Start with the number of stars in our galaxy, which is conservatively estimated at 100 billion, though is often cited as three times that. Of those 100 billion, from 20% to 50% probably harbor planetary systems—an estimate that becomes more and more reliable as the Kepler Space Telescope and various ground-based observatories detect increasing numbers of exoplanets.
Not all of those exoplanets would be capable of sustaining Earth-like life, so the equation assumes from 1 to 5 in any system could. Of those bio-friendly worlds, from 0% to 100% would actually go on to develop life. And of those world, in turn, from 0% to 100% would develop life forms that we would consider intelligent.
The mere existence of intelligent life forms tells us nothing, however, unless they have the ability to make themselves known—which means to manipulate radio waves and other forms of electromagnetic signaling. It's estimated that from 10% to 20% of the smart civilizations would clear that bar.
Finally, and perhaps most anthropocentrically, consider how long any one of those civilizations would be around to blink their signals our way. A sun like ours survives for about 10 billion years; life on Earth has been around for only about 3.5 billion years, and humans have been radio-capable for barely a century.
If we destroy ourselves in an environmental or nuclear holocaust tomorrow, our signal will go dark then. If we survive for tens of thousands of years, we will be announcing our presence to the cosmos for far longer—and the same is true of all of the other civilizations that live in the Milky Way.
If you play the game conservatively—lowballing all of the variables—you might get about 1,000 detectable civilizations out there at any given time. Play it more liberally and you get hundreds of millions. Imagine there are 10,000 detectable civilizations and we are likely to find alien life by 2040. If there are a million, we’d discover alien life by 2028.
Its far more statistically likely that aliens exist somewhere than that we are the only planet with life in the universe.
Topic: Do you believe in aliens? - page 25. (Read 86158 times)
Wow, this is a very well received topic, a lot of responses.
Considering the size of the Universe, chances of only one planet being capable of supporting life and this life evolving into a sapient species seem astronomically low.
However, considering the size of the Universe, the chances of two such species meeting eah other seem even lower.
However, considering the size of the Universe, the chances of two such species meeting eah other seem even lower.
Yes, I do. Maybe not the type of aliens we see in popular culture, but organisms that exist outside of our planet.
I dont believe them actually, because its been so many years yet theories are is theory and no one ever prove yet that they exist so right now i only knew that we are alone in the universe.
Actually I do not believe in aliens, because there is not enough evidence to prove it.
I don't believe in this stereotyped image of the aliens, but they may exist
Aliens exist and i believe on it. It's can't be ture because our universe are endless.
i don't believe because many people can be made tecnology robot etc.
No actually I don’t believe in aliens, in my opinion, they don’t even exist , aliens are just a rumour which it expands by scientist and some Hollywood movies, most people think their lives are just like a movie and when they saw anything in movies they start talking about it and start believing on it.
Not fully believe it
No, there is not enough evidence to prove it.
I do not believe that the existence of aliens, because the aliens are just nonsense
may exist, but i do not know exactly what aliens are like
YES I BELEIVE
Of course! Who do you think built the pyramids? LoL
I do not believe in aliens but I am convinced that the alien really exists in the universe
Yes I do. Who doesn't believe that aliens do exists? Is that person on this side of the planet? That person must be joking. We all hear of people meeting with celestial bodies everywhere, we even hear that some of them even meet with government official and I totally believe that, and from what I know, they acclaim to possess supernatural powers.
In a wide universe, i don't believe that we are the only creature
I believe in aliens. Do you really think that we are alone in this very vast galaxy? Or somewhere out there in outer space? So guys I'm not gonna argue with anyone who doesn't believe in aliens. We all have our own perspectives.
Jump to: