What is Kessler syndrome?

If the apocalypse was around the corner, would you want to know? Well good news for you, we may already be in it, but because it's hard to pin things down or look beyond the present it's hard to really know for sure. 

In the 1960s, states were sending things into space with reckless abandon and now it might be coming back round to bite them. Almost literally. And it doesn't help that billionaires are now rolling the dice with a bet on global communications infrastructure. So what exactly is going on? And, is it even actually going on? And does it mean anything other than resigned acceptance of inevitable collapse at the hubristic hands of billionaires?

Links:

• Collision frequency of artificial satellites: The creation of a debris belt, Journal of Geophysical Research: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA083iA06p02637