And then there was one.

One physicist in the halls of Congress, that is. Rep. Rush Holt (D-N.J.) announced Tuesday that he will retire at the end of his term, leaving hopes that Congress will retain a physicist in its ranks squarely on the shoulders of Rep. Bill Foster (D-Ill.).

As Capitol Hill's resident physics experts, Holt and Foster belong to a rare breed: scientists-turned-members of Congress.

Looking for a microbiologist? You'll find one: Rep. Louise Slaughter (D-N.Y.). How about engineers? Six. There are 19 physicians, two dentists, two veterinarians and three psychologists, all according to a Congressional Research Service profile of the 113th Congress.

In short, even under a very broad definition of scientist, only about three dozen members fall into the category. Compare that to the 214 members from both chambers who have worked in business. Or the 211 who have a background in law.

There you have it: scientific proof of the dearth of scientists in Congress.