I am sure we all remember learning about atoms when we were growing up. The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom. The protons are positively charged, and neutrons are electrically neutral. (Scientists have since learned protons and neutrons are in turn made up of particles called quarks). The other part of atoms consists of electrons, the negatively charged particles of the atom. The electrons’ create a negative charge balancing the positive charge of the protons in the atomic nucleus.
Before I continue, I cannot resist digressing about Larry Fine, Curly Howard, and Moe Howard, the Three Stooges. The three were an American vaudeville and comedy team active from 1922 until 1970, best known for their 190 short subject films. Their hallmark was physical farce and slapstick. They remain hilarious on YouTube, and you can watch here. Every time I see the word electron, I think of one of the Stooges’ episodes where Curly said he knew all about atoms. He said they consisted of electrons, protons, and fig newtons!
What was known about atoms and the contents of the nucleus was limited because it wasn’t possible to actually see atoms. That changed in 1981. That was the year I moved from Philadelphia to IBM Headquarters in Armonk, NY. I remember seeing the announcement on the bulletin board (there was no web) highlighting Gerd Binnig and Heinrich Rohrer, scientists at IBM Zürich had invented the scanning tunneling microscope (STM). The IBM inventors received the Nobel Prize in Physics in 1986 for their groundbreaking invention. The STM made it possible, for the first time, to actually see at the atomic level, distinguishing features as small as one tenth of a billionth of a meter.
New discoveries have accelerated since the availability of the STM and other technologies. One example is Albert Einstein’s discovery of the photoelectric effect, for which he received the Nobel Prize in Physics in 1921. Einstein discovered when light with energy above a certain threshold hits the surface of a metal atom’s surface, an electron bound to the metal gets knocked loose. For example, the picture above shows an electron escaping from a helium atom after getting hit by a photon.
One of the numerous mind boggling aspects of the research at the atomic level is the minuscule amount of time it takes for an electron to be ejected after a photon strike. In some experiments, researchers were able to measure activities happening in femtoseconds ( 10-15 seconds) or attoseconds (10-18 seconds). These measures of time are an eternity compared to zeptoseconds. One zeptosecond is a trillionth of a billionth of a second. The duration of the electron emerging from the helium atom was measured as taking 850 zeptoseconds.