The Great Filter

Life steps:

1. the dead chemistry that needs to assemble itself to support self-replicating, stability, resiliency, changing and evolving
2. complex organism and use energy more efficiently
3. multicellular beings with further complexity
4. species with brain
5. species now become the dominant force of our society and being able to change it according to needs

Species always look out and colonize more territory to survive, but space needs to be dead and empty.

Great Filter:

1. if the filter is behind us in the life steps, then it must be so dangerous that it has destroyed most of the civilization in our galaxy. Something has to be so dangerous that discovering it leads to our total destruction. Such as nuclear weapons. Once civilization is powerful enough to change the composition of its atmosphere, it faces its doom unavoidable.
2. if the filter is ahead of us, then it means we are closing to the doom of mankind. Only being in the right time, right place, right condition would allow us to go through the great filter.