Wednesday 13 October 2010

Toppling wooden blocks to model nuclear decay intuitively


What does a nucleus get out of the process of decay? Why does it bother?

The answer is that the nucleus becomes more stable. Systems become more stable when they go from a high energy arrangement to a lower energy one. This means the system releases energy.

For example a domino on its end is unstable. Give it a little push and it ends up flat on the table. The centre of gravity has got lower and so the energy of the system has decreased. This energy appears as vibrations of the air (i.e. sound), of the table and of the domino. The vibrations rapidly become smaller-scale and less ordered, ending up as internal energy of the atoms. So the temperature rises a little.

You can model a nucleus as two upright wooden blocks standing on top of each other. This little tower is quite unstable. Give it a little push and it falls over. There are three ways of making the tower more stable that are analogous to alpha, beta and gamma decay.

For alpha decay, simply remove the top block. Making a big nucleus a little smaller increases its stability.

For beta decay, replace the top upright block with a shorter one. Changing a nucleon from a neutron into a proton can make a nucleus more stable.

For gamma decay, place the top block on its side so the blocks stay the same but the configuration is different. Letting nucleons settle down into a lower energy pattern makes the nucleus more stable.

Here is an interactive animation modelling alpha, beta and gamma decay with wooden blocks.

2 comments:

  1. I recently came across your site and have been reading along. I thought I would leave my first comment. I don't know what to say except that I have enjoyed reading. Nice blog. I will keep visiting this blog very often.

    Susan

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  2. Darth Plagueis was a male Dark Lord of the Sith[2] who, at some point, chose Sheev Palpatine, a human from Naboo, as his apprentice. As master and disciple, Plagueis and Palpatine—who took the Sith moniker Darth Sidious—worked together, trying to unlock the secrets of immortality[4] and to execute their order's long-percolating plan of supplanting the Galactic Republic with a new Sith Empire.[5]

    According to Sidious, Plagueis was powerful enough that he could use the Force to influence the midi-chlorians to create life and keep the ones he cared about from dying, a precious knowledge that awarded him the epithet of "The Wise."[3] Plagueis, however, also developed a belief that the Force could "strike back" at him for his power.[4] In truth, he became so powerful that the only thing he still dreaded was losing his power. Ultimately, Plagueis' only fear was bound to come true. At some point Sidious had learned everything he needed from his master.[2] Moreover, he had acquired his own pupil in the Nightsister Mother Talzin's son, Darth Maul,[3] a young Dathomirian Zabrak whom Sidious had kidnapped from Talzin when he was only a child.[6] As the Rule of Two mandated that only two Sith—a master and an apprentice—could exist at any given time, one of them had to die.[7] Now that he had no further use for a teacher, Sidious disposed of Plagueis, killing him in his sleep.[2] With the death of Plagueis, Sidious not only gained the status of Master, but also acquired 11-4D, the late Sith Lord's multi-limbed protocol droid assistant. Later, after taking Darth Vader as his apprentice, he reformed the Republic into the Galactic Empire and declared himself Emperor. In the years that followed his rise to Emperor, Sidious came to genuinely, if posthumously, appreciate Plagueis for the planner and prophet he had been. Sometimes, he mused about how his late master would have reacted when confronted with the trivial, day-to-day matters of Imperial politics.[4]

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