Here's a rough calculation: there is the potential for there to be 10^54 future humans lives – lives that also have the potential to be far richer in experience than the comparatively drab ones we live today.
Such is the potential cost of existential risk. A failure to act on threats that are readily identifiable to us today could result not only in taking contemporary intelligent life on Earth out of the game forever but would also prevent 10^54 future humans lives from ever happening. That's a heavy burden.
So what, exactly, constitutes an existential risk? In today's lesson, Neil deGrasse Tyson reminds us that Earth is not the safe pale blue dot we like to think of it as but is actually in the midst of a cosmic shooting gallery. As Tyson points out, we have known about this for some time, but our failure to take appropriate action leaves us incredibly vulnerable.