How big is big? We hear about millions, billions and trillions all the time but it's hard for me at least to comprehend these numbers. So I did a little exercise.
Take a penny.
Enlarge it a million times,
Enlarge it a billion times,
Now enlarge a penny a trillion times,
The little red ball at the lower right is the sun...
At a quadrillion times the size of a penny, the orbit of Neptune looks like the blue ellipse.
That's some serious coin. This metaphor falls completely apart at greater distances, but if we shift it a bit and imagine that the orbit of Neptune were the size of a penny, the Milky Way would be this big...
Yes, you are right - Pliny was plenty bored last night, but I hope you can make some cents out of these numbers now... (rim shot!)