On the 19th of April, the Bitcoin mining difficulty had fallen to 135.59 trillion after a drop of 1.13% in the past 24 hours.

Google's quantum paper made headlines with that number. Here's what it means, what's actually at risk, and why 6.9 million bitcoin are more exposed than the rest.

Forbes contributors publish independent expert analyses and insights. I write about how bitcoin, crypto and blockchain can change the world. Bitcoin has dived almost 10% over the last week, plunging ...