What is the probability that there is life in the universe aside from earth?
Answers
Let me tell you...
The science which provides predictions which are correct 99.999 % of the times is quantum mechanics.
This is more accurate than Einstein's theory of Relativity ( NO OFFENCE ) .
It's actually a very vast subject but here I'll tell you only one basic principle of quantum mechanics which predicts that our Universe isn't the only one out there !!!
First I'll start with the Classical physics prediction which states the presence of the Big Bang singularity which started our universe.
So , in classical physics , you can tell the exact position or velocity of a body ( example - celestial body ) , if you know both it's current position and velocity.
For example , if I tell you that a car started from a point and has traveled 50 kilometers in a given time , has a constant velocity of 5 kilometers per hour. Now if I ask you to tell where was the car 2 hours ago , then you will easily tell me that since the car has traveled 50 km. and that too at a constant velocity of 50kmph , then you will multiply the speed by time ( i.e. 5 km/hr * 2 hr ) and you will get the distance traveled in 2 hrs ( which in this case is 10 kilometers ) and finally you will subtract those 10 kilometers from the total distance travelled which is 50 kilometers to tell me that the car was 40 kilometers ahead of the starting point two hours ago.
Similarly , scientists predicted from the current rate of the universe's expansion that really really long time ago ( 13.8 billion years ago to be precise ) the whole universe was scrunched up into a particle of zero size and infinite density where all the laws of science would break down. That particle is called singularity.
Now here comes quantum mechanics into play , that singularity was a particle smaller than a subatomic particle and so had infinite density.
And you can't predict anything at that singularity using the Classical physics equations which I said earlier.
So , we use this science called quantum mechanics which is used to study physics at the smallest possible level , that is , at the level of atoms, electrons, protons, quarks etc.
Now quantum mechanics has a principle called Super position which states that unless you measure/observe a quantum particle , it stays in all its possible states and at all possible points of origin ( sounds weird I know ).
For example , unless you observe a particle X which can be either in state A or B ( variables used just for better understanding ) , it will be in both state A and B at the same time and will also be present at all possible points of origin but the moment you measure / observe it , it takes either state A or B ; giving the effect that it was always in that particular state and at that particular point of space.
So , if the universe was , at a point of time , a quantum particle and no one was there to observe it ( of course there were no humans or anything else !!! ) then it would have been at many places at the same time , or more precisely , at all points where it could possibly be , at the same time.
This means that there were many big bang singularities and many big bangs , therefore occurred.
In that case , there CAN BE many Universes today but we don't know about them. This is called Multiverse.
So if there are many universes apart from our own , then there is a VERY VERY VERY strong possibility that there must be other species of life out there as well.