![]() ![]() ![]() Thomson gave a lecture detailing his and others’ experiments with the energetic beams inside cathode-ray tubes.Īs the 19th century was coming to a close, many prominent thinkers believed that all of the great discoveries in science had already been made. The more I researched, the more I contemplated what it meant to discover something.Ĭathode rays, vacuum tubes, and the birth of atomic theoryĮxactly 125 years ago, the British physicist J.J. Many people, in fact, had a reasonable claim to aspects of the electron’s discovery. The challenge then was to find a museum artifact that captured that discovery.Ī Braun vacuum tube, like the one pictured at top, seemed like a good choice, because its inventor, Karl Ferdinand Braun, created it to study beams of electrons, and Thomson used a similar instrument for his experiments.īut as I dug into the histories of Thomson and Braun, I learned that theirs were two parallel stories involving many of the same players and similar outcomes (both men won a Nobel Prize in Physics), but having little else in common. For this month’s column, I knew that I wanted to write about the 125th anniversary of the electron’s discovery, which for simplicity’s sake I pegged to Thomson’s lecture. Of course, history is always more muddled than that. Thomson is often hailed as the discoverer of the electron based on that lecture 125 years ago. Corpuscles are electrons, and the plum pudding model gave way to Ernest Rutherford’s nuclear model in 1911. Thomson, who merely endorsed the idea.Ĭorpuscles and pudding are not how we think about the structure of an atom today. The model also became known as the Thomson model, although its chief proponent was William Thomson (Lord Kelvin), not J.J. In Thomson’s analogy, negatively charged corpuscles were like raisins suspended in a positively charged cake, resulting in a neutral atom. This model of the atom became known as the “plum pudding” model, so named for the popular English dessert. Thomson described his experiments with cathode rays to verify the existence of these subatomic corpuscles. “The atoms of the ordinary elements are made up of corpuscles and holes, the holes being predominant,” he continued. Thomson, during a lecture at the Royal Institution in London, on 30 April 1897. “We shall call such particles corpuscles,” announced the physicist J.J. Join the world’s largest professional organization devoted to engineering and applied sciences and get access to this e-book plus all of IEEE Spectrum’s articles, archives, PDF downloads, and other benefits. Join the world’s largest professional organization devoted to engineering and applied sciences and get access toĪll of Spectrum’s articles, archives, PDF downloads, and other benefits. For more exclusive content and features, consider , including the ability to save articles to read later, download Spectrum Collections, and participate inĬonversations with readers and editors. 's Digital Edition is exclusive for IEEE Membersįollowing topics is a feature exclusive for IEEE MembersĪdding your response to an article requires an IEEE Spectrum accountĬreate an account to access more content and features on The Institute content is only available for membersĭownloading full PDF issues is exclusive for IEEE Membersĭownloading this e-book is exclusive for IEEE Members Saving articles to read later requires an IEEE Spectrum account Thomson did still receive many honors during his lifetime, including being awarded the Nobel Prize in Physics in 1906 and a knighthood in 1908.Enjoy more free content and benefits by creating an account However, this model of the atom soon gave way to a new model developed by New Zealander Ernest Rutherford (1871-1937) about five years later. \): The "plum pudding" model (Credit: User: Fastfission/Wikimedia Commons Source: (opens in new window) License: Public Domain)
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