# Tag Info

18

All theories of matter, starting with the ancient Greek philosophers, can be classified as either continuous or discrete (i.e., particulate). This dichotomy is due to Aristotle. Aristotle held that matter was continuous: infinitely divisible. Aristotle believed that a vacuum was impossible (indeed, he claimed to prove this). Since a particulate theory ...

14

Of course Mendeleev had no idea about protons or electrons. It is he who discovered the integer which we call atomic number, and which was later found to be the number of protons. The story of this discovery is approximately this. He was preparing to his chemistry course where he was supposed to give a survey of elements. He had to choose some logical ...

9

No, it was not the only one, but 19th century models were purely speculative, and Lewis did not publicize his 1902 cubical atom until 1916. So in 1904, when Thomson proposed his plum pudding, the only real competition was Nagaoka's 1903 Saturnian atom, a large, massive, positively charged sphere, encircled by hundreds of light-weight electrons arranged into ...

9

The Assayer & Redondi's "G3" Michele Camerota's 2008 Complete Dictionary of Scientific Biography entry on Galileo describes this theory in a section entitled "Atomism and the Eucharist": Atomism and the Eucharist. In section 48 of The Assayer (1623), Galileo set forth a theory of knowledge based on a sharp distinction between “...

8

The sources are abundant and easy to find, for example Leslie Groves, Now it can be told. A history of Manhattan project (written by a project leader from the military side), Robert Jungk, Brighter than a thousand suns, (written by a journalist). Besides this there are literally hundreds of books, including many participants memoirs, describing in great ...

6

We can see the SEP entry : Atomism from the 17th to the 20th Century by Alan Chalmers for a useful overview. See in particular the Concluding Remarks : If we take atomism to involve the claim that the properties of macroscopic matter arise as a result of the combinations and motions of tiny particles, then it is a position confirmed by the time of the ...

6

The basis is actually pure English, not Latinate. They stand for: sharp, principal, diffuse, and fundamental. You might be interested in this: The Origin of the s,p,d,f Orbital Labels, which is a short essay by the historian of chemistry William Jensen.

5

I’m afraid he no longer cared. According to Boltzmann biographer E. Broda (1981): (p. 9): One might have thought Boltzmann would, after 1900, in lectures and writings refer to Planck’s work on radiation, made possible by adoption of his own, Boltzmann’s, statistical methods. This was not the case, however. While Boltzmann continued to lecture and publish ...

5

They were the opposite of close. Geometers and atomists were bitter ideological enemies since before Euclid. The reason for such high passions was that Greek view of geometry was different from the modern relativistic/formalistic view, to them the nature of real space was at stake, not one idealized fiction among others. The indivisibles (atoms) and the ...

5

Historically, the discovery of naturally-occurring isotopes of chemical elements by means of the mass-spectrograph provided a correct explanation for the fractional character of the experimentally-measured values for the atomic weights of many chemical elements -- as compared with values that might have been expected if the atoms of a given element had been ...

5

There were both historical and experimental reasons for maintaining indivisibility of atoms in chemistry despite large number of elements. What confirmed compositeness of molecules were transformations of compounds into each other in chemical reactions. Analogous idea for atoms suggested transmutation of elements, which was not observed. In particular, it ...

4

The cathode ray experiments separated an electron from an atom. This is usually not considered splitting the atom. The discovery of alpha radiation showed that the atom could be broken up, and that nature did it as a matter of course. To 'control' the energy of the alpha particle one used different source elements. The desire to vary and control the energy ...

4

The website http://manhattanprojectvoices.org is full of interviews with participants in the Manhattan project. Some interviews address exactly the question asked here. For example, here are two interviews with members of what was called the "Special Engineering Detachment" in which the interviewed described quite specifically at what moment they were told ...

4

New scientific and engineering personal arriving at Los Alamos were given a series of lectures about the project, the relevant physics and the proposed designs of the weapons. These were later published as the Los Alamos Primer. So at least in Los Alamos, the purpose of the bomb was understood by all the technical personnel. Indeed, the ability to do so ...

4

Atomism as a scientific theory has two origins: development of chemistry and development of statistical physics. In chemistry it was experimentally discovered that that there are elements and compunds, and elements probably consist of atoms which combine into moleculas. Atomic weights were measured in the middle of 19-s century, and then came the periodic ...

4

Computed (as $\alpha=e^2/\hbar c$) in equation (12a), p. 51 of: Zur Quantentheorie der Spektrallinien, Ann. Physik (4) 51 (1916) 1–94. (Earlier he had used $\alpha = (e^2/2\hbar c)^2$ in equation (16), p. 469 of Die Feinstruktur der Wasserstoff- und der Wasserstoff-ähnlichen Linien, Münch. Ber. 1915 (1916) 459–500. For discussion see e.g. M. Eckert (ed.) ...

3

Although the concept of the existence of the atoms originates from the ancient Greek, for them it was yet more a philosophical concept, they were very far from any experimental proof.1 Later, mainly the chemistry provided the first suggestion that it might be an experimental fact. However, none of these results was strong enough at the time. In the late ...

3

It's a common assumption for planetary - ie central Newtonian field - models to consider the orbits to be circular. I don't think Bohr or Rutherford ever believed in circular orbits for electrons, but rather decided to use a circle to describe an orbit they believed was elliptic. Rutherford-Bohr Model use the planetary system as an analogy, where the ...

3

To my knowledge the first documented atomic model considering Planck’s action quantum was formulated by the Austrian Arthur Erich Haas (1884-1941). He hypothesized in 1910 a relation between the action quantum and the size of atoms. A substantial initiation progress was postulated by John William Nicholson (1881-1955) (Cambridge) who in 1912 formulated the ...

2

The book "Physics" by Cutnell and Johnson, says: "In the early part of the twentieth century a widely accepted model, due to the English physicist Joseph J. Thomson (1856-1940), pictured the atom very differently. In Thomson's view there was no nucleus at the center of an atom. Instead, the positive charge was assumed to be spread throughout the atom, ...

2

Avogadro's Law says that the number of molecules in a fixed volume of gas under fixed temperature and pressure does not depend on the gas. So the number of water molecules in one cubic meter of vapor under temperature T and pressure P is the same as the number of molecules of pure oxygen in the same volume and under the same conditions. Now add hydrogen to ...

2

A great source on the history of particle physics is Pais's Inward Bound, see also references in In which experiments the charge to mass ratio of proton was determined? thread on Physics SE. Charge to mass ratios for various ions were measured soon after Thomson's discovery of the electron, first for hydrogen apparently by Wien in 1898 based on canal (or ...

2

After a bit research I can not find anything about alternative names for quantum model of atom. For Bohr's model 1, 2, 3... was used but it was for orbit not for orbitals. According by According William B. Jensen Hund had followed Bohr’s practice of labelling the various shells and subshells in terms of their corresponding numerical quantum numbers as \$...

2

Yes, those terms come from spectroscopy; they refer to the appearance of the spectral lines. It wasn't until quantum mechanics that atomic spectra were understood as an effect of electron energy levels, including electron angular momentum. From Linus Pauling's concise in his Introduction to Quantum Mechanics ch. 5 ("The Hydrogen Atom"): The hydrogen ...

2

The difference between a point (as in Euclid) and atom in Democritus is that an interval (or a plane or solid figure) in Euclid is infinitely divisible, every interval, no matter how small can be divided further. While in the atomic theory, there is a smallest part of matter which is not further divisible. If applied to the real world, these are two opposite ...

2

Consult the Wikipedia page for atom. In its historical introduction, it presents a ladder of theories and discoveries establishing our current knowledge: First evidence-based theory Brownian motion Discovery of the electron Discovery of the nucleus etc. French physicist Jean Perrin used Einstein's work to experimentally determine the mass and dimensions of ...

1

I want to understand the extent to which scientists and technicians employed in the Manhattan project understood that they were building a bomb that would kill hundreds of thousands of people. There are two separate questions here: (1) whether they knew it was a bomb, and (2) whether they knew it would be used to kill large numbers of civilians. Even the ...

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