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Twenty tubes, one answer

At approximately 3:00 a.m. on 27 May 1961, the NIH postdoctoral fellow J. Heinrich Matthaei added synthetic RNA made entirely of uracil nucleotides — poly-U — to an E. coli cell-free protein-synthesis system.

The assay ran across 20 tubes, each with a different radioactively labelled amino acid. Only the phenylalanine tube produced the striking radioactive signal, showing that poly-U directed phenylalanine incorporation into a polypeptide.

What the paper actually claimed

Marshall W. Nirenberg had built the cell-free system with Matthaei, and the two interpreted and published the result jointly. The published paper concluded that polyuridylic acid carried information for making a protein resembling poly-L-phenylalanine and could act as a synthetic messenger-RNA template.

It was more cautious than later retellings. It concluded only that one or more uridylic-acid residues coded for phenylalanine, and said explicitly that whether the code was singlet, triplet or another length had not been determined.

Why 15 May is the wrong timestamp

A 2025 NIH obituary says the experimental series began on 15 May; the American Chemical Society's historical reconstruction dates the decisive phenylalanine assay to 3:00 a.m. on 27 May. The earlier date marks a beginning, not the result.

Matthaei physically performed the overnight assay, but describing him as working “alone” misleads if it implies sole intellectual authorship of a collaborative program.

Nirenberg presented the finding in Moscow in August 1961 to an audience of about 35 people; after Francis Crick helped arrange a repeat presentation, the larger audience gave him a standing ovation.

The Lincoln Memorial, 28 August 1963

Approximately 250,000 demonstrators assembled in Washington on 28 August 1963 for the March on Washington for Jobs and Freedom, moving from the Washington Monument to the Lincoln Memorial.

King delivered the program's concluding major address. The printed program called it simply "Remarks" and placed it as item 16 of eighteen, after Rabbi Joachim Prinz and before the pledge and the benediction.

He recalled finishing the prepared text at roughly 3:30 that morning.

Manuscript first, then memory

King began from the manuscript, invoking the Emancipation Proclamation and portraying constitutional equality as a promissory note on which the country had defaulted — a metaphor suggested by his adviser Clarence B. Jones.

Partway through he set the typescript aside and drew on material he had used in earlier sermons and speeches: the "dream" sequence, then the "let freedom ring" conclusion. The delivered address ran about sixteen minutes.

What the record actually supports

Mahalia Jackson, who had performed shortly before him, called out to King about the dream. Eyewitnesses remembered her prompting him, but analysis of the master recording suggests she may have spoken after he had already begun that passage.

Contemporary Associated Press coverage reported that King departed from his advance text and received the strongest applause of the Lincoln Memorial speeches. Afterwards, King and other movement leaders met President Kennedy and Vice President Johnson at the White House to press for civil-rights legislation.

8:00:57 p.m. EDT, 14 July 1965

NASA's Mariner 4 made the first successful spacecraft flyby of Mars on 14 July 1965, passing 6,118 miles above the surface at 8:00:57 p.m. EDT — already 15 July in Universal Time.

Beginning about 40 minutes before closest approach, its television camera recorded 21 complete images plus 22 lines of a 22nd, through red and green filters.

About 1.25 hours after closest approach the spacecraft passed behind Mars as seen from Earth. Refraction of its radio signal through the atmosphere gave a direct measurement of very low surface pressure, initially estimated at roughly 4 to 7 millibars.

A narrow strip of very old ground

The photographs covered a narrow swath and revealed heavily cratered, ancient-looking terrain rather than the detailed Earth-like landscape some observers had expected.

They were not a representative global survey. Later missions showed that Mariner 4 had happened to photograph unusually ancient cratered terrain, and that Mars also has volcanoes, canyons, channels and younger surfaces.

The pictures arrived the next day

The pictures did not come back live. The image data were stored on an onboard tape recorder for slow transmission, and the first picture elements reached Earth the following day; full playback continued for days.

While waiting for normal computer processing, JPL staff printed the numerical picture data, cut the paper into strips and coloured the values by hand. That is the origin of the often-reproduced hand-coloured image — not a colour photograph taken at Mars.

Groote Schuur, past midnight

Surgery began shortly after midnight on 3 December 1967 at Groote Schuur Hospital in Cape Town. Christiaan Barnard led a multidisciplinary University of Cape Town team that removed Louis Washkansky's irreparably damaged heart and put Denise Darvall's in its place.

Just before 6 a.m., the transplanted heart was electrically shocked and began beating in Washkansky's chest. It was the first human-to-human orthotopic heart transplant.

The donor and the consent

Darvall, 25, was struck by a car on 2 December and certified as having a lethal brain injury. Her father, Edward Darvall, consented to donation of her heart and kidneys after the same collision killed his wife.

The circumstances were legally and ethically fraught: formal brain-death and transplant statutes did not yet exist in South Africa.

Eighteen days

Washkansky, given as 54 in Barnard's contemporaneous clinical report and as 53 in some later histories, regained consciousness with a functioning donor heart.

The intensive immunosuppression intended to prevent rejection left him highly vulnerable to infection. He died of pneumonia on 21 December, 18 days after the operation.

Brooks Hall, 9 December 1968

At the Fall Joint Computer Conference in San Francisco on 9 December 1968, Douglas Engelbart took the stage for a 90-minute live session titled “A Research Center for Augmenting Human Intellect.”

He drove SRI's NLS computer in Menlo Park from the stage, working a keyboard, a three-button mouse and a five-key chord set. Engelbart had pushed for the long plenary slot because written explanations of the system had not conveyed it.

What the audience actually saw

Engelbart demonstrated hypertext links, outlining and text editing, flexible views and windows, and remote shared-screen collaboration with colleagues 30 miles away — two people at different sites editing and discussing the same material in real time.

Bill English directed the machinery behind it: computer data, live cameras, microwave video and split-screen projection onto a 20-foot screen. Seventeen members of the Augmentation Research Center contributed.

A public debut, not an invention

About 1,000 computer professionals watched, and the session ended with a standing ovation. The mouse got its public debut here; prototypes and comparative testing had come earlier.

The other pieces had histories too. Ted Nelson had published the term hypertext in 1965, and Brown University's Hypertext Editing System was operating by 1967. The nickname “Mother of All Demos” was applied later, by the computer scientist Andries van Dam.

17 October 1969, Boyle's office at Murray Hill

Jack Morton, a Bell Labs vice president, had demanded that Willard Boyle's division produce a semiconductor device to compete with magnetic-bubble memory. On 17 October 1969, Boyle and George Smith met in Boyle's office at Murray Hill, New Jersey, to answer him.

In a discussion lasting no more than an hour they sketched the basic structure of the charge-coupled device on the blackboard, defined its operating principles, and ran through preliminary applications.

The scheme stored information as isolated packets of electric charge beneath closely spaced MOS capacitors and moved each packet to its neighbour by changing electrode voltages — an electrical counterpart to the magnetic bubble.

The anniversary the sources argue about

Smith's Nobel lecture puts the meeting on 17 October 1969, and the IEEE milestone for the invention carries that date. Some secondary timelines instead give 19 October 1969, the date of a signed laboratory-notebook entry.

Nobel Foundation background material supplies a third date, 8 September 1969. The competing dates may conflate conception, documentation and later institutional anniversary traditions, and no institutional history settles the question.

From blackboard to working device

The pair decided at once to build something. In less than a week Bell Labs had cut masks, fabricated a crude device and demonstrated that a packet of charge could be handed from one site to the next.

An integrated eight-bit, three-phase structure followed, showing both shift-register action and linear imaging. The Bell System Technical Journal papers appeared in April 1970 — a publication date, not a construction date.

Imaging was listed among the possible applications in that first paper. Michael Tompsett subsequently developed practical CCD imagers, and the allocation of imaging credit remains historically contested.

19:24:59 GMT, 19 December 1972

On 19 December 1972, the command module America, carrying Eugene Cernan, Ronald Evans and Harrison Schmitt, jettisoned its service module, reentered normally and splashed down in the Pacific at 19:24:59 GMT — 2:24:59 p.m. EST.

The mission had run 301 hours, 51 minutes and 59 seconds. The splashdown point lay 648 kilometers southeast of American Samoa.

Recovery

Teams from USS Ticonderoga tracked the capsule and retrieved the astronauts by helicopter. The crew was aboard the ship 52 minutes after splashdown.

Recovery swimmers had reached the capsule, installed a flotation collar and passed life preservers through the hatch before the crew entered a raft.

The command module was recovered for postflight inspection, with the mission's samples, film and scientific data back on Earth.

What came home

The last Apollo moonwalk had ended five days earlier, on 14 December. What 19 December delivered was 110.4 kilograms — 243 pounds — of lunar material.

NASA's Apollo program director reported that the mission had been completed successfully and that all assigned primary objectives had been achieved.

A gully at Hadar, 24 November 1974

In 1974, Donald Johanson and the graduate student Tom Gray were mapping and searching for fossils at Hadar, Ethiopia, when Johanson chose an alternate route back to their Land Rover through a gully.

He spotted a right proximal ulna and recognized it as hominin. Skull, femur, rib, pelvis and jaw fragments lay nearby — the mark of an associated skeleton rather than one stray bone.

Forty percent

The team marked the locality and began recovery. Two weeks of excavation, screening and sorting produced 47 bones representing about 40 percent of a single skeleton.

The individual dates to about 3.2 million years ago and stood roughly 3.5 feet tall at an estimated 60–65 pounds. Her identification as female rests principally on her small size within a strongly sexually dimorphic fossil sample.

The name arrived that night

During the celebration that evening the Beatles' “Lucy in the Sky with Diamonds” played repeatedly, and the fossil acquired its nickname. Nobody later remembered who proposed it.

The scientific name came four years later: Johanson, Tim White and Yves Coppens formally named Australopithecus afarensis in 1978.

7:53 a.m.: the roof empties

On 30 April 1975 a Marine CH-46 lifted the final U.S. Marine security guards off the roof of the U.S. Embassy in Saigon, ending the embassy evacuation. Ambassador Graham Martin had gone at 4:58 a.m.

Official U.S. tallies for Operation Frequent Wind disagree. The modern Defense Department breakdown gives 6,968 helicopter evacuees — 1,373 Americans and 5,595 Vietnamese and third-country nationals — while a contemporaneous Joint Staff account reported 7,806 people evacuated by the U.S. military.

10:24 a.m.: the surrender

President Dương Văn Minh, who had taken office only two days earlier on 28 April, announced South Vietnam's surrender and ordered its armed forces to cease fighting.

The Hồ Chí Minh Campaign's general assault on Saigon had begun on 26 April, under Văn Tiến Dũng, and had broken through the remaining defenses.

Midday at Independence Palace

People's Army of Vietnam tanks entered central Saigon and broke through the Independence Palace gates around midday. The Vietnamese government's chronology puts the revolutionary flag over the palace at 11:30 a.m.

Communist forces controlled Saigon by the afternoon and the Republic of Vietnam no longer exercised authority in its capital. Formal reunification into one state came later, on 2 July 1976.

12:10 a.m., 9 September 1976

On 9 September 1976, Mao Zedong died in Beijing shortly after midnight, holding the offices of chairman of the Chinese Communist Party Central Committee and chairman of its Central Military Commission. He was not China's formal head of state.

He had suffered repeated heart attacks and severe chronic illness. The contemporary official announcement disclosed only that his condition had worsened despite treatment; a later medical-historical review identifies myocardial infarction as the terminal event.

Radio Peking, 4:00 p.m.

The announcement came almost 16 hours after the death. Four central bodies — the party Central Committee, the National People's Congress Standing Committee, the State Council and the Central Military Commission — jointly issued a message to the party, armed forces and population.

The government announced a national mourning period and set the central memorial ceremony for 18 September.

An open succession

Hua Guofeng, already premier and party first vice-chairman, held the strongest formal position. Deng Xiaoping had been stripped of his posts in April 1976 and did not immediately succeed Mao.

The conflict between Hua's allies and the radical faction around Mao's widow, Jiang Qing, stayed unresolved until the Gang of Four's arrest in October.

22 February, not 27

The U.S. Air Force launched Navstar 1 from Vandenberg Air Force Base, California, on an Atlas F booster. Official Air Force and Space Force histories date the launch to 22 February 1978.

The 27 February date carried in the supplied slug and listing is erroneous.

One developmental spacecraft

Rockwell International's Space Division built and tested Navstar 1 at Seal Beach, California, as the first developmental Block I Navstar/GPS spacecraft, also designated SVN-1.

It was the first purpose-built Block I GPS satellite. Earlier Navigation Technology Satellites had supported GPS development, and NTS-2 had transmitted the first true GPS signals in 1977.

Not a service, a test program

The launch started the GPS space-segment test program with an actual Block I satellite in orbit. It created no operational worldwide service that day.

Three more Navstar launches followed in 1978, and satellites 1 through 4 were set healthy on 8 January 1979 as the first four-satellite test configuration. Of eleven Block I launch attempts through 1985, ten spacecraft reached orbit.

The military council convenes at 10:20 a.m.

On 11 February 1979, Iran's Supreme Military Council convened and declared the armed forces neutral in the struggle between Prime Minister Shapour Bakhtiar's government and Khomeini's revolutionaries, ordering units back to their barracks.

Chief of Staff Abbas Gharabaghi agreed to withdraw the army from Tehran, leaving the capital under revolutionary control, according to a U.S. Embassy report written the next day. The commonly listed date of 10 February is one day early for this decision.

5:45 p.m.: the radio changes hands

Revolutionaries occupied Tehran Radio, which announced the fall of Bakhtiar's government and identified itself as the voice of the revolution.

Revolutionary forces took government buildings and police stations, opened prisons, seized weapons and arrested prominent Pahlavi officials. Contemporary reporting counted more than 200 dead and 800 wounded in Tehran from the final two days of fighting.

What did and did not end

The crisis had begun with fighting between pro-Khomeini Air Force homafaran and the loyalist Imperial Guard at Doshan Tappeh, after which armed civilians joined in and Bakhtiar's expanded curfew was openly defied.

The army declared neutrality; it did not formally transfer power. Bakhtiar vanished from public view and Mehdi Bazargan's provisional government became the practical authority. The Islamic Republic itself was proclaimed only on 1 April, after the 30–31 March referendum.