# How can I calculate how the debris of an object ripped apart at the Roche limit will spread out?

Let's say I have a moon orbiting a planet at a distance $d$. Eventually, $d leq d_R$, where $d_R$ is the Roche limit of the moon-planet system. I can figure out the mass of both bodies by experiment, as well as their radii, and thus their density (which is how I can calculate the Roche limit).

I'm curious as to how the debris will spread out, though, once the moon is ripped apart. Can I calculate the inner and outer radii of the newly formed ring, based on what I know? Or is there not a direct relationship between these radii and the initial conditions?

I think there are two key aspects to the answer. 1) Solid/rocky bodies should tend to collide before they reach the Roche limit. 2) When gaseous bodies reach the Roche limit (and undergo 'Roche-Lobe Overflow'), the dynamics are basically those of test-bodies and are fairly straightforward and well understood from binary stellar dynamics. To expand on both:

1) Rocky Roche Limit. If you are thinking about a gaseous donor (the object being disrupted), then this is an irrelevant point, but It sounds like rocky is what you had in mind. To an order of magnitude, the Roche limit is the same as the Hill sphere, or the Tidal Radius (e.g. Rees 1988) --- which is simply the radius at which the density of the donor equals the average density of the primary in a sphere of that radius:

$$R_t^3/M approx r^3/m ightarrow R_t approx r left( M/m ight)^{1/3}$$

Rocky material varies very little in density (e.g. Iron meteorites are only about twice as dense as chrondritic ones), which means that the densities will only match very near the radius of the primary. The tidal bulge in the secondary (donor) also makes it easier for the objects to collide before meeting this criteria.

e.g.

2) Gaseous Roche Lobe Overflow. Basically every text on stars and star systems will have a section on mass transferring binaries which will describe the dynamics of mass transfer (this PDF is by Philipp Podsiadlowski who is a wizard of the field). In the type of situation you are describing, like in (semi-)stable binary systems, it is a very gradual process where material is slowly syphoned off of the donor. This material can either form an accretion disk (high angular momentum material) and gradually accrete onto the primary, or directly impact the primary (low angular momentum material).

e.g.

## Japan tsunami debris spreading across Pacific

HONOLULU - Lumber, boats and other debris ripped from Japanese coastal towns by tsunamis last year have spread across some 3,000 miles (4,828 kilometers) of the northern Pacific, where they could wash ashore on the U.S. west coast as early as a year from now.

The National Oceanic and Atmospheric Administration estimated the first bits of tsunami debris will make landfall soon on small atolls northwest of the main Hawaiian Islands. Other pieces were expected to reach the coasts of Oregon, Washington state, Alaska and Canada between March 2013 and March 2014.

NOAA's tsunami marine debris coordinator, Ruth Yender, told an online news conference Tuesday that agency workers were boarding Coast Guard flights that patrol the Hawaiian archipelago. NOAA also asked scientists stationed at Midway and other atolls to look for the debris.

Debris initially collected in a thick mass in the ocean after tsunamis dragged homes, boats, cars and other parts of daily life from coastal towns out to sea. Most likely sank not far from Japan's eastern coast.

In September, a Russian training ship spotted a refrigerator, a television set and other appliances west of Hawaii. By now, the debris has likely drifted so far apart that only one object can be seen at a time, said Nikolai Maximenko, a University of Hawaii researcher and ocean currents expert.

One to 2 million tons of debris remain in the ocean, but only 1 to 5 percent of that could reach Hawaii, Alaska, Oregon, Washington state and Canada's British Columbia, Maximenko said. The tsunamis generated a total of 20 million to 25 million tons of debris, including what was left on land.

Yender said that so far, no debris confirmed to be from the tsunamis has landed on U.S, shores, including large buoys suspected to be from Japanese oyster farms found in Alaska last year. The buoys would have had to travel faster than currents to get to Alaska at that time if they were set loose by the March 11 tsunamis.

Yender said there is little chance of any debris being contaminated by radiation. The debris came from a large swath of Japan's northeastern coast, not only near the tsunami-damaged nuclear power plant in Fukushima. Further, it was dragged out to sea with the tsunamis, not while the Fukushima plant experienced multiple meltdowns.

## Airport FOD Prevention

One of the biggest battles that airfield managers and operators face is FOD prevention. FOD is a well-known acronym that stands for Foreign Object Debris or Foreign Object Damage. FOD is presented in many ways into a flight line. One of the most common ways is vehicle traffic entering from outside the airfield. These vehicles can consist of fuel trucks, maintenance trucks, crew vehicles and many more. The vehicle’s tires trap debris such as rocks, mud, vegetation, hardware (such as nuts, bolts, screws) and stones in the treads of the tire and potentially release them on the flight line. The released debris then poses significant safety concerns to property, equipment and personnel once introduced to the airfield. With the common effects of jet blast, rotor wash and propeller blast these items can be sent airborne with tremendous velocity and damage other aircraft, equipment, buildings and very easy harm or kill personnel. The other end of this danger is on the intake side. Even a small amount of debris sucked through the intake of a jet engine can damage the turbine blades and other sensitive components of the engine. The cost to repair an engine damaged from FOD can easily cost in excess of \$1 million.

### FOD Prevention Products & Practices

There are standard FOD prevention protocols that are typically focused on finding and clearing debris that is already on the airfield. Magnetic bars are attached to vehicles which are used to capture metalic debris. FOD Boss is a popular tool that uses ground friction to pick up small items left from vehicle traffic on a flight line. There are also FOD radar systems that scan the ground looking for anomalies that may indicate debris to be investigated. (Whether an airfield relies on a FOD sweeper, FOD walks or FOD radar, the risk is already present in that you are addressing debris that has been introduced from vehicles which has made its way to the flight line.)

### Preventative FOD Management

FODS mats work to prevent any material from entering the airfield by clearing the tire treads prior to entry onto the flight line. The blunt nosed pyramids on the FODS mats are an engineered solution designed to manipulate the treads of the tires to release any trapped debris onto the mat itself allowing the vehicle to be cleared of any materials prior to entry. The FOD material that is released from the tire is then captured onto the mat and not accessible to successive vehicles that travel across the mats. This material is recoverable by airfield operations staff to catalog and be able to identify consistent sources of FOD debris for further protocol to address FOD root causes. This process of FOD prevention is a tremendous solution for any private, commercial or military airfield.

### Vehicle FOD High Risk Zone

Vehicles travel along external roads and highways and then enter the airfield access roads as they travel to the apron. Access Roads often cross aircraft taxiways which may be marked with a "zipper." This intersection of vehicles and aircraft traffic poses a risk for vehicles to track external FOD directly into the path of aircraft. FOD Prevention Plans typically rely on manual inspections to prevent vehicle FOD.

Vehicle FOD High Risk Zone Shown In Red.

### FOD Prevention Mat Durability

FODS mats do not change over time with vehicle passes and remain effective for many years of FOD prevention. FODS mats are secured directly to concrete and asphalt roadways by simple sleeved anchor bolts which hold the mats steady during vehicle travel. Each pyramid has a crush rating of over 20,000 pounds. This allows vehicles of any size to travel across the mats regardless of how small or large and clear FOD debris from any size tire tread without any loss of vehicle control or impact on driver safety.

## How can I calculate how the debris of an object ripped apart at the Roche limit will spread out? - Astronomy

Destroying the Earth is harder than you may have been led to believe.

You've seen the action movies where the bad guy threatens to destroy the Earth. You've heard people on the news claiming that the next nuclear war or cutting down rainforests or persisting in releasing hideous quantities of pollution into the atmosphere threatens to end the world.

The Earth is built to last. It is a 4,550,000,000-year-old, 5,973,600,000,000,000,000,000-tonne ball of iron. It has taken more devastating asteroid hits in its lifetime than you've had hot dinners, and lo, it still orbits merrily. So my first piece of advice to you, dear would-be Earth-destroyer, is: do NOT think this will be easy.

This is not a guide for wusses whose aim is merely to wipe out humanity. I can in no way guarantee the complete extinction of the human race via any of these methods, real or imaginary. Humanity is wily and resourceful, and many of the methods outlined below will take many years to even become available, let alone implement, by which time mankind may well have spread to other planets indeed, other star systems. If total human genocide is your ultimate goal, you are reading the wrong document. There are far more efficient ways of doing this, many which are available and feasible RIGHT NOW. Nor is this a guide for those wanting to annihilate everything from single-celled life upwards, render Earth uninhabitable or simply conquer it. These are trivial goals in comparison.

This is a guide for those who do not want the Earth to be there anymore.

### Mission statement

For the purposes of what I hope to be a technically and scientifically accurate document, I will define our goal thus: by any means necessary, to change the Earth into something other than a planet or a dwarf planet.

The International Astronomical Union defines a planet as:

1. is in orbit around the Sun
2. has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
3. has cleared the neighbourhood around its orbit
1. is in orbit around the Sun
2. has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape,
3. has not cleared the neighbourhood around its orbit, and
4. is not a satellite.

Since "celestial body" does not include the Earth, we shall assume for the sake of pedantry that the IAU meant to say "astronomical body".

These definitions instantly suggest some very simple ways of stripping the Earth of its planethood, such as hurling it into interstellar space, moving it into orbit around a gas giant, or moving it into a solar orbit whose neighbourhood is not cleared (the main asteroid belt being the most obvious choice). A slightly less obvious method would be redefining "planet" not to include the Earth. Naturally, these methods (the latter of which is by far the most feasible method listed in this document) will not be considered to count - redefining something doesn't make it go away.

We are left, therefore, with the challenge of significantly altering the Earth's physical structure, or else reducing its mass such that it can maintain a shape which is not round. For example: blowing it up, turning it into a dust cloud, merging it with a larger body, et cetera.

### Methods for destroying the Earth

To be listed here, a method must actually work. That is, according to current scientific understanding, it must be possible for the Earth to actually be destroyed by this method, however improbable or impractical it may be.

Methods are ranked in order of feasibility. Feasibility ratings are given out of ten - these are based primarily on my gut instinct and do not reflect actual mathematical probabilities in any way.

Several methods involve moving the Earth a considerable distance off its usual orbital track. This is an essay in itself, so a separate page has been created for it.

#### Annihilated by an equivalent quantity of antimatter

You will need: An entire planet Earth made from antimatter

Antimatter - the most explosive substance possible - can be manufactured in small quantities using any large particle accelerator, but this will take preposterous amounts of time to produce the required amounts. If you can create the appropriate machinery, it may be possible to find or scrape together an approximately Earth-sized chunk of rock and simply to "flip" it all through a fourth spacial dimension, turning it all to antimatter at once.

Method: Once you've generated your antimatter, probably in space, just launch it en masse towards Earth. The resulting release of energy (obeying Einstein's famous mass-energy equation, E=mc 2 ) is equivalent to the amount the Sun outputs in some 89 million years. Alternatively, if your matter-flipping machinery is a little more flexible, turn half the Earth into antimatter (say, the Western Hemisphere) and watch the fireworks.

Earth's final resting place: When matter and antimatter collide, they completely annihilate each other, leaving nothing but energy. All that would be left of Earth is a scintillating flash of light expanding across space forever. This method is one of the most permanent and total on this list, as the very matter which makes up the Earth ceases to exist, making it virtually impossible to even reassemble the planet afterwards.

Feasibility rating: 2/10. It IS possible to create antimatter, so, technically, this method IS possible. But since the proposed matter-to-antimatter flipping machine is probably complete science fiction, we're looking at stupid, stupid amounts of time to pull this off.

Comments: With a significantly smaller amount of antimatter, you can simply blow the Earth up - see later.

Source: This method suggested by Thomas Wootten.

#### Fissioned

You will need: a universal fission machine (e.g. a particle accelerator), an unimaginable amount of energy

Method: Take every single atom on planet Earth and individually split each one down to become hydrogen and helium. Fissioning heavier elements to become hydrogen and helium is the opposite of the self-sustaining reaction that powers the Sun: it requires you to put energy in which is why the energy requirements here are so vast.

Earth's final resting place: While Jupiter, Saturn, Uranus and Neptune are gas giants composed primarily of hydrogen and helium, they are massive enough to actually hold on to their tenuous atmospheres. The Earth is not the gases would dissipate away. You'd get a wispy mess of gas where there should have been a planet.

Feasibility rating: 2/10. Technically possible, but, again, hopelessly, mind-bogglingly inefficient and time-consuming. You're looking at billions of years minimum, folks.

Source: This method suggested by John Routledge.

#### Sucked into a microscopic black hole

You will need: a microscopic black hole.

Note that black holes are not eternal, they evaporate due to Hawking radiation. For your average black hole this takes an unimaginable amount of time, but for really small ones it could happen almost instantaneously, as evaporation time is dependent on mass. Therefore your microscopic black hole must have greater than a certain threshold mass, roughly equal to the mass of Mount Everest.

Creating a microscopic black hole is tricky, since one needs a reasonable amount of neutronium, but may possibly be achievable by jamming large numbers of atomic nuclei together until they stick. This is left as an exercise to the reader.

Method: simply place your black hole on the surface of the Earth and wait. Black holes are of such high density that they pass through ordinary matter like a stone through the air. The black hole will plummet through the ground, eating its way to the centre of the Earth and all the way through to the other side: then, it'll oscillate back, over and over like a matter-absorbing pendulum. Eventually it will come to rest at the core, having absorbed enough matter to slow it down. Then you just need to wait, while it sits and consumes matter until the whole Earth is gone.

Earth's final resting place: a singularity with a radius of about nine millimetres, which will then proceed to happily orbit the Sun as normal.

Feasibility rating: 3/10. Highly, highly unlikely. But not impossible.

Comments: Hmm. The problem is, the microscopic black hole would still be in hydrostatic equilibrium, so it would still qualify as a planet according to the IAU!

Source: The Dark Side Of The Sun, by Terry Pratchett. It is true that the microscopic black hole idea is an age-old science fiction mainstay which predates Pratchett by a long time, he was my original source for the idea, so that's what I'm putting.

#### Cooked in a solar oven

You will need: Means for focusing a good few percent of the Sun's energy output directly on the Earth.

What I'm talking about here is: mirrors, and lots of them. Intercept several decent sized asteroids for raw materials and start cranking out kilometre-square sheets of lightweight reflective material (aluminised mylar, aluminium foil, nickel foil, iron foil or whatever you can scrape together). They need to be capable of changing focus direction at will because, while a few may be placed at the Earth-Sun system's Lagrangian points, the vast majority cannot be stationary in space and the relative positions of the Earth and Sun will be shifting as time passes, so attach a few manoeuvering thrusters and a communications and navigation system to each sheet.

Preliminary calculations suggest you would need roughly two trillion square kilometres of mirror.

Method: Command your focusing array to concentrate as much solar energy as you can directly on the Earth - perhaps on its core, perhaps at a point on its surface. So the theory goes, this will cause the Earth to generally increase in temperature until it completely boils away, becoming a gas cloud.

A variation on this method involves turning the Sun into a gigantic hydrogen gas laser.

Earth's final resting place: A gas cloud.

Feasibility rating: 3/10. The major problem here is: What's to stop the matter cooling and becoming a planet again? In fact, once the top layer of planet becomes gaseous, what would compel it to vent into space rather than remaining on the surface, absorbing more heat and preventing the lower layers from even being heated? Unless the amount of heat put in was really immense, all you'd get is a gas planet at best, and a temporary one at that. Moving the Earth towards the Sun (see later) is likely to be a far more viable method.

Source: This method suggested by Sean Timpa.

#### Overspun

You will need: some means of accelerating the Earth's rotation.

Accelerating the Earth's rotation is a rather different matter from moving it. External interactions with asteroids might move the Earth but won't have a significant effect on how fast it spins. And certainly it won't spin the Earth fast enough. You need to build rockets or railguns at the Equator, all facing West. Or perhaps something more exotic.

Method: The theory is, if you spin the Earth fast enough, it'll fly apart as the bits at the Equator start moving fast enough to overcome gravity. In theory, one revolution every 84 minutes should do it - even slower would be fine, in fact, as the Earth would become flatter and thus more prone to breaking apart as you spun it faster.

Feasibility rating: 4/10. This could be done - there is a definite upper limit on how fast something like the Earth can spin before it breaks apart. However, spinning a planet is even more difficult than moving it. It's not as simple as attaching rockets pointing in each direction to each side.

Source: This method suggested by Matthew Wakeling.

#### Blown up

You will need: 25,000,000,000,000 tonnes of antimatter.

Method: This method involves detonating a bomb so big that it blasts the Earth to pieces.

This, to say the least, requires a big bomb. All the explosives mankind has ever created, nuclear or non-, gathered together and detonated simultaneously, would make a significant crater and wreck the planet's ecosystem, but barely scratch the surface of the planet. There is evidence that in the past, asteroids have hit the Earth with the explosive yield of five billion Hiroshima bombs - and such evidence is difficult to find. It is, in short, insanely difficult to significantly alter the Earth's structure with explosives. This is not to mention the gravity problem. Just because you blasted the Earth apart doesn't mean you blasted it apart for good. If you don't blast it hard enough, the pieces will fall back together again under mutual gravitational attraction, and Earth, like the liquid metal Terminator, will reform from its shattered shards. You have to blow the Earth up hard enough to overcome that attraction.

If you do the lengthy calculations you find that to liberate that much energy is equivalent to the complete annihilation of around 1,246,400,000,000 tonnes of antimatter. That's assuming zero energy loss to heat, neutrinos and radiation, which is unlikely to be the case in reality: You'll probably need to up the dose by at least a factor of twenty. Once you've generated your antimatter, probably in space, just launch it en masse towards Earth. The resulting release of energy (obeying Einstein's famous mass-energy equation, E=mc 2 ) should be sufficient to split the Earth into a thousand pieces.

Greg Bear's novel, "The Forge Of God", contains an interesting refinement of this technique. Here, the antagonist instead generates antimatter in the form of a "slug" of anti-neutronium - superdense material massing a billion kilograms per cubic centimetre. This is fired into the Earth's core. Neutronium passes through ordinary matter as easily as a ball flies through the air, so the anti-neutronium slug doesn't annihilate immediately rather, it builds up a protective sheath of plasma around it as it plunges downwards towards the Earth's core. It's then followed up by a slug of regular neutronium, which also falls into the core, at a time calculated to meet the first slug head-on at the exact centre of the Earth, where they annihilate themselves, and soon afterwards, the Earth itself. Highly space-efficient, and with the added bonus of all the energy being released at the Earth's core, where it can do the most damage. In the book, the antagonists simultaneously detonate nuclear warheads in certain oceanic trenches, to weaken the crust and allow the planet to be blown apart more easily.

Rearranging Earth into two planets - which, provisionally, is sufficient according to my current criteria - would take slightly less energy, but considerably more finesse.

Earth's final resting place: A second asteroid belt around the Sun.

Comments: trembling writes, "I still think that antimatter is crazy s**t, i.e. wouldn't want it on my flapjacks". Charles MacGee presents a very well-realised alternate source of explosives in his blog this method involves generating the explosive energy by fusing together the lighter elements of Earth's mantle (magnesium and oxygen). Of course, this would involve the invention of an efficient magnesium fusion bomb. And then turning all of the Earth's mantle into bombs. How implausible! Well. Implausibility is a relative thing.

Feasibility rating: 4/10. Just about slightly possible.

#### Sucked into a giant black hole

You will need: a black hole, extremely powerful rocket engines, and, optionally, a large rocky planetary body. The nearest black hole to our planet is 1600 light years from Earth in the direction of Sagittarius, orbiting V4641.

Method: after locating your black hole, you need get it and the Earth together. This is likely to be the most time-consuming part of this plan. There are two methods, moving Earth or moving the black hole, though for best results you'd most likely move both at once. See the Guide to moving Earth for details on how to move the Earth. Several of the methods listed can be applied to the black hole too, though obviously not all of them, since it is impossible to physically touch the black hole, let alone build rockets on it.

Earth's final resting place: part of the mass of the black hole.

Feasibility rating: 6/10. Very difficult, but definitely possible.

Sources: The Hitch Hiker's Guide To The Galaxy, by Douglas Adams space.com.

Comments: It's clear that dropping the Earth into a singularity is massive overkill. A reasonably strong gravitational field, such as might be associated with any body between Jupiter and a neutron star, would be sufficient to rip the Earth apart via tidal forces. These possibilities are dealt with further down.

#### Meticulously and systematically deconstructed

You will need: a mass driver. A mass driver is a sort of oversized electromagnetic railgun, which was once proposed as a way of getting mined materials back from the Moon to Earth - basically, you just load it into the driver and fire it upwards in roughly the right direction. Your design should be powerful enough to hit escape velocity of 11 kilometres per second.

At a million tonnes of mass driven out of the Earth's gravity well per second, this would take 189,000,000 years. One mass driver would suffice, but ideally, lots (i.e. trillions) would be employed simultaneously. Alternatively you could use space elevators or conventional rockets.

Method: Basically, what we're going to do here is dig up the Earth, a big chunk at a time, and boost the whole lot of it into orbit. Yes. All six sextillion tonnes of it.

We will ignore atmospheric considerations. Compared with the extra energy needed to overcome air friction, it would be a relatively trivial step to completely burn away the Earth's atmosphere before beginning the process. Even with this done, however, this method would require a - let me emphasize this - titanic quantity of energy to carry out. Building a Dyson sphere ain't gonna cut it here. (Note: Actually, it would. But if you have the technology to build a Dyson sphere, why are you reading this?)

Earth's final resting place: Many tiny pieces, some dropped into the Sun, the remainder scattered across the rest of the Solar System.

Feasibility rating: 6/10. If we wanted to and were willing to devote resources to it, we could start this process RIGHT NOW. Indeed, what with all the gunk left in orbit, on the Moon and heading out into space, we already have done.

Source: this method arose when Joe Baldwin and I knocked our heads together by accident.

Comment: Could this also be achieved with a titanic, solar-powered electromagnet?

#### Pulverized by impact with blunt instrument

You will need: a big heavy rock, something with a bit of a swing to it. perhaps Mars.

Method: Essentially, anything can be destroyed if you hit it hard enough. ANYTHING. The concept is simple: find a really, really big asteroid or planet, accelerate it up to some dazzling speed, and smash it into Earth, preferably head-on but whatever you can manage. The result: an absolutely spectacular collision, resulting hopefully in Earth (and, most likely, our "cue ball" too) being pulverized out of existence - smashed into any number of large pieces which if the collision is hard enough should have enough energy to overcome their mutual gravity and drift away forever, never to coagulate back into a planet again.

A brief analysis of the size of the object required can be found here. Falling at the minimal impact velocity of 11 kilometres per second and assuming zero energy loss to heat and other energy forms, the cue ball would have to have roughly 60% of the mass of the Earth. Mars, the next planet out, "weighs" in at about 11% of Earth's mass, while Venus, the next planet in and also the nearest to Earth, has about 81%. Assuming that we would fire our cue ball into Earth at much greater than 11km/s (I'm thinking more like 50km/s), either of these would make great possibilities.

Obviously a smaller rock would do the job, you just need to fire it faster. Taking mass dilation into account, a 5,000,000,000,000-tonne asteroid at 90% of light speed would do just as well. See the Guide to moving Earth for useful information on manoeuvring big hunks of rock across interplanetary distances. For smaller chunks, there are more options - a Bussard Ramjet (scoop up interstellar hydrogen at the front and fire it out the back as propellant) is one of the most technically feasible as of right now. Of course, a run-up would be needed.

Earth's final resting place: a variety of roughly Moon-sized chunks of rock, scattered haphazardly across the greater Solar System.

Feasibility rating: 7/10. Pretty plausible.

Source: This method suggested by Andy Kirkpatrick

Comments: Earth is believed to have been hit by an object the size of Mars at some point in the distant past before its surface cooled. This titanic collision resulted in. the Moon. You can download a simulated video of the impact from this page. While the Mars-sized object in question obviously didn't hit Earth nearly as hard as we're proposing with this method, this does serve as a proof of concept.

Many useful planetary facts can be found here.

#### Hurled into the Sun

Method: Hurl the Earth into the Sun, where it will be rapidly melted and then vaporized by the Sun's heat.

Sending Earth on a collision course with the Sun is not as easy as one might think. Contrary to popular opinion, Earth's orbit is not "unstable" and Earth will not begin to spiral into the Sun if we give it the slightest of nudges (otherwise, you can bet it would have happened already). It's surprisingly easy to end up with Earth in a loopy elliptical orbit which merely roasts it for four months in every eight. Careful planning will be needed to avoid this.

There is at least one way of moving the Sun itself. Although the Sun is much bigger, and the Earth would be carried along by its gravity, it might be possible accelerate the Sun hard enough that it eventually catches the orbiting Earth, with the same net result.

Earth's final resting place: a small globule of vaporized iron sinking slowly into the heart of the Sun.

Comments: As far as energy changes are concerned, this method is inferior to the next one.

This method is essentially a variation on the Solar Oven method listed above, wherein you bring the Sun to the Earth (in a manner of speaking).

Feasibility rating: 9/10. Impossible at our current technological level, but will be possible one day, I'm certain. In the meantime, may happen by freak accident if something comes out of nowhere and randomly knocks Earth in precisely the right direction.

#### Ripped apart by tidal forces

Method: When something (like a planet) orbits something else (like the Sun), the closer in it is, the faster it orbits. Mercury, the closest planet to the Sun, moves faster along its path than Earth, which in turn moves faster than Neptune, the furthest planet.

Now, if you move Earth close enough to the Sun, you'll find that it's close enough that the side of the Earth facing the Sun wants to orbit the Sun faster than the side pointing away from it. That causes a strain. Move Earth close enough, within an imaginary boundary called the Roche Limit, and the strain will be great enough to literally tear the planet Earth apart. It'll form one or more rings, much like the rings around Saturn (in fact this may be exactly where Saturn's rings came from). So our method? Move the Earth to within the Sun's Roche limit. Or, better, move it out, to Jupiter.

Moving the Earth out to Jupiter is much the same as moving the Earth in towards the Sun, the most obvious difference being your choice of vectors. However, there is another important consideration, and that is energy. It takes energy to raise or lower an object through a gravity field it would take energy to propel the Earth into the Sun and it would take energy to propel it into Jupiter. When you do the calculations, Jupiter is actually rather preferable it takes about 38% less energy.

Alternatively, it may be simpler to move Jupiter to Earth. The theory works like this: build a massive free-standing tower or "candle", with its lower end deep inside Jupiter's depths and its upper end pointing into space. Put machinery inside the tower to pull hydrogen and helium gases in as fuel, through ports in the middle section, and vent these elements out through fusion thrusters at the top and bottom. The tower is called a "candle" because it burns at both ends, see? Now: the flame directed downwards into Jupiter serves to keep the tower afloat (although some secondary thrusters would be needed to also keep it stable and upright). But this lower flame has no direct effect on the Jupiter/candle system as a whole, because all the thrust from the flame is absorbed by Jupiter itself. The two objects are locked together, as if the candle is balanced on a spring or something. The top flame, therefore, can be used to push both the candle and Jupiter along. The top flame pushes the candle which pushes the planet. This is a little unorthodox, and it only works on gas giants, but as means for moving planets it's at least as plausible as the mass-driver and gravity-assist methods described on the earthmoving page.

Earth's final resting place: lumps of heavy elements, torn apart, sinking into the massive cloud layers of Jupiter, never to be seen again.

Feasibility rating: 9/10. As before, impossible at our current technological level, but will be possible one day, and in the meantime, may happen by freak accident if something comes out of nowhere and randomly knocks Earth in precisely the right direction.

Source: Mitchell Porter suggested this method. Daniel T. Staal clued me in on the fusion candle technique, which he got from this Shlock Mercenary comic, which in turn was inspired by the novel "A World Out Of Time" by Larry Niven.

### Fall-back methods

If your best efforts fail, you needn't fret. Nothing lasts forever the Earth is, ultimately, doomed, whatever you do. The following are ways the Earth could naturally come to an end. (They're no longer in feasibility order since it reads better this way.) Bear in mind that none of these will require any activity on your part to be successful.

#### Total existence failure

You will need: nothing

Method: No method. Simply sit back and twiddle your thumbs as, completely by chance, all two hundred thousand million million million million billion trillion atoms making up the planet Earth suddenly, simultaneously and spontaneously cease to exist. Note: the odds against this actually ever occuring are considerably greater than a googolplex (10 10 100 ) to one. Failing this, some kind of arcane (read: scientifically laughable) probability-manipulation device may be employed.

Current feasibility rating: 0/10. Even if you look at the significantly greater probability of the Earth randomly rearranging itself into separate two planets, this is utter, utter rubbish.

Source: Life, The Universe And Everything, by Douglas Adams.

#### Written off in the backlash from a stellar collision

You will need: another star. White dwarf is good, but we're not fussy.

Method: Crash your star into the Sun.

The interactions between the two stars in this very violent stellar event will cause more fusion to occur inside the Sun than normally does in 100,000,000 years. The result is not unlike a supernova explosion, though slower - a staggering amount of matter and energy is released outwards, burning the Earth to a crisp and firing it into interstellar space at best, completely incinerating it at worst.

Earth's final resting place: burnt pieces.

Feasibility rating: 4/10. This is listed under natural methods because there is absolutely no way you can move a star. Well, there are ways and means, but if you can move a star, why not move the Earth into that star? And the chances of this happening - even considering that in two billion years' time the Milky Way is going to collide with Andromeda - are very, very slim. Calculations suggest that the number of actual stellar collisions that are likely to occur in that exchange will be SIX. Six chances in about a hundred billion.

Hmm. That's actually pretty high for this list. Make it 5/10.

Source: This method suggested by Eric Thompson.

#### Swallowed up as the Sun enters red giant stage

You will need: patience

Method: Simply wait for roughly 5,000,000,000 years. During its natural progress along the Main Sequence, the Sun will exhaust its initial reserves of hydrogen fuel and expand into a red giant star - swallowing up Mercury, Venus, Earth and Mars in the process.

Earth's final resting place: Boiling red iron in the heart of the Sun.

Feasibility rating: 8/10. It is possible that the increasing solar wind combined with the Sun's decreasing mass will result in the Earth gradually moving out to a wider, cooler, safe orbit, but most recent work suggests that this method is sound.

#### Crunched

You will need: considerably more patience

Method: Our universe is rapidly expanding in all directions. It will likely continue to do so for a very, very long time. After that time, if the density of matter in the universe is greater than a certain critical value, the universe will slow to a stop due to mutual gravitational attraction, and, roughly 42,000,000,000 years from now, collapse back together again, in a reversal of the Big Bang called the Big Crunch. Conditions during the Big Crunch will be similar to those during the Big Bang: mind-boggling heat, matter ripped to subatomic particles, fundamental forces such as gravitation and electromagnetism merging back together, that sort of thing. Yes, Earth would be destroyed. So would the rest of the universe. A tiny sphere of iron stands little chance against conditions like that.

Earth's final resting place: Quark-gluon plasma? Pure energy? Part of the next universe?

Feasibility rating: 8/10. Plausible. Assumes that the Big Crunch will actually occur at all, which is currently in question.

Source: Nick Snell suggested this method.

#### Torn a new one

You will need: about half as much patience

Method: Recent experimental results seem to show that the expansion of the universe is not slowing as one might imagine it would. In fact, the expansion is accelerating. It's a bit early to say with confidence why this is happening, though phrases like "dark matter" and "phantom energy" pop up pretty frequently, but anyway, it's conjectured that if the ratio w of dark energy pressure to dark energy density in the universe is around -3/2 (buh?), then something of the order of 20,000,000,000 years from now, the universe would expand, accelerating in its expansion until it was ripped apart at the seams. To quote Wikipedia's entry: "First the galaxies would be separated from each other, then gravity would be too weak to hold individual galaxies together. Approximately three months before the end, solar systems will be gravitationally unbound. In the last minutes, stars and planets will come apart, and atoms will be destroyed a fraction of a second before the end of time." Cool, eh?

Earth's final resting place: HAH! If I knew that, I wouldn't need aftershave.

Feasibility rating: 8/10. Likely. Assumes the Big Rip theory is correct, which it probably is, but might not be.

Source: a theory proposed by Robert R. Caldwell, Marc Kamionkowski, and Nevin N. Weinberg in February 2003. Read it here (PDF warning! Also, dense, difficult physics!). Brought to my attention by Jonah Safar and nanite.

#### Decayed

You will need: all-surpassing patience

Method: If the Big Crunch doesn't happen, and the Big Rip doesn't happen either, then we come back to the third option: the Big Chill. For this, the universe will just expand, forever. The laws of thermodynamics take over. Every galaxy becomes isolated from its neighbours. All the stars burn out. Everything gets colder until it's all the same temperature. And after that, nothing ever changes in the universe. For eternity.

A lot can happen in an eternity. Protons, for example, while incredibly stable, are believed to eventually decay like any other particle. So simply wait for a period of time of the order of 1,000,000,000,000,000,000,000,000,000,000,000,000 years, and roughly half of the constituent particles of Earth will have decayed into positrons and pions. If that's still too much like a planet for you, you could wait for another 10 36 years, leaving only a quarter of the original Earth. Or wait even longer. Eventually there will be as little of Earth left as you wish.

Earth's final resting place: Miscellaneous positrons and gamma radiation (pions decay almost instantly into gamma ray photons) scattered thinly across the entire universe.

Comments: It's interesting to compare this method with the one right at the top (total existence failure). What we are essentially doing here is almost exactly the same thing, only instead of expecting every particle to disappear at once, we are waiting patiently for a significant proportion of them to disappear, one at a time, over the course of an unimaginable period of time. Essentially we've come full circle. The scientific theories involved are the same, it's just the time scale being considered which changes the feasibility rating from "astoundingly improbable" to:

Feasibility rating: 9/10. If all else fails, this one would be essentially unstoppable.

Source: This method suggested by Joseph Verock.

Bobby Florea suggested to me the intriguing idea that "Evolve an Earth-destructive form of life" might count as an additional natural method for destroying the Earth. Given that we are here, and you are reading this article, it seems like this is the plan which is furthest along at the moment. Of course, this could simply be taken to be "step zero" in all the artificial methods listed above, and not an original method at all.

### Other, less scientifically probable ways that Earth could be destroyed

Here are kept the methods which sound good on paper, but might not necessarily actually work, because the science they are based on isn't necessarily valid. Read on.

#### Whipped by a cosmic string

You will need: a cosmic string and a whole lotta luck

Method: Cosmic strings are hypothetical 1-dimensional defects in spacetime, left over from earlier phases of the universe, somewhat like cracks in ice. They are potentially universe-spanning objects, thinner than a proton but with unimaginable density - one Earth mass per 1600m of length! All you need to do is get a cosmic string near Earth, and it'll be torn apart, shredded, and sucked in. Probably the entire rest of the solar system would be too.

Earth's final resting place: String.

Feasibility rating: 1/10. Mind-bogglingly unlikely. Even if cosmic strings do exist, which they may not, there are probably only about ten of them left in the ENTIRE UNIVERSE. And they can't be steered, unless you have godlike powers, in which case you might as well chuck the Earth into the Sun and have done with it, so you're relying entirely on luck. This. Will. Never. Happen.

Source: this method suggested by Dan Winston.

#### Gobbled up by strangelets

Strange matter is a phase of matter which is even more dense than neutronium. It's theorized to form in particularly massive neutron stars when the pressure inside them becomes just too great for even neutronium to exist: the individual neutrons comprising the neutronium are instead broken down into strange quarks. The neutron star then becomes a "strange star" which is essentially a single gigantic nucleon.

Some theories suggest that a lump of strange matter ("strangelet") could remain stable outside of the intense pressure which created it. This would make it theoretically possible for strangelets of sizes all the way down to the atomic scale to exist. It's further theorized that the gravitational field of a microscopic strangelet would be enough to gobble up anything it comes in contact with, turning it into more strange matter.

Method: Hijack control of a particle accelerator. I suggest the Relativistic Heavy Ion Collider in Brookhaven National Laboratory, Long Island, New York. Use the RHIC to create a strangelet large enough to remain stable. Once created, your job is done: relax and wait as the strangelet plummets through to the Earth's core, where it will eventually swallow up the entire Earth.

Earth's final resting place: a tiny glob of strange matter, perhaps a centimetre across.

Feasibility rating: 3/10. Evidence for the existence of strange matter is sketchy at best there are a few neutron stars which look too small to be made of neutronium, there are a few earthquakes which might have been caused by a microscopic strangelet passing through the Earth at high speed, but that's about it. And even if it were possible that small stable strangelets could exist and swallow matter up in the manner described, the odds of forming one in a particle accelerator are pretty much zero.

#### Reduced to true vacuum

You will need: An expanding bubble of true vacuum decay.

Some scientific theories tell us that what we may see as vacuum is only vacuum on average, and actually thriving with vast amounts of particles and antiparticles constantly appearing and then annihilating each other. However, it's postulated that at any time a small bubble of this "false vacuum" could spontaneously decay into genuinely empty "true vacuum". Usually such a bubble would contract to nothingness instantly, but under the right conditions it could expand forever, eventually destroying the entire universe.

Method: There's no method here because such bubbles are quantum effects which can only really come into existence spontaneously, not by human machinations. You just have to wait for it to happen.

Earth's final resting place: Unknown.

Feasibility rating: 1/10. Firstly, this might be total bunk. Secondly, if it isn't total bunk, the odds against this ever happening are clearly astronomical. It's never happened at any time in the last 13.7 billion years it seems unlikely to happen anytime soon.

Source: This method suggested by Adam Mansbridge.

#### Wormholed

You will need: A stable Einstein-Podolsky-Rosen bridge, a.k.a. a wormhole.

Method: Depending on how powerful your technology is, there are a variety of possible methods. Bridging the centre of the Earth with the centre of the Sun would do the trick very efficiently, with the Sun's million-degree heat instantly boiling the Earth from the inside.

Alternatively, open a large wormhole at the Sun's core and the other end in deep space, rapidly venting all the Sun's fuel and hastening its transition to the Red Giant stage. Drain all this fuel rapidly enough and you might even be able to cause a supernova.

You could even bridge the Earth's core with deep space, causing it to implode - although the toothpaste-shaped remnant appearing at the other end may well collapse back to form a planet again.

Earth's final resting place: Variable.

Feasibility rating: 2/10. Wormholes probably aren't actually scientifically possible, and even if they are: opening one at the centre of the Sun? Come on.

Source: This method suggested by Daniel Swartzendruber.

#### Existence negated via time travel

You will need: a time machine, heavy rock-moving equipment/explosives.

Method: Using your time machine, travel back in time just over 4,500,000,000 years to shortly (i.e. a few billenia) before the formation of the Earth. What you should find in its place is a young Sun and an accretion disc formed of the dusty/rocky material that will later become our Solar System. Find the patch of material that is likely to condense into the Earth. Now blow up, split apart and otherwise stir up the material so that it never gets a chance to come together and form the Earth. Return forwards in time in several hundred-million-year jumps, repeating the process each time so that no planet of any kind ever forms at roughly 1 AU from the Sun. If you make an error, simply go back in time and try again.

If your time machine is more resilient, or you don't mind dying, you could consider going further back in time. The further you go, the less you need to change the universe to prevent the Earth ever forming. Go back to a few billionths of a second after the universe began and just by being there you'll completely alter the face of the universe to come. although it was pretty hot back then.

Earth's final resting place: When you finally return to the present day, you will be left with a largish asteroid belt where Earth should be. Alternatively, you may find that the matter has been assimilated into the bodies of other planets or the Sun.

Feasibility rating: 1/10. This method relies on fictional technology and has no basis in real events or scientific theory. Time travel in this way is almost certainly impossible.

Comments: My good friend Rob rightly informs me that this course of action does not strictly speaking "destroy" the Earth - there is no actual destruction event in which the Earth goes from existing to not existing. What one ends up with instead is a universe in which the Earth does not and never did exist.

Destroying Rob proved remarkably easy.

#### Destroyed by God

Method: Far be it from me to dictate whether God does or does not exist, but if he did, and was omnipotent, then no doubt he could destroy the Earth at a mere thought if he should decide to. Of course, the question arises of how we persuade him to do this.

The first idea which springs to mind is to simply bring about the Apocalypse described in the Christian Bible. Assuming the book of Revelation is an accurate, literal depiction of future events, verse 1 of chapter 21 reads "Then I saw a new heaven and a new earth, for the first heaven and the first earth had passed away, and there was no longer any sea".

It seems astounding that the complete destruction of an entire planet (and heaven too) would only be worth a single sentence in this lengthy account of the End Times. But on the other hand, verse 5 of the 104th Psalm reads "He [God] set the Earth on its foundations it can never be moved", and there are other verses like this, so maybe:

1. the New International Version of the Bible has "earth" written with a lower-case "e", which suggests that this verse could merely refer to, you know, the ground
2. this verse could be merely metaphorical - after all, so is the creation story described in Genesis
3. it could be that the new Earth is the same as the old Earth, and "new" just means it was "wiped clean" in some sense, like an Etch-A-Sketch

In all three cases, the new Earth would still need destroying for real.

Another suggestion, should Judaic mythology turn out to be correct, is finding and killing one or more of the Lamed Vav Tzadikim, 36 righteous men whose role in life is to justify the purpose of mankind in the eyes of God. If even one of these is missing, it is said the world would come to an end. Practically speaking, it would probably be easier to wipe out humanity than to find one of these individuals, who do not themselves know who they are.

Comments: It is of course entirely possible that the means God would choose to use to destroy the Earth would be a natural, non-miraculous event such as one of those listed above.

Earth's final resting place: potentially any form, anywhere.

Feasibility rating: this, naturally, is entirely subjective.

Mike Trainor writes, "Just because we don't have the technology to destroy the planet doesn't mean no one else in the universe does. What you need to do is to point our most powerful radio-telescope transmitters at likely solar systems and taunt them. 'The girly-beings in your miserable solar system could never destroy a planet as cool as this one. '" Thanks, Mike. We'll get SETI on it.

### Methods from fiction

This section got too big for its shell so I moved it to a separate page.

### Things which will NOT destroy the Earth

Nanotechnology. Let's be clear here: nanotechnology is nothing more than a means to an end. Programming some sort of self-replicating von Neumann machine to eat the entire Earth up has its own massive problems (like, won't the ones at the bottom be crushed into their constituent atoms?), but even if it worked - you haven't destroyed the Earth. You've just got a planet made of nanobots that still needs destroying somehow. Program them to hurl themselves into space? Well, that's Meticulous Deconstruction, above.

#### Chilled

You will need: The capability to reduce the entire planet Earth to the microscopic temperatures necessary to cause it to revert to a Bose-Einstein condensate.

Method: It's well known and reasonably well-understood that substances at extremely low temperatures can get to the point where quantum phenomena start to have macroscopic, i.e. visible, effects. For example, it can just climb right out of a container, defying gravity. As to why, you would need some quantum physics under your belt.

Could the same work for a whole planet? Could a sufficiently cold body (if it were shielded from the heat of the Sun and ambient background microwave radiation) just spontaneously begin to dissipate into space?

Another idea is to use strong magnetic fields on the condensate to cause it to display what is currently referred as an unusual characteristic, undergoing something approximating a stellar supernova on a tiny scale: imploding on itself and then exploding, with a substantial fraction of the atoms involved disappearing entirely!

Feasibility rating: 4/10. The first idea may work, but the second one probably won't. This is because the experiment specifically used rubidium-85 atoms having a "negative atom-atom scattering length". I don't know what that is, but it sounds unusual for an atom, and we know for a fact that most of Earth is not made up of rubidium-85. Plus, the "disappeared" atoms didn't actually vanish, they just escaped the experiment system under high enough energy that they weren't detected escaping. And of course, generalising quantum phenomena to gigantic scales is never a great idea.

#### Gamma Ray Burst'd

You will need: a star in Earth's stellar neighbourhood with >40 solar masses. Such massive stars are hard to come by even Betelgeuse has only 20 solar masses. The best candidate I know of is Eta Carinae, which has over 120 solar masses but is

Method: Gamma ray bursts are powerful, short-lived floods of gamma ray photons. GRBs come in two flavours, short (less than 2 seconds) and long (2 seconds to about 3 minutes) the latter are believed to be caused by stellar explosions called hypernovae, hundreds of times more violent than ordinary supernovae. Such stars are usually billions of light years away when they explode - the fact that we can detect them at this range should tell you enough about how powerful a hypernova is. So how about triggering one locally? Any such explosion within about 20 light years would probably be violent enough to destroy the Earth itself.

Feasibility rating: 0/10. This method was originally listed above, but astronomer Stephen Thorsett set me straight. It wouldn't work. Even in the titanic quantities described above, gamma rays wouldn't make a dent in Earth's actual, physical structure.

Sources: Lycurgus suggested this method. Further information from nasa.gov.

#### Burned away by muon-catalyzed fusion of the oceans

You will need: a supply of muons.

Method: The theory runs like this. A muon is a negatively-charged particle somewhat like an electron. If you dump a load of muons into some hydrogen, then some of the muons will replace the electrons in the hydrogen atoms. Because of the mass difference, the hydrogen atoms will suddenly get much smaller, causing the hydrogen molecules to be much closer together enough that the probability of the hydrogen nuclei just randomly fusing with each other is high.

So, if you instead poured your muons into the oceans, they could cause the deuterium chemically combined with the water in the oceans to spontaneously begin undergoing fusion reactions. In theory, the amount of heat/energy released by the fusion of all the water in the world would be enough to destroy it by a good few orders of magnitude.

Feasibility rating: 0/10. All known muons decay in a few microseconds - fairly long for an exotic subatomic particle, but still too short to be practical, so unless you can generate your muons in bulk, for free, you don't reach energy break-even, and the fusion stops as soon as it starts instead of being self-sustaining.

Sources: Muon-catalyzed fusion was theorized in the late 1940s by Andrei Sakharov, and brought to my attention by Jef Poskanzer.

Comments: This method was never listed as plausible, but I put it up here anyway because the idea itself is intriguing, even if it wouldn't work.

#### Blown up by vacuum energy detonation

You will need: some means of extracting huge amounts of energy from the vacuum.

Method: Some scientific theories tell us that what we may see as vacuum is only vacuum on average, and actually thriving with vast amounts of particles and antiparticles constantly appearing and then annihilating each other. It also suggests that the volume of space enclosed by a light bulb contains enough vacuum energy to boil every ocean in the world. Therefore, vacuum energy could prove to be the most abundant energy source of any kind. Which is where you come in. All you need to do is figure out how to extract this energy and harness it in some kind of power plant - this can easily be done without arousing too much suspicion - then surreptitiously allow the reaction to run out of control. The resulting release of energy would easily be enough to annihilate all of planet Earth and probably the Sun too.

Earth's final resting place: a rapidly expanding cloud of particles of varying size.

Feasibility rating: 0/10. This method was originally listed as plausible, but Alan Thomas set me straight: there are about five different ways to calculate the energy of the vacuum, all giving different answers. The methods which give the answers "large" or "infinite" are predicated on dodgy mathematics and almost certainly wrong.

Source: 3001: The Final Odyssey by Arthur C. Clarke

Allowing George W. Bush to continue to exercise his will on the world. If you think this, you're completely missing the point. The power to destroy the Earth does not currently exist, and Bush's administration is not actively seeking to create such technology. Whatever Bush does, whatever the backlash from his policies on Iraq and oil and global warming, he cannot destroy the planet.

Paradoxes as described in Back To The Future Part II. By definition, a paradox cannot actually come into existence.

Ceasing all thought (if the Earth is not observed, then how can it exist?). Philip K. Dick said it best: "Reality is that which, when you stop believing in it, doesn't go away."

Semantics. A few people suggested exploiting a loophole in my mission statement and moving the Earth into orbit around a gas giant, making it a moon rather than a planet, or hurling it into interstellar space where it would become a wandering interstellar object. Yeah, yeah, very clever. Get back to work.

Adding enough material to the planet Earth to cause it to undergo gravitational collapse and become a star instead of a planet. The main problem I have with this is that the Earth is made mainly from heavy, pre-fused elements. Most of it is iron which simply won't undergo fusion at all. The amount of material you'd have to add to the Earth would be massive enough to be a star in its own right, and at the end of X billion years when it stops shining you'd still have a core of iron remaining in orbit around the Sun!

Of course, someone suggested you could add still more material until it becomes a star heavy enough to go supernova, so I'm going to come clean here: I have an irrational dislike of this method. It's not going in. Sorry.

Detonating all the nuclear weapons ever created simultaneously, either all at one location or strategically placed around the globe. This will irradiate pretty much the entire globe and kill an awful lot of people, animals and plants, but will actually destroy very little of the planet itself.

If 1 did indeed equal 0, so it is reasoned, then since there is 1 Earth, there must be 0 Earths. so, if one could prove it, the Earth would cease to exist. This is specious logic. Finding a proof in mathematics does not magically change a fact from being false to being true. It merely verifies rigorously as true a fact that always was true. Thus, if 1=0 could be proved, then it would always have been true and the Earth should never have existed. But Earth is still here. QED.

In fact it would be impossible for there to even exist a universe in which 1 was equal to 0. For any mathematical system in which 1=0, it is extremely trivial to prove, in addition, that 1=2, 2=3, and in fact that every number is equal. Or, in other words, the mathematical system has only one number in it, 0. In a universe which obeyed such laws, there would be nothing at all.

Runaway fission at the Earth's core, as proposed by Tom Chalko. It is true that while the Earth is mainly iron, there are significant quantities of other trace elements present, including fissile materials like uranium, thorium and - get this - radioactive potassium which have sunk to the core where latest studies suggest where they are indeed undergoing fission, generating heat and keeping the interior of the Earth warm. However, if a nuclear explosion did occur at the core, it would be insulated from the surface by sixty-three hundred kilometres of liquid iron.

### General geocide strategy

Destroying the Earth is not as easy as pressing a big red button. It takes decades of hard work.

#### Planning

Without a plan, you have nothing. Sooner or later you WILL hit a snag and find yourself unable to continue: government agents will start lasering their way through your door, or you'll have your superweapon ready and armed but nowhere safe to stand when you fire it, or you'll just plain run out of money. You need to plan for as many eventualities as you can conceive of, as early as possible. When I say early, I mean early: ideally your plan should be at least 50% complete by the time you leave high school, because your career choices will be a very significant factor. You should have picked your method by this time too. (The list above isn't necessarily complete - if you come up with a better way of your own, good luck to you.) Once you have picked your method, STICK TO IT.

Assuming, of course, that you and whatever trusted advisors you will allow to side with you do not intend to "go down with the ship", it is particularly advisable to make plans for alternate living arrangements before you embark on a course of action which may result in the destruction of the Earth. Since in most cases the hypertechnology required to actually destroy the Earth is ridiculously advanced, access to an interstellar spacecraft, a space station or another habitable planet is likely to be well within your grasp, but this is not something you want to start making assumptions about.

#### Careers

At this point you need to make a very significant decision: are you going to design your doomsday machinery (all of the above methods except Total Existence Failure require a greater or lesser amount of machinery) yourself, or are you going to employ somebody else to do it for you? Unless you are an extremely gifted scientist and you really can destroy the Earth from your laboratory (which is not impossible see the Strangelet or Von Neumann Machine methods), you're fairly likely to pick the latter.

If you do decide to design (and possibly build) this thing yourself, you'd be advised to pursue mainly sciences, with the main emphasis on physics (quantum, atomic, and astrophysics in particular), but also some electronic and mechanical engineering, mathematics and possibly robotics. After this, get a job working with the technology you hope to harness, build your doomsday machine in your lab, and bam, you're done.

If you don't decide to design your doomsday device yourself, and from here on, I'll assume that this is what you decided, then the plan becomes rather more complicated and your career choices will be very different. Your time in secondary and higher education would probably be best invested studying finance, economics and politics, brushing up your management, speaking and people skills, honing your powers of persuasion, and learning to exude charisma. Charisma is a big one. These skills will enable you to hopefully ascend to a position where you have access to three things:

If this is a lab project as described above then you'll need relatively little of all of these enough money to run a lab, resources to keep it stocked, and manpower in the form of one or more brilliant scientists to (knowingly or otherwise) construct your doomsday device. That suggests that the best place to seek employment would be at a research institution for the areas of science you hope to employ, or maybe an organization like Boeing or NASA. failing that, found the organization yourself!

If this is a big, possibly space-based project then you will need MUCH more to work with. You need to either work in politics or the armed forces. Politics would be an excellent choice. I say without cynicism that today, of all the people in the world, the President of the United States of America would be the person most likely to be able to destroy the Earth should he decide to. If you feel you lack the ability to make it in politics (knowledge of your weaknesses is a strength), you should join the armed forces and shoot for Supreme General or whatever the highest rank is.

Nancy Lebovitz suggested religion as an alternate means of gaining resources, money and manpower. Religion is undeniably a very powerful force. If you could set yourself up as a religious leader you could potentially gain a lot of supporters - who would be much more dedicated to you as a leader than a soldier would be to his general or a citizen to his King/President/Supreme Dictator-For-Life. Setting oneself up as a new prophet doesn't seem to attract much more than scepticism in this day and age, so unless you were very persuasive, you'd probably experience greatest success by hijacking an existing mainstream religion for your own ends. One potential pitfall is that there's a limit to what your followers can provide you in terms of monetary offerings and labour. Manpower alone is not enough. You'd still need at least one scientific mastermind, and frankly I see scientific masterminds as being among the least likely to follow you. But this is a kink you should be able to work out.

Of course, by the time it becomes even possible to destroy the Earth, Madagascar might be the dominant superpower, or the whole world might be unified as a single nation, or maybe the whole galaxy is full of humans, there's no such thing as money, and solid platinum asteroids and robot workers are plentiful. I don't know. Whatever you can manage. Anyway, once you have everything you need at your disposal, make the calls, submit your proposals, and set the project in motion.

At this point you will probably need to set up some sort of base of operations. It should be at a safe distance from Earth. Lurking at least one AU out of range of whatever terrible destructive force you are about to unleash is strongly recommended in most cases, but for the supernova particularly you'll want to put as much as a thousand light years between yourself and the Earth when it happens. If you have to be physically on Earth to begin the destruction process (e.g. hurled into Sun, antimatter blast), then set a countdown. Make sure the countdown timer is a) thoroughly tested and b) tamper-proof. The same goes for your escape route offplanet.

If you are currently Supreme Dictator of Earth, you could simply announce your intentions directly to your enslaved populace with relative impunity. If you can come up with some really, really good reason for destroying the Earth which people will actually agree with - for example, you want to build a far more spacious Banksian Orbital (or many of them) instead - then getting humanity on your side will prove incalculably useful. However, as a rule, you will probably want to keep the true purpose of your project secret from as many people as possible for as long as possible.

You should always, always, always have an escape route.

See also The Evil Overlord list for lots more general advice on building bases, planning escape routes, handling enemy incursions, and other tangentially related topics.

#### Finally

If the method you choose can be tried more than once (e.g. hurled into Sun, vacuum energy detonation), and your budget will stretch, you could consider practicing on smaller astronomical bodies and working your way up. For example, consider destroying Mercury, or Ceres. Don't forget to take notes on what went particularly well, what didn't work, what was unnecessary, etc., just so everything goes as smoothly as possible on the big day.

Take a camera. Most of the methods listed above are incredibly spectacular and witnessing them will probably be a once-in-a-lifetime opportunity for you, so remember to capture the moment.

And lastly, if all your efforts fail, don't give up! Remember, nobody has ever successfully destroyed the Earth.

## The Enforcer/Executor

The Enforcer is the closest thing to a shotgun you’ll find, letting you fire off one shot when the R2 trigger is pulled down halfway or firing two in quick succession with a full squeeze. Having two barrels makes it a great way to deal a lot of damage to anyone trying to invade your personal space early on in the game, helping to give you more room and keep enemies at a good distance. It graduates to the Executor at level 5 and lets you fire a quadruple barrel instead of double.

Planet it becomes available: Corson V

Good for: Dispersing tightly-packed groups of enemies and giving you breathing room

## Debris disk: Ring around star

Hi,
with this post I am answering to one comment posted about three weeks ago on Roche limit.

Could there be rings around sun?

Yes they are called Debris disks. Debris disk is created from nebula which is surrounding young star. This nebula is full of gas and dust. Either all this stuff is pushed away by radiation or planetesimals are created.

Planetesimals are huge rocks, (more than one kilometer across). They do not need Brownian motion anymore to grow because they have enough strong gravity to pull other rocks, and at some point they can be enough large to be planets.

When those planetesimals collide they left dust and rock behind them. This is what is called debris disk. It is not created by Roche limit as normal planetary ring is and I did not find anything about rings around star that are made by Roche but if I do I will definitely post it here.

This dust in debris disk is usually very small: 1-100 micrometers.
Our sun has this debris disk and you have probably heard about it, it is the Kuiper belt.

There is other example of debris disk and it is around very bright star called Fomalhaut. You can see it on the right top. This star has debris disk which is moved by 1.4 billion miles (roughly 2.24 billion kilometers) to left. It is probably because of huge planet. The dark spot around star (pic. on the left and bot.) is just effect of blocking the light from Fomalhaut so we can see all the debris reflecting photons.
Fomalhaut has at least one planet and this one is called Fomalhaut B. On wiki, I am pretty sure there is mistake in one sentence since they are saying that it is star.
You can easily find Fomalhaut on Celestia, I will write about that program probably next time.

## How to explain the presence of a dense debris field around Earth?

I'm creating a sci-fi world similar to ours roughly 50 years in the future. Unobtanium, a futuristic metal and fuel source, was discovered in 2020. Its broad utility led to rapid advances across all parts of industry, but especially spaceflight, which is now commonplace for government / business leaders and military operations. However, even occasional spaceflight is beyond the means of average families.

My goal is to have have a dense cloud of debris completely blanketing the Earth. The main requirements are:

• The debris needs to not exist around present-day Earth yet be fully formed within a couple hundred years, 50 years being preferable.
• Ideally the debris would be of varying sizes, from micrometeorites to large rocks several hundred meters in diameter. It is most important to have debris in the tens-of-meters range.
• The average debris density is flexible, but, at its densest, flying through should be risky without planning or active piloting. It would be ideal if debris were present at every latitutde.
• The event that causes the debris cannot radically affect human society. Things like destruction of artifical satelites or small climate change (changes to day length, tides, global temperatures, etc.) are fine, but not things like "all humans are forced to live in underground bunkers".
• To be clear, I'm not interested in long term stability. The debris only needs to be around long enough for it to be part of "everyday life" for spacefarers.
• Bonus points if your soultion can explain the sudden appearence of large but expendable amounts of unobtanium (

My first approach was to have an asteroid impact Earth’s moon, which would be convenient for other plot reasons, but after looking into it, it seems an impact strong enough to create the sort of debris density I need would have lots of appocalyptic side effects for the residents of Earth down below.

Another approach I considered was having people attempt to break up an inbound asteroid before it stuck Earth, but it seems like a object of mass sufficent to cause the sort of debris field I want would be imposssible to stop without causing significant damage to the Earth.

TLDR: How can I explain the sudden appearence of a dense debris field around earth?

## If the Earth would break apart, how likely would the large debris stay in orbit?

In the story I'm writing, Earth gets destroyed and the few million humans that survive go to live on another Earth-like planet.

Since the destruction of the planet, the humans do visit their star system every generation as part of their history and as a memorial to visit where their former home world would be. Almost every human knows about what happened and no one wants to forget the mass of lives that were lost.

What destroys Earth is an alien weapon, like a bomb, that is powerful enough to break into the crust and bury itself into the mantle before it detonates. Designed to warp the gravitic and magnetic fields outward, it causes the crust to crack along the tectonic plates, causing the side it impacted to effectively break away, leaving at least one large plate intact but with an exposed mantle and core (looking a lot like the image below)

I don't know if the planet's remains would still be there. I've seen plenty of things, like bits and pieces in fiction and films where planets remain in orbit like:

Copyright: ABC, Marvel, Mutant Enemy, Walt Disney Distributions 2017

I know that there might be a greater chance that the debris might be pulled back into its mass again but there's also the suggestion that the remains would float off into space since there might not be enough gravity to hold it in orbit or the force of the detonation might send things in all directions.

What I want to know is: how likely are the remains to stay in orbit of the Sun for future humans to visit?

## Hubble finds big brother of Halley's Comet ripped apart by white dwarf

IMAGE: This artist's impression shows a massive, comet-like object falling towards a white dwarf. New observations with the NASA/ESA Hubble Space Telescope show evidence for a belt of comet-like bodies orbiting. view more

Credit: NASA, ESA, and Z. Levy (STScI)

The international team of astronomers observed the white dwarf WD 1425+540, about 170 light-years from Earth in the constellation Boötes (the Herdsman) [1]. While studying the white dwarf's atmosphere using both the NASA/ESA Hubble Space Telescope and the W. M. Keck Observatory the team found evidence that an object rather like a massive comet was falling onto the star, getting tidally disrupted while doing so.

The team determined that the object had a chemical composition similar to the famous Halley's Comet in our own Solar System, but it was 100 000 times more massive and had twice the proportion of water as its local counterpart. Spectral analysis showed that the destroyed object was rich in the elements essential for life, including carbon, oxygen, sulphur and even nitrogen [2].

This makes it the first detection of nitrogen in the debris falling onto a white dwarf. Lead author Siyi Xu of the European Southern Observatory, Germany, explains the importance of the discovery: "Nitrogen is a very important element for life as we know it. This particular object is quite rich in nitrogen, more so than any object observed in our Solar System."

There are already more than a dozen white dwarfs known to be polluted with infalling debris from rocky, asteroid-like objects, but this is the first time a body made of icy, comet-like material has been seen polluting a white dwarf's atmosphere. These findings are evidence for a belt of comet-like bodies, similar to our Solar System's Kuiper Belt, orbiting the white dwarf. These icy bodies apparently survived the star's evolution from a main sequence star -- similar to our Sun -- to a red giant -- and its final collapse to a small, dense white dwarf.

The team that made this discovery also considered how this massive object got from its original, distant orbit onto a collision course with its parent star [3]. The change in the orbit could have been caused by the gravitational distribution by so far undetected, surviving planets which have perturbed the belt of comets. Another explanation could be that the companion star of the white dwarf disturbed the belt and caused objects from the belt to travel toward the white dwarf. The change in orbit could also have been caused by a combination of these two scenarios.

The Kuiper Belt in the Solar System, which extends outward from Neptune's orbit, is home to many dwarf planets, comets, and other small bodies left over from the formation of the Solar System. The new findings now provide observational evidence to support the idea that icy bodies are also present in other planetary systems and have survived throughout the history of the star's evolution.

[1] The white dwarf was first found in 1974 and is part of a wide binary system, with a companion star separated by 2000 times the distance that the Earth is from the Sun.

[2] The measurements of carbon, nitrogen, oxygen, silicon, sulphur, iron and nickel and hydrogen come from the Cosmic Origins Spectrograph (COS, installed at the NASA/ESA Hubble Space Telescope . The W. M. Keck Telescopes provided the calcium, magnesium, and hydrogen.

[3] The team calculated that the accreted object originally resided about 300 astronomical units -- 300 times the distance Earth-Sun -- away from the white dwarf. This is seven times further out than the Kuiper-Belt objects in the Solar System.

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The international team of astronomers in this study consists of S. Xu (ESO, Germany), B. Zuckerman (Department of Physics and Astronomy, University of California, Los Angeles, USA), P. Dufour (Institut de Recherche sur les Exoplanètes, Université de Montréal, Canada), E. D. Young (Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles), B. Klein (Department of Physics and Astronomy, University of California, Los Angeles, USA), M. Jura (Department of Physics and Astronomy, University of California, Los Angeles, USA)

Image credit: NASA, ESA and Z. Levy (STScI)

Siyi Xu
European Southern Observatory
Garching bei München, Germany
Tel: +49 89 3200 6298
Email: [email protected]

Mathias Jäger
ESA/Hubble, Public Information Officer
Garching, Germany
Tel: +49 176 62397500
Email: [email protected]

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