What is life?

I've written several essays on life, but I would like to explore the definition so that if we ever do encounter alien life, we might be able to recognize that it's alive.

This question has bugged philosophers from day one. Back at the beginning of philosophical thought life was not all that hard to appreciate. Anything that grew, moved or reproduced was considered alive. That included plants, insects and larger creatures. Along came religion and the definition included the idea that all life was created at one time, which is the genesis theory.

Unfortunately, mankind was not aware of bacteria, viruses, and other tiny things that couldn't be seen with the naked eye. No one was aware of evolution or that millions upon millions of species had lived and died off in geological times. Early men weren't stupid. They were just ignorant.

Then along came science and stirred the pot up. At first, science wasn't interested in how the life got there. It only wanted to understand how it evolved and how to categorize it in a system that's known as taxidermy. But, even science was overwhelmed with the immeasurable number of species and variation of life that could be seen on Earth. Only after astronomy revealed that there is many other planets out there did anyone suggest that alien life was even possible.
As a matter of fact, mankind thought that the whole universe was here on Earth. No one questioned what all those points of light were up in the night sky. They thought those represented gods.

It wasn't until the concept of the biological cell was revealed before a more realistic understanding of life was possible. We now know that all life on the planet Earth is constructed from cells that contain DNA, the blueprint of life.
The basic definition of life is that it moves, exchanges chemicals and energy with its environment, and that it reproduces. We can add the ultimate characteristic: DNA now that we know that it's important to the act of reproduction.

So, how would we know if an alien planet has life? The answer is that we would use the above definition. But, would all possible life have DNA?

That's a great question. Is life possible with some other chemical scheme? The fact is we don't know. Some have suggested that life could be based on silicon instead of carbon. However, silicon chemistry is limited in scope compared to carbon chemistry, but it's still possible that silicon based creatures could be alive.

The current thought is that alien life would more than likely be carbon based and dependent on DNA as a means of reproduction. This is what NASA is currently looking for in their quest to find extraterrestrial life in outer space. But, this is just simple one-celled life like bacteria. What if we find a more advanced life form?

That's where we get into the argument about what constitutes intelligent life. We automatically assume that aliens will develop technological driven civilizations. But, what if they don't. Is technological civilization the only definition of intelligent life? Whales and dolphins have huge brains like us, yet we don't perceive them as being intelligent. They didn't create technology. The fact is they don't need it while living in the oceans. They could be as intelligent as we are but we'll never know because we haven't as yet figured out how to communicate with them. Will this be the problem when we encounter alien intelligent life?

One of the ongoing methods of searching for intelligent alien life is the SETI program. The method involves listening for a radio signal that suggests intelligent extraterrestrial life's attempt to communicate across the galaxy. However, except for the so-called 'Wow' signal, nothing definitive has been found. Does that mean that there is no intelligent alien life nearby us?

The problem with this radio signal method is that intelligent aliens may not be dumb enough to advertise their existence. Or, they may believe that they are the only intelligent life in the universe. Or, they don't rely on radio as a means of communication. Or they evolved, created a civilization but destroyed themselves. Or, they didn't find the need to develop technology. As you can see there are lots of problems with the idea of searching for intelligent alien life in that manner.

Then, there is the possibility that we won't even understand alien life when we do find it. We will inadvertently apply our human logic to whatever we find and completely miss the point.

Thanks for reading.