XKCD Query Bad Science Alert

by Henry on July 12, 2010

“XKCD’s Cartoon”:http://xkcd.com/765/ is pretty funny today, but is worded in a way that _seriously_ understates homeopathy’s order of suck.

!http://imgs.xkcd.com/comics/dilution.png!

The I’ve diluted the semen 30x’ bit is technically right, but it suggests to the average reader that there is 1/30 as much semen as in the original sample. In fact, as John Sladek says in his wonderful survey of pseudo-science, _The New Apocrypha_, the average amount of the original substance that yer average homeopathic medicine has is much, _much_ smaller. So much smaller that it’s hard to envisage.

bq. … the smaller a dose is, the more powerful its effects. Homeopathic drugs have been diluted to one decillionth of a grain … the homeopathic apothecary takes a pint of the pure drug, mixes it in ten pints of water, throws away nine pints and mixes the remainder in ten pints of water; then he repeats the process sixty times … Martin Gardner compares it to ‘letting a drop of medicine fall in the Pacific, mixing thoroughly, then taking a spoonful. But a decillionth is a far, far smaller dose than this. Try to imagine a globe of water the size of our solar system. Then imagine that every star in the galaxy, and in every other visible galaxy, is surrounded by a similar globe of water. All the water is combined, and into it we drop one 1,000 millionth of a drop of water, mix thoroughly and take as directed … if the purest imaginable water is used in a real homeopathic drug, it must still contain far more natural amounts of even the rarest elements on earth, than it can possibly contain of the medicine.

I’ll leave it to those with more time, arithmetical ingenuity, and basic medical knowledge than me to calculate the likelihood that even a single spermatazoon lurks in the stick-figure’s sample. But I’m pretty sure that the odds ain’t great.

Update: As ‘belle le triste” notes in comments:

bq. But the principle of homeopathy operates by the so-called “law of similars”: what you’re diluting isn’t what will cure the problem, it’s what would (in non-diluted doses) cause the problem. Thus a homeopathic application of macro-diluted sperm would be being deployed to _prevent_ pregnancy, not to cause it.

XKCD is unquestionably guilty of _bad homeopathy._ Can somebody please revoke his license?