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10 reasons why earth was able to develop intelligent life
The numbers say we are not alone...
The universe is a VERY big place. I'll put it into perspective for you...
Light can travel at around 186,000 miles per second. This means that Light will travel over a trillion miles in a year. This distance is known as one light year. The size of the universe is thought to be around 13.5 BILLION light years. That's a BIG place!
Our galaxy is thought to be a mere 100,000 light years across. It is one of many millions of galaxies in the universe. Each galaxy (or most standard sized galaxies) will contain hundreds of thousands, maybe millions of stars, and it has been said that there are likely to be more stars in the universe than there are grains of sand on all of the beaches on the Earth combined.
It is quite likely that the majority of these stars will have planets orbiting them, so there are probably billions of planets in the universe. Surely at least a handful of these planets could support intelligent life?
Are we alone in the universe?
This is of course one of the most interesting and profound questions that any person can ever ask. It must be right up there with; ''What's the meaning of life?'' and ''Why always me?'' (quote courtesy of Mario Balotelli).
Seriously though, it's perhaps one of the more profound life questions that we might one day be able to answer - and hopefully one day soon.
It seems very likely that there is other life out there besides the life forms that live on our planet. Scientists think that basic life forms will flourish anywhere where there is water, and it seems that water may be plentiful in it's various states (solid, liquid or gas) throughout the universe. Water is so important in helping life to form because it is an excellent mixer of chemicals and chemical compounds. And when certain chemical compounds mix together under certain temperatures, pressures and light, basic organic materials (the building blocks of life) can form.
Working on this principle, it may well be that there is life out there even within our Solar System. Europa (a moon of Jupiter) has a frozen surface layer of ice which is many kilometres thick. But underneath that layer of ice is thought to exist a huge ocean of water, which is kept from freezing by heat that comes from within Europa itself. Could this alien ocean contain life? Quite possibly yes. But complicated life? Very unlikely. The fact that there would be no sunlight in the waters under the ice of Europa would make it difficult for life to evolve to beyond a certain stage.
It seems to be the same story with most of the alien moons and planets (both inside and outside our solar system) that scientists have discovered. Some of them may be able to support basic life forms, but virtually all of them are extreme environments; they orbit too close or too far away from their stars to allow anything but basic life to develop that is able to life in extremes (otherwise known as extremophiles).
The Good Fortunes of Life on Planet Earth
The right place in the galaxy
Our solar system is fortunate to be situated near the outskirts of its galaxy, the Milky Way.Nearer the galactic centre, stars are situated far closer to each other than in the galactic suburbs. And when objects are situated closer to each other, trouble awaits....
There is a vast array of dangers out there; Giant stars which die in massive supernova explosions, deadly bursts of Gamma rays which can come from these explosions, black holes which can also result and will suck in any matter that gets too close to them, deadly radiation from Neutron Stars....and these are just a few of the dangers.
Thankfully, our solar system and therefore planet Earth is nowhere near these life destroying (not to mention planet destroying) phenomena.
The Perfect Star
Our sun is a medium sized star, and is halfway through its 10 billion year life. Larger stars burn through their fuel far quicker, and last mere millions of years, before dying in spectacular supernova explosions.
Therefore, life on Earth has had enough time to evolve to the point of being intelligent, rather than evolving to be just an organic cell or two before the star it orbits destroys the planet.
Forming in the ''goldilocks'' zone
Around each star exists a narrow band called habitable (or goldilocks) zone; A zone where life forms are able to flourish on the given planet. Any planet closer to the star than the habitable zone will be unable to support complicated life because it gets too much heat from its star. Any planet further away from the star than the habitable zone will be too cold to do so.
In our solar system, Venus and Mars lie at the opposite ends of the habitable zone, though both are still extreme worlds. Mars is a dusty and frozen desert planet, where temperatures regularly drop to below those of anywhere on Earth. By contrast, Venus is a planet blanketed by thick layers of acidic clouds, that create a massive planetary greenhouse effect, where temperatures usually exceed 500 degrees Celsius.
Both of these planets are thought to have once been able to support life forms, but because of their locations on the edge of the habitable zone, they soon lost that ability.
By contract, the Earth is exactly in the middle of the habitable zone, and has been able to support life comfortably for billions of years, giving it time to evolve into our intelligent species.
The Giant Impact Theory
It is now widely accepted by scientists that early on in its history, an object the size of the planet Mars (often known as Thea) collided with the young planet Earth. While this may sound disastrous, this collision is actually one of the reasons why we were able to evolve.
4.4 billion years ago, the Earth was a far smaller planet than it is today - until the so called 'giant impact' occurred. The impact caused massive damage to the planet and flung much of the Earth's crust into orbit around the planet, but because Earth was the larger of the two bodies, it was able to absorb the blow and remain intact, while much of Thea was either flung off into space or absorbed into the body of the Earth, making it considerably larger.
The debris from the collision that orbited the Earth was soon pulled together by gravity to form the Moon (more on that in a moment!). Meanwhile, the enlarged Earth formed a large, molten and metallic core - a core which generated a massive magnetic field around the planet.
This magnetic field allowed Earth to develop a rich atmosphere, and it also keeps much of the sun's harmful radiation and charged particles from penetrating into the Earth's atmosphere, making it far easier for complicated life forms to evolve. The planet Mars is an example of a planet which doesn't have a large magnetic field (due to it's small core) and so the surface of the planet is bombarded by harmful rays from the sun, and there is precious little of an atmosphere above the planet.
As you may have already realised, we are lucky to have the moon at all; the chances of the giant impact between Thea and Earth happening early on in the Earth's history must have been pretty small. But when the moon did form after the collision, it performed and still performs several very important and crucial functions that helped life to develop and evolve on the Earth.
First of all, it's gravity keeps the tilt of the planet at a constant angle, and stops the planet from wobbling wildly around on its axis. This constant angle of tilt creates the seasons on Earth. A wobbling Earth would have fewer but far more extreme seasons than we know today. The moon's gravity also tugs on the Earth's oceans, to create the tides. This would have helped in the early days of the Earth, when the huge rolling tides would have allowed organic compounds to mix together more easily to create life forms. Later on in the Earth's history, tides would have also helped life make the leap from the seas and on to the land. The Earth's first amphibians would probably have ventured onto land when the tide was out, because it made it easier to do so.
The tides also carry warm and cold currents around the oceans of the world, regulating the temperature and ensuring that a huge variety of life forms can flourish in them.
The moon itself is also large enough to have a big enough gravitational effect on the planet.
Earth is lucky to have a crust which has been broken into several large segments, that float on the layer of molten magma underneath (known as the continents). The continents drift on the magma and are constantly interacting with each other, causing volcanic activity, mountain formation and earthquakes.
Volcanic activity is especially important. When molten material and chemicals from volcanic activity find their way into the ocean, the chemical compounds bind together to form organic matter. Volcanic activity also releases gases into the atmosphere, which act as a blanket which keeps out some of the sun's harmful rays, and keeps the planets temperature constant.
Jupiter being in the right place
Jupiter is by far the largest planet in the solar system, and therefore has by far the largest gravitational pull of any planet. It is situated further out from the sun than planet Earth, and so most passing asteroids and comets will be drawn into Jupiter's gravity and may collide with the planet itself, rather than hurtling inwards towards the sun and possibly colliding with the Earth.
In other solar systems, many of the largest orbiting planets have formed close in to their stars, so we are very lucky that Jupiter has formed further out, where much of the dangerous space rocks come from.
Any large rocks which collide with the Earth can (and have) devastated life on the planet, and so these collisions are thankfully relatively few and far between.
Asteroids and their role in evolution
This does not mean to say that all asteroid collisions have been a bad thing, though. It is thought that much of the Earth's water came to the planet from Asteroids and Comets, which hit the planet early on in it's history, and deposited their frozen water. And water (as we know) does wonders for life...
Space rock collisions also help to keep evolution constant. During the reign of the Dinosaurs, the giant reptiles ruled the Earth while many of the Earth's smaller creatures (such as the mammals of the day) had to hide away and were unable to evolve much on their own.
But when a giant Asteroid hit the Earth 65 million years ago, the Dinosaurs were wiped out. The surviving creatures were then able to colonise the hole left behind by the Dinosaurs, and were able to evolve into bigger and more intelligent life forms. Asteroids can help when evolution gets stuck in a rut...
Mass extinctions can and have come in all shapes and sizes in the planet's history;
750 Million Years Ago; The Earth suffered a gigantic and long lasting global ice age, which killed many of the species on the planet at the time.
450 Million Years Ago: Some sort of event (some scientists think it was a gamma ray burst from a distant star that hit the earth) destroyed much of the life on Earth.
250 Million Years Ago: A huge upsurge in volcanic activity released massive amounts of climate changing gasses into the atmosphere. This lasted for millions of years, and up to 95% of life on the planet perished as a result.
65 Million Years Ago: 70% of the Earth's species died out after a massive Asteroid slammed into the gulf of mexico, creating a massive shockwave and blanket of dust and gas, which changed the world's climate.
Ice Ages: There have been many global ice ages since the age of the Dinosaurs, the most recent being a few thousand years ago. Each of these has served to wipe a few species off the face of the planet forever.
In short, what these seemingly catastrophic events have done is to ensure that evolution has never stalled. No species of life has been able to dominate for too long, giving the chance for other species to survive them, take their place and evolve further.
Not too many Mass Extinctions....
If these events happened too often, then life wouldn't have enough time to evolve much. If they didn't happen often enough, life would get stuck in a rut. Thankfully, they happen at just the right rate.
And finally - So far, we've been lucky...
As developed and intelligent humans, we have yet to endure a so called ''mass extinction'' event. Luckily, we have had time to evolve and grow brainy and intelligent. But the question remains; Would we be able to survive one? Could we adapt to the aftermath of a mass extinction? Only time will tell.
In Yellowstone Park, a Supervolcano will likely erupt within the next few hundred thousand years, devastating the planet. In outer space, rocks hurtle around the sun at thousands of miles per hour, avoiding our planet for now....
Intelligence - The Final Verdict
So we must take all of our planets enormous good fortune into account;
1) Being the right place in the galaxy
2) Orbiting around the perfect star
3) Being in the middle of the habitable zone around the sun
4) The Giant Impact with Thea
5) Our Moon
6) Having Plate Techtonics
7) Jupiter being in the right place in the Solar System
8) Having had Asteroid collisions with the Earth
9) The right number of Mass Extinction events
10) No large Mass Extinctions In the history of intelligent mankind. Yet.
And these are just some of the reasons why our planet has been so fortunate, and able to develop intelligent life.
With all of these and far more variables, it is easy to see why we are yet to discover any other intelligent life in the universe; It would have to be hellishly lucky to have evolved to that point in the first place.
Despite the massive odds against though, it must be remembered just how vast the universe is. Because of the probable sheer billions, if not trillions of worlds out there, it is quite possible that the odds have triumphed somewhere, and that we are truly not alone.
But it is also likely that we will never meet our fellow Brainiacs, because the universe is so vast a place.