For years and years everyone from science fiction writers to scientists have been talking about all of these scenarios and what not about how the world will end (be it by our own hands, or a random act of nature).
While I find many of these scenarios interesting, many of them have a common flaw: they don't actually end the Earth, just human civilization, and perhaps the human species.
So, how exactly could the Earth REALLY be destroyed (as in cease to exist)?
Well I've thought about it, and I've come up with about 11 different ways of how it could happen.
So if you don't mind possibly being scared to death, below are those 11 possible scenarios:
We all know the dangers that a direct impact from either a comet or meteor poses to the Earth as it has been the subject of several movies and books, and is a legitimate threat because it has happened before, and it has wiped out entire species and caused major damage to the Earth throughout our planet's history.
While some people might believe that it would be the end of the world if a large meteor or comet was to hit us today, it wouldn't be. It might be the end of human civilization, maybe even our species, but the world will still exist... unless something really big, or really heavy was to hit us...
Lets say something nearly the size of the Earth, or bigger, was to hit us, or something very heavy like a neutron star. The fact is that there would be no way for the Earth to survive an impact by something close to, or larger, or heavier than the Earth. Our world would be broken apart and probably turned into an asteroid field by such an impact.
High speed impact
The amount of damage a object can do not only depends on how large an object is, but also by how fast said object is going.
A one mile wide meteor hitting the Earth would be devastating. If that one mile wide meteor was to hit the Earth while traveling nearly the speed of light, the amount of kinetic energy released from such an impact would rip the Earth apart, and we wouldn't even know it until it actually happened (assuming we survived long enough) because such an object would most likely be impossible to find, let alone track.
von Neumann machine
A von Neumann machine is a type of robot first conceived of by John von Neumann (hence the name) that can basically self replicate, and could even manufacture materials on it's own inother to do so. It would even be possible for it to seek out the resources it needs to manufacture those materials.
While such a machine would be an extraordinary leap forward in terms of robotics and manufacturing, some people fear that one day one of those robots could go haywire (or someone could build one for the purpose of unregulated self replicating) and continue to self replicate without knowing when to shut off, and ultimately end up destroying the Earth a small part at a time until there is nothing left.
While a larger machine might not actually be able to do this before we stopped it, a small machine like a nano-probe might just be able to do this.
Knocked into the sun
Lets say a very large object (like a star) was to pass through our solar system, what do you think would happen?
The answer is that the Earth would be knocked out of orbit.
After that one of two things would then happen: The Earth would be knocked away from the sun and become a rogue planet (as well as a giant ball of ice), or we would get knocked into the sun and be burnt into nothing.
If you've ever seen Star Wars then you probably know what I'm talking about, if you don't then I'll explain (although I do still recommend seeing Star Wars).
A laser is a device that creates a focused beam of light that can actually be quiet destructive, and depending on how much energy you put into the laser, it's destructive power can range from being harmless (unless you look directly into the beam) to being used to take out a vehicle. Taking this in mind it is theoretically possible to build a laser powerful to destroy the Earth.
Fortunately we don't have to worry about this one right now due to the fact that the total amount of energy produced world wide is no where near enough to power a laser that would be capable of doing so.
A bomb is the most powerful weapon that has ever been invented. We have bombs that are so powerful and destructive that they can wipe a large city off the face of the Earth in an instant, and also leave the area surrounding it uninhabitable for years, so it shouldn't be to surprising that a bomb could be used to destroy the Earth.
The only real problem with this would be finding either a material that could produce a explosive force powerful enough to actually destroy the Earth, or enough explosive material to destroy the Earth.
The Earth stops
If the Earth was to suddenly stop rotating on it's axis or revolving around the Sun the results would be catastrophic.
It might not seem like it to some people, but the speed at which the Earth is both rotating on it's axis and going around the Sun is pretty high, and with that speed brings with it a lot kinetic energy. If the Earth was to suddenly stop rotating or revolving around the Sun... well that kinetic energy has to go somewhere.
Suffice to say that the end result would be the Earth ripping itself apart.
A black hole is one of the most destructive forces in the universe. It's gravity is so strong that nothing can escape it, not even light, so if one was to fly by us, or to hit us, or if we accidentally created one that we couldn't control, the planet wouldn't just be ripped apart, it would be sucked in and cease to exist.
The Sun expands into a red giant.
In about 4 to 5 billion years or so the Sun is going to expand into a red giant, beginning it's final stages before it's own death.
While no one is really sure how far out the Sun will expand, it is possible that the Sun will expand enough that it will either expand into the Earth's orbit and incinerate the Earth, or cause the Earth to fall into the Sun.
The Sun goes nova
Even if the Earth does survive the expansion of the Sun, it is very unlikely that the planet would survive the Sun blowing it's outer layers of gas off before it finally became a white dwarf.
The destructive force would be so huge that not only would the Earth not survive, nothing in the solar system would survive.
The Universe ends
Even if by some miracle the Earth managed to survive the end of the Sun, ultimately the Universe itself will end, and so will it the Earth as well.
No one is sure when or really even how the Universe will end, but some day it will end, and if somehow the Earth is still around, it will go along with it.