How many times have you had it when you realize you and a friend or colleague have someone in common that you never knew?
Whether it be posting on Instagram and getting that "How do you know..." message, or turning up at a party and seeing someone you forgot you went to school with, that's just immediate connections.
The 'six degrees of separation' theory claims that you can know anyone in the world through a chain of no more than six people.
While it might seem wild that we could be connected to Elon Musk, Hugh Jackman, Emily Blunt, or President Donald Trump, one YouTuber is here to put this theory to the test.
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There might be complaints that we're less connected than ever, as artificial intelligence is in danger of replacing genuine human interactions in 2025, but any look at the mutuals you have with someone in your 'suggested friends' section of Facebook, and you'll realize you might not be as far away from Mark Zuckerberg as you'd think.
Over on YouTube, Veritasium's Derek Muller explained how German newspaper Die Zeit ran an experiment on the six degrees theory in 1999.
The outlet asked Salah Ben Ghaly, an Iraqi former theatre director and falafel stand owner, who in the world he'd most like to be connected to, with him selecting his favorite actor, Marlon Brando.
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Managing to track down a friend of Salah Ben Ghaly's in California, they worked alongside a man who was the boyfriend of a woman who was the sorority sister of the daughter of the producer of Don Juan DeMarco. It just so happens the 1994 comedy romance starred...Marlon Brando.
Crunching the numbers, let's assume that everyone in the world knows 100 people. 100 times 100 equals is already two steps away from 10-to-the-fourth people, so if you do 100 to the fifth power, that's more than the eight billion people on Earth.
The difference is, we tend to live in local clusters of friends and acquaintances, suggesting that six degrees of separation isn't just random. Muller did his own experiment in 2015, deducing that the average Veritasium viewer was just 2.7 steps away from him.
He then spoke to mathematician Steve Strogatz, who tried to solve the 'small world problem' (like where we bump into someone at the airport) in a '90s experiment with Duncan Watts. Strogatz concluded: "Our math showed, the question is not why is the world small, it's really how could it be otherwise?"
Muller also used a simulation to show how disease could spread through the small world problem, with the alarming notion that it would take 73 days for an infection to take over the world in a 'regular world'. Add in the connections of the small world theory, and it would take just 26 days.
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In 1998, Albert-Laszlo Barabasi deduced that the 800 million websites on the internet could be connected to each other in around 19 clicks, whereas the small world theory and six degrees have also been used to tackle HIV outbreaks in Thailand. You only have to look at how taking out one airport due to flight issues, or Atlantic cod from the food chain, can have devastating effects, showing how everything is eerily more connected than you might think.
Muller also concluded that connecting us through social media has allowed keyboard warriors to say things they wouldn't normally say in real life: "You look at the net effect of it and it's actually been pretty negative by a lot of measures."
We went on to say: "It's a thing I try to teach my kids too, like if someone's annoying you, just ignore them. Like there's nothing to be gained by continuing to interact with people who are bringing negativity into your life."