Incoming links: Radioactive decay
100 Greatest Discoveries by the Discovery Channel (2004-2005) Updated 2025-05-07 +Created 1970-01-01
Hosted by Bill Nye.
Physics topics:
- Galileo: objects of different masses fall at the same speed, hammer and feather experiment
- Newton: gravity, linking locally observed falls and the movement of celestial bodies
- TODO a few more
- superconductivity, talk only at Fermilab accelerator, no re-enactment even...
- quark, interview with Murray Gell-Mann, mentions it was "an off-beat field, one wasn't encouraged to work on that". High level blablabla obviously.
- fundamental interactions, notably weak interaction and strong interaction, interview with Michio Kaku. When asked "How do we know that the weak force is there?" the answer is: "We observe radioactive decay with a Geiger counter". Oh, come on!
biology topics:
- Leeuwenhoek microscope and the discovery of microorganisms, and how pond water is not dead, but teeming with life. No sample of course.
- 1831 Robert Brown cell nucleus in plants, and later Theodor Schwann in tadpoles. This prepared the path for the idea that "all cells come from other cells", and the there seemed to be an unifying theme to all life: the precursor to DNA discoveries. Re-enactment, yay.
- 1971 Carl Woese and the discovery of archaea
Genetics:
- Mendel. Reenactment.
- 1909 Thomas Hunt Morgan with Drosophila melanogaster. Reenactment. Genes are in Chromosomes. He observed that a trait was linked to sex, and it was already known that sex was related to chromosomes.
- 1935 George Beadle and the one gene one enzyme hypothesis by shooting X-rays at bread mold
- 1942 Barbara McClintock, at Cold Spring Harbor Laboratory
- 1952 Hershey–Chase experiment. Determined that DNA is what transmits genetic information, not protein, by radioactive labelling both protein and DNA in two sets of bacteriophages. They observed that only the DNA radioactive material was passed forward.
- Crick Watson
- messenger RNA, no specific scientist, too many people worked on it, done partially with bacteriophage experiments
- 1968 Nirenberg genetic code
- 1972 Hamilton O. Smith and the discovery of restriction enzymes by observing that they were part of anti bacteriophage immune-system present in bacteria
- alternative splicing
- RNA interference
- Human Genome Project, interview with Craig Venter.
Medicine:
- blood circulation
- anesthesia
- X-ray
- germ theory of disease, with examples from Ignaz Semmelweis and Pasteur
- 1796 Edward Jenner discovery of vaccination by noticing that cowpox cowpox infected subjects were immune
- vitamin by observing scurvy and beriberi in sailors, confirmed by Frederick Gowland Hopkins on mice experiments
- Fleming, Florey and Chain and the discovery of penicillin
- Prontosil
- diabetes and insulin
Their energy is very high compared example to more common radiation such as visible spectrum, and there is a neat reason for that: it's because the strong force that binds nuclei is strong so transitions lead to large energy changes.
A decay scheme such as Figure "caesium-137 decay scheme" illustrates well how gamma radiation happens as a byproduct of radioactive decay due to the existence of nuclear isomer.
Gamma rays are pretty cool as they give us insight into the energy levels/different configurations of the nucleus.
They have also been used as early sources of high energy particles for particle physics experiments before the development of particle accelerators, serving a similar purpose to cosmic rays in those early days.
But gamma rays they were more convenient in some cases because you could more easily manage them inside a laboratory rather than have to go climb some bloody mountain or a balloon.
The positron for example was first observed on cosmic rays, but better confirmed in gamma ray experiments by Carl David Anderson.
The half-life of radioactive decay, which as discovered a few years before quantum mechanics was discovered and matured, was a major mystery. Why do some nuclei fission in apparently random fashion, while others don't? How is the state of different nuclei different from one another? This is mentioned in Inward Bound by Abraham Pais (1988) Chapter 6.e Why a half-life?
The term also sees use in other areas, notably biology, where e.g. RNAs spontaneously decay as part of the cell's control system, see e.g. mentions in E. Coli Whole Cell Model by Covert Lab.