Quote:
Originally Posted by GregE
They would sure need a lot of patience however. The nearest possible earth like planets are tens of thousands of light years distant.
|
Our sun is relatively young in the lifespan of the universe. There are far older stars with far older Earth-like planets, which should in theory mean civilizations far more advanced than our own. As an example, let?s compare our 4.54 billion-year-old Earth to a hypothetical 8 billion-year-old Planet X.
Planet X
If Planet X has a similar story to Earth, let?s look at where their civilization would be today (using the orange timespan as a reference to show how huge the green timespan is):
Planet X vs Earth
The technology and knowledge of a civilization only 1,000 years ahead of us could be as shocking to us as our world would be to a medieval person. A civilization 1 million years ahead of us might be as incomprehensible to us as human culture is to chimpanzees. And Planet X is 3.4 billion years ahead of us?
There?s something called The Kardashev Scale, which helps us group intelligent civilizations into three broad categories by the amount of energy they use:
A Type I Civilization has the ability to use all of the energy on their planet. We?re not quite a Type I Civilization, but we?re close (Carl Sagan created a formula for this scale which puts us at a Type 0.7 Civilization).
A Type II Civilization can harness all of the energy of their host star. Our feeble Type I brains can hardly imagine how someone would do this, but we?ve tried our best, imagining things like a Dyson Sphere.
Dyson Sphere
A Type III Civilization blows the other two away, accessing power comparable to that of the entire Milky Way galaxy.
If this level of advancement sounds hard to believe, remember Planet X above and their 3.4 billion years of further development. If a civilization on Planet X were similar to ours and were able to survive all the way to Type III level, the natural thought is that they?d probably have mastered inter-stellar travel by now, possibly even colonizing the entire galaxy.
One hypothesis as to how galactic colonization could happen is by creating machinery that can travel to other planets, spend 500 years or so self-replicating using the raw materials on their new planet, and then send two replicas off to do the same thing. Even without traveling anywhere near the speed of light, this process would colonize the whole galaxy in 3.75 million years, a relative blink of an eye when talking in the scale of billions of years:
Colonize Galaxy
Source: Scientific American: ?Where Are They?
Continuing to speculate, if 1% of intelligent life survives long enough to become a potentially galaxy-colonizing Type III Civilization, our calculations above suggest that there should be at least 1,000 Type III Civilizations in our galaxy alone?and given the power of such a civilization, their presence would likely be pretty noticeable. And yet, we see nothing, hear nothing, and we?re visited by no one.