How many times must a sheet of paper (thickness, $t=0.1\,\mathrm{mm}$ but otherwise any size required) be folded to reach the moon (distance from Earth, $d=384,400\;\mathrm{km}$)?
The thickness of the paper on the $n$th fold is $2^nt$, so we require $2^nt \ge d \Rightarrow n_\mathrm{min} = \lceil \log_2(d/t) \rceil$:
>>> d = 384400 * 1.e3 # distance to moon, m
>>> t = 1.e-4 # paper thickness, m
>>> math.log(d / t, 2) # base-2 logarithm
41.805745474760016
Hence the paper must be folded 42 times to reach to the moon ($\lceil x \rceil$ denotes the ceiling of $x$: the smallest integer not less than $x$).