I’m listening to a book where the earth is invaded then the aliens that defended earth start recruiting our troops to fight in low level intergalactic wars. This book got me thinking about the chances of meeting aliens and I thought about how time is the major factor preventing this.

I’m not just thinking about how any intelligent life form would likely be hundreds or thousands of light years away. I’m thinking about time since the universe began. The universe is about 13.5 billion years old. Earth is about 4.5 billion years old. The earth has missed 2/3rds of all existence. Even then Homo Sapiens have only been around for 200,000 years or 0.0044% of the earth’s existence. And we’ve had just over 100 years of radio transmissions, that’s about 0.0000022% of the earth’s existence. (That’s 0.00000074% of the existence of the universe,)

Now when you look at 100 years over the span of the life of the universe, it becomes evident that entire civilizations could have survived for 5 thousands years and could have died off 5,000 or 50,000 or 500,000 or 5 million, or 50 million, or 500 million, or 5 billion years ago, great distances from us, and we’d never know.

Let’s say intelligent life is abundant in the universe, giving us a great opportunity to meet aliens. And let’s say that life didn’t start for the first 3.5 billion years of universe development. That still leaves 10 billion years of inelegant life. There could be 1,000 civilizations that existed and died and each one could have missed the birth of another civilization by a million years.

Let’s face it, we are developing technologies that make it unlikely that we will survive another 2,000 years. In less than 100 years high school students will have the technological know how, and the tools, to build a deadly virus or a deadly bomb that could set our civilization back hundreds of years. I give humanity a 50/50 chance of getting through the next 200 years.

I’m willing to bet that even if there were thousands of intelligent civilizations across the universe most space travel ready civilizations wouldn’t make it to 2,000 years. So forgetting the vast expanse of the Milky Way and the universe beyond that, it’s highly unlikely that any close enough for contact aliens are even around now… They are probably either long destroyed, or they are in their version of the dinosaur age, still millions of years from developing to where we are, much less to the point of light speed travel.

So following this train of thought, it’s likely that intelligent life is/has been abundant in the universe, and yet we are very much alone.