A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.

I know a nine-letter word having only one vowel.
Do you ?

Can you count the number of triangles in the given picture?

As we know that white starts the game of chess. Can you find the scenario shown in the picture below is possible when all the white pieces are at the original place while the black pawn is not as in the below picture?

Different lights make me strange by changing me into different sizes. What am I?

John is the son of Jacob.
So,
Jacob is the_____of John's father?

Can you count the number of lines in the below picture?

Can it be possible to build a house that has all its four walls facing towards the South?

In a secret society, a buried chamber can be accessed only via a secret password. The password is seven characters long and comprises of just letters and numbers.

You find a code that can help you in cracking the password. The code says "You force heaven to be empty".

Can you deduce the password from that?

What work can one never finish?