The famous paper's author list contained one name, not three — and the date usually given as its publication is the day the journal stamped it “received.”
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Zeitschrift für Physik recorded receipt of Werner Heisenberg's manuscript “Über quantentheoretische Umdeutung kinematischer und mechanischer Beziehungen” on 29 July 1925. That is the journal's receipt date: Springer's current record gives an issue date of December 1925, while an American Physical Society historical account says the paper appeared in September.
The submitted paper proposed a quantum-theoretical mechanics based exclusively on relationships between quantities that were, in principle, observable, deliberately discarding pictures of electron paths in favour of quantities tied to observable atomic transitions.
One author, not three
The manuscript was Heisenberg's alone. Max Born and Pascual Jordan were not its coauthors.
Born and Jordan's “Zur Quantenmechanik” was a separate paper, received on 27 September 1925, and the three-author Born–Heisenberg–Jordan paper was yet another work, “Zur Quantenmechanik II,” submitted in November.
Born recognizes the algebra
Heisenberg had written down an unfamiliar multiplication rule without identifying it as matrix multiplication. Born then identified those rules with matrix algebra and, with Jordan, rapidly developed a more explicit mathematical formulation in their separate paper.
The 1925 paper should not be read as already containing Heisenberg's 1927 uncertainty principle or the later general operator formalism.
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The event date is securely the journal’s receipt date, not its publication date. Springer’s current record gives an issue date of December 1925, while an American Physical Society historical account says the paper appeared in September; either way, it was not published on 29 July.
While working in Copenhagen in February 1927, Werner Heisenberg sent Wolfgang Pauli a 14-page letter outlining the new uncertainty relation and his gamma-ray-microscope reasoning. The letter is dated 23 February.
Heisenberg argued that making an electron's position increasingly definite necessarily made its momentum increasingly indefinite, and vice versa.
The imaginary microscope
The gamma-ray-microscope thought experiment connected the attainable spatial resolution with an unavoidable uncertainty in the electron's momentum — gamma rays precisely because their short wavelength promised sharp vision.
Heisenberg had developed the argument while Niels Bohr was away; Bohr returned and challenged part of its optical reasoning before publication.
Which formulation is which
The February letter became the basis of Heisenberg's paper “Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik,” received by the journal on 23 March 1927 — so accounts that treat March as the event are describing a different milestone.
Heisenberg's original relation was approximate. The familiar exact standard-deviation bound of ℏ/2 is Earle Hesse Kennard's later 1927 formulation, and modern treatments distinguish intrinsic statistical spread in a quantum state from measurement error and disturbance, two ideas the popular statement mixes together.
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Date corrected. The research places this at 1927-02-23.
What the sources leave uncertain
February is the formulation milestone, independently supported by Heisenberg's dated letter to Pauli. The formal journal article was received on 23 March 1927, so accounts that call March the publication event are describing a different milestone.
The precise modern inequality using standard deviations and the bound ℏ/2 is Kennard's later 1927 formulation, not exactly the approximate relation as Heisenberg first wrote it.
27 February 1932: “Possible Existence of a Neutron”
Nature published James Chadwick's short communication “Possible Existence of a Neutron” on 27 February 1932, reporting experiments conducted at the Cavendish Laboratory in Cambridge. Chadwick had dated the letter 17 February.
He argued that the penetrating radiation produced when beryllium was bombarded with alpha particles was better explained as neutral particles of approximately proton mass than as extremely energetic gamma rays, and explicitly proposed particles with mass 1 and charge 0.
Two weeks from puzzle to publication
The Joliot-Curies' observation that beryllium radiation could eject very fast protons from paraffin made the prevailing gamma-ray explanation physically implausible to Chadwick, prompting rapid repeat experiments with several target materials.
Chadwick did not observe a neutral particle directly. He inferred its mass and lack of charge from the recoil energies of nuclei struck by the beryllium radiation, moving from the Paris results to a published report in about two weeks.
Who supplied what
The report converted earlier anomalous results by Bothe and Becker and by Irène and Frédéric Joliot-Curie into evidence for a new neutral nuclear particle. The Joliot-Curies supplied the crucial proton-ejection result but interpreted the radiation through a gamma-ray model; Chadwick supplied the neutron interpretation.
Rutherford's earlier “neutron” had generally been conceived as a tightly bound proton-electron combination rather than the independent particle Chadwick's evidence established. Chadwick immediately continued the work for a fuller Royal Society paper, “The Existence of a Neutron,” received on 10 May.
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Date corrected. The research places this at 1932-02-27.
What the sources leave uncertain
The discovery has several defensible milestone dates. Chadwick's Nature letter was dated 17 February and published 27 February; his fuller paper, “The Existence of a Neutron,” was received on 10 May and published on 1 June. The listed event gives only 1932, so 27 February is used as the first public report.
Some timelines use 10 May because that is the receipt date printed on the fuller Royal Society paper, not the first announcement.
Hiryū's aviators struck Yorktown twice and believed they had hit two different carriers — because the crew had restored the ship so quickly after the first raid.
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At approximately 06:30 on 4 June 1942, Japanese carrier aircraft bombed installations on Midway Atoll, inflicting only slight damage to the island's facilities while causing disastrous losses among the defending Marine fighters. U.S. cryptanalysis had disclosed Japan's objective and approximate timetable, letting Admiral Chester Nimitz place Enterprise, Hornet, Yorktown and Midway-based aircraft in ambush positions.
Between roughly 09:30 and 10:30, U.S. carrier torpedo squadrons attacked and were nearly wiped out. Dive bombers from Enterprise and Yorktown then fatally damaged Akagi, Kaga and Sōryū.
Hiryū strikes back
Aircraft from the surviving Japanese carrier Hiryū struck Yorktown twice, forcing the American carrier's abandonment during the afternoon.
Late that afternoon, U.S. dive bombers flying from Enterprise mortally damaged Hiryū, the fourth Japanese carrier.
What 4 June did and did not settle
The destruction of the Japanese carrier striking force compelled Admiral Isoroku Yamamoto to abandon the planned seizure of Midway and begin withdrawing westward. The cost on the American side was heavy: 307 personnel killed and about 145 aircraft lost, with 40% of the carrier aircraft in the first strike lost or left unairworthy.
The battle did not end that evening. The carriers were mortally damaged on 4 June, with some scuttled on 5 June; Mikuma was sunk on 6 June, and Yorktown and Hammann were torpedoed by submarine I-168 on 6 June and sank later.
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Sources variously date the entire battle 3–6, 4–6, or 4–7 June, depending on whether they include preliminary contact on 3 June and the sinking of Yorktown on 7 June. The decisive carrier action occurred on 4 June.
Representatives of the 50 countries attending the United Nations Conference on International Organization signed the Charter on 26 June 1945, in the Herbst Theatre auditorium of San Francisco's Veterans War Memorial Building. Blue-leather-bound Charter books lay on an eleven-foot round table backed by the silk flags of the 50 countries.
China signed first; after a seven-hour ceremony, 153 signatures had been placed on the documents. The signed instrument included the Statute of the International Court of Justice as an integral part of the Charter.
Adopted one day, signed the next
The conference had unanimously adopted the completed Charter and the ICJ Statute at the San Francisco Opera House on 25 June, making the documents ready for signature the following day.
President Harry S. Truman witnessed the United States delegation's signing and addressed the conference at its closing session.
Signed, but not yet in force
Signing did not bring the Charter into force. That occurred on 24 October 1945, after the required ratifications had been deposited.
Nor were all original members present: Poland's delegation was absent on 26 June and signed on 15 October, which is why the 50 signatories of that day became 51 original members.
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At 2:00 p.m. in Beijing on 1 October 1949, the Central People's Government Council held its first meeting. Its chairman, vice-chairmen and members took office, and it appointed Zhou Enlai premier and foreign minister, among other senior officials.
One hour later the founding ceremony began at Tiananmen, where Mao Zedong announced that the Central People's Government of the People's Republic of China had been established.
Flag, proclamation, parade
The new five-star national flag was raised while “March of the Volunteers,” then the provisional national anthem, was played. Mao read the Central People's Government proclamation, which declared the new government to be China's sole legal government and offered diplomatic relations to governments accepting equality, mutual benefit and respect for territorial sovereignty.
The ceremony continued with a People's Liberation Army review and a mass civilian procession in and around Tiananmen Square. Sources report 300,000 soldiers and civilians present, while the official military account describes 54 guns firing 28 salvos and 14 aircraft overhead.
A proclamation, not an ending
The proclamation did not instantly end the Chinese Civil War or transfer every mainland territory: substantial fighting and the Nationalist withdrawal continued, and the Republic of China government had not completed its move to Taiwan. Mao had already announced the coming establishment of the PRC at the CPPCC's opening on 21 September.
Zhou Enlai sent the proclamation to foreign governments. Representation at the United Nations changed far later: PRC representatives took China's seat in 1971 under General Assembly Resolution 2758.
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At Texas Instruments in Dallas on 12 September 1958, Jack Kilby demonstrated a working phase-shift oscillator whose transistor, resistor and capacitor elements were formed from one piece of germanium and connected with thin gold wires. The demonstrated circuit contained five components.
The test showed that active and passive circuit elements could be fabricated from the same semiconductor substrate and made to operate together as a complete circuit.
Proving a notebook idea
Kilby's supervisor, Willis Adcock, had been interested but skeptical of the monolithic-circuit proposal Kilby recorded on 24 July 1958, and asked him to prove that a circuit made from semiconductor elements could work.
Kilby recorded the successful demonstration on page 20 of his engineering notebook, signing and dating the entry 12 September 1958.
Kilby's prototype, Noyce's architecture
The prototype used external gold “flying wires” rather than the practical planar, on-chip interconnection system later proposed by Robert Noyce. The two men made distinct contributions: Kilby produced the first working integrated circuit, while Noyce's silicon planar design supplied a more manufacturable architecture.
Texas Instruments now had a functioning proof of concept, documented in Kilby's notebook, that became the basis for subsequent patent and development work; the patent application followed on 6 February 1959.
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A false cockpit signal made controllers fear Friendship 7's heat shield had come loose — so Glenn reentered with the spent retrorocket package still strapped on.
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An Atlas rocket launched John Glenn in Friendship 7 from Launch Complex 14 at Cape Canaveral at 9:47:39 a.m. EST on 20 February 1962.
Glenn completed three Earth orbits, becoming the first American in orbit — though not the first American in space, a distinction already held by the suborbital flights of Alan Shepard and Virgil Grissom. He alternated between automatic and manual control after a yaw-control jet apparently clogged.
The heat-shield warning
A faulty telemetry switch suggested that the capsule's heat shield might be loose. Controllers therefore told Glenn to retain the spent retrorocket package during reentry, so its straps might help hold the shield in place.
Postflight inspection showed the warning had been false — but controllers did not know that during reentry.
Splashdown and recovery
Friendship 7 splashed down in the Atlantic at 2:43 p.m. EST after 4 hours, 55 minutes and 23 seconds, having covered 75,679 statute miles. The destroyer USS Noa recovered Glenn and the capsule, which was aboard 21 minutes after splashdown.
A medical examination aboard USS Noa found Glenn slightly dehydrated but otherwise in excellent condition.
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Kennedy's open limousine entered Dealey Plaza at about 12:30 p.m. CST on 22 November 1963, on the 10-mile motorcade route from Love Field. As it passed the Texas School Book Depository on Elm Street, bullets struck Kennedy in the neck and then the rear of the head, and wounded Texas governor John Connally in the back.
The limousine rushed both men to Parkland Memorial Hospital, where Kennedy was pronounced dead at 1:00 p.m. Connally underwent surgery and survived.
An arrest and an oath, the same afternoon
Police found three cartridge cases near a sixth-floor Depository window and a bolt-action rifle elsewhere on that floor. Lee Harvey Oswald, a Depository employee, was arrested at the Texas Theatre shortly before 2:00 p.m.
At 2:38 p.m., federal judge Sarah T. Hughes administered the presidential oath to Lyndon B. Johnson aboard Air Force One at Love Field, in a crowded compartment with Kennedy's coffin aboard the same aircraft. The plane then carried Kennedy's body, Jacqueline Kennedy and the new president toward Washington.
Charges filed, and what was never settled
Oswald was formally arraigned that evening for the murder of Dallas patrolman J. D. Tippit. The complaint accusing him of murdering Kennedy was signed at 11:26 p.m., with arraignment following after midnight; he was never convicted of either killing, because Jack Ruby killed him before trial.
The Warren Commission concluded that Oswald fired the shots and acted alone. The House Select Committee's later probable-conspiracy finding depended on acoustic evidence that subsequent expert analysis rejected.
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The date and principal timeline are firmly documented. Responsibility remains culturally contested, but the Warren Commission concluded that Oswald fired the shots and acted alone. The House Select Committee’s later probable-conspiracy finding depended on acoustic evidence subsequently rejected by later expert analysis.
Luna 9 did not settle onto landing legs: a capsule was ejected, bounced across the Moon inside an inflatable cushion, then unfolded like a four-petaled metal flower.
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The Soviet Luna 9 spacecraft completed its rocket-braked descent at approximately 18:45:30 UT on 3 February 1966, landing in Oceanus Procellarum and becoming the first human-made object to achieve a survivable landing on another celestial body.
About an hour before touchdown, roughly 8,300 kilometres from the Moon, the spacecraft stopped spinning and oriented its engine along the lunar vertical using Sun- and Earth-tracking optics.
Radar, retrorocket, bounce
At approximately 75 kilometres altitude the radar altimeter commanded the braking engine to fire, cutting the descent velocity from about 2,600 metres per second to a few metres per second near the surface.
Near the surface the protected spherical landing capsule separated, struck the Moon at about 22 km/h inside its inflated cushioning system, bounced several times, and came to rest. Four minutes and ten seconds later its four petals and antennas deployed and radio communication began.
Pictures had to wait for the Sun
The first surface pictures were not transmitted at touchdown: imaging waited roughly seven hours for a higher Sun angle, so the first photographic transmission from the surface of another planetary body began early on 4 February.
Luna 9's precise resting place remains uncertain. The coordinates published in 1966 were approximate, and a 2026 machine-learning study reported possible artificial-object candidates rather than a confirmed identification of the lander.
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Luna 9’s precise resting place remains uncertain. The coordinates published in 1966 were approximate, and a 2026 machine-learning study reported possible artificial-object candidates rather than a confirmed identification of the lander.
Sources use both “soft landing” and the more literal “survivable landing.” The descent was rocket-controlled, but the small capsule itself was ejected near the surface and cushioned by an inflatable impact system.
Israel opened the war on 5 June 1967 with Operation Focus, a surprise morning air attack on Egyptian airfields that destroyed most of Egypt's usable combat aircraft on the ground and severely damaged its air bases. Contemporary Israeli estimates reported by U.S. Naval Institute Proceedings claimed more than 300 aircraft destroyed in the opening waves.
Israel committed nearly its entire striking air force to the raid, leaving only a small defensive force at home. At the same time, Israeli armored and infantry forces crossed into the Egyptian-held Sinai Peninsula and Gaza Strip.
The fighting widens the same morning
Jordanian aircraft and artillery entered the fighting later that morning. Jordanian troops occupied the UNTSO Government House compound in Jerusalem — the UN observers' own headquarters — after which Israeli forces displaced them amid heavy fighting reported to begin around 11:30 GMT.
After Jordanian, Syrian and Iraqi aircraft attacked, the Israeli Air Force struck their airfields as well, so combat spread from the Egyptian front to the Jordanian and Syrian fronts on the war's first day.
By nightfall
U.S. diplomatic reporting judged by the end of 5 June that Israel had won a decisive victory over the Egyptian air force and also over the Jordanian and Syrian air forces. Israeli ground troops were advancing in Sinai and Gaza, with sustained combat around Jerusalem and along the Syrian frontier.
Two common misplacements belong to other days: the Battle of Ammunition Hill began at approximately 2:30 a.m. on 6 June, and Israel's ground offensive against the Golan Heights came later in the war. Whether the opening attack is best characterized as preemptive, preventive or aggressive remains disputed; the operational sequence is not.
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Whether Israel’s opening attack should be characterized as “preemptive,” “preventive,” or aggressive remains politically and historiographically disputed. The operational sequence is not disputed: Israel launched the large opening air and ground attacks on Egypt on June 5.
Contemporary aircraft-loss totals generally originated with belligerents and vary by source. The figure included here is explicitly labeled as an Israeli estimate reported in a professional military history.
At UCLA on 29 October 1969, student programmer Charley Kline attempted to log in from an SDS Sigma 7 host to SRI's SDS 940 host in Menlo Park, while SRI programmer Bill Duvall monitored the receiving system.
Kline typed LOGIN, but only L and O reached SRI before the receiving system crashed. The original handwritten UCLA log records the event at 10:30 p.m., noting that the host crashed after the O.
Working within the hour
Duvall corrected the problem, and within about an hour the teams were successfully transmitting and completing the login between the two hosts. Kline and Duvall kept a telephone line open throughout, verbally confirming each character the computers sent.
The data passed through BBN-built Interface Message Processors at UCLA and SRI, making this the first documented host-to-host connection on ARPANET.
What “LO” was not
“LO” was not a deliberately composed message: it was the first two letters of the LOGIN command before the receiving host crashed. Nor was this the first occasion on which any two remote computers had communicated — it was the first documented ARPANET host-to-host transmission.
Only UCLA and SRI were connected that evening. The four-node diagram commonly shown for 1969 represents the network at year's end, and the permanent UCLA–SRI link is separately dated 21 November 1969.
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Institutional retellings differ over the clock time: the Computer History Museum says Kline began typing at around 9 p.m. and that the connection was fully working by 10:30, while UCLA, IEEE, DARPA’s log caption, and many later accounts assign 10:30 p.m. to the documented first transmission. The date and sequence—failed “LO,” repair, successful login—are well supported.
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