Courtesy of Spaz at Mind of Spaz. He's smart, funny, and writes thoughtful posts. Oh, and he's another awesome Canadian blogwriter. He makes me laugh. A lot. Thanks for the post!
Our world is in constant motion. The planet earth teems with life, and all life puts energies into the planet. Plants grow, animals rear young, and the human industrial machine is moving forward at an exponential rate.
Still, all the energies put out by life on this planet that seem astronomically huge to the average human are naught compared to the movement of the planet itself. Our thirteen-thousand kilometre wide planet spins on its axis one full rotation every twenty-four hours, and hurtles through space at an astounding thirty kilometres every second! Not only do earth and the other planets rotate around our sun, but our sun rotates around our galaxy. Our sun, and by proxy, our planet with us on it, makes the trip around the galaxy once every two-hundred and thirty million years.
My intention is not to bore you with remedial facts about energies and motion, but to introduce the concept of our celestial cycles.
Our sun does not stay on its plane as it screams through the galaxy. Scientists have discovered that it makes an up and down motion as it travels. The suns motion would be much akin to a child’s yo-yo toy, as he bobs it up and down while walking down the street. As the sun’s permanent partner in this never ending road trip, we actually see a large portion of our galaxy.
Therein lies the problem.
The galaxy contains an almost unimaginable number of stars. There are four hundred thousand million stars that we call neighbours, yet they are spread out over a diameter of one-hundred thousand light years. To put that kind of size in perspective, the speed of light is approximately three-hundred thousand kilometres per second, which gives our galaxy a diameter of, well, my calculator gives me an eighteen digit number. The spacing of our galaxy allows for light years in between stars.
Our solar system spends most of its time dwelling in the low density area of the arms in our spiral galaxy. Because the solar system travels in an up and down motion as well as a forward one, every thirty million years we pass through the high density central area of our galaxy. Scientists call this area the "danger zone", and for good reason.
The spacing between stars in the danger zone is still unfathomable to the human imagination, there is no argument there. But compared to our usual position in the galaxy, the star spacing can be akin to a subway during rush hour. By the standards of celestial mechanics, it’s much too close for comfort.
The very out most edge of our solar system contains a vast sphere of huge chunks of ice and dirt, some tens of kilometres in diameter. At the thirty million year mark, when our solar system passes through the danger zone, increased gravitational forces push some of these large masses speeding towards our solar system at incredible rates of speed. As they get closer to the sun, they develop plumes of gas and dust, and we now know them as comets.
These thirty million year comets take one million years to reach our solar system. That means that every thirty one million years, our odds for getting struck by a massive celestial body increase exponentially.
Compared to the average human lifetime, and even the time that we have been around on this planet, thirty-one million years seems like forever. But there is something that you need to know, something that puts all that time into sharp focus.
We are now at our thirty one million years.
That is some very sobering information. We are at our thirty one million years, and an unknown amount of comets of unknown sizes are at this very moment speeding towards us.
Are they millennia, centuries, decades, or years away from us? Will they hit us, or miss us by millions of kilometres? We don’t know for sure, as astronomers cannot pick up or track these bodies until they are very close to us. They are coming, and they are very close, as evidenced by the shoemaker-levy comet hitting Jupiter in 1994. The comet was massive. Even though the intense gravity of Jupiter broke the comet into pieces before it hit, each piece created an impact area larger than earth itself.
Jupiter is, by and large, our saving grace. The massive planet pulls in many of the travelling celestial bodies that otherwise might cross paths with earth. Our solar system is a very active place, and without Jupiter, we surely would not be here to this day.
That does not mean we go without our fair share of space missiles impacting our planet. We get hit on a daily basis; luckily most of the bodies that rain down from the heavens are so small as to burn up in our atmosphere before ever reaching the ground. Some are large enough to do some damage, and there is evidence all over our planet of large craters. Indeed, some are so massive as to still be seen despite our planets ability to erase and change its surface through dirt deposits, ecological activities, tectonic plate movements and the like.
There is, however, a reason to be concerned with our thirty-one million year mark. Evolutionary history is not a constant. Rather, it is a series of events, springing from the ashes of evolution before it. Palaeontologists have found that there are massive extinction events which are very common to the history of life on earth. Scientists discovered approximately twenty events in history where the majority of life on earth vanished, was extinct, was wiped from the face of the earth.
There is an ominous pattern to these extinction events. Whether it’s from comet strikes are not, mass planetary wide extinctions seem to have a pattern of every thirty million years or so.
The evidence seems clear. Our time on this planet is limited, and it may not be of our own doing.
Indeed, the shrill shrieks of the planets eco warriors and the grunts of our greedy money driven industrialized economy are trivial in comparison to the celestial pattern of destruction and rebirth.
What are we to do, then, if we are interested assuring continued human existence?
There are two bodies of thought for protecting ourselves from being hit by a large body from space. The first involves a method of blowing it up, or using rockets to nudge it out of the way. This may or may not work. The only way we will know is to try it, and if it doesn’t work, we can kiss our lives good bye.
The second way is to colonize the universe.
Diversification is the best way to assure the survival of our species. If we can put our energies into developing the technology to finding other habitable worlds and to getting there, the destruction of earth will be the great tragedy, but not the apocalypse.
Compared to the ultimate certainty of the next impending mass extinction, all human differences are moot. When it happens, the differences of religion, race, creed, colour, and locale mean nothing. To assure continued human survival past the next and ultimate event, the human race must realize the folly of hatred and intolerance.
We must push aside our class structure, our greed, our quest to be financially successful. All of our energies must be put towards the technology needed to purchase the ultimate of all insurance policies.
It is only when our species spreads throughout the stars that we will be truly safe from destruction.