Editing Trinity (nuclear test) (section)

==Explosion==

===Detonation===
The scientists wanted good visibility, low humidity, light winds at low altitude, and westerly winds at high altitude for the test. The best weather was predicted between July 18 and 21, but the [[Potsdam Conference]] was due to start on July 16 and President [[Harry S. Truman]] wanted the test to be conducted before the conference began. It was therefore scheduled for July 16, the earliest date at which the bomb components would be available.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=364}}

The detonation was initially planned for 04:00 MWT but was postponed because of rain and lightning from early that morning. It was feared that the danger from [[radiation]] and fallout would be increased by rain, and lightning had the scientists concerned about a premature detonation,<ref name="trialrun">{{cite web |title=Countdown |work=Los Alamos: Beginning of an Era, 1943–1945 |publisher=Los Alamos Scientific Laboratory |url=http://atomicarchive.com/Docs/pdfs/00285808.pdf |access-date=August 24, 2014 |archive-date=August 26, 2014 |archive-url=https://web.archive.org/web/20140826133845/http://atomicarchive.com/Docs/pdfs/00285808.pdf |url-status=live }}</ref> as had happened with a model of the electrical system.{{r|wellerstein20150716}} A crucial favorable weather report came in at 04:45,{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=365}} and the final twenty-minute countdown began at 05:10, read by [[Samuel King Allison|Samuel Allison]].{{sfn|Norris|2002|p=404}} A rocket launched at 5:25 to signal five minutes before detonation; another rocket fired at 5:29. At 5:29:15, a switch in the control bunker started the detonation timer.{{r|wellerstein20150716}} By 05:30 the rain had gone.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=365}} There were some communication problems: the shortwave radio frequency for communicating with the B-29s was shared with the [[Voice of America]], and the FM radios shared a frequency with a railroad freight yard in [[San Antonio]], Texas.{{sfn|Bainbridge|1975|p=44}}

Two circling B-29s observed the test, with Shields again flying the lead plane. They carried members of [[Project Alberta]] who would carry out airborne measurements during the atomic missions. These included [[Captain (United States O-6)|Captain]] [[Deak Parsons]], the associate director of the Los Alamos Laboratory and the head of Project Alberta; [[Luis Walter Alvarez|Luis Alvarez]], [[Harold Agnew]], [[Bernard Waldman]], [[Wolfgang Panofsky]], and [[William Penney]]. The overcast sky obscured their view of the test site.{{sfn|Dvorak|2013|pp=11–13}}

At 05:29:21 MWT{{efn|name=MWT}} (11:29:21 [[Greenwich Mean Time|GMT]]) ± 15 seconds,{{sfn|Gutenberg|1946|pp=327–330}} the device exploded with an energy equivalent to {{convert|24.8|+/-|2|ktonTNT}}.<ref name="Trinity_yield">{{cite journal |last1=Selby |first1=Hugh D. |last2=Hanson |first2=Susan K. |last3=Meininger |first3=Daniel |last4=Oldham |first4=Warren J. |last5=Kinman |first5=William S. |last6=Miller |first6=Jeffrey L. |last7=Reilly |first7=Sean D. |last8=Wende |first8=Allison M. |last9=Berger |first9=Jennifer L. |last10=Inglis |first10=Jeremy |last11=Pollington |first11=Anthony D. |last12=Waidmann |first12=Christopher R. |last13=Meade |first13=Roger A. |last14=Buescher |first14=Kevin L. |last15=Gattiker |first15=James R. |last16=Vander Wiel |first16=Scott A. |last17=Marcy |first17=Peter W. |title=A New Yield Assessment for the Trinity Nuclear Test, 75 Years Later |journal=Nuclear Technology |issn=0029-5450 |date=October 11, 2021 |volume=207 |issue=sup1 |pages=321–325 |doi=10.1080/00295450.2021.1932176 |arxiv=2103.06258 |bibcode=2021NucTe.207S.321S |s2cid=244134027 }}</ref> The desert sand, largely made of [[silica]], melted and became a mildly radioactive light green glass, which was named [[trinitite]].{{sfn|Parekh|Semkow|Torres|Haines|2006|pp=103–120}} The explosion created a crater approximately {{convert|4.7|ft}} deep and {{convert|88|yd}} wide. The radius of the trinitite layer was approximately {{convert|330|yd}}.<ref name=Trinitite>{{cite journal |last1=Hermes |first1=Robert E. |authorlink1=Robert E. Hermes |last2=Strickfaden |first2=William B. |last3=Eckles |first3=Jim |title=A New Look at Trinitite |journal=Nuclear Weapons Journal |year=2005 |pages=2–7 |issue=2 |url=https://www.lanl.gov/orgs/padwp/pdfs/11nwj2-05.pdf |access-date=September 15, 2020 |archive-date=October 19, 2020 |archive-url=https://web.archive.org/web/20201019161711/https://www.lanl.gov/science/weapons_journal/wj_pubs/11nwj2-05.pdf |url-status=live }}</ref> The 100-foot shot tower was completely vaporized. At the time of detonation, the surrounding mountains were illuminated "brighter than daytime" for one to two seconds, and the heat was reported as "being as hot as an oven" at the base camp. The observed colors of the illumination changed from purple to green and eventually to white. The roar of the shock wave took 40 seconds to reach the observers. It was felt over {{convert|100|mi}} away, and the [[mushroom cloud]] reached {{convert|7.5|mi}} in height.{{sfn|Smyth|1945|pp=247–254}}
Many observers recalled their amazement at the light from the explosion. Conant wrote, "The enormity of the light and its length quite stunned me". Lawrence, {{convert|27|mi}} away, wrote of being "enveloped with a warm brilliant yellow white light—from darkness to brilliant sunshine in an instant".{{r|wellerstein20150716}} Ralph Carlisle Smith, watching from Compania Hill, wrote:{{blockquote|I was staring straight ahead with my open left eye covered by a welder's glass and my right eye remaining open and uncovered. Suddenly, my right eye was blinded by a light which appeared instantaneously all about without any build up of intensity. My left eye could see the ball of fire start up like a tremendous bubble or nob-like mushroom. I dropped the glass from my left eye almost immediately and watched the light climb upward. The light intensity fell rapidly, hence did not blind my left eye but it was still amazingly bright. It turned yellow, then red, and then [[ionized air glow|beautiful purple]]. At first it had a translucent character, but shortly turned to a tinted or colored white smoke appearance. The ball of fire seemed to rise in something of toadstool effect. Later the column proceeded as a cylinder of white smoke; it seemed to move ponderously. A hole was punched through the clouds, but two fog rings appeared well above the white smoke column. There was a spontaneous cheer from the observers. Dr. von Neumann said, "that was at least 5,000 tons and probably a lot more."<ref>{{cite web |url=http://www.wsmr.army.mil/PAO/Trinity/Pages/RalphSmithseyewitnessaccountoftheTrinitytriptowatchblast.aspx |title=Ralph Smith's eyewitness account of the Trinity trip to watch blast |publisher=White Sands Missile Range, Public Affairs Office |access-date=August 24, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140904084107/http://www.wsmr.army.mil/PAO/Trinity/Pages/RalphSmithseyewitnessaccountoftheTrinitytriptowatchblast.aspx |archive-date=September 4, 2014 |df=mdy-all }}</ref>}}

Mary Argo was the only female staff member to be officially invited to watch the test. [[Joan Hinton]] snuck in to watch the test despite not being invited:<ref name=howesherzenberg2003>{{cite book | author=Ruth H. Howes | author-link=Ruth Howes|author2=Caroline L. Herzenberg
| author2-link=Caroline Herzenberg|publisher=Temple University Press | year = 2003| title=Their Day in the Sun: Women of the Manhattan Project | url=https://books.google.com/books?id=Ys0N4rFgt6UC&pg=PA51 | pages=51,56| isbn=9781592131921}}</ref> <blockquote>It was like being at the bottom of an ocean of light. We were bathed in it from all directions. The light withdrew into the bomb as if the bomb sucked it up. Then it turned purple and blue and went up and up and up. We were still talking in whispers when the cloud reached the level where it was struck by the rising sunlight so it cleared out the natural clouds. We saw a cloud that was dark and red at the bottom and daylight on the top. Then suddenly the sound reached us. It was very sharp and rumbled and all the mountains were rumbling with it. We suddenly started talking out loud and felt exposed to the whole world.</blockquote>

In his official report on the test, Thomas Farrell (who initially exclaimed, "The long-hairs have let it get away from them!"<ref>{{cite book |last1=Reed |first1=Bruce Cameron |title=The History and Science of the Manhattan Project |date=2019 |publisher=[[Springer Science]] |isbn=978-3-662-58174-2 |page=351 |url=https://books.google.com/books?id=YtaIDwAAQBAJ&q=%22The+long-hairs+have+let+it+get+away+from+them!%22&pg=PA351 |access-date=October 7, 2020 |archive-date=September 28, 2023 |archive-url=https://web.archive.org/web/20230928191000/https://books.google.com/books?id=YtaIDwAAQBAJ&q=%22The+long-hairs+have+let+it+get+away+from+them!%22&pg=PA351#v=snippet&q=%22The%20long-hairs%20have%20let%20it%20get%20away%20from%20them!%22&f=false |url-status=live }}</ref>) wrote: {{blockquote|The lighting effects beggared description. The whole country was lighted by a searing light with the intensity many times that of the midday sun. It was golden, purple, violet, gray, and blue. It lighted every peak, crevasse and ridge of the nearby mountain range with a clarity and beauty that cannot be described but must be seen to be imagined&nbsp;...<ref>{{cite web |url=http://www.nuclearfiles.org/menu/key-issues/nuclear-weapons/history/pre-cold-war/hiroshima-nagasaki/decision-drop-bomb-chronology.htm |title=Chronology on Decision to Bomb Hiroshima and Nagasaki |access-date=November 30, 2006 |archive-url=https://web.archive.org/web/20090827103545/http://www.nuclearfiles.org/menu/key-issues/nuclear-weapons/history/pre-cold-war/hiroshima-nagasaki/decision-drop-bomb-chronology.htm |archive-date=August 27, 2009 |url-status=dead |df=mdy-all }}</ref>}}

[[William L. Laurence]] of ''[[The New York Times]]'' had been transferred temporarily to the Manhattan Project at Groves's request in early 1945.{{sfn|Groves|1962|pp=325–326}} Groves had arranged for Laurence to view significant events, including Trinity and the atomic bombing of Japan. Laurence wrote press releases with the help of the Manhattan Project's public relations staff.{{sfn|Jones|1985|p=554}} He later recalled: {{blockquote|A loud cry filled the air. The little groups that hitherto had stood rooted to the earth like desert plants broke into dance, the rhythm of primitive man dancing at one of his fire festivals at the coming of Spring.{{sfn|Laurence|1946|p=14}}}}

After the initial euphoria of witnessing the explosion had passed, Bainbridge told Oppenheimer, "Now we are all sons of bitches."{{sfn|Bainbridge|1975|p=41}} Rabi noticed Oppenheimer's reaction: "I'll never forget his walk"; Rabi recalled, "I'll never forget the way he stepped out of the car&nbsp;... his walk was like ''[[High Noon]]''&nbsp;... this kind of strut. He had done it."{{sfn|Monk|2012|pp=456–457}}

Oppenheimer later recalled that, while witnessing the explosion, he thought of a verse from a [[Hindu]] holy book, the ''[[Bhagavad Gita]]'' (XI,12):
{{Verse translation|lang=sa|italicsoff=y|
दिवि सूर्यसहस्रस्य भवेद्युगपदुत्थिता।
यदि भाः सदृशी सा स्याद्भासस्तस्य महात्मनः।।
|If the radiance of a thousand suns were to burst at once into the sky,
that would be like the splendor of the mighty one.<ref>{{cite web |url=https://www.gitasupersite.iitk.ac.in/srimad?language=dv&field_chapter_value=11&field_nsutra_value=12&choose=1 |date=September 2, 2017 |title=Bhagavad Gita XI.12 |website=Gita Supersite by [[Indian Institute of Technology Kanpur]] |access-date=November 22, 2019 |archive-date=August 4, 2023 |archive-url=https://web.archive.org/web/20230804015213/https://www.gitasupersite.iitk.ac.in/srimad?language=dv&field_chapter_value=11&field_nsutra_value=12&choose=1 |url-status=live }}</ref>
}}

Years later he would explain that another verse had also entered his head at that time:
{{blockquote|We knew the world would not be the same. A few people laughed, a few people cried. Most people were silent. I remembered the line from the Hindu scripture, the ''Bhagavad Gita''; [[Vishnu]] is trying to persuade [[Arjuna|the Prince]] that he should do his duty and, to impress him, takes on [[Vishvarupa|his multi-armed form]] and says, 'Now I am become Death, the destroyer of worlds.' I suppose we all thought that, one way or another.<ref name="The Decision to Drop the Bomb"/>{{efn|1=Oppenheimer spoke these words in the television documentary ''[https://archive.org/details/90984-the-decision-to-drop-the-bomb-vwr The Decision to Drop the Bomb]'' (1965).<ref name="The Decision to Drop the Bomb">{{cite web |url=https://www.atomicarchive.com/media/videos/oppenheimer.html |title=J. Robert Oppenheimer on the Trinity test (1965) |access-date=26 April 2023 |publisher=Atomic Archive |archive-date=May 16, 2008 |archive-url=https://web.archive.org/web/20080516104658/http://www.atomicarchive.com/Movies/Movie8.shtml |url-status=live }}</ref> Oppenheimer read the original text in [[Sanskrit]], "{{IAST|kālo'smi lokakṣayakṛtpravṛddho lokānsamāhartumiha pravṛttaḥ}}" (XI,32),<ref>{{cite web |access-date=October 24, 2012 |url=https://www.asitis.com/11/32.html |title=Chapter 11. The Universal Form, text 32 |publisher=Bhagavad As It Is |archive-date=November 17, 2012 |archive-url=https://web.archive.org/web/20121117120052/http://www.asitis.com/11/32.html |url-status=live }}</ref> which he translated as "I am become Death, the destroyer of worlds". In the literature, the quote usually appears in the form ''shatterer'' of worlds, because this was the form in which it first appeared in print, in [[Time (magazine)|''Time'' magazine]] on November 8, 1948.<ref>{{cite news |newspaper=[[Time (magazine)|Time]] |date=November 8, 1948 |title=The Eternal Apprentice |url=http://content.time.com/time/magazine/article/0,9171,853367-8,00.html |access-date=March 6, 2011 |archive-date=December 16, 2013 |archive-url=https://web.archive.org/web/20131216042355/http://content.time.com/time/magazine/article/0,9171,853367-8,00.html |url-status=live }}</ref> It later appeared in Robert Jungk's ''Brighter than a Thousand Suns: A Personal History of the Atomic Scientists'' (1958),{{sfn|Jungk|1958|p=201}} which was based on an interview with Oppenheimer. See Hijiya, ''The Gita of Robert Oppenheimer''{{sfn|Hijiya|2000|pp=123–124}}}}}}

John R. Lugo was flying a U.S. Navy transport at {{convert|10000|ft|m}}, {{convert|30|mi|km}} east of [[Albuquerque]], en route to the west coast. "My first impression was, like, the sun was coming up in the south. What a ball of fire! It was so bright it lit up the cockpit of the plane." Lugo radioed Albuquerque. He got no explanation for the blast but was told, "Don't fly south."<ref>{{cite web |url=http://larrycalloway.com/historic.html?_recordnum=105 |archive-url=https://web.archive.org/web/20051018112209/http://larrycalloway.com/historic.html?_recordnum=105 |archive-date=October 18, 2005 |date=May 10, 2005 |title=The Trinity Test: Eyewitnesses |first=Larry |last=Calloway }}</ref>

<gallery mode="packed" heights="220">
File:Trinity-ground-zero-men-in-crater.jpg|Ground zero after the test
File:Trinity Test Fireball 25ms.jpg|The ''Trinity'' explosion, 25 ms after detonation. The viewed fireball hemisphere's highest point in this image is about {{convert|200|m}} high.
File:Trinity crater (annotated) 2.jpg|An aerial photograph of the Trinity crater shortly after the test.{{efn|1=The small crater in the southeast corner was from the earlier test explosion of {{convert|108|tonTNT}}.}}
</gallery>

===Instrumentation and measurements===
{{See also|Nuclear weapon yield#Calculating yields and controversy}}
[[File:Trinity Test - Lead lined Sherman tank.jpg|thumb|Lead-lined Sherman tank used in Trinity test]]

The T (Theoretical) Division at Los Alamos had predicted a yield of between {{convert|5|and|10|ktonTNT}}. Immediately after the blast, two lead-lined [[M4 Sherman]] tanks made their way to the crater. [[Nuclear weapon yield|Radiochemical analysis]] of soil samples that they collected indicated that the total yield (or energy release) had been around {{convert|18.6|ktonTNT}}.{{sfn|Widner|2009|pp=10–24}} This method turned out to be the most accurate means of determining the efficiency of a nuclear explosion and was used for many years after.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=376}}

The energy of the [[blast wave]] was measured by a large number of sensors using a variety of physical principles. The piezoelectric blast gauges were thrown off scale and no records were obtained. The excess-velocity blast-yield measurement (precise measurement of the velocity of sound at the site of the explosion and then comparing it with the velocity of the blast wave){{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=359}} provided among the most accurate measurements of the blast pressure. Another method was to use the aluminum diaphragm box gauges designed to record the peak pressure of the blast wave. These indicated a blast energy of {{convert|9.9|ktonTNT}} ± {{convert|1.0|ktonTNT}}. They were supplemented by a large number of other types of mechanical pressure gauges. And only one of them gave a reasonable result of about {{convert|10|ktonTNT}}.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|pp=375-376}}

Fermi prepared his own experiment to measure the energy that was released as blast. He later recalled:{{blockquote|About 40 seconds after the explosion the air blast reached me. I tried to estimate its strength by dropping from about six feet small pieces of paper before, during, and after the passage of the blast wave. Since, at the time, there was no wind I could observe very distinctly and actually measure the displacement of the pieces of paper that were in the process of falling while the blast was passing. The shift was about 2 1/2 meters, which, at the time, I estimated to correspond to the blast that would be produced by ten thousand tons of T.N.T.<ref>{{cite web |url=http://www.dannen.com/decision/fermi.html |title=Trinity Test, July 16, 1945, Eyewitness Accounts – Enrico Fermi |publisher=Gene Dannen |access-date=November 4, 2014 |archive-date=November 4, 2014 |archive-url=https://web.archive.org/web/20141104122441/http://www.dannen.com/decision/fermi.html |url-status=live }}</ref>}}

{| class="wikitable floatright" width="250px"
|+Fission bomb's energy distribution in the "moderate" kiloton range near sea level
| colspan=2 |Contemporary fundamental physics, data from the Trinity test, and others, resulted in the following total blast and thermal energy fractionation being observed for fission detonations near sea level<ref name="fas.org">{{cite web |url=https://fas.org/nuke/guide/usa/doctrine/dod/fm8-9/1ch3.htm |title=Chapter 3 Effects of Nuclear Explosions Section I – General |access-date=October 29, 2015 |archive-date=January 11, 2016 |archive-url=https://web.archive.org/web/20160111173824/http://fas.org/nuke/guide/usa/doctrine/dod/fm8-9/1ch3.htm |url-status=live }}</ref><ref>[https://web.archive.org/web/20170125171152/https://ke.army.mil/bordeninstitute/published_volumes/nuclearwarfare/chapter1/chapter1.pdf "Nuclear Events and Their Consequences"]. Borden Institute. "...&nbsp;approximately 82% of the fission energy is released as kinetic energy of the two large fission fragments. These fragments, being massive and highly charged particles, interact readily with matter. They transfer their energy quickly to the surrounding weapon materials, which rapidly become heated"</ref><ref>{{cite web |url=http://www.oektg.at/wp-content/uploads/02-Nuclear-Engineering-Overview1.pdf |archive-url=https://web.archive.org/web/20180515201022/http://www.oektg.at/wp-content/uploads/02-Nuclear-Engineering-Overview1.pdf |title=Nuclear Engineering Overview |archive-date=May 15, 2018 |publisher=Technical University Vienna}} The various energies emitted per fission event p. 4. 167 MeV is emitted by means of the repulsive electrostatic energy between the two daughter nuclei, which takes the form of the kinetic energy of the fission fragments, this kinetic energy results in both later blast and thermal effects. 5 MeV is released in prompt or initial gamma radiation, 5 MeV in prompt neutron radiation (99.36% of total), 7 MeV in delayed neutron energy (0.64%) and 13 MeV in beta decay and gamma decay (residual radiation).</ref>
|-
|Blast||50%
|-
|Thermal energy||35%
|-
|Initial [[ionizing radiation]]||5%
|-
|Residual [[fallout]] radiation||10%
|}

There were also several gamma ray and [[neutron detector]]s; few survived the blast, with all the gauges within {{convert|200|ft}} of ground zero being destroyed,{{sfn|Widner|2009|pp=10–25}} but sufficient data were recovered to measure the gamma ray component of the ionizing radiation released.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=375}}

Some fifty different cameras had been set up, taking motion and still photographs. Special [[Fastax]] cameras taking 10,000 frames per second would record the minute details of the explosion. [[Spectrograph]] cameras would record the wavelengths of light emitted by the explosion, and [[pinhole camera]]s would record gamma rays. A rotating drum spectrograph at the {{convert|10000|yd|adj=on}} station would obtain the spectrum over the first hundredth of a second. Another, slow recording one would track the fireball. Cameras were placed in bunkers only {{convert|800|yd}} from the tower, protected by steel and lead glass, and mounted on sleds so they could be towed out by the lead-lined tank.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|pp=354–355}} Some observers brought their own cameras despite the security. Segrè brought in [[Jack Aeby]] with his 35&nbsp;mm Perfex 44. He took the only known well-exposed color photograph of the detonation explosion.<ref name="ABQ">{{cite news |url=https://www.abqjournal.com/trinity/trinity1.htm |newspaper=[[Albuquerque Journal]] |date=July 1995 |title=The Nuclear Age's Blinding Dawn |first=Larry |last=Calloway |access-date=February 1, 2019 |archive-date=October 7, 2018 |archive-url=https://web.archive.org/web/20181007173637/https://www.abqjournal.com/trinity/trinity1.htm |url-status=live }}</ref>

The official estimate for the total yield of the Trinity bomb, which includes the energy of the blast component together with the contributions from the [[bhangmeter|explosion's light output]] and both forms of [[ionizing radiation]], is {{convert|21|ktonTNT}},<ref>{{cite web |url=http://www.dtra.mil/docs/documents-ntpr-factsheets/trinity---2014.pdf?sfvrsn=0 |archive-url=https://web.archive.org/web/20141125082310/http://www.dtra.mil/docs/documents-ntpr-factsheets/trinity---2014.pdf?sfvrsn=0 |archive-date=November 25, 2014 |publisher=[[Defense Threat Reduction Agency]] |title=Fact Sheet – Operation Trinity |access-date=November 15, 2014 |url-status=dead }}</ref> of which about {{convert|15|ktonTNT}} was contributed by fission of the plutonium core, and about {{convert|6|ktonTNT}} was from fission of the natural uranium tamper.<ref>{{cite web |url=http://blog.nuclearsecrecy.com/2014/11/10/fat-mans-uranium/ |title=The Fat Man's uranium |first=Alex |last=Wellerstein |date=November 10, 2014 |publisher=Restricted Data: The Nuclear Secrecy Blog |access-date=November 15, 2014 |archive-date=November 13, 2014 |archive-url=https://web.archive.org/web/20141113044340/http://blog.nuclearsecrecy.com/2014/11/10/fat-mans-uranium/ |url-status=live }}</ref> A re-analysis of data published in 2021 put the yield at {{convert|24.8|+/-|2|ktonTNT}}.<ref name="Trinity_yield" />

As a result of the data gathered on the size of the blast, the detonation height for the bombing of Hiroshima was set at {{convert|1885|ft}} to take advantage of the [[Mach stem]] blast reinforcing effect.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=374}} The final Nagasaki burst height was {{convert|1650|ft}} so the Mach stem started sooner.<ref>{{citation |url=http://www.rerf.jp/shared/ds02/index.html |title=Reassessment of the Atomic Bomb Radiation Dosimetry for Hiroshima and Nagasaki |publisher=Radiation Effects Research Foundation |access-date=August 25, 2015 |page=47 |archive-date=September 24, 2015 |archive-url=https://web.archive.org/web/20150924090132/http://www.rerf.jp/shared/ds02/index.html |url-status=live }}</ref> The knowledge that implosion worked led Oppenheimer to recommend to Groves that the uranium-235 used in a [[Little Boy]] gun-type weapon could be used more economically in a [[Fat Man]] implosion-type weapon containing a [[pit (nuclear weapon)|composite core]] with plutonium and enriched uranium. It was too late to do this with the first Little Boy, but the composite cores would soon enter production.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=377}}

===Civilian detection===
The light from the test was visible as far as [[Amarillo, Texas]], {{convert|280|mi}} and a mountain range away from Trinity.{{r|wellerstein20150716}} The Second Air Force issued a press release with a cover story that Groves had prepared weeks before, which described the explosion as the accidental destruction of a [[Magazine (artillery)|magazine]] on the base. The press release, written by Laurence, stated: {{blockquote|Alamogordo, N.M., July 16
The commanding officer of the Alamogordo Army Air Base made the following statement today: "Several inquiries have been received concerning a heavy explosion which occurred on the Alamogordo Air base reservation this morning. A remotely located ammunition magazine containing a considerable amount of high explosives and pyrotechnics exploded. There was no loss of life or injury to anyone, and the property damage outside of the explosives magazine was negligible. Weather conditions affecting the content of gas shells exploded by the blast may make it desirable for the Army to evacuate temporarily a few civilians from their homes."<ref>{{cite news |title=Blast Occurs At Alamogordo Air Base |newspaper=Clovis News-Journal |date=July 16, 1945 |page=6 |url=https://www.newspapers.com/clip/3985915// |access-date=January 7, 2016 |archive-date=September 28, 2023 |archive-url=https://web.archive.org/web/20230928190924/https://www.newspapers.com/article/3985915/ |url-status=live }}</ref>{{sfn|Norris|2002|p=407}}}}

Laurence had prepared four releases, covering outcomes ranging from a cover story for a successful test (the one which was used) to catastrophic scenarios involving serious damage to surrounding communities, evacuation of nearby residents, and a placeholder for the names of those killed.{{sfn|Sweeney|2001|pp=205–206}}{{sfn|Laurence|1970|pp=39–41}}<ref>{{cite web |title=Weekly Document #1: Trinity test press releases (May 1945) |url=http://blog.nuclearsecrecy.com/2011/11/10/weekly-document-01/ |publisher=Restricted Data: The Nuclear Secrecy Blog |last=Wellerstein |first=Alex |access-date=June 12, 2021 |archive-date=May 16, 2021 |archive-url=https://web.archive.org/web/20210516054809/http://blog.nuclearsecrecy.com/2011/11/10/weekly-document-01/ |url-status=live }}</ref> As Laurence was a witness to the test, he knew that the last release, if used, might be his own obituary.{{sfn|Sweeney|2001|pp=205–206}} A newspaper article published the same day stated that "the blast was seen and felt throughout an area extending from [[El Paso, Texas|El Paso]] to [[Silver City, New Mexico|Silver City]], [[Gallup, New Mexico|Gallup]], Socorro, and [[Albuquerque, New Mexico|Albuquerque]]."<ref>{{cite news |title=Army Ammunition Explosion Rocks Southwest Area |newspaper=[[El Paso Herald-Post]] |date=July 16, 1945 |page=1 |url=https://www.newspapers.com/clip/3985966// |access-date=January 7, 2016 |archive-date=September 28, 2023 |archive-url=https://web.archive.org/web/20230928190926/https://www.newspapers.com/article/3985966/ |url-status=live }}</ref> The articles appeared in New Mexico, but East Coast newspapers ignored them,{{sfn|Sweeney|2001|pp=205–206}} and local residents who saw the light accepted the cover story.{{r|wellerstein20150716}}

Information about the Trinity test was made public shortly after the bombing of Hiroshima. The [[Smyth Report]], released on August 12, 1945, gave some information on the blast, and the edition released by [[Princeton University Press]] a few weeks later incorporated the War Department's press release on the test as Appendix 6, and contained the famous pictures of a "bulbous" Trinity fireball.{{sfn|Smyth|1945|pp=vii–viii, 138–139, 247–254}}

===Official notifications===
The results of the test were conveyed to [[Secretary of War]] [[Henry L. Stimson]] at the Potsdam Conference in Germany in a coded message from his assistant [[George L. Harrison]]:

{{blockquote|Operated on this morning. Diagnosis not yet complete but results seem satisfactory and already exceed expectations. Local press release necessary as interest extends great distance. Dr. Groves pleased. He returns tomorrow. I will keep you posted.{{sfn|Jones|1985|p=517}}}}

The message arrived at the "Little White House" in the Potsdam suburb of [[Babelsberg]] and was at once taken to Truman and Secretary of State [[James F. Byrnes]].{{sfn|Alperovitz|1996|p=240}} Harrison sent a follow-up message which arrived on the morning of July 18:{{sfn|Alperovitz|1996|p=240}}

{{blockquote|Doctor has just returned most enthusiastic and confident that the little boy is as husky as his big brother. The light in his eyes discernible from here to Highhold and I could have heard his screams from here to my farm.{{sfn|Jones|1985|p=517}}}}

Because Stimson's summer home at Highhold was on [[Long Island]] and Harrison's farm near [[Upperville, Virginia]], this indicated that the explosion could be seen {{convert|250|mi}} away and heard {{convert|50|mi}} away.{{sfn|Jones|1985|p=518}}

Three days later, on July 21, a 13-page report written by Groves arrived at Potsdam via a courier. It stated:

{{blockquote|At 0530, 16 July 1945, in a remote section of the Alamogordo Air Base, New Mexico, the first full scale test was made of the implosion type atomic fission bomb. For the first time in history there was a nuclear explosion. And what an explosion! ... The test was successful beyond the most optimistic expectations of anyone.{{sfn|Sherwin|1987|p=308}}}}

It continued on to estimate the yield of the test (15-20 kilotons) and describe the effects vividly. Stimson took the report to Truman, who was "tremendously pepped up by it." [[Winston Churchill]], who observed Truman's newly confident approach with the Soviets the same day, concluded that he had become "a changed man" as a result of the news.

===Fallout===
[[Film badge]]s used to measure exposure to radioactivity indicated that no observers at N-10,000 had been exposed to more than 0.1 [[roentgen (unit)|roentgens]] (half of the [[National Council on Radiation Protection and Measurements]] recommended daily radiation exposure limit),<ref>{{cite journal |last1=Clarke |first1=R. H. |first2=J. |last2=Valentin |s2cid=71278114 |title=The History of ICRP and the Evolution of its Policies |journal=Annals of the ICRP |year=2009 |volume=39 |series=ICRP Publication 109 |issue=1 |pages=75–110 |doi=10.1016/j.icrp.2009.07.009 |url=http://www.icrp.org/docs/The%20History%20of%20ICRP%20and%20the%20Evolution%20of%20its%20Policies.pdf |access-date=May 12, 2012 |archive-date=May 8, 2012 |archive-url=https://web.archive.org/web/20120508205030/http://www.icrp.org/docs/The%20History%20of%20ICRP%20and%20the%20Evolution%20of%20its%20Policies.pdf |url-status=live }}</ref> but the shelter was evacuated before the radioactive cloud could reach it. The explosion was more efficient than expected, and the thermal updraft drew most of the cloud high enough that little fallout fell on the test site. Nevertheless, the fission consumed only {{convert|3|lb|disp=flip}} out of the {{convert|13|lb|disp=flip}} of plutonium,<ref>{{cite web |url=https://www.nps.gov/articles/000/trinity-test-downwinders.htm |title=Trinity Test Downwinders |author=<!--Not stated--> |publisher=[[National Park Service]] |access-date=August 9, 2023 |archive-date=August 7, 2023 |archive-url=https://web.archive.org/web/20230807223723/https://www.nps.gov/articles/000/trinity-test-downwinders.htm |url-status=live }}</ref> leaving {{convert|10|lb|disp=flip}} to be spread through the atmosphere and as fallout. The crater was far more radioactive than expected due to the formation of [[trinitite]], and the crews of the two lead-lined Sherman tanks were subjected to considerable exposure. Anderson's dosimeter and film badge recorded 7 to 10 roentgens, and one of the tank drivers, who made three trips, recorded 13 to 15 roentgens.{{sfn|Hacker|1987|pp=99–101}}

[[File:Trinity Ground Zero.jpg|thumb|left|Groves and Oppenheimer at the remains of one leg of the test tower. Canvas overshoes kept [[trinitite]] off shoes.<ref>{{cite magazine |magazine=[[Time (magazine)|Time]] |date=September 17, 1945 |url=http://content.time.com/time/magazine/article/0,9171,854500-2,00.html |title=Science: Atomic Footprint |access-date=March 16, 2011 |archive-date=February 1, 2014 |archive-url=https://web.archive.org/web/20140201222410/http://content.time.com/time/magazine/article/0,9171,854500-2,00.html |url-status=live }}</ref>]]

The heaviest fallout contamination outside the restricted test area was {{convert|30|mi}} from the detonation point, on Chupadera Mesa. The fallout there was reported to have settled in a white mist onto some of the livestock in the area, resulting in local [[beta burns]] and a temporary loss of [[dorsum (anatomy)|dorsal]] or back hair. Patches of hair grew back discolored white. The Army bought 88 cattle in all from [[rancher]]s; the 17 most significantly marked were kept at Los Alamos, while the rest were shipped to [[Clinton Engineer Works|Oak Ridge]] for long-term observation.<ref>{{cite web |url=http://www.lahdra.org/reports/LAHDRA%20Report%20v5%202007_App%20N_Trinity%20Test.pdf |title=Interim Report of CDC'S LAHDRA Project– Appendix N. pp. 17, 23, 37 |url-status=dead |archive-url=https://web.archive.org/web/20140317164653/http://www.lahdra.org/reports/LAHDRA%20Report%20v5%202007_App%20N_Trinity%20Test.pdf |archive-date=March 17, 2014 }}</ref><ref name="massburns">{{cite book |url=https://books.google.com/books?id=sDQrAAAAYAAJ&q=%22beta+burns%22&pg=PA248 |page=248 |title=Mass burns: proceedings of a workshop, 13–14 March 1968 |author=National Research Council (U.S.). Committee on Fire Research, United States. Office of Civil Defense |publisher=National Academies |year=1969 |access-date=October 7, 2020 |archive-date=January 26, 2021 |archive-url=https://web.archive.org/web/20210126135602/https://books.google.com/books?id=sDQrAAAAYAAJ&q=%22beta+burns%22&pg=PA248 |url-status=live }}</ref>{{sfn|Hacker|1987|p=105}}{{sfn|Szasz|1984|p=134}}

Dose reconstruction published in 2020 under the auspices of the [[National Cancer Institute]]<ref>{{cite web |url=https://dceg.cancer.gov/research/how-we-study/exposure-assessment/trinity |title=Study to Estimate Radiation Doses and Cancer Risks Resulting from Exposure to Radioactive Fallout from the Trinity Nuclear Test |date=March 28, 2014 |publisher=[[National Cancer Institute]] |access-date=September 17, 2021 |archive-date=February 19, 2015 |archive-url=https://web.archive.org/web/20150219220622/http://dceg.cancer.gov/research/how-we-study/exposure-assessment/trinity |url-status=live }}</ref> documented that five counties in New Mexico experienced the greatest radioactive contamination: [[Guadalupe County, New Mexico|Guadalupe]], [[Lincoln County, New Mexico|Lincoln]], [[San Miguel County, New Mexico|San Miguel]], [[Socorro County, New Mexico|Socorro]], and [[Torrance County, New Mexico|Torrance]].{{sfn|Bouville|Beck|Thiessen|Hoffman|2020|p=405}} People living in the surrounding area near the site were unaware of the project and later not included in the 1990 [[Radiation Exposure Compensation Act]] support for affected "downwinders" which addressed serious community health problems resulting from similar tests conducted at the [[Nevada Test Site]].<ref name="NG" /> Efforts in Congress to add the New Mexico residents to the population covered by the bill continued in 2024.<ref>{{Cite web |last=Prokop |first=Danielle |date=March 8, 2024 |title=RECA expansion passes U.S. Senate • Colorado Newsline |url=https://coloradonewsline.com/2024/03/07/reca-expansion-passes-u-s-senate/ |access-date=March 8, 2024 |website=Colorado Newsline |language=en-US |archive-date=March 8, 2024 |archive-url=https://web.archive.org/web/20240308013634/https://coloradonewsline.com/2024/03/07/reca-expansion-passes-u-s-senate/ |url-status=live }}</ref>

In August 1945, shortly after the bombing of Hiroshima, the [[Kodak]] Company observed [[autoradiograph|spotting]] and [[fogging (photography)|fogging]] on its film, which was at that time usually packaged in cardboard containers.{{r|wellerstein20150716}} J. H. Webb, an employee of the Kodak Company, studied the matter and concluded that the contamination must have come from a nuclear explosion somewhere in the United States. He discounted the possibility that the Hiroshima bomb was responsible because of the timing of the events. A hot spot of fallout contaminated the river water that a [[paper mill]] in [[Indiana]] used to manufacture the [[paper pulp|cardboard pulp]] from [[corn husks]].<ref name="Ortmeyer">{{cite journal |url=https://www.ieer.org/latest/iodnart.html |title=Let Them Drink Milk |first1=Pat |last1=Ortmeyer |first2=Arjun |last2=Makhijani |date=November–December 1997 |journal=[[Bulletin of the Atomic Scientists]] |access-date=September 22, 2014 |archive-date=August 20, 2014 |archive-url=https://web.archive.org/web/20140820105629/http://www.ieer.org/latest/iodnart.html |url-status=live}} Originally published under the title "Worse Than We Knew".</ref> Aware of the gravity of his discovery, Webb kept this secret until 1949.<ref>{{cite web |url=https://www.orau.org/ptp/collection/hiroshimatrinity/kodakfilm.htm |title=Oak Ridge's Merril Eisenbud – Hiroshima, the Trinity Test, Nuclear Weapons. |access-date=February 1, 2019 |archive-date=March 5, 2019 |archive-url=https://web.archive.org/web/20190305144533/https://www.orau.org/ptp/collection/hiroshimatrinity/kodakfilm.htm |url-status=live}}, discussing {{cite journal |first1=J. H. |last1=Webb |title=The Fogging of Photographic Film by Radioactive Contaminants in Cardboard Packaging Materials |journal=[[Physical Review]] |volume=76 |issue=3 |pages=375–380 |year=1949 |bibcode=1949PhRv...76..375W |doi=10.1103/PhysRev.76.375 }}</ref>

This incident, along with the next continental US tests in 1951, set a precedent. In subsequent atmospheric nuclear tests at the Nevada Test Site, [[United States Atomic Energy Commission]] officials gave the photographic industry maps and forecasts of potential contamination, as well as expected fallout distributions, which enabled them to purchase uncontaminated materials and take other protective measures.<ref name="Ortmeyer" />

{{Wide image|Trinity-Gadget BDA.jpg|700px|Post-Trinity detonation [[bomb damage assessment]] and effects evaluation.}}