How Facebook updated 'six degrees of separation' (it's now 3.57)

The maths has been done using the social media giant's handy data set of 1.6 billion people.

Facebook wanted to test the age-old "six degrees of separation" theory to mark its 12th birthday.

"This is a significant reflection of how closely connected the world has become," the firm says.

"When people connect, powerful things happen and lives are changed.

"We see this on Facebook every day, whether it's an exchange with an old friend that brings a smile to your face or a new connection that changes your life path, or even the world."

It means that each person in the world (at least among the 1.59 billion people active on Facebook) is connected to every other person by an average of three and a half other people.