Spring cleaning is running a little late at the Sirola household. Susan detected something fetid in the refrigerator the other day. Today she made the mistake of investigating.
She described the smell as "funky feet," except she used more words and some of a nature that can't be reprinted in a family newspaper.
The worst fridge story I have regards Hurricane Katrina. We had just bought a lot of meat before having to leave ahead of the hurricane. Two weeks later, we returned to something no longer native to this planet.
I don't feel so bad about today's cleanup because I sacrificed myself post-Katrina.
Physics went through a similar - well, if you ignore the putrid smell and foul language - cleaning about a century ago.
Physics folks tend to split up our history into three basic periods. First, there's physics before Isaac Newton, circa 1700. Then, physics developed theories of mechanics, electromagnetism and thermodynamics up until circa 1900, which we label "classical" physics. Finally, there was the advent of relativity and quantum mechanics in the early 20th century.
Einstein gets most of the credit for relativity. But quantum mechanics came about through contributions of a host of scientists, many whose names are not so familiar. to the general public.
The atom was one of those objects that needed cleaning. First, people had to be convinced that atoms existed - a notion not universally accepted back then. Second, while folks figured out atoms had equal numbers of negative and positive electric charges, their distribution was unknown.
The first reasonable model was by that of J.J. Thomson of England, who thought electrons would be spread out among a general positive region, like raisins in a pudding. The second model came from Ernest Rutherford of New Zealand. His experiments showed the nucleus has to be extremely tiny - a good analogy is a quarter in the middle of a football field. Electrons would orbit the nucleus like planets orbit the sun.
Unfortunately for Rutherford, his model had two fatal flaws. First, because like electric charges repel like charges, the positively charged nucleus should split apart. Second, because electric charges moving in circles emit radiation, the electrons should lose energy and spiral into the nucleus within one hundred-thousandth of a second.
The person to get a working handle on the atom was Niels Bohr from Denmark.
Bohr suggested the atom consists of two separate particles, the proton and the neutron. The proton carries positive charge while the neutron has none. However, the neutron exerts a different force of nature (now called the "strong nuclear force"), which bound the nucleus together.
Further, the notion of "atomic number" comes from Bohr. Each atom is characterized by the number of protons in its nucleus - hydrogen is element No. 1 because it has one proton, for example. Hydrogen can have zero, one or two neutrons (we call these "isotopes"), but remains hydrogen. Other atoms behave the same way.
Next: The other half of the Bohr atom - how do electrons behave? See you then!