difference between "in the world' n "around the world" ???

eng stupid

hiii all, this is my 1st post n i wanna know the difference between "in the world" n "around the world".

Hi, everyone. This is my first post and I would like to know the difference between "in the world" and "around the world". 

i aint sure abt their application n which one i should use under a certain situation,

I am not sure about their application and which one I should use in any situation.

n also, is it possible that both of them could be used at one situation?

And also, is it possible that both of them could be used in the same situation?

 

p.s. If there are any mistakes in my words, please give me advice, thank you =)

That must be the biggest building in the world.   I have been around the world and have never found a bigger one.

When the news of her death went around the world, no-one could believe that Princess Diana was no longer in the world. 

You cannot use the two phrases to say the same thing, since "around the world" indicates that something is all over the world.