hard vacuum, during which time eggs were laid and hatched. It seems likely that any of the various "disassemble Earth" methods would fail to kill them. Similarly any chunk of Earth with a sealed ecosystem, like some caves, might continue to keep going indefinitely.
Killing everything might require vaporizing the planet in the sun or eating it with a black hole.
EDIT: really what it comes down to is how many 9s of biocide do you want. Ramming Luna into the Earth might accomplish 7 or 8 9s, but if you want to kill everything, 100% of life from LEO down not just practically everything it's going to take more finesse than that.
In terms of Archimedes:
"Give me a place to stand, and I will move the Earth", proclaimed Archimedes upon discovering the principles of leverage. Unfortunately, that place needs to be immovable, which is impossible. Also, what he didn't specify is that he also needs an equally immovable fulcrum - equally impossible - and a lever of stunning length which is unbreakable. Hah! Nice try, Archimedes.
No, it merely needs to be of sufficient mass. As a practical strategy for moving the earth, this would clearly be infeasible, but, strictly speaking, I don't think that it is impossible.
Did you read the article?
I read it the last couple times it was posted here.
That isn't what the article is about.
I mean, if you've got 25,000,000,000,000 tonnes of antimatter just laying around in a warehouse somewhere, I don't care if you want to kill me and destroy the earth- I want to shake your hand.
In the context of this article such people would be termed either "wannabes" or "lacking in vision".
Moving Jupiter via fusion candle is vision, RISC is optimization.
I don't know what the original title was, but I do know the contents of the article, in which the author makes it abundantly (and if you read everything in that section, repeatedly) clear that he is aware of the usual use of the phrase "destroy the Earth". It is not a "strawman", it is the topic of the essay. If anyone is erecting a strawman, it is those who refuse to deal with the text on its own terms and insist on forcing their personal definitions of various terms onto the text, despite clear, repeated disclaimers, and the obvious fact that the entire idea of the essay is predicated on the author's definition.
Maybe you were just reacting to this title, but this has been linked in a few places and every time it seems this reminder needs to be given, so even if you are now satisfied by the new title, this still needs saying. An author is free to choose their topic and the precise meaning of some of the terms they are using; nothing else makes any sense.
That's like the proposal to achieve AI by simulating a whole human body down to the molecules. It sounds clever to college freshmen, but it really just shows people are ignorant of the orders of magnitude of what they're discussing.