International Space Station programme

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/International_Space_Station_programme 

 

International Space Station programme

Program overview
Organisation	CSA ESA JAXA NASA Roscosmos
Manager	CSA: Pierre Jean ESA: Bernardo Patti JAXA: Yoshiyuki Hasegawa NASA: Joel Montalbano (2020–present) Roscosmos: Alexey Krasnov
Status	Active
Programme history
Cost	$150 billion (2010)
Duration	1983–present
First flight	Zarya November 20, 1998
First crewed flight	STS-88 December 4, 1998
Launch site(s)	Baikonur (1998–present) Kennedy (1998–present) Cape Canaveral (2010–present) Wallops (2013–present)
Vehicle information
Uncrewed vehicle(s)	Progress (2000–present) ATV (2008–2015) HTV (2009–2020) Dragon (2010–2020) Cygnus (2013–present) Cargo Dragon (2020-present)
Crewed vehicle(s)	ISS (1998–present) Space Shuttle (1998–2011) Soyuz (2000–present) Crew Dragon (2020–present)
Crew capacity	ISS: 7 Soyuz: 3 Crew Dragon: 4
Launch vehicle(s)	Proton (1998–present) Space Shuttle (1998–2011) Soyuz (2000–present) Falcon 9 (2010–present) Antares (2013–present) Atlas V (2015–2017)

The International Space Station programme is tied together by a complex set of legal, political and financial agreements between the fifteen nations involved in the project, governing ownership of the various components, rights to crewing and utilisation, and responsibilities for crew rotation and resupply of the International Space Station. It was conceived in September 1993 by the United States and Russia after 1980s plans for separate American (Freedom) and Soviet (Mir-2) space stations failed due to budgetary reasons. These agreements tie together the five space agencies and their respective International Space Station programmes and govern how they interact with each other on a daily basis to maintain station operations, from traffic control of spacecraft to and from the station, to utilisation of space and crew time. In March 2010, the International Space Station Program Managers from each of the five partner agencies were presented with Aviation Week's Laureate Award in the Space category, and the ISS programme was awarded the 2009 Collier Trophy.

History and conception

In the early 1980s, NASA planned to launch a modular space station called Freedom as a counterpart to the Soviet Salyut and Mir space stations. In 1984 the ESA was invited to participate in Space Station Freedom, and the ESA approved the Columbus laboratory by 1987. The Japanese Experiment Module (JEM), or Kibō, was announced in 1985, as part of the Freedom space station in response to a NASA request in 1982.

In early 1985, science ministers from the European Space Agency (ESA) countries approved the Columbus programme, the most ambitious effort in space undertaken by that organisation at the time. The plan spearheaded by Germany and Italy included a module which would be attached to Freedom, and with the capability to evolve into a full-fledged European orbital outpost before the end of the century. The space station was also going to tie the emerging European and Japanese national space programmes closer to the US-led project, thereby preventing those nations from becoming major, independent competitors too.

In September 1993, American Vice-President Al Gore and Russian Prime Minister Viktor Chernomyrdin announced plans for a new space station, which eventually became the International Space Station. They also agreed, in preparation for this new project, that the United States would be involved in the Mir programme, including American Shuttles docking, in the Shuttle–Mir programme.

On 12 April 2021, at a meeting with Russian President Vladimir Putin, then-Deputy Prime Minister Yury Borisov announced he had decided that Russia might withdraw from the ISS programme in 2025. According to Russian authorities, the timeframe of the station’s operations has expired and its condition leaves much to be desired. On 26 July 2022, Borisov, who had become head of Roscosmos, submitted to Putin his plans for withdrawal from the programme after 2024. However, Robyn Gatens, the NASA official in charge of space station operations, responded that NASA had not received any formal notices from Roscosmos concerning withdrawal plans.

1998 agreement

A commemorative plaque honouring Space Station Intergovernmental Agreement signed on January 29, 1998

The legal structure that regulates the station is multi-layered. The primary layer establishing obligations and rights between the ISS partners is the Space Station Intergovernmental Agreement (IGA), an international treaty signed on January 28, 1998 by fifteen governments involved in the space station project. The ISS consists of Canada, Japan, the Russian Federation, the United States, and eleven Member States of the European Space Agency (Belgium, Denmark, France, Germany, Italy, The Netherlands, Norway, Spain, Sweden, Switzerland and the United Kingdom). Article 1 outlines its purpose:

This Agreement is a long term international co-operative framework on the basis of genuine partnership, for the detailed design, development, operation, and utilization of a permanently inhabited civil Space Station for peaceful purposes, in accordance with international law.

The IGA sets the stage for a second layer of agreements between the partners referred to as 'Memoranda of Understanding' (MOUs), of which four exist between NASA and each of the four other partners. There are no MOUs between ESA, Roskosmos, CSA and JAXA because NASA is the designated manager of the ISS. The MOUs are used to describe the roles and responsibilities of the partners in more detail.

A third layer consists of bartered contractual agreements or the trading of the partners' rights and duties, including the 2005 commercial framework agreement between NASA and Roscosmos that sets forth the terms and conditions under which NASA purchases seats on Soyuz crew transporters and cargo capacity on uncrewed Progress transporters.

A fourth legal layer of agreements implements and supplements the four MOUs further. Notably among them is the ISS code of conduct made in 2000, setting out criminal jurisdiction, anti-harassment and certain other behavior rules for ISS crewmembers.

Programme operations

Expeditions

Zarya and Unity were entered for the first time on 10 December 1998.

 

Soyuz TM-31 being prepared to bring the first resident crew to the station in October 2000

 

Each permanent crew is given an expedition number. Expeditions run up to six months, from launch until undocking, an 'increment' covers the same time period, but includes cargo spacecraft and all activities. Expeditions 1 to 6 consisted of three-person crews. Expeditions 7 to 12 were reduced to the safe minimum of two following the destruction of the NASA Shuttle Columbia. From Expedition 13 the crew gradually increased to six around 2010. With the arrival of crew on US commercial vehicles beginning in 2020, NASA has indicated that expedition size may be increased to seven crew members, the number ISS was originally designed for.

Private flights

Travellers who pay for their own passage into space are termed spaceflight participants by Roscosmos and NASA, and are sometimes referred to as "space tourists", a term they generally dislike. As of 2021, seven space tourists have visited the ISS; all seven were transported to the ISS on Russian Soyuz spacecraft. When professional crews change over in numbers not divisible by the three seats in a Soyuz, and a short-stay crewmember is not sent, the spare seat is sold by MirCorp through Space Adventures. Space tourism was halted in 2011 when the Space Shuttle was retired and the station's crew size was reduced to six, as the partners relied on Russian transport seats for access to the station. Soyuz flight schedules increased after 2013, allowing five Soyuz flights (15 seats) with only two expeditions (12 seats) required. The remaining seats were to be sold for around US$40 million to members of the public who could pass a medical exam. ESA and NASA criticised private spaceflight at the beginning of the ISS, and NASA initially resisted training Dennis Tito, the first person to pay for his own passage to the ISS.

Anousheh Ansari became the first self-funded woman to fly to the ISS as well as the first Iranian in space. Officials reported that her education and experience made her much more than a tourist, and her performance in training had been "excellent." She did Russian and European studies involving medicine and microbiology during her 10-day stay. The 2009 documentary Space Tourists follows her journey to the station, where she fulfilled "an age-old dream of man: to leave our planet as a 'normal person' and travel into outer space."

In 2008, spaceflight participant Richard Garriott placed a geocache aboard the ISS during his flight. This is currently the only non-terrestrial geocache in existence. At the same time, the Immortality Drive, an electronic record of eight digitised human DNA sequences, was placed aboard the ISS.

Fleet operations

Dragon and Cygnus cargo vessels were docked at the ISS together for the first time in April 2016.

 

Japan's Kounotori 4 berthing

 

Commercial Crew Program vehicles Starliner and Dragon

A wide variety of crewed and uncrewed spacecraft have supported the station's activities. Flights to the ISS include 37 Space Shuttle missions, 83 Progress resupply spacecraft (including the modified M-MIM2, M-SO1 and M-UM module transports), 63 crewed Soyuz spacecraft, 5 European ATVs, 9 Japanese HTVs, 1 Boeing Starliner, 30 SpaceX Dragon ( both crewed and uncrewed) and 18 Cygnus missions.

There are currently twelve available docking ports for visiting spacecraft:

1. Harmony forward (with IDA 2)
2. Harmony zenith (with IDA 3)
3. Harmony nadir
4. Unity nadir
5. Prichal nadir
6. Prichal aft
7. Prichal forward
8. Prichal starboard
9. Prichal port
10. Nauka forward
11. Poisk zenith
12. Rassvet nadir
13. Zvezda aft

Crewed

As of 24 April 2021, 244 people from 19 countries had visited the space station, many of them multiple times. The United States sent 153 people, Russia sent 50, nine were Japanese, eight were Canadian, five were Italian, four were French, three were German, and there were one each from Belgium, Brazil, Denmark, Great Britain, Kazakhstan, Malaysia, the Netherlands, South Africa, South Korea, Spain, Sweden and the United Arab Emirates.

Uncrewed

Uncrewed spaceflights to the International Space Station (ISS) are made primarily to deliver cargo, however several Russian modules have also docked to the outpost following uncrewed launches. Resupply missions typically use the Russian Progress spacecraft, European Automated Transfer Vehicles, Japanese Kounotori vehicles, and the American Dragon and Cygnus spacecraft. The primary docking system for Progress spacecraft is the automated Kurs system, with the manual TORU system as a backup. ATVs also use Kurs, however they are not equipped with TORU. Progress and ATV can remain docked for up to six months. The other spacecraft — the Japanese HTV, the SpaceX Dragon (under CRS phase 1) and the Northrop Grumman Cygnus — rendezvous with the station before being grappled using Canadarm2 and berthed at the nadir port of the Harmony or Unity module for one to two months. Under CRS phase 2, Cargo Dragon will dock autonomously at IDA-2 or 3 as the case may be. As of May 2022, Progress spacecraft have flown most of the uncrewed missions to the ISS.

Repairs

Astronaut Scott Parazynski of STS-120 conducted a 7-hour, 19-minute spacewalk to repair (essentially sew) a damaged solar panel which helps supply power to the International Space Station. NASA considered the spacewalk dangerous with potential risk of electrical shock.

 

Since construction started, the International Space Station programme has had to deal with several maintenance issues, unexpected problems and failures. These incidents have affected the assembly timeline, led to periods of reduced capabilities of the station and in some cases could have forced the crew to abandon the space station for safety reasons, had these problems not been resolved.

Mission control centres

The components of the ISS are operated and monitored by their respective space agencies at mission control centres across the globe, including:

• Roscosmos' RKA Mission Control Center at Korolyov, Russia — manages the maintaining of the station, controls launches of the crewed missions, guides launches from Baikonur Cosmodrome
• ESA's ATV Control Centre, at the Toulouse Space Centre (CST) in Toulouse, France – controlled flights of the uncrewed European Automated Transfer Vehicle
• JAXA's JEM Control Center and HTV Control Center at Tsukuba Space Center (TKSC) in Ibaraki, Japan – responsible for operating the Kibō complex and all flights of the White Stork HTV Cargo spacecraft, respectively
• NASA's Christopher C. Kraft Jr. Mission Control Center at Lyndon B. Johnson Space Center in Houston, Texas – serves as the primary control facility for the United States segment of the ISS
• NASA's Payload Operations and Integration Center at Marshall Space Flight Center in Huntsville, Alabama – coordinates payload operations in the USOS
• ESA's Columbus Control Center at the German Aerospace Center in Oberpfaffenhofen, Germany – manages the European Columbus research laboratory
• CSA's MSS Control at Saint-Hubert, Quebec, Canada – controls and monitors the Mobile Servicing System

Space centres involved with the ISS programme

Politics

  Primary contributing nations

  Formerly contracted nations

 

Politics of the International Space Station have been affected by superpower rivalries, international treaties and funding arrangements. The Cold War was an early factor, overtaken in recent years by the United States' distrust of China. The station has an international crew, with the use of their time, and that of equipment on the station, being governed by treaties between participant nations.

Usage of crew and hardware

Allocation of US Orbital Segment hardware usage between nations.

There is no fixed percentage of ownership for the whole space station. Rather, Article 5 of the IGA sets forth that each partner shall retain jurisdiction and control over the elements it registers and over personnel in or on the Space Station who are its nationals. Therefore, for each ISS module only one partner retains sole ownership. Still, the agreements to use the space station facilities are more complex.

The station is composed of two sides: the Russian Orbital Segment (ROS) and U.S. Orbital Segment (USOS).

• Russian Orbital Segment (mostly Russian ownership, except the Zarya module)
  • Zarya: first component of the Space Station, storage, USSR/Russia-built, U.S.-funded (hence U.S.-owned)
  • Zvezda: the functional centre of the Russian portion, living quarters, Russia-owned
  • Pirs: airlock, docking, Russia-owned (Decommissioned)
  • Poisk: redundancy for Pirs, Russia-owned
  • Rassvet: storage, docking, Russia-owned
  • Nauka: Russian multipurpose laboratory module
• U.S. Orbital Segment (mixed U.S. and international ownership)
  • Columbus laboratory: 51% for ESA, 46.7% for NASA and 2.3% for CSA.
  • Kibō laboratory: Japanese module, 51% for JAXA, 46.7% for NASA and 2.3% for CSA.
  • Destiny laboratory: 97.7% for NASA and 2.3% for CSA.
  • Crew time, electrical power and rights to purchase supporting services (such as data upload & download and communications) are divided 76.6% for NASA, 12.8% for JAXA, 8.3% for ESA, and 2.3% for CSA.

Future of the ISS

The heads of the ISS agencies from Canada, Europe, Japan, Russia and the United States meet in Tokyo to review ISS cooperation.

Former NASA Administrator Michael D. Griffin says the International Space Station has a role to play as NASA moves forward with a new focus for the crewed space programme, which is to go out beyond Earth orbit for purposes of human exploration and scientific discovery. "The International Space Station is now a stepping stone on the way, rather than being the end of the line," Griffin said. Griffin has said that station crews will not only continue to learn how to live and work in space, but also will learn how to build hardware that can survive and function for the years required to make the round-trip voyage from Earth to Mars.

Despite this view, however, in an internal e-mail leaked to the press on August 18, 2008 from Griffin to NASA managers, Griffin apparently communicated his belief that the current US administration had made no viable plan for US crews to participate in the ISS beyond 2011, and that the Office of Management and Budget (OMB) and Office of Science and Technology Policy (OSTP) were actually seeking its demise. The e-mail appeared to suggest that Griffin believed the only reasonable solution was to extend the operation of the Space Shuttle beyond 2010, but noted that Executive Policy (i.e. the White House) was firm that there would be no extension of the Space Shuttle retirement date, and thus no US capability to launch crews into orbit until the Orion spacecraft would become operational in 2020 as part of the Constellation programme. He did not see purchase of Russian launches for NASA crews as politically viable following the 2008 South Ossetia war, and hoped the incoming Barack Obama administration would resolve the issue in 2009 by extending Space Shuttle operations beyond 2010.

A solicitation issued by NASA JSC indicates NASA's intent to purchase from Roscosmos "a minimum of 3 Soyuz seats up to a maximum of 24 seats beginning in the Spring of 2012" to provide ISS crew transportation.

On September 7, 2008, NASA released a statement regarding the leaked email, in which Griffin said:

The leaked internal email fails to provide the contextual framework for my remarks, and my support for the administration's policies. Administration policy is to retire the shuttle in 2010 and purchase crew transport from Russia until Ares and Orion are available. The administration continues to support our request for an INKSNA exemption. Administration policy continues to be that we will take no action to preclude continued operation of the International Space Station past 2016. I strongly support these administration policies, as do OSTP and OMB.

— Michael D. Griffin

On October 15, 2008, President Bush signed the NASA Authorization Act of 2008, giving NASA funding for one additional mission to "deliver science experiments to the station". The Act allows for an additional Space Shuttle flight, STS-134, to the ISS to install the Alpha Magnetic Spectrometer, which was previously cancelled.

President of the United States Barack Obama has supported the continued operation of the station, and supported the NASA Authorization Act of 2008. Obama's plan for space exploration includes finishing the station and completion of the US programmes related to the Orion spacecraft.

End of mission

Many ISS resupply spacecraft have already undergone atmospheric re-entry, such as Jules Verne ATV

According to the Outer Space Treaty, the United States and Russia are legally responsible for all modules they have launched. Several possible disposal options were considered: Natural orbital decay with random reentry (as with Skylab), boosting the station to a higher altitude (which would delay reentry), and a controlled targeted de-orbit to a remote ocean area. In late 2010, the preferred plan was to use a slightly modified Progress spacecraft to de-orbit the ISS. This plan was seen as the simplest, cheapest and with the highest margin of safety.

OPSEK was previously intended to be constructed of modules from the Russian Orbital Segment after the ISS is decommissioned. The modules under consideration for removal from the current ISS included the Multipurpose Laboratory Module (Nauka), launched in July 2021, and the other new Russian modules that are proposed to be attached to Nauka. These newly launched modules would still be well within their useful lives in 2024.

At the end of 2011, the Exploration Gateway Platform concept also proposed using leftover USOS hardware and Zvezda 2 as a refuelling depot and service station located at one of the Earth-Moon Lagrange points. However, the entire USOS was not designed for disassembly and will be discarded.

On 30 September 2015, Boeing's contract with NASA as prime contractor for the ISS was extended to 30 September 2020. Part of Boeing's services under the contract related to extending the station's primary structural hardware past 2020 to the end of 2028.

There have also been suggestions in the commercial space industry that the station could be converted to commercial operations after it is retired by government entities.

In July 2018, the Space Frontier Act of 2018 was intended to extend operations of the ISS to 2030. This bill was unanimously approved in the Senate, but failed to pass in the U.S. House. In September 2018, the Leading Human Spaceflight Act was introduced with the intent to extend operations of the ISS to 2030, and was confirmed in December 2018. Congress later passed similar provisions in its CHIPS and Science Act, signed into law by President Joe Biden on 9 August 2022.

In January 2022, NASA announced a planned date of January 2031 to de-orbit the ISS using a deorbit module and direct any remnants into a remote area of the South Pacific Ocean.

New partners

China has reportedly expressed interest in the project, especially if it would be able to work with the RKA. Due to national security concerns, the United States Congress passed a law prohibiting contact between US and Chinese space programmes. As of 2019, China is not involved in the International Space Station. In addition to national security concerns, United States objections include China's human rights record and issues surrounding technology transfer. The heads of both the South Korean and Indian space agencies announced at the first plenary session of the 2009 International Astronautical Congress on 12 October that their nations intend to join the ISS programme. The talks began in 2010, and were not successful. The heads of agency also expressed support for extending ISS lifetime. European countries not a part of the International Space Station programme will be allowed access to the station in a three-year trial period, ESA officials say. The Indian Space Research Organisation has made it clear that it will not join the ISS and will instead build its own space station.

Cost

The ISS has been described as the most expensive single item ever constructed. As of 2010, the total cost was US$150 billion. This includes NASA's budget of $58.7 billion ($89.73 billion in 2021 dollars) for the station from 1985 to 2015, Russia's $12 billion, Europe's $5 billion, Japan's $5 billion, Canada's $2 billion, and the cost of 36 shuttle flights to build the station, estimated at $1.4 billion each, or $50.4 billion in total. Assuming 20,000 person-days of use from 2000 to 2015 by two- to six-person crews, each person-day would cost $7.5 million, less than half the inflation-adjusted $19.6 million ($5.5 million before inflation) per person-day of Skylab.

Public opinion

The International Space Station has been the target of varied criticism over the years. Critics contend that the time and money spent on the ISS could be better spent on other projects—whether they be robotic spacecraft missions, space exploration, investigations of problems here on Earth, or just tax savings. Some critics, like Robert L. Park, argue that very little scientific research was convincingly planned for the ISS in the first place. They also argue that the primary feature of a space-based laboratory is its microgravity environment, which can usually be studied more cheaply with a "vomit comet".

One of the most ambitious ISS modules to date, the Centrifuge Accommodations Module, has been cancelled due to the prohibitive costs NASA faces in simply completing the ISS. As a result, the research done on the ISS is generally limited to experiments which do not require any specialized apparatus. For example, in the first half of 2007, ISS research dealt primarily with human biological responses to being in space, covering topics like kidney stones, circadian rhythm, and the effects of cosmic rays on the nervous system.

Other critics have attacked the ISS on some technical design grounds:

1. Jeff Foust argued that the ISS requires too much maintenance, especially by risky, expensive EVAs. The magazine The American Enterprise reports, for instance, that ISS astronauts "now spend 85 percent of their time on construction and maintenance" alone.
2. The Astronomical Society of the Pacific has mentioned that its orbit is rather highly inclined, which makes Russian launches cheaper, but US launches more expensive.

Critics also say that NASA is often casually credited with "spin-offs" (such as Velcro and portable computers) that were developed independently for other reasons. NASA maintains a list of spin-offs from the construction of the ISS, as well as from work performed on the ISS.

In response to some of these criticisms, advocates of human space exploration say that criticism of the ISS programme is short-sighted, and that crewed space research and exploration have produced billions of dollars' worth of tangible benefits to people on Earth. Jerome Schnee estimated that the indirect economic return from spin-offs of human space exploration has been many times the initial public investment. A review of the claims by the Federation of American Scientists argued that NASA's rate of return from spin-offs is actually "astoundingly bad", except for aeronautics work that has led to aircraft sales.

It is therefore debatable whether the ISS, as distinct from the wider space programme, is a major contributor to society. Some advocates argue that apart from its scientific value, it is an important example of international cooperation. Others claim that the ISS is an asset that, if properly leveraged, could allow more economical crewed Lunar and Mars missions.

Quark–gluon plasma

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Quark%E2%80%93gluon_plasma 

 

QCD phase diagram. Adapted from original made by R.S. Bhalerao.

Quark–gluon plasma (QGP) or quark soup is an interacting localized assembly of quarks and gluons at thermal (local kinetic) and (close to) chemical (abundance) equilibrium. The word plasma signals that free color charges are allowed. In a 1987 summary, Léon van Hove pointed out the equivalence of the three terms: quark gluon plasma, quark matter and a new state of matter. Since the temperature is above the Hagedorn temperature—and thus above the scale of light u,d-quark mass—the pressure exhibits the relativistic Stefan-Boltzmann format governed by temperature to the fourth power (${\displaystyle T^4}$) and many practically massless quark and gluon constituents. It can be said that QGP emerges to be the new phase of strongly interacting matter which manifests its physical properties in terms of nearly free dynamics of practically massless gluons and quarks. Both quarks and gluons must be present in conditions near chemical (yield) equilibrium with their colour charge open for a new state of matter to be referred to as QGP.

In the Big Bang theory, quark–gluon plasma filled the entire Universe before matter as we know it was created. Theories predicting the existence of quark–gluon plasma were developed in the late 1970s and early 1980s. Discussions around heavy ion experimentation followed suit and the first experiment proposals were put forward at CERN and BNL in the following years. Quark–gluon plasma was detected for the first time in the laboratory at CERN in the year 2000.

Timeline of the CERN-SPS relativistic heavy ion program before QGP discovery.

General introduction

Quark–gluon plasma is a state of matter in which the elementary particles that make up the hadrons of baryonic matter are freed of their strong attraction for one another under extremely high energy densities. These particles are the quarks and gluons that compose baryonic matter. In normal matter quarks are confined; in the QGP quarks are deconfined. In classical quantum chromodynamics (QCD), quarks are the fermionic components of hadrons (mesons and baryons) while the gluons are considered the bosonic components of such particles. The gluons are the force carriers, or bosons, of the QCD color force, while the quarks by themselves are their fermionic matter counterparts.

Quark–gluon plasma is studied to recreate and understand the high energy density conditions prevailing in the Universe when matter formed from elementary degrees of freedom (quarks, gluons) at about 20μs after the Big Bang. Experimental groups are probing over a ‘large’ distance the (de)confining quantum vacuum structure, the present day relativistic æther, which determines prevailing form of matter and laws of nature. The experiments give insight to the origin of matter and mass: the matter and antimatter is created when the quark–gluon plasma ‘hadronizes’ and the mass of matter originates in the confining vacuum structure.

How the quark–gluon plasma fits into the general scheme of physics

QCD is one part of the modern theory of particle physics called the Standard Model. Other parts of this theory deal with electroweak interactions and neutrinos. The theory of electrodynamics has been tested and found correct to a few parts in a billion. The theory of weak interactions has been tested and found correct to a few parts in a thousand. Perturbative forms of QCD have been tested to a few percent. Perturbative models assume relatively small changes from the ground state, i.e. relatively low temperatures and densities, which simplifies calculations at the cost of generality. In contrast, non-perturbative forms of QCD have barely been tested. The study of the QGP, which has both a high temperature and density, is part of this effort to consolidate the grand theory of particle physics.

The study of the QGP is also a testing ground for finite temperature field theory, a branch of theoretical physics which seeks to understand particle physics under conditions of high temperature. Such studies are important to understand the early evolution of our universe: the first hundred microseconds or so. It is crucial to the physics goals of a new generation of observations of the universe (WMAP and its successors). It is also of relevance to Grand Unification Theories which seek to unify the three fundamental forces of nature (excluding gravity).

Five reasons to study quark–gluon plasma. The background of the slide is based on the Sistine Chapel ceiling fresco "The Creation of Adam" by Michelangelo. This picture ornamented the poster  of the first quark–gluon plasma summer school "Particle Production in Highly Excited Matter".

Reasons for studying the formation of quark–gluon plasma

The generally accepted model of the formation of the Universe states that it happened as the result of the Big Bang. In this model, in the time interval of 10⁻¹⁰–10⁻⁶ s after the Big Bang, matter existed in the form of a quark–gluon plasma. It is possible to reproduce the density and temperature of matter existing of that time in laboratory conditions to study the characteristics of the very early Universe. So far, the only possibility is the collision of two heavy atomic nuclei accelerated to energies of more than a hundred GeV. Using the result of a head-on collision in the volume approximately equal to the volume of the atomic nucleus, it is possible to model the density and temperature that existed in the first instants of the life of the Universe.

Relation to normal plasma

A plasma is matter in which charges are screened due to the presence of other mobile charges. For example: Coulomb's Law is suppressed by the screening to yield a distance-dependent charge, ${\displaystyle Q\to Q{e}^{-r/\alpha }}$, i.e., the charge Q is reduced exponentially with the distance divided by a screening length α. In a QGP, the color charge of the quarks and gluons is screened. The QGP has other analogies with a normal plasma. There are also dissimilarities because the color charge is non-abelian, whereas the electric charge is abelian. Outside a finite volume of QGP the color-electric field is not screened, so that a volume of QGP must still be color-neutral. It will therefore, like a nucleus, have integer electric charge.

Because of the extremely high energies involved, quark-antiquark pairs are produced by pair production and thus QGP is a roughly equal mixture of quarks and antiquarks of various flavors, with only a slight excess of quarks. This property is not a general feature of conventional plasmas, which may be too cool for pair production (see however pair instability supernova).

Theory

One consequence of this difference is that the color charge is too large for perturbative computations which are the mainstay of QED. As a result, the main theoretical tools to explore the theory of the QGP is lattice gauge theory. The transition temperature (approximately 175 MeV) was first predicted by lattice gauge theory. Since then lattice gauge theory has been used to predict many other properties of this kind of matter. The AdS/CFT correspondence conjecture may provide insights in QGP, moreover the ultimate goal of the fluid/gravity correspondence is to understand QGP. The QGP is believed to be a phase of QCD which is completely locally thermalized and thus suitable for an effective fluid dynamic description.

Production

Production of QGP in the laboratory is achieved by colliding heavy atomic nuclei (called heavy ions as in an accelerator atoms are ionized) at relativistic energy in which matter is heated well above the Hagedorn temperature T_H= 150 MeV per particle, which amounts to a temperature exceeding 1.66×10¹² K. This can be accomplished by colliding two large nuclei at high energy (note that 175 MeV is not the energy of the colliding beam). Lead and gold nuclei have been used for such collisions at CERN SPS and BNL RHIC, respectively. The nuclei are accelerated to ultrarelativistic speeds (contracting their length) and directed towards each other, creating a "fireball", in the rare event of a collision. Hydrodynamic simulation predicts this fireball will expand under its own pressure, and cool while expanding. By carefully studying the spherical and elliptic flow, experimentalists put the theory to test.

Diagnostic tools

There is an overwhelming evidence for production of quark–gluon plasma in relativistic heavy ion collisions.

The important classes of experimental observations are

• Strangeness production
• Elliptic flow
• Jet quenching
• J/ψ melting
• Hanbury Brown and Twiss effect and Bose–Einstein correlations
• Single particle spectra (thermal photons and thermal dileptons)

Expected properties

Thermodynamics

The cross-over temperature from the normal hadronic to the QGP phase is about 156 MeV. This "crossover" may actually not be only a qualitative feature, but instead one may have to do with a true (second order) phase transition, e.g. of the universality class of the three-dimensional Ising model. The phenomena involved correspond to an energy density of a little less than 1 GeV/fm³. For relativistic matter, pressure and temperature are not independent variables, so the equation of state is a relation between the energy density and the pressure. This has been found through lattice computations, and compared to both perturbation theory and string theory. This is still a matter of active research. Response functions such as the specific heat and various quark number susceptibilities are currently being computed.

Flow

The discovery of the perfect liquid was a turning point in physics. Experiments at RHIC have revealed a wealth of information about this remarkable substance, which we now know to be a QGP. Nuclear matter at "room temperature" is known to behave like a superfluid. When heated the nuclear fluid evaporates and turns into a dilute gas of nucleons and, upon further heating, a gas of baryons and mesons (hadrons). At the critical temperature, T_H, the hadrons melt and the gas turns back into a liquid. RHIC experiments have shown that this is the most perfect liquid ever observed in any laboratory experiment at any scale. The new phase of matter, consisting of dissolved hadrons, exhibits less resistance to flow than any other known substance. The experiments at RHIC have, already in 2005, shown that the Universe at its beginning was uniformly filled with this type of material—a super-liquid—which once the Universe cooled below T_H evaporated into a gas of hadrons. Detailed measurements show that this liquid is a quark–gluon plasma where quarks, antiquarks and gluons flow independently.

Schematic representation of the interaction region formed in the first moments after the collision of heavy ions with high energies in the accelerator.

In short, a quark–gluon plasma flows like a splat of liquid, and because it's not "transparent" with respect to quarks, it can attenuate jets emitted by collisions. Furthermore, once formed, a ball of quark–gluon plasma, like any hot object, transfers heat internally by radiation. However, unlike in everyday objects, there is enough energy available so that gluons (particles mediating the strong force) collide and produce an excess of the heavy (i.e. high-energy) strange quarks. Whereas, if the QGP didn't exist and there was a pure collision, the same energy would be converted into a non-equilibrium mixture containing even heavier quarks such as charm quarks or bottom quarks.

The equation of state is an important input into the flow equations. The speed of sound (speed of QGP-density oscillations) is currently under investigation in lattice computations. The mean free path of quarks and gluons has been computed using perturbation theory as well as string theory. Lattice computations have been slower here, although the first computations of transport coefficients have been concluded. These indicate that the mean free time of quarks and gluons in the QGP may be comparable to the average interparticle spacing: hence the QGP is a liquid as far as its flow properties go. This is very much an active field of research, and these conclusions may evolve rapidly. The incorporation of dissipative phenomena into hydrodynamics is another active research area.

Jet quenching effect

Detailed predictions were made in the late 1970s for the production of jets at the CERN Super Proton–Antiproton Synchrotron. UA2 observed the first evidence for jet production in hadron collisions in 1981, which shortly after was confirmed by UA1.

The subject was later revived at RHIC. One of the most striking physical effects obtained at RHIC energies is the effect of quenching jets. At the first stage of interaction of colliding relativistic nuclei, partons of the colliding nuclei give rise to the secondary partons with a large transverse impulse ≥ 3–6 GeV / s. Passing through a highly heated compressed plasma, partons lose energy. The magnitude of the energy loss by the parton depends on the properties of the quark–gluon plasma (temperature, density). In addition, it is also necessary to take into account the fact that colored quarks and gluons are the elementary objects of the plasma, which differs from the energy loss by a parton in a medium consisting of colorless hadrons. Under the conditions of a quark–gluon plasma, the energy losses resulting from the RHIC energies by partons are estimated as dE / dx = 1 GeV / fm. This conclusion is confirmed by comparing the relative yield of hadrons with a large transverse impulse in nucleon-nucleon and nucleus-nucleus collisions at the same collision energy. The energy loss by partons with a large transverse impulse in nucleon-nucleon collisions is much smaller than in nucleus-nucleus collisions, which leads to a decrease in the yield of high-energy hadrons in nucleus-nucleus collisions. This result suggests that nuclear collisions cannot be regarded as a simple superposition of nucleon-nucleon collisions. For a short time, ~ 1 μs and in the final volume, quarks and gluons form some ideal liquid. The collective properties of this fluid are manifested during its movement as a whole. Therefore, when moving partons in this medium, it is necessary to take into account some collective properties of this quark–gluon liquid. Energy losses depend on the properties of the quark–gluon medium, on the parton density in the resulting fireball, and on the dynamics of its expansion. Losses of energy by light and heavy quarks during the passage of a fireball turn out to be approximately the same.

In November 2010 CERN announced the first direct observation of jet quenching, based on experiments with heavy-ion collisions.

Direct photons and dileptons

Direct photons and dileptons are arguably most penetrating tools to study relativistic heavy ion collisions. They are produced, by various mechanisms spanning the space-time evolution of the strongly interacting fireball.  They provide in principle a snapshot on the initial stage as well. They are hard to decipher and interpret as most of the signal is originating from hadron decays long after the QGP fireball has disintegrated.

Glasma hypothesis

Since 2008, there is a discussion about a hypothetical precursor state of the quark–gluon plasma, the so-called "Glasma", where the dressed particles are condensed into some kind of glassy (or amorphous) state, below the genuine transition between the confined state and the plasma liquid. This would be analogous to the formation of metallic glasses, or amorphous alloys of them, below the genuine onset of the liquid metallic state.

Although the experimental high temperatures and densities predicted as producing a quark–gluon plasma have been realized in the laboratory, the resulting matter does not behave as a quasi-ideal state of free quarks and gluons, but, rather, as an almost perfect dense fluid. Actually, the fact that the quark–gluon plasma will not yet be "free" at temperatures realized at present accelerators was predicted in 1984 as a consequence of the remnant effects of confinement.

In-laboratory formation of deconfined matter

A quark–gluon plasma (QGP) or quark soup is a state of matter in quantum chromodynamics (QCD) which exists at extremely high temperature and/or density. This state is thought to consist of asymptotically free strong-interacting quarks and gluons, which are ordinarily confined by color confinement inside atomic nuclei or other hadrons. This is in analogy with the conventional plasma where nuclei and electrons, confined inside atoms by electrostatic forces at ambient conditions, can move freely. Experiments to create artificial quark matter started at CERN in 1986/7, resulting in first claims that were published in 1991. It took several years before the idea became accepted in the community of particle and nuclear physicists. Formation of a new state of matter in Pb-Pb collisions was officially announced at CERN in view of the convincing experimental results presented by the CERN SPS WA97 experiment in 1999, and later elaborated by Brookhaven National Laboratory's Relativistic Heavy Ion Collider. Quark matter can only be produced in minute quantities and is unstable and impossible to contain, and will radioactively decay within a fraction of a second into stable particles through hadronization; the produced hadrons or their decay products and gamma rays can then be detected. In the quark matter phase diagram, QGP is placed in the high-temperature, high-density regime, whereas ordinary matter is a cold and rarefied mixture of nuclei and vacuum, and the hypothetical quark stars would consist of relatively cold, but dense quark matter. It is believed that up to a few microseconds (10⁻¹² to 10⁻⁶ seconds) after the Big Bang, known as the quark epoch, the Universe was in a quark–gluon plasma state.

The strength of the color force means that unlike the gas-like plasma, quark–gluon plasma behaves as a near-ideal Fermi liquid, although research on flow characteristics is ongoing. Liquid or even near-perfect liquid flow with almost no frictional resistance or viscosity was claimed by research teams at RHIC and LHC's Compact Muon Solenoid detector. QGP differs from a "free" collision event by several features; for example, its particle content is indicative of a temporary chemical equilibrium producing an excess of middle-energy strange quarks vs. a nonequilibrium distribution mixing light and heavy quarks ("strangeness production"), and it does not allow particle jets to pass through ("jet quenching").

Experiments at CERN's Super Proton Synchrotron (SPS) begun experiments to create QGP in the 1980s and 1990s: the results led CERN to announce evidence for a "new state of matter" in 2000. Scientists at Brookhaven National Laboratory's Relativistic Heavy Ion Collider announced they had created quark–gluon plasma by colliding gold ions at nearly the speed of light, reaching temperatures of 4 trillion degrees Celsius. Current experiments (2017) at the Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) on Long Island (NY, USA) and at CERN's recent Large Hadron Collider near Geneva (Switzerland) are continuing this effort, by colliding relativistically accelerated gold and other ion species (at RHIC) or lead (at LHC) with each other or with protons. Three experiments running on CERN's Large Hadron Collider (LHC), on the spectrometers ALICE, ATLAS and CMS, have continued studying the properties of QGP. CERN temporarily ceased colliding protons, and began colliding lead ions for the ALICE experiment in 2011, in order to create a QGP. A new record breaking temperature was set by ALICE: A Large Ion Collider Experiment at CERN in August 2012 in the ranges of 5.5 trillion (5.5×10¹²) kelvin as claimed in their Nature PR.

The formation of a quark–gluon plasma occurs as a result of a strong interaction between the partons (quarks, gluons) that make up the nucleons of the colliding heavy nuclei called heavy ions. Therefore experiments are referred to as relativistic heavy ion collision experiments. Theoretical and experimental works show that the formation of a quark–gluon plasma occurs at the temperature of T ≈ 150–160 MeV, the Hagedorn temperature, and an energy density of ≈ 0.4–1 GeV / fm³. While at first a phase transition was expected, present day theoretical interpretations propose a phase transformation similar to the process of ionisation of normal matter into ionic and electron plasma.

Quark–gluon plasma and the onset of deconfinement

The central issue of the formation of a quark–gluon plasma is the research for the onset of deconfinement. From the beginning of the research on formation of QGP, the issue was whether energy density can be achieved in nucleus-nucleus collisions. This depends on how much energy each nucleon loses. A influential reaction picture was the scaling solution presented by Bjorken. This model applies to ultra-high energy collisions. In experiments carried out at CERN SPS and BNL RHIC more complex situation arose, usually divided into three stages:

• Primary parton collisions and baryon stopping at the time of complete overlapping of the colliding nuclei.
• Redistribution of particle energy and new particles born in the QGP fireball.
• The fireball of QGP matter equilibrates and expands before hadronizing.

More and more experimental evidence points to the strength of QGP formation mechanisms—operating even in LHC-energy scale proton-proton collisions.

Anti-union violence in the United States

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Anti-union_violence_in_the_United_States 

 

Massachusetts militiamen with fixed bayonets surround a group of strikers during the Lawrence, Massachusetts Textile Strike of 1912

Anti-union violence in the United States is physical force intended to harm union officials, union organizers, union members, union sympathizers, or their families. It has most commonly been used either during union organizing efforts, or during strikes. The aim most often is to prevent a union from forming, to destroy an existing union, or to reduce the effectiveness of a union or a particular strike action. If strikers prevent people or goods to enter or leave a workplace, violence may be used to allow people and goods to pass the picket line.

Violence against unions may be isolated, or may occur as part of a campaign that includes spying, intimidation, impersonation, disinformation, and sabotage. Violence in labor disputes may be the result of unreasonable polarization, or miscalculation. It may be willful and provoked, or senseless and tragic. On some occasions, violence in labor disputes may be purposeful and calculated, for example the hiring and deployment of goon squads to intimidate, threaten or even assault strikers.

According to labor historians and other scholars, the US has had the bloodiest and most violent labor history of any industrialized nation.

History

Union organizer Frank Little was pulled from his bed and lynched in 1917 because of his union activities.

Historically, violence against unions has included attacks by detective and guard agencies, such as the Pinkertons, Baldwin Felts, Burns, or Thiel detective agencies; citizens groups, such as the Citizens' Alliance; company guards; police; national guard; or even the military. In particular, there are few curbs on what detective agencies are able to get away with. In the book From Blackjacks To Briefcases, Robert Michael Smith states that during the late nineteenth and early twentieth centuries, anti-union agencies spawned violence and wreaked havoc on the labor movement. One investigator who participated in a congressional inquiry into industrial violence in 1916 concluded that,

Espionage is closely related to violence. Sometimes it is the direct cause of violence, and, where that cannot be charged, it is often the indirect cause. If the secret agents of employers, working as members of the labor unions, do not always investigate acts of violence, they frequently encourage them. If they did not, they would not be performing the duties for which they are paid, for they are hired on the theory that labor organizations are criminal in character.

In U.S. Senate testimony in 1936 about an employer who wanted to contract with the Pinkerton agency, known personally to the author of the book The Pinkerton Story, this employer was characterized as a "sincerely upright and Godly man." Yet Pinkerton files record that the employer wanted the agency "to send in some thugs who could beat up the strikers." In 1936, the Pinkerton agency changed its focus from strike-breaking to undercover services. Pinkerton declined the request from this employer.

According to Morris Friedman, detective agencies were themselves for-profit companies, and a "bitter struggle" between capital and labor could be counted upon to create "satisfaction and immense profit" for agencies such as the Pinkerton company. Such agencies were in the perfect position to fan suspicion and mistrust "into flames of blind and furious hatred" on the part of the companies.

Agencies sell tactics including violence

Harry Wellington Laidler wrote a book in 1913 detailing how one of the largest union busters in the United States, Corporations Auxiliary Company, had a sales pitch offering the use of provocation and violence. The agency would routinely tell employers—prospective clients—of the methods used by their undercover operatives,

Once the union is in the field its members can keep it from growing if they know how, and our man knows how. Meetings can be set far apart. A contract can at once be entered into with the employer, covering a long period, and made very easy in its terms. However, these tactics may not be good, and the union spirit may be so strong that a big organization cannot be prevented. In this case our man turns extremely radical. He asks for unreasonable things and keeps the union embroiled in trouble. If a strike comes, he will be the loudest man in the bunch, and will counsel violence and get somebody in trouble. The result will be that the union will be broken up.

Different types of violence

Striking Pennsylvania mine workers began their protest march near Harwood. Many would soon be killed by the Luzerne County sheriff.

Some anti-union violence appears to be random, such as an incident during the 1912 textile strike in Lawrence, Massachusetts, in which a police officer fired into a crowd of strikers, killing Anna LoPizzo.

Anti-union violence may be used as a means to intimidate others, as in the hanging of union organizer Frank Little from a railroad trestle in Butte, Montana. A note was pinned to his body which said, "Others Take Notice! First And Last Warning!". The initial of the last names of seven well-known union activists in the Butte area were on the note, with the "L" for Frank Little circled.

Anti-union violence may be abrupt and unanticipated. Three years after Frank Little was lynched, a strike by Butte miners was suppressed with gunfire when deputized mine guards suddenly fired upon unarmed picketers in the Anaconda Road Massacre. Seventeen were shot in the back as they tried to flee, and one man died.

Machine gun equipped armored car built with steel from CF&I's Pueblo steel works, known to the striking miners as the Death Special. "The machine gun was turned on striking miners and used to riddle the Forbes tent colony."

The unprovoked attack was similar to another event, which had occurred twenty-three years earlier in Pennsylvania. During the Lattimer massacre, nineteen unarmed immigrant coal miners were suddenly gunned down at the Lattimer mine near Hazleton, Pennsylvania, on September 10, 1897. The miners, mostly of Polish, Slovak, Lithuanian and German ethnicity, were shot and killed by a Luzerne County sheriff's posse. In this group as well, all of the miners had been shot in the back. The shooting followed a brief tussle over the American flag carried by the miners. Their only crime was asserting their right to march in the face of demands that they disperse.

In 1927, during a coal strike in Colorado, state police and mine guards fired pistols, rifles and a machine gun into a group of five hundred striking miners and their wives in what came to be called the Columbine Mine Massacre. In this incident as well, many of the miners were immigrants, and there had been a disagreement over the question of trespassing onto company property in the town of Serene, with the miners asserting it was public property because of the post office. There was, once again, a tussle over American flags carried by the strikers.

While the Columbine mine shooting was a surprise, newspapers played a deadly role in conjuring the atmosphere of hate in which the violence occurred. Lurid editorials attacked the ethnicity of the strikers. Newspapers began calling for the governor to no longer withhold the "mailed fist", to strike hard and strike swiftly, and for "Machine Guns Manned By Willing Shooters" at more of the state's coal mines. Within days of these editorials, state police and mine guards fired on the miners and their wives, injuring dozens and killing six.

In all of the above incidents, the perpetrators were never caught, or went unpunished. An exception resulted from a shooting of strikers at the Williams & Clark Fertilizing Company near the Liebig Fertilizer Works at Carteret, New Jersey, in 1915. One striker was killed outright, and more than twenty were injured in an unprovoked attack when deputies fired on strikers who had stopped a train to check for strikebreakers. The strikers found no strikebreakers and were cheering as they exited the train. Forty deputies approached and suddenly fired on them with revolvers, rifles, and shotguns. As the strikers ran, "the deputies ... pursued, firing again and again." According to attending physicians, all the strikers' wounds were on the backs or legs, indicating the guards were pursuing them. A local government official who witnessed the shooting called it entirely unprovoked. Four more of the strikers, all critically injured, would die. Twenty-two of the guards were arrested and the crime was investigated by a Grand Jury; nine deputies were subsequently convicted of manslaughter.

Other anti-union violence may seem orchestrated, as in 1914 when mine guards and the state militia fired into a tent colony of striking miners in Colorado, an incident that came to be known as the Ludlow Massacre. During that strike, the company hired the Baldwin Felts agency, which built an armored car so their agents could approach the strikers' tent colonies with impunity. The strikers called it the "Death Special". At the Forbes tent colony,

[The Death Special] opened fire, a protracted spurt that sent some six hundred bullets tearing through the thin tents. One of the shots struck miner Luka Vahernik, fifty, in the head, killing him instantly. Another striker, Marco Zamboni, eighteen ... suffered nine bullet wounds to his legs... One tent was later found to have about 150 bullet holes...

After deaths of women and children at Ludlow,

[T]he backlash was vicious and bloody. Over the next ten days striking miners poured out their rage in attacks across the coalfields...

The U.S. Army was called upon to put an end to the violence, and the strike sputtered to an end that December.

As a result of Operative Smith's "clever and intelligent" work, a number of union organizers received severe beatings at the hands of unknown masked men, presumably in the employ of the company.

Morris Friedman offers examples of these incidents:

About February 13, 1904, William Farley, of Alabama, a member of the [UMWA] National Executive Board ... and the personal representative of [UMWA] President Mitchell ... addressed coal miners' meetings ... [on their return trip] eight masked men held them up with revolvers, dragged them from their wagon, threw them to the ground, beat them, kicked them, and almost knocked them into insensibility.

And,

On Saturday, April 30, 1904, W.M. Wardjon, a national organizer of the United Mine Workers, while on board a train en route to Pueblo, was assaulted by three men at Sargents, about thirty miles west of Salida. Mr. Wardjon was beaten into unconsciousness.

Friedman accused the Colorado Fuel and Iron Company (CF&I), operated by John D. Rockefeller and his lieutenant in Colorado, Jesse Welborn, of responsibility for the beatings during the 1903–04 strike.

Sometimes, there is simultaneous violence on both sides. In an auto workers strike organised by Victor Reuther and others in 1937, "[u]nionists assembled rocks, steel hinges, and other objects to throw at the cops, and police organized tear gas attacks and mounted charges."

Colorado labor war, 1903–1904

General Sherman Bell. Photo from The Pinkerton Labor Spy, published in 1907.

 

Karl Linderfelt, center. Original photo caption: "OFFICERS OF THE COLORADO NATIONAL GUARD From left to right: Captain R. J. Linderfelt, Lieut. T. C. Linderfelt, Lieut. K. E. Linderfelt, (who faced the charge of assault upon Louis Tikas, the dead strike leader), Lieut. G.S. Lawrence and Major Patrick Hamrock. The last three were in the Ludlow battle of April 20, 1914."

A study of industrial violence in 1969 concluded, "There is no episode in American labor history in which violence was as systematically used by employers as in the Colorado labor war of 1903 and 1904."

About the middle of February 1904, leadership of the Colorado National Guard became concerned that the Mine Owners were failing to cover the payroll of the soldiers. General Reardon ordered Major Ellison to take another soldier he could trust to "hold up or shoot the men coming off shift at the Vindicator mine" in order to convince the mine owners to pay. The implication of the secrecy was that the incident would then be blamed on the union.

However, Major Ellison reported that the miners took a route out of the mine that would not make ambush possible. Reardon ordered Ellison to pursue an alternative plan, which was shooting up one of the mines. Major Ellison and Sergeant Gordon Walter fired sixty shots into two mine buildings. The plan worked, and the mine owners paid up. Ellison would later testify (in October 1904) that General Reardon informed him Adjutant General Sherman Bell and Colorado Governor James Peabody knew about the plan. Major Ellison's testimony about the shooting plot, and about the staged attacks on striking miners, was corroborated by two other soldiers.

Ludlow massacre, 1914

Professor James H. Brewster, a faculty attorney with the University of Colorado who was investigating the strike for Governor Ammons, was aware that militia Lieutenant Karl Linderfelt was guilty of abuse and beatings of innocent citizens, including a small Greek boy "whose head was split open". Professor Brewster sent a telegram to Governor Ammons requesting Linderfelt's removal. No action was taken. In a subsequent face to face meeting with the governor, three months prior to the Ludlow Massacre, Brewster again insisted that Linderfelt be removed, but again, Ammons declined. In later testimony, Professor Brewster stated that Linderfelt was the reason for the massacre. On the day that the Ludlow Massacre occurred, Lieutenant Karl Linderfelt, commander of one of two companies of the Colorado National Guard, had Louis Tikas, leader of the Ludlow tent colony of striking miners, at gunpoint. Tikas was unarmed, and the miners would later explain that he approached the militia to ask them to stop shooting. While two militiamen held Tikas, Linderfelt broke a rifle butt over his head. Tikas and two other captured miners were later found shot dead. Tikas had been shot in the back. Their bodies lay along the Colorado and Southern railroad tracks for three days in full view of passing trains. The militia officers refused to allow them to be moved until a local of a railway union demanded the bodies be taken away for burial. A court martial found Lieutenant Linderfelt guilty of assaulting Tikas with a Springfield rifle, "but attaches no criminality thereto. And the court does therefor acquit him."

1916 Congressional investigation

In 1916, the Commission on Industrial Relations, created by the U.S. Congress, issued a final report on its investigation of industrial unrest. On the question of violence in industrial disputes, the Commission stated, in part,

Many instances of the use of physical force by the agents of employers have ... come before the Commission, indicating a relatively wide use, particularly in isolated communities.

Late 20th century anti-union violence

By the early 1900s, public tolerance for violence during labor disputes began to decrease. Yet violence involving strikebreaking troops and armed guards continued into the 1930s. The level of violence that anti-union agencies engaged in eventually resulted in their tactics becoming increasingly public, for there were a very great number of newspaper and muckraking articles written about such incidents. Resources that once were allocated to overt control over workforces began to be assigned to other methods of control, such as industrial espionage. After the Great Depression in 1929, the public no longer considered companies unassailable. Yet legislation related to employer strategies such as violent strike breaking would have to wait until after World War II. Beginning in the 1950s, employers began to embrace new methods of managing workers and unions which were still effective, but much more subtle.

A 1969 study of labor conflict violence in the United States examined the era following the 1947 passage of the Taft–Hartley Act and noted that attacks on strikers by company guards had all but disappeared. Violence still occurs in labor disputes, for example, when one side miscalculates. Bringing in outside security forces, as one example, can lead to violence in modern labor disputes.

The use of cameras and camcorders may affect levels of violence in labor disputes today.

Examples since 1940

• Victor Reuther, a leader of the United Auto Workers in Detroit, survived an assassination attempt in 1949, with the loss of his right eye.

Threats

Sometimes, threats of violence cause damage to union members or supporters. Other times, threats against unions or their members may backfire. For example, Indiana Deputy Attorney General Jeffrey Cox was fired after suggesting that Wisconsin Governor Scott Walker should use live ammunition against pro-union protesters involved in the 2011 Wisconsin protests. More recently, a Deputy Prosecutor in Indiana's Johnson County, Carlos Lam, suggested that Governor Walker should mount a "false flag" operation which would make it appear as if the union was committing violence. After initially claiming that his email account was hacked, Lam admitted to sending the suggestion and resigned.

Cullen Werwie, press secretary for Governor Walker, states that Walker's office was unaware of Lam's email. According to CBS News, Werwie also commented, "Certainly we do not support the actions suggested in (the) email. Governor Walker has said time and again that the protesters have every right to have their voice heard, and for the most part the protests have been peaceful. We are hopeful that the tradition will continue."