In the year 1950, nuclear physicist Enrico Fermi asked a question now known as the Fermi Paradox: If there are so many alien civilizations in our galaxy, the Milky Way, as some scientists suggest, why have we seen no evidence of their existence? (0) 1. Decades of searching for alien civilizations have not produced any results.
With an estimated two hundred and fifty billion stars in the Milky Way - and an estimated one hundred and forty billion of her galaxies in the visible universe - there should be a LOT of planets out there that can support life. We just have to find them.
The first planet orbiting a star other than our sun was discovered only in 1995. Since then, we have only managed to find another three hundred or so, and nothing to suggest the existence of an alien civilization. Maybe NASA's Kepler mission will speed things up.
One problem is that the universe is BIG. If you leave the solar system, you come across a lot of nothing. You enter a vacuum - emptier than any vacuum we can create in a laboratory.
This is Proxima Centauri, which is 4.3 light years away. And the next thing you'll bump into, Sirius, is another 4.6 light years away.
According to the Drake equation, formulated by Dr. Frank Drake in 1961, there should be millions of civilizations in the Milky Way galaxy alone.
The trouble is, because the Milky Way is so big, the average distance between any two civilizations would be around two hundred light years. Let's imagine that aliens that far away are watching our world at this very moment through a telescope.
They're watching a world at the beginning of the nineteenth century - with no cars, no computers and no mobile phones.
There is also the problem of travel. Voyagers 1 and 2 are travelling through space at 56,000 kilometres an hour - the fastest speed ever achieved by a man-made object.
It took them all of 12 years to cross the orbit of Pluto and it'll take 10,000 to reach the Oort cloud at the edge of our solar system. At this speed, it would take over 60,000 years to reach the nearest star and around three million to reach the nearest theoretical civilisation.
Finally, humans have been technologically sophisticated for only about a hundred years. That is one hundred years in a solar system that is 4.6 billion years old and a universe that is almost as old as 14 billion years. So what are the chances of another life form becoming technologically sophisticated at the same time as us?
Alien civilizations may have appeared and disappeared hundreds of millions of years before us, or are scheduled to appear hundreds of millions of years after us.
All in all, for an alien civilization to appear at the same time as ours and near enough to ours is very unlikely indeed. Maybe we are not alone, but in practical terms, we most certainly are.
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