Imagine this: You’re walking along the street on a lovely Sunday afternoon. Then, all of the sudden, a giant ball of ice falls out of the sky and crushes you before you have time to blink.

Sounds a bit far-fetched, right? Well, this does happen.

This is called a megacryometeor, and they do exist.

These balls skull-crushing hail can weigh up to 450 pounds.

That’s as much as one of these:

If that’s not terrifying enough, here’s a picture of the damage one left after crashing though someones house:

And a picture of a crater left by one:

The worst part? Scientists don’t even know why they happen.

Imagine one falls on you while you’re asleep.

Sweet dreams.

I am going to take "us" to mean collectively all of humanity.

A Gamma Ray Burst.

The source could be from several things. A star going Supernova nearby or the energetic jet of a Pulsar that swings in Earth's direction for just a moment. Another possible scenario is a large rogue chunk of Antimatter entering our solar system and impacting with one of the planets or the asteroid field. Any of these could cause a Gamma Ray Burst.

The craziest part is that this Gamma-ray burst could have been travelling towards us for hundreds, 10's of thousands or even millions of years before it hits us. The burst that instantly kills us at the speed of light may have happened on a distant star before humanity even started recording history. By the time you see the GRB it has already hit. There would be no warning at all.

An instantly fatal GRB would likely need to be within several hundred light years distance but that still means the GRB that kills us happened before we were even born. There are several possible GRB sources we know of within 150 - 1,100 light years and possibly many more we have not yet found that could be far closer.

A direct strike by the jet of a Pulsar could bathe the entire Earth in the equivalent of one nuclear bomb per square inch and we would all die before we even knew what hit us or why.

Our fate would have been sealed hundreds or thousands of years ago, hundreds or thousands of light years away and we had no way of knowing it was coming.

This is an excerpt from a beautiful book of BILL BRYSON called A SHORT HISTORY OF NEARLY EVERYTHING. The thought of an asteroid attack as mentioned here shudders my soul.

Anderson and Witzke no longer had the crater that killed the dinosaurs, “but we still had the largest and most perfectly preserved impact crater in the mainland United States,” Anderson said. (A little verbal dexterity is required to keep Manson’s superlative status. Other craters are larger—notably, Chesapeake Bay, which was recognized as an impact site in 1994—but they are either offshore or deformed.) “Chicxulub is buried under two to three kilometers of limestone and mostly offshore, which makes it difficult to study,” Anderson went on, “while Manson is really quite accessible. It’s because it is buried that it is actually comparatively pristine.”

I asked them how much warning we would receive if a similar hunk of rock was coming toward us today.

“Oh, probably none,” said Anderson breezily. “It wouldn’t be visible to the naked eye until it warmed up, and that wouldn’t happen until it hit the atmosphere, which would be about one second before it hit the Earth. You’re talking about something moving many tens of times faster than the fastest bullet. Unless it had been seen by someone with a telescope, and that’s by no means a certainty, it would take us completely by surprise.”

How hard an impactor hits depends on a lot of variables—angle of entry, velocity and trajectory, whether the collision is head-on or from the side, and the mass and density of the impacting object, among much else—none of which we can know so many millions of years after the fact. But what scientists can do—and Anderson and Witzke have done—is measure the impact site and calculate the amount of energy released. From that they can work out plausible scenarios of what it must have been like—or, more chillingly, would be like if it happened now.

An asteroid or comet traveling at cosmic velocities would enter the Earth’s atmosphere at such a speed that the air beneath it couldn’t get out of the way and would be compressed, as in a bicycle pump. As anyone who has used such a pump knows, compressed air grows swiftly hot, and the temperature below it would rise to some 60,000 Kelvin, or ten times the surface temperature of the Sun. In this instant of its arrival in our atmosphere, everything in the meteor’s path—people, houses, factories, cars—would crinkle and vanish like cellophane in a flame.

One second after entering the atmosphere, the meteorite would slam into the Earth’s surface, where the people of Manson had a moment before been going about their business. The meteorite itself would vaporize instantly, but the blast would blow out a thousand cubic kilometers of rock, earth, and superheated gases. Every living thing within 150 miles that hadn’t been killed by the heat of entry would now be killed by the blast. Radiating outward at almost the speed of light would be the initial shock wave, sweeping everything before it.

For those outside the zone of immediate devastation, the first inkling of catastrophe would be a flash of blinding light—the brightest ever seen by human eyes—followed an instant to a minute or two later by an apocalyptic sight of unimaginable grandeur: a roiling wall of darkness reaching high into the heavens, filling an entire field of view and traveling at thousands of miles an hour. Its approach would be eerily silent since it would be moving far beyond the speed of sound. Anyone in a tall building in Omaha or Des Moines, say,who chanced to look in the right direction would see a bewildering veil of turmoil followed by instantaneous oblivion.

Within minutes, over an area stretching from Denver to Detroit and encompassing what had once been Chicago, St. Louis, Kansas City, the Twin Cities—the whole of the Midwest, in short—nearly every standing thing would be flattened or on fire, and nearly every living thing would be dead. People up to a thousand miles away would be knocked off their feet and sliced or clobbered by a blizzard of flying projectiles. Beyond a thousand miles the devastation from the blast would gradually diminish.

But that’s just the initial shockwave. No one can do more than guess what the associated damage would be, other than that it would be brisk and global. The impact would almost certainly set off a chain of devastating earthquakes. Volcanoes across the globe would begin to rumble and spew. Tsunamis would rise up and head devastatingly for distant shores. Within an hour, a cloud of blackness would cover the planet, and burning rock and other debris would be pelting down everywhere, setting much of the planet ablaze. It has been estimated that at least a billion and a half people would be dead by the end of the first day. The massive disturbances to the ionosphere would knock out communications systems everywhere, so survivors would have no idea what was happening elsewhere or where to turn. It would hardly matter. As one commentator has put it, fleeing would mean “selecting a slow death over a quick one. The death toll would be very little affected by any plausible relocation effort, since Earth’s ability to support life would be universally diminished.”

The amount of soot and floating ash from the impact and following fires would blot out the sun, certainly for months, possibly for years, disrupting growing cycles. In 2001 researchers at the California Institute of Technology analyzed helium isotopes from sediments left from the later KT impact and concluded that it affected Earth’s climate for about ten thousand years. This was actually used as evidence to support the notion that the extinction of dinosaurs was swift and emphatic—and so it was in geological terms. We can only guess how well, or whether, humanity would cope with such an event.
And in all likelihood, remember, this would come without warning, out of a clear sky.
But let’s assume we did see the object coming. What would we do? Everyone assumes we would send up a nuclear warhead and blast it to smithereens. The idea has some problems, however. First, as John S. Lewis notes, our missiles are not designed for space work. They haven’t the oomph to escape Earth’s gravity and, even if they did, there are no mechanisms to guide them across tens of millions of miles of space. Still less could we send up a shipload of space cowboys to do the job for us, as in the movie Armageddon; we no longer possess a rocket powerful enough to send humans even as far as the Moon. The last rocket that could, Saturn 5, was retired years ago and has never been replaced. Nor could we quickly build a new one because, amazingly, the plans for Saturn launchers were destroyed as part of a NASA housecleaning exercise.
Even if we did manage somehow to get a warhead to the asteroid and blasted it to pieces, the chances are that we would simply turn it into a string of rocks that would slam into us one after the other in the manner of Comet Shoemaker-Levy on Jupiter—but with the difference that now the rocks would be intensely radioactive. Tom Gehrels, an asteroid hunter at the University of Arizona, thinks that even a year’s warning would probably be insufficient to take appropriate action. The greater likelihood, however, is that we wouldn’t see any object—even a comet—until it was about six months away, which would be much too late.
Shoemaker-Levy 9 had been orbiting Jupiter in a fairly conspicuous manner since 1929, but it took over half a century before anyone noticed.
Interestingly, because these things are so difficult to compute and must incorporate such a significant margin of error, even if we knew an object was heading our way we wouldn’t know until nearly the end—the last couple of weeks anyway—whether collision was certain. For most of the time of the object’s approach we would exist in a kind of cone of uncertainty. It would certainly be the most interesting few months in the history of the world. And imagine the party if it passed safely.
“So how often does something like the Manson impact happen?” I asked Anderson and Witzke before leaving.
“Oh, about once every million years on average,” said Witzke.
“And remember,” added Anderson, “this was a relatively minor event. Do you know how many extinctions were associated with the Manson impact?”
“No idea,” I replied.
“None,” he said, with a strange air of satisfaction. “Not one.”
Of course, Witzke and Anderson added hastily and more or less in unison, there would have been terrible devastation across much of the Earth, as just described, and complete annihilation for hundreds of miles around ground zero. But life is hardy, and when the smoke cleared there were enough lucky survivors from every species that none permanently perished.
The good news, it appears, is that it takes an awful lot to extinguish a species. The bad news is that the good news can never be counted on. Worse still, it isn’t actually necessary to look to space for petrifying danger. As we are about to see, Earth can provide plenty of danger of its own.

One interesting technique I picked up from a detective book:

If one can prick with a needle the point where the medulla oblongata ends and the first cervical vertebra (atlas) starts, it will result in instantaneous death.
Medulla Oblongata is the last portion of the brain and is also called the life centre as it moderates our heartbeat and breathing. This junction is the spot where the skull ends and the vertebral column begins - leaving the medulla oblongata very slightly exposed.
A similar instantaneous death can be caused by what I read to be the sand bag technique of free-hand combat - a sure chop with the back of your hand on that exact spot described above. The hit breaks the bony processes from the second vertebra, which hits the medulla and causes immediate death.

Source: Gray's Anatomy and Arthamanartham (a brilliant sleuth-story in Bengali)by Saradindu Banerjee

Botulinum Toxin. I have fibromyalgia. In the early 90s, physicians were doing test studies using the toxin, calling it BT-1. I used to joke and say I would be BaTman if I was able to get the treatment. Never happened, the research went to a different part of the medical community. Plastic/cosmetic surgery. BT-1 is injected with a needle, but a drop of it on your tongue could kill you instantly. BT-1 is botulism, a plague. BT-1 is also now called...Botox.

Okay depends whether by "us" you mean, us individually, or humans as a species. For humans individually, many things can of course. For instance, anything that kills you within the reaction time, of about a fifth of a second, so you don't have time to register that anything has happened.

So whether you can be aware of anything then depends on what you think happens after you die. Certainly as a living human being you have no opportunity to be aware of what happened. And after you die, if awareness continues in some form (I think it does myself though in what form I think is a big mystery that may have different equally valid answers), again you might well have no memory of the event itself.

This answer is a bit out of date - the ideas I suggest here are theoretical, if you are worried about the practical possibility the answer is no. Not for human extinction and there isn’t anything could do it slowly either really. See

• Could anything make us extinct in this century?

BLACK HOLES

But for humans as a species, about the only likely thing I can think of is a Primordial black hole if they exist.

A large black hole, large enough so that it would take almost no time for Earth to collapse into it, would be visible from some distance as it approaches our solar system from the matter it picks up swirling into it.

These could be very small, however, micro black holes, so hard to spot.

Even then, first, if it travels at any speed relative to the Earth, it would be most likely to go right through the Earth and out the other side and continue without doing any harm to anything.

If it did manage to get trapped inside the Earth would take some time to collapse into the black hole because its event horizon is tiny and all the matter has to pass through its event horizon for Earth to collapse. Maybe even take many years if the black hole is tiny. Even millions of years if it is really tiny, because it has a small event horizon, for instance if its event horizon is atom sized, it can only swallow up the Earth one atom at a time which would take a long time.

That's an unlikely scenario though, because the sun is a far larger target and so more likely target than the Earth, which is tiny.

So if there were any micro black holes in our stellar neighbourhood and one of them drifted our way - it would be far more likely for the sun to suddenly stop shining (over some period of time as it collapsed into the growing black hole) than for the Earth to disappear into the black hole - so then not instantaneous as many people would survive for a long time, and in principle you could have a few people at least survive indefinitely using geothermal heat sources after a vanishing sun, so not instantaneous .

Anyway, if these micro black holes exist, we'd see stars suddenly "winking out" in the galaxy. Since that's never happened in observations of huge numbers of stars - then I think we can safely assume that these mini black holes are either vanishingly rare - or else - that for some reason they are unable to swallow up planets and stars . In either case, surely our sun and Earth are both safe from being swallowed by mini black holes.

If Earth was hit by a primordial micro black hole, because of its high speed and small cross section, it would go right through the Earth and do no noticeable damage.

Primordial black hole

ASTEROIDS

An approaching asteroid wouldn't be able to catch all of humanity unawares in this way either. An asteroid large enough to make all humans extinct would be far larger than Mars's moons Phobos and Deimos and be visible the other side of the solar system, easily, even in the larger amateur telescopes.

And - it would be almost certain to make many close flybys of Earth before it hits us, because the Earth is such a small target in the solar system. So during those flybys we'd have an opportunity to deflect it.

And any comet from the outer solar system would be very unlikely to be in the plane of the orbit of the Earth initially. So although an "Earth crosser" it would be like Halley's comet and pass either a long way above or a long way below Earth's orbit when it passes Earth, at least until it has had many flybys and gravity assists, probably of Jupiter, to flatten its orbit out and turn it into a short period comet.

It would also be likely to be ripped apart by Jupiter first, or hit the sun, or another planet - and - it turns out - that our solar system doesn't have any really large craters on any of the inner planets of the solar system since about 3.8 billion years ago.

There are no craters big enough to make humans extinct on Earth on Mercury, Mars, the Moon or Earth itself, in the last over three billion years. Plenty that could make dinosaurs extinct - but they didn't have boats, or planes or submarines, or ability to build fireproof shelters or stockpile food and oxygen for the moment of impact (never mind also ability to deflect asteroids which we could do with enough warning).

So - I think that shows an large asteroid impact is unlikely. Probably because we are protected by Jupiter.

These could be devastating if you live on another solar system that doesn't have the protection of Jupiter - or may be devastating also in some future version of our own solar system, e.g. if some other star gets so close that large numbers of comets from its Oort cloud start coming into our own solar system. But not for present day solar system it seems. And we'd have millions of years of warning of an event such as an approaching star hugely increasing the numbers of large comets entering the inner solar system.

BURSTS OF RADIATION

As for supernova and gamma ray burst - that would be sudden and impossible to predict for the side of Earth facing the blast.

But - first - this is unlikely. Since they are visible over a large part of the galaxy, then statistically you'd expect to see many more distant supernovae and gamma ray bursts first before you see a nearby one. So the next one we see is far more likely to be a long distance away and harmless. And so far we haven't seen anything at all - lots in other galaxies, but no supernovae in our galaxy since the seventeenth century.

And there are no nearby stars that are obvious candidates to go supernova in the next few thousand years - not close enough to harm us beneath the protective layer of the atmosphere - bear in mind that our atmosphere provides as much shielding against radiation as ten meters thickness of water.

But on remote chance it did happen, anyone deep underground, or in a submarine, or indeed, everyone on the other side of the Earth would survive.

So again wouldn't make all humans extinct. The Earth's atmosphere and ecosystem would be severely disrupted surely. Many creatures would go extinct. Ozone layer damaged. But the atmosphere would remain breathable and Earth would still have its oceans etc, and its plants, would remain by far the best place for humans in our solar system.

FALSE VACUUM

That leaves the false vacuum. There - yes - that could work like that. Not with a bang, but with a Big Rip: how the world will end

But the hypothesis of the false vacuum generally postulates that this happens some time in the distant future - in that article - twenty billion years into the future. So, we don't need to worry about it quite yet. And - it is just one of many possible scenarios for the far distant future, and new ideas there keep being suggested.

For a long time one popular hypothesis was that the universe collapses back again as a "big crunch" but now that's generally thought unlikely. But I wouldn't be surprised if that changed again :). My own favourite is Roger Penrose's "Conformal mapping" where the universe keeps expanding and decaying until there is no matter left, only light. At that point, because there's only light it loses its sense of scale, and then turns into a new big bang and the universe starts again.

Anyway - if it happens twenty billion years in the future, I think probably doesn't count for the purposes of this question.

CONCLUSION

So, I can't think of anything that we know of that would make all of humanity go extinct instantaneously, or indeed extinct at all in the next few hundred million years.

In theory a big comet or asteroid could do it, but we'd have at least many months of warning, but much more likely it would do many flybys of the inner solar system first.

And anyway it is a pretty sure thing that any asteroid or comet this large would get broken up by Jupiter or impact into the sun or Jupiter first, since an impact this large has never happened to any of the planets in the inner solar system for the last well over 3 billion years.

- A Thought, yes it could.

Sun Kings

Strange extraterrestrials offer humanity an extreme means of escaping a devastating gamma ray pulse capable of destroying all life on Earth.

The giant robotic structure could not be accommodated within the halls of the United Nations building. Nor did it want to be.

The robotic body was twenty five feet tall, squat and low to the ground, a massive cylinder surrounded in materials making it repel the forces of gravity, holding it above the Earth.

A mighty container for the being held within, there were no holes for entry or exit, nor would any human dare to. The container, made with rock harvested from the lunar surface was altered into a polarized material, capable of blocking radiation.

The creature within still shone with a soft white light. Without the protective shielding, nothing living on the surface of the Earth could withstand its presence. Its ability to control that polarization made it possible to be in its presence without fear.

The setting was an outdoor courtyard with an over sized tent, made of netting to block the direct and unpleasant radiations of a sun on a world with a weakening ozone layer.

The meeting was held out of doors, since the entity held within its containment field complained of claustrophobia inside of buildings away from the light of the sun. The seating arrangements which would accommodate eight hundred people, as comfortable as could be found were arranged with tables, place cards, microphones and servers who would be waiting upon these envoys of the world's nations.

Security personnel who did not even bother to hide their presence or their countries of origin swamped the site sweeping for bugs, bombs and anything that might be a threat to their country's representatives. Though many of these countries expected to be represented by their countries finest, a few nations feared to send their leader to the event expecting some form of treachery from the alien guest or guests of honor.

But none of these men were as important as the photo of a Black man at the podium today. While the many men here could say they had the responsibility of a nation, Dr. and professor of xenobiology from MIT, Winston Harrison represented a planet to an alien species. He was the scientist responsible for deciphering the alien transmission. How he ended up in the containment field with the alien intelligences representing the Earth was still unknown.

The aliens spent a few days on the moon and then came to Earth on the White House lawn in their containment fields. Dr. Harrison explained what they wanted and set a date and location for this gathering. The containment cylinders floated away without even mussing the White House lawn. By the time the F-22's were overhead the aliens were long gone.

The representatives slowly filed in, looking for their seats. The seating arrangements could not be seen from outside the tent and it would act as ballistic mesh, preventing bullets or bombs, with a series of concrete bunkers around the tent preventing a car-bomb from being driven up.
Not that any of these precautions were necessary, so assured the Professor and his alien hosts who had been dubbed in the media, the Sun Kings. The aliens didn't seem to mind, so the name stuck. They assured us they came in peace.

As the UN representatives milled toward their seats, their hushed tones and fearful glances toward the unmoving structure revealed their discomfiture. It was only when the US president and the Russian president arrived did the room quiet down.

Both men wearing dark power suits, were flanked by aides who they whispered to frantically before the monstrosity moved and indicated it was ready to speak. There were attempts to bring microphones to the object before it responded very quietly, that it didn't need them. The techs shrugged and ran away.

"Good afternoon, ladies and gentlemen." The voice boomed across the audience and a sound man in the back waved indicating something quieter was in order. "Three months ago, I was chosen as an envoy to a group of extraterrestrials who entered our solar system and requested asylum and respite in our sun."

The guests looked around trying to discover the source of the voice. "I am within the container you see before you. I am riding in tandem with one of the Sun Kings."

"These aliens who appeared to be forms of radiant coherent gas clouds came to our attention while they were moved at superluminal speeds through our star system. One of their members broke away and came to Earth sending a stream of prime numbers until we were able to detect and translate the signal.

"The aliens were remarkably intelligent and could learn most of our languages in under a day. Once we were able to communicate we offered them the opportunity to come to Earth and meet with them, discussing the terms of their asylum and path through our solar system. They were stopping here in order to use our sun as a temporary respite, hoping to refuel and recharge within. The second reason for their visit was far more germane to our survival.

"They were moving through our star system in order to warn organic sentient life of an impending gamma ray burst which is due to pass through our solar system in under five years. For those of you unfamiliar with gamma ray bursts, suffice it to say, they are a threat to anything along the path of their radiation stream. The burst which we are to expect has taken place some eight thousand light years from Earth. Two small unstable binary stars now orbit each other at a percentage of the speed of light. Both are small but massive and theoretically could generate a gamma ray burst of the type described."

Hands go up in the audience but the robot continues.

"According to the Sun Kings, this has already happened, but the light and radiation from that event had not reached us yet. Since you do not appear to be patient people I will take your questions now, with the understanding you may not like the answers you receive."

"Cody Nadier, DNN Colorado. Professor, can we still call you that?"

"Yes, Mr. Nadier. What is your question?"

"Why should an event that is eight thousand light-years away be of any concern to us, professor. I understand that the speed of light means we won't be aware of it for another eight thousand years."

The polarized surface of the robot created a representation of the professor's face. "Mr. Nadier, what you said would be true, that we would have eight thousand years to worry about this event if the two stars collapsed together, today. What the Sun Kings inform us is the event has already happened seven thousand nine hundred and ninety nine, point five years ago."

The carapace of the robot began to glow and a three dimensional display was able to be seen over the entire courtyard. It showed the perspective of the Sun Kings who were both in the path and outside of it. Tens of thousands of dots move into harm's way, attempting to rescue species very different from themselves.

"To our human telescopes we would still see them as they were back then because light may be the fastest known phenomenon in the universe, the Sun Kings are able to move faster and communicate far faster than the speed of light. From their perspective, this collapses has already occurred. They have been on a mission of mercy to talk with intelligent species along the radiation path in an effort to save them, if they wanted assistance."

"Benji Crocker, Reuters News Service. Do we have any information to confirm what they have told you thus far. Is it possible they are not telling the truth?"

"While we cannot directly confirm what has been said, we can see features of instability built into that system. Using a projection, we are able to determine with ninety percent accuracy, that in the next two to four years, give or take, something will happen to that binary star that we will be able to see. Our initial estimates say it will be the brightest supernova since the Crab Nebula was formed in 1054 AD."

The President rose and spoke before even being recognized. "What assurances do we have these aliens are not seeking to take over the Earth?"

"The fact they could have simply taken up residence in the sun and not bothered to tell us anything at all. Once they refueled they would be on their faster-than-light merry way, leaving us none the wiser."

The president's assistant whispered in his ear and he continued. "What do they suppose will be the result of this event? Why should we even care about an event so incredibly far away. My team of scientific advisers say it is unlikely to be a threat at that distance."

"No disrespect to your scientific advisers but when an alien species with the capacity to alter matter at the atomic level, move at faster than light speeds through a universe where as far as we know, the speed of light is the speed limit, can learn every language spoken on Earth in a day and move my living body into mental communion with one of their greatest scientific minds, I am going to err on the side of the species with the most advanced technology in the room."

The President of Russia stood up before the US President could even get his thoughts together and asked, "Do these beings offer us any solution to our problem or are they just space canaries telling us we are going to die soon? What will happen to the Earth when this gamma ray pulse sweeps over the planet?"

The Professor answered trying to explain this as clearly as he could. "The exact effects vary from planet to planet. But what the Sun Kings are certain of, is our ozone layer already weak and depleted will likely be obliterated within the hour of the radiation sweeping the planet. Any life on the side of the planet where the radiation strikes may receive strong doses of gamma ray radiation capable of killing everything exposed. But that is a short term problem. The true threat is the long term loss of the ozone layer. Without it, plants and animals all over the globe will receive lethal doses of radiation from our sun. Plants die. Animals without food, will die soon after. Food crops will perish and soon after starvation will sweep the planet. This is certain to be an extinction level event for Humanity."

The room exploded into chaos. The professor tried to regain control of the room but shouting, arguing and fighting began to break out.

The crystalline structure of the cylinder began to change and soon blazing white light filled the tent, so bright it was impossible to ignore.

"Please be silent." This voice was omnipresent, filling every corner of the space in a way the professor's hadn't. "We understand you are distressed. We have noted your technological level and realize you will be insufficiently prepared even in the five solar years before the event. We are partially to blame and beg your forgiveness. We had not considered there would be organic, intelligent life in this corner of the galaxy. Most of the life we have seen thus far has been inorganically-based and immune to the radiation of the gamma-ray pulse. If your scientists are correct, life on your world will be impossible to sustain. We come bearing a solution but we will only offer it to those willing to participate. Will you hear our offer?"

Everyone returned to their seat hoping the offer being presented would be better than the news they had received thus far.

The more human voice of the Professor returned. "I am being asked to explain the idea because I was, in theory, a proof-of-concept. You see, I was dying. I had an inoperable brain tumor and had only a few more months to live. The Sun Kings offered me the chance to ascend into a form of pure consciousness and become part of their collective of minds."

The murmurs began but stayed below the threshold of the Professor's voice. "They are prepared to take the entire human race into their collective mind. It would take just under five years to convert us all, but once they were refueled, we could continue on, trying to warn or save as many organic species as we could."

The president raised his hand to speak. "Our choices are die, starving and cold on a rock that will, as my advisers warn me, eventually return to life a few million years from now, or become part of an alien civilization we know nothing about, to leave the Earth and never return to a corporeal existence. Stop me if I said something incorrect."

"No, Mr. President, you summed it up quite nicely." The Professor's voice had dropped to a barely audible whisper.

"I can't speak for anyone else, the President continued, but I will live and die as a human being. Humans are resourceful. With five years, who knows what we might accomplish? You have already made your choice, professor, the rest of us still have one to make. Can I speak to the Sun King?"
"Certainly," the great booming voice returned.

"Can you selectively take Humans who want to go with you? Or is it an all or nothing proposition?"

"We can take any one or all of you as you see fit. It is not being forced upon you. Only those who wish to accompany us need do so. We will designate areas where your people can choose to go to be converted. Those of you who do not, may stay with your planet and accept whatever fate befalls you."

"What if I decide to tell my people not to accompany you? What if I tell them you can't be trusted, we know nothing about you or what your true motivations may be?"

The Sun King was silent for quite some time before answering,"That is your prerogative. However, we will still offer the same service to any who wish it. We will offer this until twelve hours before the pulse sweeps your world.

Then we will enter the Luminal Space and leave your world behind. You can tell your people whatever you like. We will still offer the service to anyone wishing to leave. Please do not make this decision. Your people deserve to make a choice independent of any social conflicts your perspective may place upon them. Millions may perish that did not need to."

The meeting ended soon after. World leaders returned to their countries. Some revealed the truth. Others colored it. Some lied outright. The Sun Kings said nothing. They retreated to the sun to recharge their powers with some returning to Earth taking up geosynchronous stations high above the planet barely visible from the ground. Humanity busied itself with the mission of preparing for the end of life as they knew it.

This was the most productive the human race had ever been. Wars dwindled as resources were rerouted into research and development. Vast construction projects took place boring into the surface of the planet's mountain ranges creating underground caverns and cities. Once the construction began, the Sun Kings dropped digging machines capable of using their powerful energies as boring beams into the mountainsides facilitating the building of these underground cities.

It was clear even with all of these amazing efforts, it would only house approximately thirty percent of the human population. No world leader would relent and tell their people they should go. With less than a year remaining, the Sun Kings returned to Earth and took over every form of media on the planet. Their message was simple.

"Your leaders have done everything possible to save and protect your species and your way of life. That life has come to an end. We can now accurately predict the arrival of the gamma ray pulse down to the second. Though your leaders have done what they think is best for you, we offer you a final alternative. If you desire to live beyond the gamma ray energies arrivals on your world, you have the option to give up your human form and live on as beings of luminous energy within us. You would still be individuals, with your own distinctive characteristics.

But you would also be part of a greater whole, a part of our civilization. We will not force you to do so. You must choose. We will place one thousand and twenty four of these cylinders on your planet. If you wish to leave with us, travel to one in the coming year and a half. Each cylinder will have a clock capable of telling you how long you have before we leave. No matter where you live on the planet, we will leave you with the choice of escape no more than a ten days travel from any one. If you choose to stay, we understand and wish you well. Be mindful of the time, we shall leave promptly twelve hours before the arrival of the pulse. We will not delay one second beyond that time."

With their message sent, modern media spun the story as little more than hype until the cylinders arrived all over the planet. They could not be moved once they landed. They could not be damaged or even scratched in any way. All a person had to do was walk up to a cylinder and say "I am ready." There was a flash of light and a still body was all that remained. If families preferred to take a body away, they were able to, if a person came alone, nothing was left to clean up.

A quiet exodus began. Entire cities cleared out over the remaining year, with fewer and fewer flashes taking place until everyone who wanted to leave was almost gone. The Professor had taken to manipulating his own much smaller cylinder into cities trying to convince the last holdouts to leave the planet. He had the Sun Kings create a more sophisticated cylinder for him, something that could be transformed into a human-like appearance. With this, he traveled to MIT to see his wife who refused to leave.

He found her working in her lab, researching new seed strains which were much more radiation-tolerant. His new body was clearly not human, but articulated enough to move as a human might. His footfalls were unable to be silenced but he wanted her to know he was coming. He had made several attempts already to convince her.

"Hello Dr. Harrison." He had spent many months working on the voice modulation, hoping to sound more human than before.

"I told you not to come back." She appeared to be packing up the last of her samples. "I am heading for the Cheyenne Mountain facility tonight." Two young soldiers were helping her with the last of her equipment. She waved them off and they wheeled the rest of her gear to the makeshift helipad on the campus.

"Karen, please reconsider. I have seen the energy-wave with my own eyes. The Sun Kings were right. We don't have much time. We can still be together."

She turned and walked over to the eight foot tall man-shaped machine. "Eyes, huh? Do you still have eyes? Do you still have the capacity to see visible light the way I do? Leave me. My husband is dead."
"I'm right here, baby. In a new body, but I have never left you."

"How do I know you aren't some alien trick. You know the government says the Sun Kings are killing people. None of them ever come back to see their loved ones. How do you explain that?" Karen stood in front of the roboform and looked up into its eyes.

"Most people take quite some time to adjust. It is hard to relearn all of your senses, how to think in your new energy state. Most of them will be months or even years before they are able to fully integrate with the Community."
"How did you manage so quickly?"

"You always said I was a fucking genius, remember? It's what you hated about me when I was your student. Your young and impressionable student. You remember the time..."

"Don't do that. You will never be able to do that with me again. You aren't my husband, anymore. You're this, this, thing." Karen began to weep uncontrollably. "You promised me you would never leave me." She began to strike the robotic body, flailing wildly against it. Its structure softened becoming softer, like a clay.

Winston took his wife in his malleable arms and held her. "I never would have left you. I would have died on schedule without them. They saved me. Let me save you. Tonight is the last night. By dawn, they will be gone."

"Will they ever come back to Earth?" Karen began to regain her composure. She wiped her face on her lab coat and took it off, putting some space between her and the now kneeling robot.

"They said it would take them some time because there were several other Organics they knew about and wanted to warn along the way. They told me we could be back in as little as thirty years."

"My husband died five years ago. I know you think you are Winston but you aren't. Winston was a body, not a machine-created consciousness. He was flesh, given human frailties by God and you are not him. Please see yourself out."

"I could make you come with me. Transfer your consciousness even without your permission."

"I suspected as much. Winston would never do that."

"You are saying, if I loved you as Winston might, I would leave you to die here on Earth, starving and cold on a planet barely able to support life in thirty-six hours, right? You know what, you're right, I am not Winston. Winston might have been a genius but he was a human genius with all the failings and frailties a man could have.

"How could he have known an alien race would come to Earth and say 'Sorry, your lease is up' and transform his dying body into an immortal god-like one. How could he have known he would one day race a beam of light and win, see radiation and all the hidden mysteries of the Universe? He couldn't. You are right, your Winston Harrison is dead. But I love you, and if I told you this was the right thing for us, once upon a time you would have believed it and never questioned it.

"Why would you do that now? We still have time. We can get you to the local cylinder in Boston and you can still join us. Join me. Until death do us part. I didn't die, Karen."

She looked at the machine, its inorganic lines and nearly featureless face. She listened to the words, the sound, the cadence and the rhythm of its voice and she knew what she had to do. She turned and ran from the building.
Winston did not follow.

No need to walk, he floated down out of a window and down to the ground. He watched the last of the crews and helicopters going up. They were racing daylight. Most would get to their bunker cities in the Appalachians just under the wire. The pilots knew this and flew as fast as they could. The emptied streets spoke in the same voices as a cemetery might, of longing, of hopes long dashed against the shores of time. Winston rose into the sky and began his final flight to the cylinder.

In the street below him he spotted a single person running and waving. He thought it might have been a person left behind. He had sufficient speed to get whoever it was to the bunker city before they closed the door. A last gesture of humanity before leaving, he mused.

Swooping toward the ground, he recognized the hair and suit. It was Dr. Karen Harrison. "Did you miss your ride, Doctor?"

"No sir. I was hoping you might be able to give me a lift to see my husband."

"I think that can be arranged. Hold on tight, we will have to be moving quite fast to beat the deadline."

Karen smiled and held tightly onto the robotic body. "My husband was known for breaking barriers all the time."

"Yes, he was. But there was never anyplace I wanted to be that you weren't. I could've worked at Oxford."

Karen chuckled, "Do these Sun Kings have an energy equivalent of coffee?"
"Nope, but once you've drunk from a star, coffee just doesn't hold up."

"Then make sure we get a cup of sunshine, to go."

"I think I can arrange that. I know someone, who knows someone."

The last cylinder left the Earth, twelve hours before August 15, 2034 PST.
The doctors Harrison dipped through the corona of the Sun on their way out of the solar system, never looking back.

Sun Kings © Thaddeus Howze 2014, All Rights Reserved

Anything that destroys our consciousness before our Mind gets a chance to interpret it as the end of consciousness ( consciousness is the projection of mind as identity) can kill us without our knowing ( not knowledge, mind you)

It does not necessarily have to be instantaneous - people can die in sleep, or in a coma, or a bullet passing through the midbrain. In the first two instances, mind can't interpret the threat at all, whilst in the last case, midbrain that is the seat of important nerve plexus that control the body ( respiratory, circulation) etc is instantly severed off from forebrain where most of the interpretation takes place.

ETA : the above three are just examples I have chosen. The basic principle and the answer to your question is in the first paragraph of my response.

Any high-order detonation that happens near to you. Not talking pipe bombs here, which are typically filled with class B explosive mixtures that wreak their destruction by bursting their container and projecting shrapnel away from the explosion.

Class A explosives (dynamite, TNT, many military explosives) generate an air shock wave that is thin, dense as steel, and that moves outward from the explosion at many km/sec. This shock wave can completely emulsify tissue (brain included), and pretty much instantly stops brain function. A victim's nervous system would not even have time to generate a perception of the event before the victim was completely dead.

If by “us” you mean “the entirety of life on Earth”, a vacuum metastability event would do the job quite nicely.

The false vacuum hypothesis postulates that the vacuum our universe exists in is not, in fact, the lowest energy state possible. While to us, it would be plausibly indistinguishable from a true vacuum, a false vacuum is fundamentally unstable and cannot survive indefinitely. This can be visualized as such:

Our current universe (under this theory) would exist at the “dot”, seen at the local minimum of the energy states - the right “valley” of the graph. While it is the smallest energy state for our section of the graph, it is possible that a large enough release of energy could push us over the hill on the left, so to speak, and into the lower energy state of the absolute minimum - the one at the bottom of the left “valley”. Such a change in vacuum states would create a bubble of lower-energy vacuum space that expands unstoppably outward at the speed of light.

As the new vacuum bubble expanded, it would leave the universe almost unrecognizable. From Wikipedia:

everything around us, from subatomic particles to galaxies, and all fundamental forces, would be reconstituted into new fundamental particles and forces and structures. The universe would lose all of its present structures and become inhabited by new ones… based upon the same quantum fields.

Not only would such a universe be uninhabitable to life, it is very likely that matter as we know it would no longer exist. The fundamental forces of the Universe would be drastically changed, potentially resulting in atoms decaying within seconds of forming or leaving complex chemical bonds impossible. Needless to say, we would die. Instantly. And since the vacuum bubble perpetuates at the speed of light, there would be no possible way of knowing it was coming. We would simply cease to exist.

So, I hear you ask, is the false vacuum hypothesis correct? Are we, at any point, instants away from being blasted out of existence?

The answer is we're not sure. The inflationary model of the universe allows for both true and false vacuum states to form, and differentiating between them is extremely difficult from the inside. We can make predictions on the state of our vacuum based on the energy of the Higgs Boson and the top quarks, but both of these measurements are still rough and any change in the Standard Model would cause these predictions to be immediately invalidated (in case you were wondering, the current measurements are just on the edge between a true vacuum and a metastable one that is prone to collapse).

So, the next time you think you had a bad day, you can always console yourself by appreciating the fact that the universe has continued to allow you (and the rest of the world) to exist.