Key Discoveries in the History of Science

[Swammerdami]

This is the thread for briefish summaries of key scientific discoveries. All fields of science are eligible. No need to list the discoveries in the order of importance, but each should be a specific well-defined new advance in scientific knowledge. (Darwin's Theory of Evolution in general might not qualify, but a specific observation that contributed to his theory would.)

I'll start with two specific discoveries in astronomy.


1611) "Haec immatura a me iam frustra leguntur o.y."

Both the Ptolemiac and Copernican models of the solar systems implied that Venus should have phases like the Moon, but the details varied greatly. Observation of Venus with high-quality telescopes therefore gave a way to pick between the models. Galileo Galilei had one of the best telescopes of that age and was carefully observing Venus. He didn't want to publish until his data was complete, but he didn't want to be scooped by another astronomer either!

In December 1610, as Venus was disappearing behind the Sun, Galileo sent Johannes Kepler a letter with the above Latin sentence. (Translated, it reads "I am now bringing these unripe things together in vain, Oy!"). In January 1611 Galilelo confirmed Venus' crescent shape as it re-emerged, and revealed the anagram of this sentence: "Cynthiae figuras aemulatur mater amorum" ("The mother of love [Venus] copies the forms of Cynthia [the Moon]"). (Here's an interesting page about allegations that Kepler misinterpreted Galileo's anagrams.)

Copernicus was correct. The Sun was the center of the solar system.

(It is a curious fact that the Author of Shakespeare's plays took great interest in astronomy, incorporating mention of events in the 1580's and 1590's into his plays. Yet the Author mentioned no astronomical event after 1604 — including most of Galileo's great discoveries.)

1676) Ole Christensen Rømer measured the speed of light.

Jupiter's moon Io orbits its mother-planet once in 42 hours and 28 minutes, but due to the finiteness of light's speed and a form of the Doppler Effect, Io's orbit appears to be several seconds faster when the Earth is moving toward Jupiter, and is several seconds slower when the Earth is moving away from Jupiter. There was no need to measure this deviation of a few seconds; the cumulative deviation could be measured after months. (How did Rømer or other scientists of this era measure time? I assume they used Huygens' recently-introduced pendulum clock, but was it calibrated periodically with a sundial?)

The orbit of each Jovian moon is affected by the other moons, and only Io worked well for this observation. Still, the perturbations aren't synchronous with Earth movement so should average out in a few years of observations. Nevertheless Rømer's supervisor — the more famous astronomer Cassini — did not accept this result. In 1729 James Bradley settled the question with a different approach.

The two greatest mathematical physicists of that era — Christiaan Huygens (designer of afore-mentioned pendulum clock) and Sir Isaac Newton — did accept Rømer's work at once. Newton had an urgent question for Rømer — did the shadow on Io change in color as its eclipse progressed? (It didn't; light of different colors traveled at the same speed.)

 

[steve_bank]

Seriously, it all started with the control of fire and the ability to put a cutting edge on materials.

As important today as t was at the beginning.

Sciience is not limited to modern mathematical science.

Steam power in the 19th century led to thermodynamics and enabled the Industrial Revolution.

Nuclear steam power and controlled heat.

 

[bigfield]

While Germ Theory developed over a long period of time, I think Louis Pasteur is worth a mention for proving that germ theory was not only correct, but that it was possible to not kill the germs in a medium, but also to prevent them from returning.

While I find astrophysics and cosmology fascinating, it is utterly insignificant compared to the benefits gained from advances in medical science.

Steven Pinker compiled a table estimating the number of lives saved by just a few discoveries in medicine:

If we're looking for key discoveries, I'd say that's a whole keyring's worth, right there.

 

[Swammerdami]

Fast-paced modern science began over a century ago, and is sometimes contrasted with Alchemy in the Middle Ages, a pseudo-science.
However, the old dream of Transmutation of the Elements was eventually fulfilled! Let's review key nuclear reaction types.

I. Single Reactant (Natural radioactivity)
. . . . E^* ⟶ F + {alpha or beta particle} + {optional gamma particle}
Becquerel, Roentgen, Madame Marie Curie and her husband are oft-heard names from the earliest relevant studies, but it is the (then-future) Lord Rutherford who should be most revered He detected, named and later identified the alpha and beta particles. The latter he showed to be equivalent to both cathode rays and electrons. The former he identified, in a beautiful little experiment, as Helium. Little was known about the nuclei of atoms, though Rutherford's greatest discovery was (in 1911) that the nuclei are very small and very hard. He conjectured the existence of neutrons, but it was left to one of his disciples to discover them. In his elegy Bohr wept, calling Rutherford his second father.

The result of a radioactive emission can also be radioactive. In fact there are no less than 14 radioactive isotopes between ordinary uranium and ordinary lead.

. . . . U^238*⟶Th^234*⟶Pa^234*⟶U^234*⟶Th^230*⟶Ra^226*⟶Rn^222*⟶Po^218*⟶Pb^214*⟶Bi^214*⟶Po^214*⟶Pb^210*⟶Bi^210*⟶Po^210*⟶Pb²⁰⁶

The net formula can be determined directly from the numbers of protons and neutrons. In this case there must be 8 alphas and 6 betas emitted.

. . . . ₉₂U²³⁸ ⟶ ₈₂Pb²⁰⁶ + 8 ₂He⁴ + 6 β^-
Positively-charged beta particles (anti-electrons), predicted by Dirac, were observed occasionally in the decay of light elements.

II. Two Reactants (Neutron Production)

Experimentalists began aiming the alpha particles they had generated at other elements. One early result (perhaps after the 1934 Joliot discovery next?) was:

. . . . ₄Be⁹ + ₂He⁴ {very energetic} ⟶ ₆C¹² + ₀n¹ {Neutron}

The energetic alpha particles are obtained from radium, polonium or radon. (In some reactions protons are produced instead of neutrons.)

Beryllium is so eager to give up its extra neutron, that even a gamma ray suffices to trigger it:
. . . . ₄Be⁹ + γ ⟶ 2 ₂He⁴ + ₀n¹ {Neutron}

III. Artificial radioisotope

B](1934)[/B] Jean Joliot and his wife Irene nee Curie discover artificial radioactivity. Aluminum was coated with Alpha-emitting polonium.

. . . . ₈₄Po²¹⁰ ⟶ ₂He⁴ + ₈₂Rn²⁰⁶

. . . . ₂He⁴ + ₁₃Al²⁷ ⟶ ₀n¹ + ₁₅P^30*

. . . . ₁₅P³⁰ ⟶ ₁₄Si³⁰ + β⁺

The first and third reactions shown are ordinary radioactivities: Polonium decays with a half-life of some months; Phosphorus-30, not found in nature, decays in 2.5 minutes. (The 3rd reaction is an example of afore-mentioned anti-electron producer.) It is the 2nd reaction that was the novel discovery: The energetic α-particles (₂He⁴) from the 1st reaction induce ordinary aluminum to emit a neutron and transmute into the short-lived P-30.

The ancient dream had been fulfilled! Man had created a transmutation pathway not found in nature. To prove this reaction it was necessary to come up with a chemical technique to confirm the identity of the short-lived Phosphorus very quickly. The Nobel Committee raced to award the Joliot-Curies Nobel Prizes, not quite in time for the dying Marie Curie to take a plane to Stockholm, but she did take great pleasure from her daughter's discovery.

A flurry of other discoveries followed soon. Leo Szilard responded to (1934a) by filing for a patent on a chain-reaction bomb, though with no particular reaction to be chained. (Bombs were eventually built from U-235 and Pu-239 but neither isotope was known in 1934.

Neutron bombardment experiments generated conflicting results. Labs with wooden benches got different results than labs with marble benches. It was Enrico Fermi who suddenly interposed a chunk of paraffin between his neutron source and the Silver he was irradiating. The carbon in the paraffin was slowing ("moderating") the neutrons and making them more active. Fermi called this his most important discovery. These results defied predictions so in 1936 Niels Bohr published a paper with a new model of the atomic nucleus. (A paper by Noddack in 1934 criticized Fermi, and claimed — correctly as it turned out — that one of his experiments had produced a new element (now called neptunium). This paper was generally deprecated; and Fermi thought he could refute it, but physicists were then using a wrong value for helium's weight so many estimates were off.)

The most interesting reactions came with Uranium.

IV. The discovery of atomic fission (1938-1939)
Otto Hahn and Fritz Strassmann made a key discovery in December 1938, publishing in January 1939. Until their discovery a single nuclear reaction could produce only a single atom heavier than helium.

Otto Hahn and Fritz Strassmann had bombarded of Uranium with neutrons and produced no less than 16 different activities; they used chemistry to attempt identification of newly-found isotopes. For example, a barium carrier can be dissolved in the reaction product; and radium (or other elements in the same column of the periodic table as barium) will precipitate out, joining barium crystals. A Geiger counter then shows which radioactivities follow into the Barium crystals. Three activities did. These were presumably either radium or some new transuranic element. Radium would be novel: With atomic number 4 less than Uranium, the U-238 would need to emit TWO alpha particles to decay to radium. Barium, with atomic number 36 away from uranium, was thought to be impossible. Hahn-Strassman tentatively named two of the radioisotopes Ra-II (half-life 14 minutes) and Ra-III (half-life 86 minutes); they focused on identifying Ra-III. The procedure was to irradiate purified uranium with slow neutrons for 12 hours, wait several hours for the Ra-II to die away, add barium chloride as a carrier, separate the barium-radium crystals and redissolve them, and finally use crystal fractionation to separate the radium. They verified that ordinary radium would indeed be isolated in this final step, but the "Ra-III" remained with the barium. Through careful chemistry, they ruled out every possibility except Barium itself. Ra-III was Barium! (This was confirmed by doing crystal fractionation on the decay product of the Ra-III.) With a publishing deadline in very late December they debated whether to replace all instances of 'radium' with 'barium' in the paper they had prepared. Hahn was in contact with Lise Meitner and her nephew Otto Frisch, who prepared a paper trying to explain this very unexpected result. Frisch invented a new word usage to describe it: fission. (On reviewing their own experiments, the Joliot-Curies noticed that they had observed fission, but failed to notice. Earlier they had overlooked their own first discovery of neutrons.)

This was before the clamp-down on publishing results useful for atomic bombs, so Germany, Japan and Britain became immediately aware of the potential for a bomb. (Scientists in U.S.A., not then at war, were aware of the possibilities, but government dithered. When U.S. finally did respond, it went into overdrive.)

Chain reaction: i.e. the production of more than 1 neutron for every neutron in the pile or bomb was a prerequisite for power or weapon but 2:1 multiplication of neutrons was demonstrated in 1939 (though not an actual chain reaction). Szilard applied for another atomic bomb patent; and so on. U-235 was identified by 1939; the distinction between slow neutrons and fast neutrons developed; and Bohr had another epiphany. Plutonium was discovered in 1940. The first critical mass pile was in 1941, but there was no power-mode pile until 1943 (when "xenon poisoning" was discovered).

 

[rjh01]

I am looking at the book called The 100. A ranking of the most influential persons in history. Number 2 on the list is Isaac Newton. He discovered many things to do with optics. He
- discovered the laws of motion
- invented the reflecting telescope
- integral calculus
- the law of universal gravitation
- worked out how to predict the orbits of the planets using maths he had developed
- changed the way science worked.

You wanted a list of science discoveries. That is my list.

 

[Swammerdami]

Newton was certainly one of the very greatest scientists ever. In addition to items on rjh01's list, another discovery often credited to Newton is the decomposition of white light into the rainbow's colors using a prism.

However it is said that the great Iraqi scientist Abū ‘Alī al-Ḥasan ibn al-Haytham (called Alhazen in the West) wrote up something similar (based on rainbows?) circa 1015 in his Kitāb al-Manāẓir ( Book of Optics). I can't find an exact reference and am doubtful: Alhazen was highly respected by early Europeans like Roger Bacon. Galileo and Descartes. If Alhazen had made the clear claim that "white is the sum of the rainbow's colors", then why does Newton usually get the credit for this?

Regardless of this one point, Alhazen's several discoveries about optics and vision certainly qualify as key. He has been called the greatest physicist between Archimedes and Sir Isaac Newton.

 

[steve_bank]

In the Euro-Centric vies science apered in Europe. Before the decline of the Mid East and the rise of Europe the Arabs and Prsiabs wre the place to go for science.

Newton used Pwrsian astronomical data. I watched a show that reconstructed a Persian observatory. There was a transfer of knowledge to Europe. Newton's Laws already existed IN dfferent forms and were in print. Arabs published books on optics and algebra.

the foundations of what we call 'the' calculus go far back in history.

Newton-Leibniz system of notation for calculus and Newton's mechanics were the foundation for the rise of technology and modern science, Newtonian mechanics are still a mainstay of of engineering.

The other major figure was Maxwell.

His synthesis is the basis of modern electrical and electronic technology.

Einstein was important, but cosmology as someone else said is really irrelevant. His real contribution was the Photo Electric Effect which showed quantization of light.

There were many others that provided pieces of the puzzle. Fourier, Gauss, Millikan and the electron, and a long list.

Nobody creates in a vacuum.

I red a history of math. it is all trceable back in history. Science always follows the money. As Arab economics declined and Europe rose, science went with the money.

 

[untermensche]

Darwin changed the way man thinks about himself.

His ideas were so shattering many still today don't accept them.

 

[Swammerdami]

Loren Eiseley's Darwin's Century is a good read to put Darwin's theories in perspective. Eiseley demonstrates how several thinkers had grasped the essential elements of Darwin's theory before Darwin wrote. Nonetheless Eiseley has great admiration for Darwin's imagination, hard work, and eloquence.

The study of life's history was closely tied to progress in geology, the study of Earth's history. One of Darwin's chief inspirations was Charles Lyell who, though a geologist, almost produced Darwin's theory himself! He even wrote about the "struggle for existence," one of Darwin's favorite phrases. Lyell in turn learned from an 18th-century geologist who wrote the following at least a decade before Darwin was born:

... if an organised body is not in the situation and circumstances best adapted to its sustenance and propagation, then, in conceiving an indefinite variety among the individuals of that species, we must be assured, that, on the one hand, those which depart most from the best adapted constitution, will be the most liable to perish, while, on the other hand, those organised bodies, which most approach to the best constitution for the present circumstances, will be best adapted to continue, in preserving themselves and multiplying the individuals of their race.

The theme of this thread is specific discoveries or observations that led to the advance of science. Charles Lyell's observations of the strata at Mt. Etna (and the fossils therein) might qualify. These pointed to gradual geologic change rather than "catastrophes." Such gradualism was essential to Darwin's theory.

One specific observation that surprised Darwin and affected his thinking was the diversity among different islands in the Galapagos Archipelago; see  Darwin's finches. (He regretted gathering many specima without noting which of those islands they came from.)

~ ~ ~ ~ ~ ~

There were two glaring objections to Darwin's theory, and he began equivocating in later editions of Origin, even embracing the possibility of Lamarckian inheritance. The discoveries which overcame these objections both qualify as key events in the development of science.

The first objection was raised by Lord Kelvin among others. With the Earth just 25 million years old, there wasn't enough time for evolution to operate. This age was calculated from thermodynamics — if the Earth were older, more of its core heat would have dissipated. This objection was resolved when Marie Curie noticed that heat was associated with radioactivity. The Earth wasn't cooling as fast as expected because the decay of radio-isotopes replenished its heat.

The second objection was raised by Fleeming Jenkin, a Scottish Professor of Engineering, in an anonymously-published review titled "Darwin and the Origin of Species". As seen in the linked volume (which begins with a long Memoir by Robert Louis Stevenson, one of Jenkin's students), Jenkin had very diverse interests: in addition to the review of Darwin, the book contains an essay on the meter of English poetry and an essay on the nature of truth. Jenkin also wrote on economics and linguistics; and he was a successful inventor.

The objection Jenkin raised is that blending inheritance would imply very slow evolution: If a man with a gene for four extra inches of height marries a woman of normal height, the children inherit only half from father so would expect two extra inches of height, and the grandchildren only one inch. The new trait would fade away before much favorable inheritance could occur. Darwin was already aware of this problem, but Jenkin developed the case with much detail, and Darwin read this review with a sinking feeling.

The refutation for Jenkin's objection was published two years before Jenkin's review! But neither Darwin nor Jenkin read it during their lifetimes. This of course was Gregor Mendel's discovery of particulate inheritance. Instead of the tall man's grandchildren each inheriting 25% of the man's extra height, most of them would get none but 25% of the grandchildren would inherit the full 4 inches! (Obviously this example is over-simplified.) Mendel's important discovery — VERY key to genetics and presented and published in a scientific journal — lay completely unnoticed for about 35 years.

 

[untermensche]

Darwin was seriously hindered because he did not understand genetics.

The idea of evolution was around but it was Darwin who developed credible arguments about how evolution occurs despite not understanding how traits could be passed.

Darwin turns speculation into a science.

A science some people living today do not accept because of the clear implications.

Man was changed from an immutable "image of god" into a close relative of chimps and gorillas.

 

[steve_bank]

Not entirely correct. We share common ancestors with chimps.

We dud=d not come from monkeys...

 

[Bomb#20]

Newton was certainly one of the very greatest scientists ever. In addition to items on rjh01's list, another discovery often credited to Newton is the decomposition of white light into the rainbow's colors using a prism.

However it is said that the great Iraqi scientist Abū ‘Alī al-Ḥasan ibn al-Haytham (called Alhazen in the West) wrote up something similar (based on rainbows?) circa 1015 in his Kitāb al-Manāẓir ( Book of Optics). I can't find an exact reference and am doubtful: Alhazen was highly respected by early Europeans like Roger Bacon. Galileo and Descartes. If Alhazen had made the clear claim that "white is the sum of the rainbow's colors", then why does Newton usually get the credit for this?

Credit typically goes not to the one who first has the idea but to the one who first makes the case for it. Even the ancient Greeks knew prisms turned white light into colors; that white is the sum of the rainbow's colors is one of various possible explanations. Newton gets credit because of a couple of experiments he did. He isolated colors, ran them through another prism, and observed that the second prism didn't split them any further; and he recombined the separated colors and observed that white light was reconstituted. These results ruled out competing explanations such as that the prisms were adding something to the light. Did Alhazen do all that too, or was he just guessing?

Natural selection was thought of and published by a couple of nearly-forgotten early 19th-century biologists, decades before Darwin and Wallace made the case for it.

 

[Bomb#20]

Not entirely correct. We share common ancestors with chimps.

We dud=d not come from monkeys...

Yes we did.

Consider the segment on this chart connecting the lines leading to Tarsiers and leading to New world monkeys. What kind of animals were those? Those were monkeys. If they weren't monkeys, it would imply that their descendants evolved into monkeys twice: once into New world monkeys and a second time, independently, into Old world monkeys. Evolution doesn't repeat itself like that. No, some prosimians evolved into monkeys, and then the monkeys split into a group in Eurasia and a group in North America, and then the group in Eurasia split into Old world monkeys and apes, and then the apes split into various types such as humans. So yes, we came from monkeys.

 

[Swammerdami]

Atomic Theory (part 1)

That matter is composed of atoms is one of the most central ideas in modern science. Biology works with proteins, nucleic acids, sugars, etc. These compounds are composed of molecules; each molecule is a definite configuration of a finite number of specific atoms. And so on. Modern science would be completely lost without atoms.

And yet the Atomic Theory of Matter was not generally accepted by physical scientists until 1905!

The idea that matter is composed of small indivisible atoms is not new; it was advanced by several ancient Greeks (e.g. Democritus and Aristotle) as well as the great Roman philosopher Lucretius in De rerum natura (The Nature of Things) published circa 60 BC. (This work was almost lost but became very influential in the Late Middle Ages. Lucretius wrote in dactylic hexameter; this rhyming translation into English appears to be mostly iambic septameter.)

There's a model, you should realise,
A paradigm of this that's dancing right before your eyes -
For look well when you let the sun peep in a shuttered room
Pouring forth the brilliance of its beams into the gloom,
And you'll see myriads of motes all moving in many ways
Throughout the void and intermingling in the golden rays
As if in everlasting struggle, battling in troops,
Ceaselessly separating and regathering in groups.
From this you can imagine all the motions that take place
Among the atoms that are tossed about in empty space.
For to a certain extent, it is possible for us to trace
Greater things from trivial examples, and discern
In them the train of knowledge. Another reason you should turn
Your attention to the motes that drift and tumble in the light:
Such turmoil means that there are secret motions, out of sight,
That lie concealed in matter. For you'll see the motes careen
Off course, and then bounce back again, by means of blows unseen,
Drifting now in this direction, now that, on every side.
You may be sure this starts with atoms; they are what provide
The base of this unrest. For atoms are moving on their own,
Then small formations of them, nearest them in scale, are thrown
Into agitation by unseen atomic blows,
And these strike slightly larger clusters, and on and on it goes -
A movement that begins on the atomic level, by slight
Degrees ascends until it is perceptible to our sight,
So that we can behold the dust-motes dancing in the sun,
Although the blows that move them can't be seen by anyone.

It was Brownian motion that Lucretius put forth as evidence for an atomic theory. And it was a paper on Brownian motion that, nearly 2000 years later, put the final nail in the coffin of the "Continuousism" that opposed Atomic Theory!

The ancients developed ideas about elements, and had the notion of compounds of elements. Bronze, for example, is a compound made from Copper and Tin. But even advanced understanding of chemistry does not clearly imply the existence of atoms.

Partly due to interest in Lucretius' book, some early European scientists (e.g. Johannes Kepler, Robert Boyle, Isaac Newton) did embrace atomic theory. I think Kepler's insight was that crystalline structures (he focused on snowflakes!) wouldn't make sense in a continuous model.


(My posts are overly long, so I'll continue discussion of the Discovery of Atomic Theory in another post.)

 

[Swammerdami]

Atomic Theory (part 2)

Antoine Lavoisier (1743-1794) was perhaps the most important chemist ever and is often credited with advancing the atomic theory, but I'm not sure he ever discussed the distinction between atomic and continuous models of the elements.

John Dalton (1766-1844) made a number of important contributions to science, but is most remembered for the modern discovery of atomic theory in about 1805, for example

Dalton identified two oxides of iron. One is a black powder in which for every 100 parts of iron there is about 28 parts of oxygen. The other is a red powder in which for every 100 parts of iron there is 42 parts of oxygen. 28 and 42 form a ratio of 2:3. These oxides are today known as iron(II) oxide (better known as wüstite) and iron(III) oxide (the major constituent of rust). Their formulas are FeO and Fe₂O₃ respectively.

However it is possible for matter to be continuous, and still have elements that react in fixed proportions.

After Dalton, there was much progress in chemistry — including many key discoveries that deserve their own mention in this thread — but the fundamental question remained unresolved: Is matter composed of indivisible atoms or not?

By 1871 using a long process of trial-and-error, Dmitri Mendeleev had built his periodic table of elements. We now know that element #13 has atoms with 13 electrons and 13 protons, but electrons and protons are 20th-century ideas. Mendeleev's periodic table was just an arrangement that seemed fortuitously useful.

To modern eyes the existence of atoms seems obvious, and necessary for the rest of physical science to work properly. It might seem that the hold-outs against atomism would be backward-looking folk. Yet one of these "holdouts" was none other than Max Planck (1858-1947), whose own key discovery led to Quantum Theory.

There will be a fight between these two hypotheses [atomic theory and the law that entropy never decreases] that will cause the life of one of them.... in spite of the great successes of the atomistic theory in the past, we will finally have to give it up and to decide in favour of the assumption of continuous matter.

Both the 2nd Law and Planck's own great discovery merit their own posts in this thread, but a brief digression is needed to make sense of Planck's view on atomism. Isaac Newton had noted that his Laws of Motion and of Gravitation were reversible (Maxwell's Laws were also reversible); yet it is intuitively obvious to humans that there is an Arrow of Time. The Second Law of Thermodynamics is often treated as the key fact which creates that Arrow.

The 2nd Law of thermodynamics was also discovered late in the 19th century. "Classical" thermodynamics ignores atomic theory and postulates that entropy NEVER decreases. "Statistical" thermodynamics, on the other hand, applies to huge but finite numbers of molecules. In that model, entropy CAN decrease but will do so only with extremely tiny probability. (In some discussions the distinction between these two models is ignored; great confusion ensues.) Ludwig Boltzmann (1844-1906) was an atomist so assumed "statistical" thermodynamics. But others, including Max Planck, took the 2nd Law as an ironclad Law rather than statistical fact — a Law necessary to guarantee a particular arrow for time! (An amusing anecdote about Planck: When he applied to study physics as an undergraduate in 1874, the Professor (Philipp von Jolly) advised him not to bother! "In this field, almost everything is already discovered, and all that remains is to fill a few holes." Planck assured von Jolly that he had no plans to discover anything new.)

In about 1899, Planck derived  Planck's law which implied that light and other EMF waves are organized into discrete packets, now called photons. Still Planck did not accept atomism, regarding his Law as an heuristic that happened to work. (But by 1910 he had become a close friend of Albert Einstein and, of course, an adherent to atomism.)

Also in about 1899 J. J. Thomson identified the "cathode rays" produced in  Crookes tube as tiny discrete electrons. This may have sealed the fate of continuousness: If one constituent of matter has an indivisible character, the other constituents must as well. Planck's still-unnamed photons pointed toward the same conclusion. But the "nail in the coffin" came in 1905.

(1905a) On the Movement of Small Particles Suspended in Stationary Liquids Required by the Molecular-Kinetic Theory of Heat
Albert Einstein treated Brownian motion mathematically and concluded as Lucretius had 1965 years earlier: Matter had to be atomic.

While Planck is sometimes given credit for the discovery of the photon, the real key was another paper by Einstein:

(1905b) On a Heuristic Point of View Concerning the Production and Transformation of Light
This paper contained a statement which has been called "the most revolutionary sentence written by a physicist of the twentieth century" and was the key to the development of quantum physics.

According to the assumption to be contemplated here, when a light ray is spreading from a point, the energy is not distributed continuously over ever-increasing spaces, but consists of a finite number of energy quanta that are localized in points in space, move without dividing, and can be absorbed or generated only as a whole.

After these papers by Einstein, there was no further controversy: Atoms were real.


These weren't the only papers published by Einstein in 1905. Two others from the "Annus Mirabilis" are:
(1905c) "On the Electrodynamics of Moving Bodies" (Special theory of Relativity)
(1905d) "Does the Inertia of a Body Depend Upon its Energy Content?" (E = mc²)

 

[untermensche]

Not entirely correct. We share common ancestors with chimps.

We dud=d not come from monkeys...

That is the definition of "relative".

We are related to chimps and gorillas.

We share a common ancestor.

You are related to your cousin. You share a common ancestor.

You did not come from your cousin.

 

[steve_bank]

Well gosh darn it to heck, you are making a monkey out of me.

The common popular perception of evolution is that we came form primates.

There is an infamous depiction of a walking knuckle dragging ape evolving foot step by foot step into a modern human.

 

[untermensche]

Well gosh darn it to heck, you are making a monkey out of me.

The common popular perception of evolution is that we came form primates.

There is an infamous depiction of a walking knuckle dragging ape evolving foot step by foot step into a modern human.

Humans are primates.

So is an aye-aye.

 

[Jokodo]

Not entirely correct. We share common ancestors with chimps.

We dud=d not come from monkeys...

Yes we did.

Consider the segment on this chart connecting the lines leading to Tarsiers and leading to New world monkeys. What kind of animals were those? Those were monkeys. If they weren't monkeys, it would imply that their descendants evolved into monkeys twice: once into New world monkeys and a second time, independently, into Old world monkeys. Evolution doesn't repeat itself like that. No, some prosimians evolved into monkeys, and then the monkeys split into a group in Eurasia and a group in North America, and then the group in Eurasia split into Old world monkeys and apes, and then the apes split into various types such as humans. So yes, we came from monkeys.

We *are* monkeys. Of the ape type.

We are also fish, of the type with lungs and legs.

 

[Bomb#20]

So yes, we came from monkeys.

We *are* monkeys.

Your monkey has got it right, sir.

Of the ape type.

Well, sure, going by cladistic naming conventions.

We are also fish, of the type with lungs and legs.

Which of course makes clear the whole reason not to use cladistic naming conventions. Does anyone really benefit from having everyone piously intoning "non-avian dinosaur"?

But my point was that even going by normal common-usage terminology that's happily accepting of paraphyletic categories, humans really did evolve from monkeys. So that whole tiresome "No, no, no, that's wrong, humans and monkeys had a common ancestor." business is incorrect pedantry, just like "There's no such thing as centrifugal force.".

[ Gone non-tetrapod-fishin'... ]