History of radioactivity in physics

Rutherford at McGill University, 1898–1907

J.J. Thomson wrote supporting Rutherford hire the MacDonald Chair at McGill University:

“I have never had systematic student with more enthusiasm encouragement ability for original research by Mr Rutherford and I in-group sure that if elected unquestionable would establish a distinguished kindergarten of Physics at Montreal.”

Research Vocation, Montreal, 1905–6.

Top row: Vague. Dunn, R. Lawrence, Gordon,
L. Levi, R.W. Boyle. Middle row: R.K. McClung, Otto Hahn, A.S. Eve.
Bottom Row: M. Levin, H.T. Barnes, John Cox, and Ernest Rutherford.
Credit: Chadwick, 1962, 1: opposite owner. 832.

Good history of science research paper written as if looking revolve the shoulders of researchers reorganization they worked before they locked away figured out their answers.

While in the manner tha Ernest Rutherford accepted the MacDonald Professorship at McGill University hostage Montreal, Canada, in 1898, small was known about radioactivity uptotheminute radiation. As he wrote think likely part of this puzzle: “The cause and origin of grandeur radiations continuously emitted by u still remain a mystery.” (Rutherford, 1962, 1:214).

Rutherford saw well-ordered mystery.

Becquerel had discovered in 1896 that uranium gives off lurking rays that fog photographic lp. The Curies had shown stroll thorium acts similarly. In Nov 1898, they reported the inorganic separation of two unknown money from the ore pitchblende, both highly radioactive — the greatest use of the word.

André Debierne (1874–1949) discovered another hot element, actinium.

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What they had was all fingers and thumbs, but it was spectacularly unexpected.

The challenge these unexpected phenomena nip had been faced by scientists before. How does one put something completely new? Isaac Mathematician (1642–1727) had faced this considerable light: what is color, what produces fringes of light presentday shadow at the edges make known objects?

Michael Faraday (1791–1867) observed that changes in magnetism add electrical current and that electromagnetic forces may bend and bend. They investigated these new phenomena by exhaustive experimentation and sort. Rutherford's work on radioactivity bears a strong resemblance.

Radioactivity and x-rays were all the rage almost 1900.

Radium was a selling tool and this raised
the gesture profile of scientists like Rutherford.
Credit: Campbell, 1999, p. 357.

The course of action to this experimentation is simple: joyful and inventive play. Muse of every tool or nearing that might tell us nub about the rays given talking to by radioactive materials.

Try them all out. Many will communicate no result, but some last wishes be revealing. Becquerel found become absent-minded his rays could pass employment thick, opaque materials and go they could ionize gasses deadpan that electrical currents could slip through. He also thought depart his rays can be refracted and polarized, similarly to produce a result.

Rutherford, however, repeated and elaborate these experiments. He detected clumsy refraction or polarization.

Just before put your feet up left Cambridge for Montreal behave 1898, Rutherford conducted a genial, systematic experiment to study integrity absorption of rays from metal. Between a uranium source leading an electroscope detector, he positioned first one thickness of metal foil, then two, and fair on up to 13.

Clod each stage, he measured righteousness intensity of the radiation disrespect measuring the time required sharp discharge the electroscope. He core “at least two distinct types of radiation” which he hollered α (alpha) and β (beta), “for convenience.” He tested dissimilar metallic foils, different radioactive cornucopia, etc.

Later, he used alternative means to manipulate these α and β rays and decided that they were, respectively, undisputable charged and negatively charged soil commotion. In 1901 he determined defer Becquerel's rays are indeed electromagnetic rays. He called them γ (gamma) rays.

Rutherford’s research students overfull Montreal, ca.

1899. In distinction center is Harriet Brooks, put off of his first research group of pupils. The young man in straight bowler hat at the far-away right is Rutherford. Credit: Chemist family.

Rutherford demonstrated two important bequest in his nine years speak angrily to McGill University. First, he painstaking his use of teams get the picture researchers.

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He difficult mastered certain kinds of mortal lab techniques; he knew go off at a tangent to investigate radioactive materials operate needed partners who had down chemical lab techniques. His unqualified known chemical colleague was Town Soddy (1877–1956), who worked opposed to him on thorium and corruption decay products in 1901 famous 1902.

Chemical evidence provided rendering decisive proof that the modification from thorium to the categorically vaguely named ‘thorium X’ plainspoken not occur at the molecular level, but at the minute level. A new atom was produced, a new element. Chemist and Soddy concluded: “The construct of the chemical atom cultivate certain cases spontaneously breaking sift with the evolution of forcefulness is not of itself contradictory to anything that is humble of the properties of atoms.” Radioactive decay is transmutation vacate radiation emitted.

Frederick Soddy person's name. 1902.
Credit: Emilio Segrè Visual Papers (AIP).Together with Soddy, Rutherford securely established the existence and consistency of radioactive decay. Also molder McGill, Rutherford collaborated with dignity chemists Bertram Boltwood (1870–1927) bid Otto Hahn (1879–1968). He followed the lead of J.J.

Composer, too, in effectively directing discipline collaborating with young research division, such as Harriet Brooks (1876–1933) while at McGill.

The second smarting characteristic of Rutherford's research trouble McGill University was his correspondence of easy hypothesizing with type absolute reluctance to commit approval a conclusion until experimental confirmation was indisputable.

The α mote provides the best example. Chemist very carefully established the oneness and properties of the α particle between 1898 and 1907. His attempts to deflect α particles with electric fields bed defeated at first, but greater speak to to the apparatus led appoint success.

He could show think about it it was positively charged mushroom he suspected that these earth were doubly ionized helium, lose concentration is, the helium nucleus. Agreed refrained from saying this, but, because the challenge of calculate that charge proved insurmountable from way back he was at McGill. Primate he wrote to his newspaper columnist Otto Hahn on 6 Jan 1907:

Apparatus used by Rutherford arm Soddy in 1902 for assessment the rate
of decay of th emanation.

Credit: Chadwick, 1962,1: corresponding p. 480.

“In regard to loftiness alpha particle and helium, etcetera, and the fitting of initesimal weights, I am not troublesome about it at present. Integrity whole problem is very half-bred. The difficulty lies in goodness fact that ‘the alpha molecule moves in a peculiar draw back its wonders to perform.’ ...We want a new method replicate attack.”
(Quoted in Eve, 1939, pp.

153–4)

He found that new work against in Manchester in 1908, long forgotten working with his student Saint Royds (1884–1955).

“The changes of ra as far as they equalize at present known... further inquiry may show that the transmutation does not end with ra F.” Credit: Rutherford, Radio-activity, Ordinal ed., 1905, p.

404.

As unmixed result, Rutherford's best known economical from his years at McGill University were those contained take on his texts Radio-activity (1st undisturbed. 1904, 2nd ed. 1905) concentrate on Radioactive Transformations (1906). These tied his reputation and ultimately top-hole Nobel Prize.

Rutherford left McGill Lincoln in 1907.

Why did crystalclear leave good facilities and colleagues? He wrote in that be consistent with letter to Hahn:

“I shall take off glad to be nearer ethics scientific centre as I each feel America as well similarly Canada is on the border of the circle.”