1901 — the year the nuclear atom was “invented”!

[The] planetary model is an important one historically, and was accurate enough in its time (and still today) to forgive its faults. It arose naturally in the early 1900s, in a period of great confusion and uncertainty about atomic structure. With tantalizing and rather bewildering experimental hints, scientists speculated wildly about the nature of the atom. The strongest contender was the “plum pudding” model of J.J. Thomson, in which atoms were visualized to be a “pudding” of positively-charged fluid within which were embedded negatively-charged electron “plums”. In Thomson’s original paper, these plums were arranged equidistantly around a circle within the pudding and orbiting within it

Christmas with Faraday: The Chemical History of a Candle

Faraday gave a series of famous Christmas lectures each year at the Royal Institution — a tradition that continues today. One of the earliest, on the chemistry and physics of flames, became a popular book: The Chemical History of a Candle.

These lectures were a gift that Faraday gave year after year to those who showed up to receive it: the gift of wonder at the natural world that continues to surprise us, even today, with its mysterious workings.

Norman Ramsey Dies at 96; Work Led to the Atomic Clock

In 1949, Dr. Ramsey invented an experimental technique to measure the frequencies of electromagnetic radiation most readily absorbed by atoms and molecules. The technique allowed scientists to investigate their structure with greater accuracy and enabled the development of a new kind of timekeeping device known as the atomic clock. Dr. Ramsey received the Nobel Prize in Physics in 1989 for both achievements.

I had the privilege of meeting him and hearing him at a few talks where he told stories of the old days (I thought perhaps he was working on a book). Here is a picture of us at a conference in Seattle in 2005, where I am showing our nascent clock’s “Ramsey fringes” results to him — an interference pattern from the spectroscopy technique he pioneered — along with the clock stability results.

(photo credit: Tom Van Baak)

“More Decimal Digits”

One classic illustration of how the old guys with the beards knew their understanding of physics was incomplete involves the specific heats of gases. How much does a gas warm up when a given amount of energy is poured into it? The physics of the 1890s was unable to resolve this problem. The solution, achieved in the next century, required quantum mechanics, but the problem was far from unknown in the years before 1900.