Account Share

Discover and read the best of Twitter Threads about #OTD

Most recents (24)
The Apollo 11 mission touched down on the moon #OTD in 1969. Neil Armstrong and Buzz Aldrin landed the lunar module Eagle on the surface, while Michael Collins remained in orbit aboard the command module Columbia.
Image: NASA
Here are all the photos from all the Apollo missions, in @NASA's Project Apollo Archive on @flickr.…
Images: NASA
Every human being except for Michael Collins is in the frame of this photo. Taken just before the Lunar Module Eagle rejoined the Command Module Columbia. #MoonDay
Image: NASA
Read 6 tweets
Astrophysicist Brian May was born #OTD in 1947. He completed his thesis (“A Survey of Radial Velocities in the Zodiacal Dust Cloud”) in 2007, 37 years after starting his PhD. Not sure what the delay was, but you can read it here:…
Image: Brian May Archive
The young @DrBrianMay with his homemade Fabry-Pérot Spectrometer, the Red Special. Note the disk magnets in the pickups and the custom pulse-counting electronics.
Image: Brian May Archive
May was also named a science team collaborator for @NASANewHorizons during the Pluto flyby in 2015.
Read 3 tweets
The astronomer Wendy Freedman was born #OTD in 1957. She was co-PI on the Hubble Space Telescope Key Project, which reported the value of the Hubble Constant as H₀ = 72 ± 8 km/sec/Mpc back in December of 2000.…
Photo: John Zich
With a decade of new data, Freedman and her collaborators updated their result in 2012, quoting a value of H₀ = 74.3 ± 2.1 km/sec/Mpc.
Fast forward to today's final data release from the @Planck collaboration. Their ΛCDM model gives H₀ = 67.27 ± 0.60 km/sec/Mpc. That's a 3.5σ disagreement with the astrophysical measurements of Freedman et al and other groups -- a real head-scratcher.…
Read 5 tweets
Did Thread Reader help you today?
Support me: I'm a solo developer! Read more about the story
Become a 💎 Premium member ($30.00/year) and get exclusive features!
Too expensive?
Make a small donation instead. Buy me a coffee ($5) or help for the server cost ($10):
Donate with 😘 Paypal or  Become a Patron 😍 on
Using crypto? You can help too!
1/ #OTD IN COUNTERINTELLIGENCE AND SECURITY HISTORY: On July 17, 1950, Soviet spy Julius Rosenberg was arrested for espionage. The Army Security Agency and FBI had been cooperating in the decryption of intelligence messages -- a portion of which were collectively referred to...
2/ as "VENONA" -- exchanged by the Soviet KGB and GRU with their agents in the Western Hemisphere. Some of these messages incriminated Rosenberg, but this highly classified evidence could not and would not be used during his trial.
3/ Rosenberg's wife Ethel was arrested on Aug. 11, 1950 on suspicion of assisting him. Thanks to key testimony from David Greenglass, Ethel's brother, Julius Rosenberg was exposed as the central figure in a very active spy ring that was passing weapons technology information...
Read 6 tweets
The physicist and astronomer Georges Lemaître was born #OTD in 1894. A Jesuit, in 1927 he proposed a model of an expanding Universe. Then, in 1931, he hypothesized its origin in a “unique atom” or “unique quantum” that would eventually become known as the ~Big Bang~.
Lemaître and the expanding universe are the subject of today’s Google doodle.
Image: the Google doodle team
(The first serious work on an expanding Universe, by Alexander Friedman, began four or five years earlier.)
Read 7 tweets
Four years to the day, we mourn the loss of #EricGarner, a faithful father, husband, and friend. He was 43 at the time of his death. #OTD
Garner was killed by a NYPD Officer Pantaleo who placed him in a chokehold in violation of departmental policies.….
Just yesterday, the the #NYPD finally announced it will be moving forward with holding Officer Pantaleo accountable for using a banned chokehold and killing #EricGarner. This is long, long overdue.…
Read 4 tweets
Jocelyn Bell Burnell was born #OTD in 1943. As a grad student at Cambridge in 1967, she discovered a new type of celestial object: Pulsars!

Photo: National Science & Media Museum / Science & Society Picture Library
Here’s a thread from this past November about her discovery.
Jocelyn Bell and Russell Hulse both made pulsar discoveries, but only one got a share of a Nobel Prize.
Read 3 tweets
Two rural Alaska airlines sued the U.S. over a new law effectively driving them out of business in favor of big airlines. #OTD 7/13/2005 the Ninth Circuit oral argument addressed time travel, Alice in Wonderland, & invisible aliens...
1/ Okay, this is a story about aliens and time travel and whatnot, but mostly, it's a story about how the normal rules for proving your case in court change when you're bringing economic liberty constitutional claims against the government...
2/ The 2002 law basically said that if an airline wants to deliver mail to rural areas, it also has to deliver passengers, too. Allegedly, the law would create an incentive for passenger air travel to rural places. BUT the law exempted the big airlines...
Read 26 tweets
In 2015, Sandra Bland died in police custody at the Waller County, TX jail following her arrest during a traffic stop. Our thoughts are with her family. #OTD
Bland was on a "road trip to start a new job" when she was stopped by a police officer for not using a turn signal. She was found dead in her jail cell 3 days later. Officials alleged she committed suicide, but her family asserts she wasn't depressed.…
The former officer involved in her arrest was charged with perjury for making a false statement about the arrest. The charges were dropped after he agreed to surrender his law enforcement license and never work as an officer again.…
Read 4 tweets
Thanks in no small part to @Lin_Manuel's crazy-popular @HamiltonMusical, Twitter is abuzz that #OTD 7/11/1804 Aaron Burr killed Alexander Hamilton in a duel. But what happened next? Litigation, of course! Today's #CourtingHistory covers Burr's indictments in New Jersey & New York
1/ In the musical, Burr laments "I survived, but I paid for it // Now I’m the villain in your history." Did killing Hamilton make Burr a villain? Recall that Burr was popular enough in 1800 that he was just one vote away from becoming President when the election deadlocked...
2/ But Burr's star was falling fast even *before* killing Hamilton. He's the VP at the time, but he's disliked by POTUS. And in Mar. 1804, he loses the election for NY governor to a relative unknown. Even if Burr wasn't already a villain before shooting Hamilton, he was no hero.
Read 48 tweets
#OTD in 1804, Alexander Hamilton and Aaron Burr dueled in New Jersey. Hamilton was mortally wounded and brought to the Bayards' home. Both his wife, Eliza Schuyler Hamilton, and her sister, Angelica Schuyler Church, were called to his side. Their story is as follows: (1/7)
After the duel, as Hamilton's boat reached the Manhattan shore, he said, according to the doctor present at the scene, David Hosack, "'Let Mrs. Hamilton be immediately sent for—let the event be gradually broken to her; but give her hopes.'" (…) (2/7)
Eliza was summoned from the Hamiltons' home, the Grange, to the Bayard's residence in Manhattan. She was told that her husband was having spasms and wanted her by his side. It is likely that she did not learn the truth until she'd arrived at the Bayards'. (3/7)
Read 7 tweets
Joseph Larmor was born #OTD in 1857. A prominent figure during a transitional period in physics, he made a number of contributions that were saddled by adherence to 19th century ideas yet figured prominently in important developments of the 20th century.
Image: Royal Society
Larmor determined the rate at which an accelerating electron radiated energy, and contributed to the understanding of the splitting of spectral lines in a magnetic field observed by Zeeman.
But Larmor's attempt to develop a notion of discrete charge within Maxwell's theory conceptualized the electron (he adopted George Stoney's term) as a sort of vortex within the aether, entirely separate from the atom.
Read 8 tweets
The first calculation of black hole formation was submitted to Physical Review by Robert Oppenheimer and Hartland Snyder #OTD in 1939.…
Their work was full of simplifying assumptions but captured essential features of BH formation. They [ahem] observe that a collapsing sphere of pressureless matter "tends to close itself off from any communication with a distant observer; only its gravitational field persists."
Ideas familiar from the popular understanding of black holes appear here: the intense red shifting of light; the fact that collapse seems to require cosmic patience from a distant observer but proceeds in comparatively short order for someone plunging inward.
Read 5 tweets
1/ #OTD IN COUNTERINTELLIGENCE AND SECURITY HISTORY – On July 9, 2010 -- after a multi-year investigation by the FBI and other elements of the US Intelligence Community -- ten deep-cover Russian “illegals” (operatives of the Russian Foreign Intelligence Service (SVR)) were...
2/ exchanged in Vienna, Austria, for four individuals who had been jailed in Russia for alleged contact with Western intelligence agencies. The day before, the Russian illegals pleaded guilty in federal court in NYC to conspiring to serve as Russian agents in a case that...
3/ served as a chilling reminder that espionage on U.S. soil did not disappear with the end of the Cold War. The Russian govt. spent significant funds and many years training and deploying these “SVR illegals” to establish a presence in the U.S. and develop sources of info. ...
Read 5 tweets
The physicist John Archibald Wheeler, a titan of 20th century science, was born #OTD in 1911. He introduced the S-Matrix; developed the first general theory of fission (with Bohr); coined the terms "black hole" and "worm hole"; trained Feynman, Everett, Thorne, and many others. Young John Archibald Wheeler, Credit: Voices of the Manhattan ProjectJohn Archibald Wheeler in front of blackboard, Credit: Voices of the Manhattan ProjectEinstein, Yukawa, Wheeler, and Bhabha go for a walk. Credit: Phys.orgApologies to Edward Gorey, image pulled from
Just out for a walk in the woods near the Institute for Advanced Study with Einstein, Yukawa, and Bhabha, as one does.
Image: the Wheeler family, via
Here is a thread about Wheeler from last year (the olden days, when tweets were 140 characters).
Read 6 tweets
Today marks the 150th anniversary of the 14th Amendment which was designed to give full citizenship to African Americans who had been formerly enslaved. #14thAmendment #CivilRights
The promise of full citizenship was meant to include the ability to participate equally in the political process. #CourtsMatter #VotingMatters #OTD
The 14th Amendment's relevance can't be overstated, especially in today's legal landscape. "We can only hope that, in the words of Frederick Douglass, it will continue to “give full freedom to every person without regard to race or color in the U.S.”…
Read 3 tweets
“WILL A WOMAN ALTER THE COURT?” Headlines like this marked Pres. Reagan’s nomination of Sandra Day O’Connor #OTD 7/7/1981 as the first woman to join the Supreme Court. Read more about speculation before & reactions after her nomination...
1/ When running for president in 1981, Reagan promised that if elected and given the chance, he would name the first female Justice of the US Supreme Court...
2/ That opportunity came just months into Reagan’s first term when Justice Potter Stewart announced his resignation...
Read 21 tweets
Vannevar Bush wrote to President Truman #OTD in 1945, responding to a request made by Roosevelt in 1944. He submitted "Science the Endless Frontier," a report outlining a plan for federal support for the sciences and the establishment of the @NSF.…
That same month, July 1945, Vannevar Bush published "As We May Think" in @TheAtlantic, a forward-looking essay that anticipated hypertext, the web, and other information technologies in the form of a desk-like device he called a "memex."…
☝️July 1945 was quite a month for Vannevar Bush. He sent a report to the president that led to the NSF and made funding the sciences a federal priority. He also published a piece in The Atlantic that forecast hypertext, the Web, Wikipedia, and more.
Read 3 tweets
Sir Isaac Newton's "Philosophiæ Naturalis Principia Mathematica," which lays out his laws of motion and his universal law of gravitation, was published #OTD in 1687.
You can digitally page through Newton's own annotated copy of the Principia, courtesy of the Cambridge Library:…
I think this Newton fellow might be on to something, and you should definitely check it out, but honestly a lot of what you need to know is in this old @xkcdComic.
Read 4 tweets
The astronomer Henrietta Swan Leavitt was born #OTD in 1868. She established the period-luminosity relation for Cepheid variable stars, an essential tool for understanding the scale of our universe.
Image: Harvard-Smithsonian Center for Astrophysics
Cepheids were our first standard candles - astronomical phenomena that allow us to reliably determine galactic and extragalactic distances. They brighten and dim with a very regular period that correlates with their maximum brightness. Measure the former and you know the latter.
And if you compare their brightness, inferred from their period, to how bright they *appear*, then you can determine how far away they must be.
Read 11 tweets
A kind of quaint paper with a cute title submitted #OTD in 1980. Ray D'Inverno and Inge Frick show the reader the basics of SHEEP, an early computer algebra system for handling tensor calculations in GR.
Ref: General Relativity and Gravitation, Vol. 14, No.1 0, 1982
SHEEP started life as ALAM (Atlas Lisp Algebraic Manipulator), written by D'Inverno as a PhD student in 1969. The first application was working out the Riemann tensor for the Bondi metric. That calculation took Bondi et al. six months. ALAM did it in 4 minutes & found 6 mistakes.
That was kind of the "Whoa" moment that convinced lots of relativists that computer algebra would be a really important tool going forward.
Read 3 tweets
Born #OTD: The great, prolific Hans Bethe. Bethe made so many contributions to so many fields of physics that the astronomer John Bahcall joked that there was a conspiracy by dozens of people to publish their paper under the name 'Hans Bethe'.
Bethe's stamina, concentration, all-encompassing knowledge of physics and contributions made him a legend. His most famous student, Freeman Dyson, once joked to me that if he really focused on a problem he could be one tenth as good as Bethe. Physicist David Wark captures the awe
Bethe won the Nobel Prize for solving an elemental problem that had puzzled humanity for hundreds of years: What makes the sun shine? It took him until 1968 to get the prize because they were figuring out which one of his many contributions to recognize.
Read 9 tweets
The nuclear physicist Harriet Brooks, who was probably the first person to notice the recoil of an atomic nucleus due to emissions during nuclear decay, was born #OTD in 1876.
Brooks was the first Canadian woman to work in the nascent field of nuclear physics. Her advisor & colleague Ernest Rutherford —she was his first grad student— lauded her work as a critical step in sorting out the mechanisms of nuclear decay.
Credit: Notman Archives/Musée McCord
(☝️cc @Perimeter!)
Read 16 tweets
Alexander Friedmann submitted "On the Curvature of Space" to Zeitschrift für Physik #OTD in 1922, describing a homogeneous and isotropic universe that expands over time according to its matter & energy content. It's the arena for all of modern cosmology.…
The Instituut-Lorentz has scans of his original manuscript, with handwritten notes, as well as some of his correspondence with Ehrenfest and others.…
When speaking of his pioneering work applying general relativity to cosmology, Friedmann was said to frequently quote Dante: "The waters I am entering, no one yet has crossed."
Read 7 tweets
Related hashtags
Did Thread Reader help you today?
Support me: I'm a solo developer! Read more about the story
Become a 💎 Premium member ($30.00/year) and get exclusive features!
Too expensive?
Make a small donation instead. Buy me a coffee ($5) or help for the server cost ($10):
Donate with 😘 Paypal or  Become a Patron 😍 on
Using crypto? You can help too!