I have loads of reading to do with a theology class I’m taking (in San Diego!) at the beginning of February, which is precisely why I’ve started reading Bill Bryson’s A Short History of Nearly Everything again. Because that’s what I do when there are things to get done: distract myself with other things.
I came across this in a passage about supernovae and it ground my brain to a halt:
The question that naturally occurs is “What would it be like if a star exploded nearby?” Our nearest stellar neighbour…is Alpha Centauri, 4.3 light years away. I had imagined that if there were an explosion there we would have 4.3 years to watch the light of this magnificent event spreading across the sky, as if tipped from a giant can. What would it be like if we had four years and four months to watch an inescapable doom advancing toward us, knowing that when it finally arrived it would blow the skin right off our bones? Would people still go to work? Would farmers still plant crops? Would anyone deliver them to the stores?
Weeks later, back in the town in New Hampshire where I live, I put these questions to John Thorstenson, an astronomer at Dartmouth College. “Oh no,” he said, laughing. “The news of such an event travels out at the speed of light, but so does the destructiveness, so you’d learn about it and die from it in the same instant” (36).
So it takes 4.3 years to reach us, moving through 4.3 light years of space in that time–that is, moving from A to B and covering the distance between–but we would never see it approaching. I imagined it, much like Bryson, rather like watching a ball approach one’s face from a distance. Not so.
Instead, it would kind of be like the running scene in Monty Python and the Holy Grail, except without the extended approach–Sir Lancelot would simply appear suddenly at the gate and kill the guards without warning.
I understand that (as far as we know) light is the fastest thing in the universe and we wouldn’t see the event until it reached us, meaning that as soon as we saw the event it would have arrived. Conceptually I get it. But it nevertheless boggles my mind–I can’t “see” it in my imagination.