A depressing mental image, via Reuters:
President Ronald Reagan once famously said that a stack of $1,000 bills equivalent to the U.S. government's debt would be about 67 miles high.
That was 1981. Since then, the national debt has climbed to $14.3 trillion. In $1,000 bills, it would now be more than 900 miles tall.
In $1 bills, the pile would reach to the moon and back twice.