Why alien life would be our Doom ? The Great Filter

Why alien life would be our Doom ? The Great Filter

Imagine NASA announced today that they found aliens. Bacteria on mars, weird alien fish in the ocean of Europa and also ancient alien ruins on Titan. Wouldn't that be great ? Well no, that would be horrible new, devastating even. It could mean that the end of humanity is almost certain and it might be coming soon. Why ? Why would the most exciting discovery of our lifetime be bad ?

Imagine the development of life from its inception to us today as a flight of stairs.

•  The first step is dead chemistry that needs to assemble itself into self replicating patterns, stable and resilient, but also to change and evolve.
•  The second step is for our early life to become more complex and able to build more complicated structures and use the available energy much more efficiently.
• On the next step, These cells combine to become the multicellular being, enablong unbelievable variety and further complexity.
• The step above sees the species evolve big brains, enabling the use of tools, culture and shared knowledge, which creates even higher complexity.
• The species can now become the dominant lifeform on it's planet and change it according to it's needs. First shy attempts to leave it's planet are now happening. This is where we are now. 

   It's the nature of life to reach out and cover every niche it can. And since planet have a limited capacity and lifespan, if a species want to survice it would look for more ppaces to spread to. So the steps above the current one seems logical. Colonize your entire solar system then spread further to reach other stars to the final step : becoming a galaxy - wide civilization.

It's very likely that this is a universal principal for civilizations, no matter where they are from.
If a species is competative and driven enough to take control over it's civilisation, they would probably not stop there.
       We know that there are upto 500 billion planets in the milky way. At least 10 billion earth - like planets. Many have been around billions of years longer than the earth. But we are observing zero - galactic civilisation. But we should be able to see something but there is nothing. Space seems to be empty and dead. This means something is preventing the living things from climbing the staircase, beyong the step we are right now. Something that makes becoming a galactic civilisation extremely hard, maybe impossible. This is the Great Filter. A challenge or danger so hard to overcome that it eliminates every species that encounters it.
   There are two scenerios:

• One means that we are incredibly special and lucky
• The other means that we are doomed and practically already dead.

It depends upon where the filter is on our staircase : behind, or ahead of us ? 

• Scenario 1 : The filter is behind us.we are the first. If the filter is behind us this means that one of the steps we passed is almost impossible to take. Which step It could be ? Is life itself extremely rare ? It's very hard to make predictions about how likely it is for life to emerge from dead things. There is no concensus. Some scientists thinks that it develops everywhere where the condition are right; others think that the earth might be the only living place in the universe. Another candidate is the step of complex animal cell. A very specific thing happened on this step and as far as we know, It happened exactly once. A primitive hunter cell swallowed another cell, but instead of devouring it, the two cells formed a union. The bigger cell provided shelter, took care of interacting with the environment and providing resources, while the smaller one used it's new home and free stuff to focus on providing a lot of extra energy for it's host. With the abundant energy, the host cell could grow more than before and build new and expensive things to improve itself, while the guest became the powerhouse of the cell.
  
  These cells make up every animal on this planet. Maybe there are billions of bacteria - covered planets in the  Milky Way, but not a single one apart from us has achieved our level of complexity or intelligence. We humans feel very smart and sophisticated with our crossword puzzles and romantic novels. But a big brain is first and formost, a very expensive evolutionary investment. They are fragile, They don't help in a fistfight with a bear, they cost enormous amounts of energy, and despite them, it took modern humans, 200,000 years to get from sharp sticks to civilization. Being smart doesn't mean that you get to win automatically. Maybe intelligence is not just so great, and we're lucky that it worked out for us. 

• Scenario 2 : The filter is ahead of us. Plenty of others died already. A Great Filter ahead of us is orders of magnitude more dangerous than anything we have encountered so far. Even if a major disaster killed most of us or threw us back a thousand years, we would survive and recover. And if we can recover, even if it takes a million years, then it's not a Great Filter, but just a roadblock to an eventual galactic civilization. On universal timescales, even millions of years are just the blink of an eye. If a Great Filter really lies before us, it has to be so dangerous, so purely devastating and powerful, that it has destroyed most, if not all advanced civilizations in our galaxy over billions of years. A really daunting and depressing hypothesis is that once a species takes control over it's planet, it's already on the path to self - destruction. Technology is a good way to achieve that. It needs to be something that's so obvious, that virtually everybody discovers it, and so dangerous, that it's discovery leads to almost universally to an existential disaster.
  
  A large scale nuclear war, nanotechnology taht gets out of control, genetic engineering of the perfect superbug, an experiment that lights the whole atmosphere on fire. It might be a super - intelligent AI that accidentally ( or purposly ) destroys it's creators. Or things that we can't even see coming right now. Or it's way simpler : species competative enough to take over their planet necessarily destro it while competing each other for resources. Maybe there are runaway chain reactions in every ecosystem that once set in motion, are not fixable. And so when a civilization is powerful enough to change the conposition of it's atmosphere, they make their planet uninhabitable 100 % of the time. Let's hope that that's not the case. If the the filter is ahead of us, our odds are really bad.

What we can hope for ?

 This is why finding life beyond Earth would be horrible. The more common life is in th euniverse, and the more Advanced and complex it is, the more it becomes that a filter is ahead of us. Bacteria would be bad, small animals would be worse, intelligent life would be alarming. Ruins of ancient alient civilizations would be horrible. The best case scenario for us right now is that Mars is sterile, that Europa's oceans are devoid of life, and the vast arms of the milkyway harbor only empty oceans hugging dead continents. That there are billions of empty planets waiting to be discovered and to be filled up with life. Billions of new homes waiting for us to finally arrive. 

How likely it it that we will find life outside of Earth that is similar to us ? 

Well, that depends on how many planets are out there in their star's Goldilocks Zone - the area around the star where water can be liquid.

       Because stars come in all sizes and configurations, this zone is different for every star system and requires a little bit of physics to figure out. 

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And If  you do find life on other planets, It may be wise to leave them alone for a while.