Scale, or how much is a trillion, really?

Megan McArdle tries to put those mind-crogglingly large numbers into a bit of perspective:

A trillion is, in some sense, a meaningless number. Perhaps this is a problem with inflation in both our currency and the size of our government — the spending figures are now beyond any normal person's imagining. In the comments to another thread, two readers try to put some emotional weight to these hefty numbers

To many of us, there's not enough verbal distinction between a million and a billion . . . a billion is bigger, yes, but most of us don't really grasp how much bigger (especially if you're on the left side of the Atlantic, where a billion is a much smaller number than it is on the right side). A trillion? Is that really a number? To most of us, no.