Are we alone in this Galaxy, or even the universe? A question that has no answer right now or in the foreseeable future.
When you take several factors into account it is hard to imagine that we are alone. There are hundreds of billions of galaxies in the universe and in our Milky Way Galaxy alone there are hundreds of billion of stars. Orbiting around those stars are millions of rocky planets in the Goldilocks zone.
Water, the most essential element of life as we know it, is abundant. It seems to exist everywhere. Just recently the scientists believe they have found the presence of amino acids on Mars that are the building blocks of life.
But, we have never found life itself outside of earth. And, scientists have never been able to produce life from the same compounds that are known to be essential.
However, the amount of sky we can explore is limited, so the jury is still out.
Consider this. We, that is humans, are an accident. A freakishly unlikely accident. A series of events, that would be highly unlikely to be reproduced on another world, resulted in us, by us I mean a sentient being able to produce high technology.
First of all, we find ourselves in the Goldilocks band in our orbit around the Sun. Just the right distance for liquid water. Not that unusual.
Another fortunate characteristic is, we have a molten core which produces a magnetic field that protects us from the deadly cosmic radiation. That is common to all rocky planets, but we are just the right age to have a molten core with a solid crust. I.e not too old and not too young. Radiation exists everywhere in the galaxy. Without that magnetic field, life on the surface of the earth would be impossible. Life on Mars is impossible now because the molten core that it once had has cooled and solidified. The magnetic field has long since collapsed and cosmic rays bombard the surface.
Our Solar System is located at the edge of the galaxy at the outer edge of one of the spiral arms. Deeper into the galaxy, it is likely that cosmic radiation would be too intense for a higher form of life to flourish.
Back when the earth was young, it seems that a collision by another large object was so violent that a huge chunk of the earth was ripped away and became, after a few million years, our large moon. It is a large moon. It's relatively the largest in the solar system. Without that moon we wouldn't be here. It stabilized the earth's rotation around a stable axis. The earth once rotated at a rate of 4 hours per cycle. It's the reason we have had a constant near 24 hour rotation period for millions of years allowing the growth of higher level organisms. Of the millions of rocky planets in the Milky Way, how many of them are fortunate enough to have a large stabilizing moon? Unknown.
We live in one of the older and largest galaxies in the universe. As far as we can see we are not producing stars any more. But our time is only a split second in the total time line of the universe. Other planets in this galaxy and others may have already come and gone. After all, when our core cools off we are doomed.
The earth has undergone multiple mass extensions during it's life. Mass extensions always eliminate the current dominate species allowing a new form of life to emerge. The second to last mass extinction resulted in the rise of the dinosaurs who ruled the earth for over a hundred million years. The last mass extinction was likely caused by a huge comet or asteroid impacting the earth near what is now the Yucatan peninsula. This doomed the dinosaur to history. Without that event the mammal would never have been allowed to grow from a small little rodent like creature. The big guys would have just ate him.And, there is no way I can see the dinosaur evolving into a sentient creature. No need too.
We, that is Homo Sapiens, almost didn't make it according to people who study such things. We were close to extinction ourselves at one time in our birthplace, Africa.
When the first creature climbed out of the oceans onto land they had 4 appendages. Somehow 4 appendages turned out to be the optimal number, at least in our environment, so every air breathing creature except the insects and spiders who subsequently evolved from those primordial days have exactly that number. The 4 appendages turned out to be just the right amount for the development of upright posture that let our hands free for other things except moving and climbing trees. What if the first creature had 6 appendages, or only 2? Would that creature have evolved to an upright walking, big brained being that is us? Certainly not like us. The world would have been completely different.
The most fortunate evolution that produced Homo Sapiens is the development of the opposable thumb. Something that no other species on earth has. Without that feature, we would be forever at the level of an ape. Pretty smart, but not able to produce any kind of complex tool. Another freakish accident?
Of course the question arises; what made the first creatures leave the seas and come onto land? It was probably self preservation. The oceans were teeming with other creatures that love to eat. So, perhaps the first creatures to leave the oceans did so to escape the carnivores. But, what if in another world there were no such carnivorous creatures? Then there would be no reason for our distant ancestors to leave the comfort of the oceans.
It is likely that life actually developed on other planets in our galaxy and in the universe. The numbers say that it did happen. Not necessarily at the same time as we developed. After all, we are only 4 billion years old. However, I think that any such life would look nothing like us, even though we would likely have much of the same characteristics. They would likely be O2 breathers, although maybe not with lungs as we know them. Oxygen is essential for the burning of carbon based fuel, and it is likely that any life in this universe would be carbon based.
My conclusion. The universe and this galaxy is probably teaming with life, but I think that a level of sentience able to produce higher technology is exceedingly, and I mean exceedingly, rare. We may very well be unique in this galaxy and even, perhaps, the whole universe. Wouldn't that be something? We will likely never know.
There are few ways we might find out. Perhaps we will get some kind of signal from outer space indicating that a high level of intelligence exists. Certainly we're constantly looking for such an indication.The only other way is--- to do to the impossible. Find a way to travel great distances much faster than light and go exploring. The UFO hunters will say it is possible because some other intelligent species has already done it and have visited earth many times in the past. If you believe that, I have a bridge in Brooklyn I would like to sell you. However, I've been wrong before, so we'll see.
