In the vastness of the Cosmos, we are just a "pale blue dot" as Carl Sagan said. With over 400,000,000,000 (400 Billion) stars in the Milky Way Galaxy Alone and about 6 billion people on planet Earth, that translates to 66.66 stars in this Galaxy for every human being on this planet. Now multiply that by the 100s of billions of 'known' galaxies and you get a huge, huge number. That coupled with the fact that since 1995, we have found hundreds of extrasolar planets, it is almost certain that we cannot be alone in this universe. But despite all the vastness of the Cosmos, one fact remains - Earth is still our only home. We have nowhere else to go yet. So the opinion of Dr. Stephen Hawking about whether we should be careful about inviting alien species here for fear of them being hostile to us is a very wise opinion. The Earth is just too precious.
But there are other aspects to this whole debate. Take the example of Christopher Columbus travelling across the Atlantic and finding the Native Americans. Their communication technology of that time was limited to perhaps 'smoke signals'. So, its not that Columbus knew that they were there when he came. He would have come anyways. Likewise, the aliens would not necessarily even be able to detect our radio and TV signals. Who knows what kind of technology they use. Maybe our technology is actually too primitive to be detected.
Take the case of ants, dolphins and whales on our world. They obviously are able to communicate with each other. Ants are able to make complex colonies. Yet we humans don't even know what they say to each other. We don't treat them like fellow intelligent beings. Why would an alien even bother about us? How would they communicate with us if they are much higher on the evolutionary scale. It is like us trying to communicate with ants. Perhaps they are so far ahead of us that they are already here and we are not able to observe them, much like amoebae do not have any idea when we watch them under a microscope. There are so many possibilities.
But the one thing that we need to do is keep on looking for life. Even if we are never able to have a meaningful conversation with an alien either too ahead or too behind our scale on the evolutionary ladder, we must keep looking for those who are more or less at the same level.
Perhaps we will only learn the secret of interstellar travel when we have been able to survive without killing each other. Maybe we will come into contact only when we evolve into a higher state of consciousness as a species. Maybe we are still in the stage of a cocoon and must evolve more before we are able to venture out into the Cosmos. Maybe. Maybe. Maybe. Perhaps. Perhaps. Perhaps. One day we will find the answers.
But unfortunately we are still earthbound and this is something we need to take very seriously. We have all kinds of issues here on terra firma - terrorism, environmental problems, poverty, etc. We need to tackle these first and then ultimately if we are to survive as a race - we must venture out into the stars - aliens or no aliens - the future of humanity is in space. If our civilisation is to survive in the long term, we have to colonise the Galaxy or at least to begin with our little measly corner in it.
