"Paradox"!!! I have always found the word "paradox" very cool. Seeing the word again and again in various books and sci-fi movies made me dig into this topic few years ago. I found out that it is not just a term used to make something sound cooler(My theory of Paradox when i was little XD).So here it is.

A paradox is a statement or a situation that contradicts itself but it may be true at the same time
[It is to be noted that most of these are not valid in reality but they indeed promote a lot of >logical and creative thinking]

While digging about paradoxes i found out there are a lot of mind boggling ones.So,here's a list of 7 famous paradoxes!!!

1.Achilles and the Tortoise

img source-Wikipedia

In this paradox,Achilles,the Greek Hero of the Trojan War is in a footrace with a tortoise.He allows the tortoise a headstart (say 100 feet).Assuming that they move at constant speeds,after sometime Achilles will reach the starting point of the tortoise after running 100 feet.But,in that time the tortoise will have travelled some more distance(say 10 feet).Thus, Achilles has to run 10 more feet to reach the tortoise but in the same time the tortoise will have travelled further.The tortoise will always be ahead of Achilles.Thus in this way Achilles will never be able to cross the tortoise because though the distance between them is decreasing yet he has to cross infinite points making the task impossible!!!

2. The Barber Paradox

This paradox was derived from the Russel's Paradox.In this paradox there is a barber who only shaves those who do not shave themselves.Now the fun starts when someone raises the question "Does the barber shave himself?"
•If the barber shaves himself, he cannot shave himself as he only shaves those who do not shave themselves.
•If the barber doesn't shave himself,he has to shave himself thus arriving at the same condition as above. Hence, arriving at a paradox!

3. Theseus Paradox

The Ship of Theseus or the Theseus Paradox is a thought experiment that raises a question that if all the parts of something are replaced by new ones,Will that thing be fundamentally the same thing? The paradox was recorded by Plutarch in Life of Theseus

So according to the paradox if all the components of the ship of Theseus were replaced one by one by new ones,would the ship remain the same as original?!!!

A modified version of this paradox states that if using the old parts of the ship an identical ship
is constructed,which would be the original one?

4.Omnipotence Paradox

This paradox tries to put a limit to the word 'omnipotence' and the idea of an all powerful being.
According to this paradox,Could an omnipotent being create a stone so heavy that He Himself cannot lift?
Thus creating a paradox!!If the being is omnipotent he should be able to do anything.But,creating a stone that he himself cannot lift contradicts his ability to do anything!

5.Crocodile Paradox

This one is an ancient logic puzzle.In this paradox,a crocodile snatches a kid.When approached upon by the kid's mother to return him,the crocodile answers that he would return him only under one condition.That is:she would have to guess correctly whether or not the crocodile will return the boy to her

Now,If she answers that it will not return the boy,we arrive at a paradox.

•If she is right and the crocodile was not thinking of returning the kid,the crocodile has to give back her son.But,this in turn contradicts the mother's answer and crocodile's action.

•If she is wrong,the crocodile has to keep the boy though he intended not to.Thus,this again contradicts the answer and action.

6.Bootstrap Paradox

The Bootstrap is a time travel paradox which has been an inspiration of many plotlines of science fiction books,movies,etc.(e.g: Doctor Who,The Terminator series)
Here how it goes,

Suppose a time traveller travels back in time to the point where Einstein had not found out The Theory of Relativity.He then explains everything about relativity to Einstein (Since in the future it has already been found out).Einstein publishes the paper claiming as his own work.The theory is accepted and revolutionizes physics.Books are published and people research about it for hundreds of years till a day comes when the time traveller learns about it and travels back in time.

Now,in this situation who found out The theory of Relativity?

[Other famous time travel paradoxes are The Grandfather Paradox and the Predestination Paradox]

7. Unexpected Hanging Paradox

A judge declares that a condemned prisoner would be hanged in a weekday in the following week at noon.He also tells that the hanging would be a surprise for him and he would not know it until the executioner knocks on his door
on that particular day.

The prisoner gives some thought to the judge's statement and deduces that he would escape from his punishment.According to him,the surprise hanging cannot be on a Friday because if he is not hanged till Thrusday evening,there would be only a day left and it won't be a surprise.Similary he could not be hanged on Thrusday as he would know it if he's not hanged until Wednesday.Thus,in the same way he deduces that he cannot be hanged on Wednesday,Tuesday or Wednesday too.
He becomes happy & confident and returns to his cell.
But, to his utter surprise the executioner knocks his door on Wednesday noon the next week.The judges statement became true in the end.

Thats all guys!Please upvote and comment if you like this post

Thank You for reading

Reference: Wikipedia