Discover and read the best of Twitter Threads about #OTD

Most recents (24)

30 years ago #OTD Chris Gueffroy was shot to death trying to cross the Berlin Wall. He was the last person killed by East German border guards in the attempt.
Gueffroy heard rumour that the "order to shoot" had been lifted and thought a visit from Swedish PM would make crossing safe. But the order to shoot was still in effect and the Swedish PM already gone; Gueffroy was shot repeatedly and died on site.
Killing Chris Gueffroy damaging to SED at time of rising unrest. Order to shoot at Berlin Wall lifted in April 1989. Of the 140 who died as the result of the creation of the Berlin Wall, Gueffroy was 139th.
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1/#OTD in 1870, Jonathan Jasper Wright became the first black state supreme court justice in American history. He served on the South Carolina Supreme Court, the next stop on our #52courts52weeks tour! #BlackHistoryMonth
2/ When Wright was on the Court, he and his colleagues worked out of the State House. It was not until 1971 that the Court finally moved into its own building – the renovated Columbia Post Office.
3/ Before serving on the Court, Wright was active and influential in law and politics. He was one of the first three African-American attorneys admitted to the South Carolina bar in 1868.
Read 16 tweets
#OTD
Enquanto Mariana e Brumadinho choram, as lágrimas de Unaí ainda não secaram. Há exatamente 15 anos, em 28 de janeiro de 2004, três auditores fiscais do trabalho e um motorista do ministério foram mortos numa emboscada perto da cidade mineira de Unaí, a 166 km de Brasília.
Os auditores investigavam trabalho escravo na zona rural, quando foram emboscados e mortos por três pistoleiros contratados por fazendeiros. O @MPF_MG denunciou oito pessoas por quatro homicídios qualificados, entre eles Norberto Mânica e o ex-prefeito de Unaí, Antério Mânica.
Os júris federais foram realizados em Belo Horizonte. O dos 3 pistoleiros ocorreu em 2013 e já cumprem pena. Erinaldo Vasconcelos Silva (74 anos de prisão após fazer acordo de delação premiada); Rogério Alan Rocha Rios (94 anos de reclusão); e William Gomes de Miranda (54 anos).
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The Irish statesman and philosopher, Edmund Burke was born #OTD 1729.

Unlike the beautiful, Burke's aesthetic concept of the Sublime required the spectator to experience the awe of sublimity through terror, power, darkness, vastness & infinity thus overwhelming our finite mind.
Burke’s define the Sublime in his treatise "A Philosophical Enquiry into the Origin of Our Ideas of the Sublime and Beautiful" (1757) anticipating the Romantic movement's idea of the transcending power of Nature as a source of inspiration [1]
Nature's sublime experience with its terrifying beauty of incomprehensible power threatens our human finiteness with the infinitude of spaces. Human speech fails to fully describe its vast power likewise it cannot be defined ethically [good or evil].
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#OTD 1941, in his State of the Union address, FDR delivered the 'Four Freedoms' speech.

Four fundamental freedoms that people "everywhere in the world" ought to enjoy were listed. They are:

Freedom of speech
Freedom of worship
Freedom from want
Freedom from fear

Thread
1/7
Freedom of Speech (Freedom of Expression) "is a principle that supports the freedom of an individual or a community to articulate their opinions and ideas without fear of retaliation, censorship, or legal sanction".

2/7
Freedom of worship "is a principle that supports the freedom of an individual or community, in public or private, to manifest religion or belief in teaching, practice, worship, and observance. It also includes the freedom to change one's religion or beliefs."

3/7
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Edwin Hubble announced that Andromeda and other spiral nebulae were separate galaxies outside the Milky Way, in a paper read to a @AAAS meeting by H.N. Russell #OTD in 1925. He built on observations by Slipher and relied on Henrietta Swan Leavitt’s studies of Cepheid variables. Image of M31 by Isaac Roberts
The universe was more than just our little island of stars, vaster than anything most astronomers had imagined.
On the one hand, January 1st is a pretty arbitrary date, astronomically. On the other hand, happy 94th anniversary of humanity taking a monumental step towards understanding our place in a vast, mysterious, but ultimately knowable Universe.

Happy New Year!
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The chemist & educator St. Elmo Brady was born #OTD in 1884. He was the first African American to receive a PhD in Chemistry (University of Illinois, 1916). Brady worked on organic acids, infrared spectroscopy, and halogen compounds, and he expanded chem programs at four schools. Portrait of chemist St. Elmo Brady. Image: University of Illinois Archives
Dr. Brady in his lab at Fisk University, sometime around 1950.
Image: Fisk University / University of Illinois Archives
After completing his PhD, Brady returned to Tuskegee University. In 1917 he wrote a series of monographs called "Household Chemistry for Girls," intended to introduce the subject to students with no scientific training. You can read the first one here: iiif.lib.harvard.edu/manifests/view…
Read 4 tweets
Martin Kruskal submitted his paper "Maximal Extension of Schwarzschild Metric," which explained the full spacetime structure of Schwarzschild's black hole solution of general relativity, #OTD in 1959.
journals.aps.org/pr/abstract/10…
A notable feature of Kruskal's work was the interpretation of the "interior" region of the Schwarzschild black hole as a wormhole that might connect two different spaces, or perhaps two different regions of space. Alas, the wormhole is not traversable.
Oh neat. Martin Kruskal invented a magic trick which often confounds magicians because it is actually a math trick related to Markov chains.
arxiv.org/abs/math/01101…
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Apollo 8, the first mission to carry astronauts out of low Earth orbit, and then reach and orbit the Moon, launched #OTD in 1968.
Images: NASA, via Project Apollo on Flickr
flickr.com/photos/project…
Look, it’s a nice planet, with everything we need. Maybe let’s not destroy the thin, ephemeral layer that keeps us all alive.
Image: NASA
Today is the 50th anniversary of humans leaving low Earth orbit for the first time, and heading to the Moon.
Images: NASA
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Albert Michelson, pioneer of optical interferometry, was born #OTD in 1852. He refined measurements of the speed of light, failed to find evidence of the aether, and developed a method that now underlies gravitational wave detection.
Photo: “Practical Physics,” Millikan & Gale
Here is something you may not know about famed physicist Albert Michelson: The “Look to the Stars” episode of the TV show "Bonanza" features a young Michelson performing various experiments and measuring the speed of light. The Cartwrights help him get into the US Naval Academy.
Anyway, here is a thread about Michelson, his famous "failed experiment" that eventually led Einstein to propose special relativity, and how his work relates to @LIGO and the discovery of gravitational waves.
Read 3 tweets
Roger Penrose submitted "Gravitational Collapse and Space-Time Singularities" #OTD in 1964. He showed that singularities appear to be a generic consequence of gravitational collapse in general relativity, not just a feature of highly symmetric spacetimes.
journals.aps.org/prl/abstract/1…
Here is Penrose's main conclusion, along with four possible avenues for resolving spacetime singularities. In one form or another these are all still active areas of research 53 years later.
Before this paper it wasn't clear whether singularities were in some sense contrived; the end result of evolution from an especially symmetric initial configuration that is too perfect to occur in the real world. Penrose showed that they were probably generic and unavoidable.
Read 3 tweets
Gilbert Lewis, a physical chemist at UC Berkeley, coined the name "photon" for the quantum of light in a letter to the editor of Nature #OTD in 1926.
nature.com/articles/11887…
"I therefore take the liberty of proposing for this hypothetical new atom, which is not light but plays an essential part in every process of radiation, the name 𝒑𝒉𝒐𝒕𝒐𝒏." It turns out that photons aren't conserved in the way that Lewis proposed, but the name stuck.
"The photon" is certainly a catchier name than Einstein's "das lichtquant,"
Read 3 tweets
This is maybe the dumbest thing I’ve ever heard anyone say on this godforsaken website.
Friends he said climate change can’t be a threat to the planet because Venus “is still there.”
If you’ve been sitting on a horrendously dumb take I advise you to air it out right now because nothing else anyone says today is going to top this.
Read 8 tweets
Happy 95th birthday to physicist Freeman Dyson, born #OTD in 1923! He is known for his work in quantum electrodynamics and –among many other things– his eschatological musings about physics and the prospects for life in the far-flung future.
Photo: Heka Davis / AIP
Here is a thread about Dyson and some of his contributions:
If you make it through the part about QED, you’ll be rewarded with some very fun speculation about the deep future, with sentences like "...ordinary low-mass stars that have settled down into white dwarf configurations and become cold spheres of pure iron," and tables like this:
Read 4 tweets
Max Planck presented findings on the emission of radiation from a blackbody to the German Physical Society #OTD in 1900, based on his quantum hypothesis: the postulate that light of frequency f is emitted or absorbed by matter only in discrete chunks of energy E=hf.
Image: AIP
As I was saying, before I was so rudely interrupted by a day of grading exams: Planck presents his quantum hypothesis, which would end up transforming 20th century physics, to the German Physical Society #OTD in 1900. But he didn't think it was *real*.
Rather, Planck regarded it as a mathematical trick. He was sure that perfectly pedestrian physics governed the emission or absorption of radiation by matter. It's just that the details weren't quite understood, and invoking quanta gave a quick route to the answer.
Read 5 tweets
The last moonwalk began #OTD in 1972. No one has set foot on the moon since Apollo 17 astronauts Eugene Cernan and Harrison Schmitt, 46 years ago.
Images: NASA
More images of Cernan and Schmitt on the lunar surface #OTD in 1972. Command Module Pilot Ronald Evans remained in orbit.
Images: NASA, flickr.com/photos/nasacom…
Friends, you could do worse than spending a few hours looking through @NASA's Project Apollo Archive on @Flickr.
flickr.com/photos/project…
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The astronomer Annie Jump Cannon was born #OTD in 1863. She was a pioneer of stellar classification and co-creator of the Harvard Classification Scheme. Over her lifetime she *manually* classified around 350,000 stars.
Image: Harvard University, Radcliffe Archives
Cannon expanded on the classification used by Edward Pickering (director of the Harvard Observatory) and Williamina Fleming, adding the O, B, A, F, G, K, M spectral classes. The Harvard Classification system, adopted by the International Astronomical Union in 1922, is still used.
Like her colleague Henrietta Swan Leavitt, Cannon was deaf. Her hearing loss began in childhood — likely due to a case of scarlet fever — and progressed over the years.
Image: Annie Jump Cannon and Henrietta Swan Leavitt In 1913 (Harvard University Library)
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Ada Lovelace, née Augusta Ada Byron, was born #OTD in 1815. A mathematician and the first published computer programmer, she offered a prophetic vision of what computing would become.
Portrait: Margaret Sarah Carpenter (1836)
In 1842, Charles Babbage asked Lovelace to translate Louis Menebrea's essay on the Analytical Engine. She produced an article three times as long, with a "Notes" section full of wildly original ideas that anticipate many of the ways we use computers today.
fourmilab.ch/babbage/sketch…
A thread on "poetical scientist" Ada Lovelace and her germinal contributions to computing.
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Computer science pioneer and United States Navy rear admiral Grace Hopper was born #OTD in 1906. As far as I’m aware, she is the only person with both a supercomputer and a US Navy destroyer named after her.
Image: Computer History Museum
Here’s a thread about some of Dr. Hopper’s contributions. She didn’t coin the term “bug,” nor did she invent COBOL. The actual stories are more interesting.
Grace Hopper was fond of explaining the nanosecond with something you could hold, a short length of wire representing the distance light would travel in that little sliver of time.
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The physicist Arnold Sommerfeld was born #OTD in 1868. He made important early contributions to atomic physics and quantum mechanics, and trained a who's-who of prominent 20th century physicists.
Image: Archives of the Max Planck Society
Sommerfeld was a strong advocate for and early adopter of the important new theories that emerged in the early 20th century. He had incorporated special relativity into his teaching by 1907, and he refined Bohr's model of the hydrogen atom within the old quantum theory.
Sommerfeld's modifications of Bohr's model are described in his 1919 book "Atomic Structure and Spectral Lines." Van der Waerden would later remark that the young physicists who developed quantum mechanics all learned the old quantum theory from this book.
archive.org/details/Atomic…
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“Dear Radioactive Ladies and Gentlemen”
Wolfgang Pauli sent a letter to a group of nuclear physicists #OTD in 1930, proposing a new and hard-to-detect particle to explain energy that went missing in some beta decays. He called them “neutrons,” but we now call them “neutrinos.”
You can see a scan of Pauli’s neutrino letter (along with a translation) here:
microboone-docdb.fnal.gov/cgi-bin/Retrie…
It was Fermi who coined the name “neutrino,” for “little neutral one.”

When Pauli realized how elusive the particles must be, he said:
“I have done something very bad today by proposing a particle that cannot be detected; it is something no theorist should ever do.”
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"I, at any rate, am convinced that He is not playing at dice."
Einstein sent a letter to Max Born #OTD in 1926, giving his famous objection to the probability interpretation of the wavefunction in quantum mechanics.
physicstoday.scitation.org/doi/full/10.10…
Born was disappointed that Einstein would oppose this interpretation of quantum mechanics on philosophical grounds, instead of some more concrete objection. He felt like this attitude marked a generation gap in physics, with him on one side and Einstein on the other.
One thing not a lot of people know about this exchange between Einstein and Born is that Max Born was also Olivia Newton John’s grandfather.
Read 4 tweets
Ernst Florens Friedrich Chladni, often referred to as the "father of acoustics," was born #OTD in 1756. He studied the mathematical theory of sound waves, the speed of sound in various materials, and complex patterns formed by vibrational modes of solid objects.
Image: Wikimedia
Chladni famously drew a violin bow along the edge of a thin metal plate, lightly dusted with flour, to excite the plate's vibrational modes. Here he is, performing the demonstration for Napoleon.
Image: Deutsches Museum Munich, no. 527”7
The flour would collect along nodal lines -- points on the vibrating plate that remained fixed -- and form complex patterns, like so:
Read 7 tweets
Jocelyn Bell Burnell made the first observation of a pulsar #OTD in 1967. She and advisor Antony Hewish initially dubbed the object LGM-1 (“Little Green Men”) for its regular signal, but it was soon identified as a rotating, magnetized neutron star.

Photo: National Media Museum Dame Jocelyn Bell Burnell, age 24, in front of a large radio dish. National Media Museum / Science & Society Picture Library
Here is a thread from last year about her remarkable discovery.
Also, Russell Hulse was born #OTD in 1950. He & advisor Joseph Taylor made the first observation of a pulsar in a binary system in 1974. This led to the first indirect detection of gravitational waves via the precisely timed decay of the system's orbit.
Image: US Dept of Energy
Read 10 tweets

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