I want to make one
clarification on my video on supernovae, because that's
the plural for supernova, is that I said this supernova
occurred 1,000 years ago. That's actually not
precisely right. The supernova was first
observed 1,000 years ago, or the light from
that first explosion was observed by astronomers
we believe 1,000 years ago. But we have to be
very clear here. Because the Crab
nebula at its core is roughly 6,500
light years away, even this light, even this
image we see right here is that nebula as it
was 6,500 years ago. And so the supernova itself, if
we think about when it actually occurred, it actually must have
occurred about 7,500 years ago. So it must have occurred
about 7,500 years ago. And that first slide
from that first explosion from that first energetic
event reached us about 1,000 years ago. So it took 6,500
years to get to us, and reached us 1,000 years ago. So first light 1,000 years ago. Just wanted to make that clear. Might have been obvious
to some of you all, but always important
to think about it. When I said 1,000
years ago, I really should have said it
was first observed, the explosion was
observed 1,000 years ago. But since it's so
far, the actual event must have occurred
7,500 years ago.