We already know that the encryption behind BitCoin is sound. But every time encryption has been challenged in recent days it's been because of a bug in the implementation of that encryption. It is never due to some ingenious brute force algorithm that actually breaks the key.

The question we really need to be asking is - have all the major vulnerabilities in the implementation of BitCoin - the ones that could actually threaten its existence - been discovered? Are we sure?

I say this as someone who has been evangelizing to everyone he knows about BitCoin.

This tells me how secure the algorithm is. Great.

This doesn't really answer the question "how secure is bitcoin" though, at least not the way I imagine most people would ask - which is "how secure is using bitcoin?"

Now imagine what that system looks like from the outside. It's dark and cold, yet still has mass to implement gravity and emits neutrinos (presumably).

If you want to explain dark matter, no need to go further than this.

this is going to need a lot more context for people that aren't too familiar with bitcoin, i think.