Dec 16 2009
Grasping the Big
A new cosmological finding got me thinking about how darn huge the universe is. Ironically, the theme of the piece was about nearness.
Black Hole Found to Be Much Closer to Earth Than Previously Thought
How close is that black hole to us? 7800 light years. Only 7800? My that is close.
Or is it? How close is 7800 light years? With a few back-of-the-envelope computations, let’s see if I can put it in perspective.
The circumference of the Earth is roughly 40,000 km. Time it would take to walk around our planet: about 1000 days. Time it would take to drive around the planet: about 400 hours. Time it would take to fly around the planet: about 40 hours.
Now we get to the unit of cosmic distances: the light-year. Time it takes for a photon to travel the distance of the Earth’s circumference: about 1/10th of a second.
How long does it take for a photon to travel from the Sun to the Earth? About 8 . . . minutes.
The distance between between the Sun and Earth is roughly 150 million kilometers. The Sun is that far away, and still sizable in the sky?! It’s huge!
Time it takes for a photon to travel to that black hole: 7800 light years. Not 7800 seconds, not minutes, not hours, not days. Years. That’s far. That’s blow-your-mind far.
And yet, from a cosmic perspective, it’s “much closer” than previously thought. Wrap your mind around that.
