Genesis 11, Tower of Babel

Genesis 11:4 NIV
Then they said, “Come, let us build ourselves a city, with a tower that reaches to the heavens, so that we may make a name for ourselves; otherwise we will be scattered over the face of the whole earth.”

Here not understand why they wanted to built the tower. What it mean otherwise they will be scattered ?

Genesis 11:7 NIV
Come, let us go down and confuse their language so they will not understand each other.”

創世記 11:7 我們下去，在那裡變亂他們的口音，使他們的言語，彼此不通。 (分享自Android快速聖經)

Notice 'let us' not let Me. So God sent angels down to confused them ?

Book of Jubilee,  from wiki,  God did tumbled down the tower with strong wind. It also mentioned the height of the tower about 8000 ft  or 3 times of Burj  Khalifa,  the world tallest building now. So we are far behind the tower of babel. 

Bible did not mentioned the name of the tower. Also did not mentioned the tower was tumble down.