Global warming is a long-term rise in the average temperature of the Earth's climate system, an aspect of climate change shown by temperature measurements and by multiple effects of the warming. Though earlier geological periods experienced episodes of warming, the term refers to the observed and continuing increase in average air and ocean temperatures since 1900 caused by emissions of greenhouse gasses in the modern industrial economy. In the modern context the terms global warming and climate change are used interchangeably, but climate change includes both global warming and its effects, such as changes to precipitation and impacts that differ by region. Many of the observed warming changes since the 1950s are unprecedented in the instrumental temperature record, in historical and paleoclimate proxy records of climate change over thousands to millions of years. In 2013, the Intergovernmental Panel on Climate Change Fifth Assessment Report concluded, "It is likely that human influence has been the dominant cause of the observed warming since the mid-20th century."
The largest human influence has been the emission of greenhouse gases such as carbon dioxide and nitrous oxide. Climate model projections summarized in the report indicated that during the 21st century, the global surface temperature is to rise a further 0.3 to 1.7 °C to 2.6 to 4.8 °C depending on the rate of greenhouse gas emissions and on climate feedback effects. These findings have been recognized by the national science academies of the major industrialized nations and are not disputed by any scientific body of national or international standing. Future climate change effects are expected to include rising sea levels, ocean acidification, regional changes in precipitation, expansion of deserts in the subtropics. Surface temperature increases are greatest in the Arctic, with the continuing retreat of glaciers and sea ice. Predicted regional precipitation effects include more frequent extreme weather events such as heat waves, wildfires, heavy rainfall with floods, heavy snowfall. Effects directly significant to humans are predicted to include the threat to food security from decreasing crop yields, the abandonment of populated areas due to rising sea levels.
Environmental impacts appear to include the extinction or relocation of ecosystems as they adapt to climate change, with coral reefs, mountain ecosystems, Arctic ecosystems most threatened. Because the climate system has a large "inertia" and greenhouse gases will remain in the atmosphere for a long time, climatic changes and their effects will continue to become more pronounced for many centuries if further increases to greenhouse gases stop. Possible societal responses to global warming include mitigation by emissions reduction, adaptation to its effects, possible future climate engineering. Most countries are parties to the United Nations Framework Convention on Climate Change, whose ultimate objective is to prevent dangerous anthropogenic climate change. Parties to the UNFCCC have agreed that deep cuts in emissions are required and that global warming should be limited to well below 2.0 °C compared to pre-industrial levels, with efforts made to limit warming to 1.5 °C. Some scientists call into question climate adaptation feasibility, with higher emissions scenarios, or the two degree temperature target.
Public reactions to global warming and concern about its effects are increasing. A 2015 global survey showed that a median of 54% of respondents consider it "a serious problem", with significant regional differences: Americans and Chinese are among the least concerned. Multiple independently produced datasets confirm that between 1880 and 2012, the global average surface temperature increased by 0.85 °C. Since 1979 the rate of warming has doubled. Climate proxies show the temperature to have been stable over the one or two thousand years before 1850, with regionally varying fluctuations such as the Medieval Warm Period and the Little Ice Age. Although the increase of the average near-surface atmospheric temperature is used to track global warming, over 90% of the additional energy stored in the climate system over the last 50 years has accumulated in the oceans; the rest warmed the continents and the atmosphere. The warming evident in the instrumental temperature record is consistent with a wide range of observations, as documented by many independent scientific groups.
Examples include sea level rise, widespread melting of snow and land ice, increased heat content of the oceans, increased humidity, the earlier timing of spring events, e.g. the flowering of plants. Global warming refers with the amount of warming varying by region. Since 1979, global average land temperatures have increased about twice as fast as global average ocean temperatures; this is due to the larger heat capacity of the oceans and because oceans lose more heat by evaporation. Where greenhouse gas emissions occur does not impact the location of warming because the major greenhouse gases persist long enough to diffuse across the planet, although localized black carbon deposits on snow and ice do contribute to Arctic warming; the Northern Hemisphere and North Pole have heated much faster than the South Pole and Southern Hemisphere. The Northern Hemisphere not only has much more land, its arrangement around the Arctic Ocean has resulted in the maximum surface area flipping from reflective snow and ice cover to ocean and land surfaces that absorb more sunlight.
Richard E. Taylor
Richard Edward Taylor, was a Canadian physicist and Stanford University professor. He shared the 1990 Nobel Prize in Physics with Jerome Friedman and Henry Kendall "for their pioneering investigations concerning deep inelastic scattering of electrons on protons and bound neutrons, which have been of essential importance for the development of the quark model in particle physics." Taylor was born in Alberta. He studied for his BSc and MSc degrees at the University of Alberta in Canada. Newly married, he applied to work for a PhD degree at Stanford University, where he joined the High Energy Physics Laboratory, his PhD thesis was on an experiment using polarised gamma rays to study pion production. After 3 years at the École Normale Supérieure in Paris and a year at the Lawrence Berkeley Laboratory in California, Taylor returned to Stanford. Construction of the Stanford Linear Accelerator Center was beginning. In collaboration with researchers from the California Institute of Technology and the Massachusetts Institute of Technology, Taylor worked on the design and construction of the equipment, was involved in many of the experiments.
In 1971, Taylor was awarded a Guggenheim fellowship that allowed him to spend a sabbatical year at CERN. The experiments run at SLAC in the late 1960s and early 1970s involved scattering high-energy beams of electrons from protons and deuterons and heavier nuclei. At lower energies, it had been found that the electrons would only be scattered through low angles, consistent with the idea that the nucleons had no internal structure. However, the SLAC-MIT experiments showed that higher energy electrons could be scattered through much higher angles, with the loss of some energy; these deep inelastic scattering results provided the first experimental evidence that the protons and neutrons were made up of point-like particles identified to be the up and down quarks, proposed on theoretical grounds. The experiments provided the first evidence for the existence of gluons. Taylor and Kendall were jointly awarded the Nobel Prize in 1990 for this work. Taylor died at his home in Stanford, California near the campus of Stanford University on 22 February 2018 at the age of 88.
Taylor has received numerous awards and honours including
Strategic Defense Initiative
The Strategic Defense Initiative was a proposed missile defense system intended to protect the United States from attack by ballistic strategic nuclear weapons. The concept was first announced publicly by President Ronald Reagan on 23 March 1983. Reagan was a vocal critic of the doctrine of mutual assured destruction, which he described as a "suicide pact", he called upon the scientists and engineers of the United States to develop a system that would render nuclear weapons obsolete; the Strategic Defense Initiative Organization was set up in 1984 within the United States Department of Defense to oversee development. A wide array of advanced weapon concepts, including lasers, particle beam weapons and ground- and space-based missile systems were studied, along with various sensor and control, high-performance computer systems that would be needed to control a system consisting of hundreds of combat centers and satellites spanning the entire globe. A number of these concepts were tested through the late 1980s, follow-on efforts and spin-offs continue to this day.
Under the SDIO's Innovative Sciences and Technology Office, headed by physicist and engineer Dr. James Ionson, the investment was predominantly made in basic research at national laboratories, in industry. In 1987, the American Physical Society concluded that the technologies being considered were decades away from being ready for use, at least another decade of research was required to know whether such a system was possible. After the publication of the APS report, SDIs budget was cut. By the late 1980s, the effort had been re-focused on the "Brilliant Pebbles" concept using small orbiting missiles not unlike a conventional air-to-air missile, expected to be much less expensive to develop and deploy. SDI was controversial throughout its history, was criticized for threatening to destabilize the MAD-approach and to re-ignite "an offensive arms race". SDI was derisively nicknamed by Democratic Senator Ted Kennedy as "Star Wars", after the 1977 film by George Lucas. By the early 1990s, with the Cold War ending and nuclear arsenals being reduced, political support for SDI collapsed.
SDI ended in 1993, when the administration of President Bill Clinton redirected the efforts towards theatre ballistic missiles and renamed the agency the Ballistic Missile Defense Organization. BMDO was renamed the Missile Defense Agency in 2002; the US Army had considered the issue of ballistic missile defense as early as late in World War II. Studies on the topic suggested attacking a V-2 rocket would be difficult because the flight time was so short that it would leave little time to forward information through command and control networks to the missile batteries that would attack them. Bell Labs pointed out that although longer-range missiles flew much faster, their longer flight times would address the timing issue and their high altitudes would make long-range detection by radar easier; this led to a series of projects including Nike Zeus, Nike-X, Sentinel and the Safeguard Program, all aimed at deploying a nationwide defensive system against attacks by Soviet ICBMs. The reason for so many programs was the changing strategic threat.
Low-cost countermeasures like radar decoys required additional interceptors to counter. An early estimate suggested one would have to spend $20 on defense for every $1 the Soviets spent on offense; the addition of MIRV in the late 1960s further upset the balance in favor of offense systems. This cost-exchange ratio was so favorable that it appeared the only thing building a defense would do would be to cause an arms race; when faced with this problem, President Eisenhower asked ARPA to consider alternative concepts. Their Project Defender studied all sorts of systems, before abandoning most of them to concentrate on Project BAMBI. BAMBI used a series of satellites carrying interceptor missiles that would attack the Soviet ICBMs shortly after launch; this boost phase intercept rendered MIRV impotent. The operational cost of such a system would be enormous, the US Air Force continually rejected such concepts. Development was cancelled in 1963. Through this period, the entire topic of BMD became controversial.
Early deployment plans were met with little interest, but by the late 1960s, public meetings on the Sentinel system were met by thousands of angry protesters. After thirty years of effort, only one such system would be built. A Soviet military A-35 anti-ballistic missile system was deployed around Moscow to intercept enemy ballistic missiles targeting the city or its surrounding areas; the A-35 was the only Soviet ABM system allowed under the 1972 Anti-Ballistic Missile Treaty. In development since the 1960s and in operation from 1971 until the 1990s, it featured the nuclear-tipped A350 exoatmospheric interceptor missile. George Shultz, Secretary of State under Reagan, suggests that a 1967 lecture by physicist Edward Teller (the so-called "father
Nuclear warfare is a military conflict or political strategy in which nuclear weaponry is used to inflict damage on the enemy. Nuclear weapons are weapons of mass destruction. A major nuclear exchange would have long-term effects from the fallout released, could lead to a "nuclear winter" that could last for decades, centuries, or millennia after the initial attack; some analysts dismiss the nuclear winter hypothesis, calculate that with nuclear weapon stockpiles at Cold War highs, although there would be billions of casualties, billions more rural people would survive. However, others have argued that secondary effects of a nuclear holocaust, such as nuclear famine and societal collapse, would cause every human on Earth to starve to death. So far, two nuclear weapons have been used in the course of warfare, both by the United States near the end of World War II. On August 6, 1945, a uranium gun-type device was detonated over the Japanese city of Hiroshima. Three days on August 9, a plutonium implosion-type device was detonated over the Japanese city of Nagasaki.
These two bombings resulted in the deaths of 120,000 people. After World War II, nuclear weapons were developed by the Soviet Union, the United Kingdom and the People's Republic of China, which contributed to the state of conflict and extreme tension that became known as the Cold War. In 1974, in 1998, two countries that were hostile toward each other, developed nuclear weapons. Israel and North Korea are thought to have developed stocks of nuclear weapons, though it is not known how many; the Israeli government has never admitted or denied to having nuclear weapons, although it is known to have constructed the reactor and reprocessing plant necessary for building nuclear weapons. South Africa manufactured several complete nuclear weapons in the 1980s, but subsequently became the first country to voluntarily destroy their domestically made weapons stocks and abandon further production. Nuclear weapons have been detonated on over 2,000 occasions for testing demonstrations. After the collapse of the Soviet Union in 1991 and the resultant end of the Cold War, the threat of a major nuclear war between the two nuclear superpowers was thought to have declined.
Since concern over nuclear weapons has shifted to the prevention of localized nuclear conflicts resulting from nuclear proliferation, the threat of nuclear terrorism. The possibility of using nuclear weapons in war is divided into two subgroups, each with different effects and fought with different types of nuclear armaments; the first, a limited nuclear war, refers to a small-scale use of nuclear weapons by two belligerents. A "limited nuclear war" could include targeting military facilities—either as an attempt to pre-emptively cripple the enemy's ability to attack as a defensive measure, or as a prelude to an invasion by conventional forces, as an offensive measure; this term could apply to any small-scale use of nuclear weapons that may involve military or civilian targets. The second, a full-scale nuclear war, could consist of large numbers of nuclear weapons used in an attack aimed at an entire country, including military and civilian targets; such an attack would certainly destroy the entire economic and military infrastructure of the target nation, would have a devastating effect on Earth's biosphere.
Some Cold War strategists such as Henry Kissinger argued that a limited nuclear war could be possible between two armed superpowers. Some predict, that a limited war could "escalate" into a full-scale nuclear war. Others have called limited nuclear war "global nuclear holocaust in slow motion", arguing that—once such a war took place—others would be sure to follow over a period of decades rendering the planet uninhabitable in the same way that a "full-scale nuclear war" between superpowers would, only taking a much longer path to the same result; the most optimistic predictions of the effects of a major nuclear exchange foresee the death of many millions of victims within a short period of time. More pessimistic predictions argue that a full-scale nuclear war could bring about the extinction of the human race, or at least its near extinction, with only a small number of survivors and a reduced quality of life and life expectancy for centuries afterward. However, such predictions, assuming total war with nuclear arsenals at Cold War highs, have not been without criticism.
Such a horrific catastrophe as global nuclear warfare would certainly cause permanent damage to most complex life on the planet, its ecosystems, the global climate. If predictions about the production of a nuclear winter are accurate, it would change the balance of global power, with countries such as Australia, New Zealand, China and Brazil predicted to become world superpowers if the Cold War led to a large-scale nuclear attack. A study presented at the annual meeting of the American Geophysical Union in December 2006 asserted that a small-scale regional nuclear war could produce as many direct fatalities as all of World War II and disrupt the global climate for a decade or more. In a regional nuclear conflict scenario in w
Northrop Grumman B-2 Spirit
The Northrop B-2 Spirit known as the Stealth Bomber, is an American heavy strategic bomber, featuring low observable stealth technology designed for penetrating dense anti-aircraft defenses. The bomber can deploy both conventional and thermonuclear weapons, such as eighty 500-pound class Mk 82 JDAM Global Positioning System-guided bombs, or sixteen 2,400-pound B83 nuclear bombs; the B-2 is the only acknowledged aircraft that can carry large air-to-surface standoff weapons in a stealth configuration. Development started under the "Advanced Technology Bomber" project during the Carter administration; the ATB project continued during the Reagan administration, but worries about delays in its introduction led to the reinstatement of the B-1 program. Program costs rose throughout development. Designed and manufactured by Northrop Northrop Grumman, the cost of each aircraft averaged US$737 million. Total procurement costs averaged $929 million per aircraft, which includes spare parts, equipment and software support.
The total program cost, which included development and testing, averaged $2.1 billion per aircraft in 1997. Because of its considerable capital and operating costs, the project was controversial in the U. S. Congress; the winding-down of the Cold War in the latter portion of the 1980s reduced the need for the aircraft, designed with the intention of penetrating Soviet airspace and attacking high-value targets. During the late 1980s and 1990s, Congress slashed plans to purchase 132 bombers to 21. In 2008, a B-2 was destroyed in a crash shortly after takeoff. Twenty B-2s are in service with the United States Air Force, which plans to operate them until 2032; the B-2 is capable of all-altitude attack missions up to 50,000 feet, with a range of more than 6,000 nautical miles on internal fuel and over 10,000 nautical miles with one midair refueling. It entered service in 1997 as the second aircraft designed to have advanced stealth technology after the Lockheed F-117 Nighthawk attack aircraft. Though designed as a nuclear bomber, the B-2 was first used in combat dropping conventional, non-nuclear ordnance in the Kosovo War in 1999.
It served in Iraq and Libya. By the mid-1970s, military aircraft designers had learned of a new method to avoid missiles and interceptors, known today as "stealth"; the concept was to build an aircraft with an airframe that deflected or absorbed radar signals so that little was reflected back to the radar unit. An aircraft having stealth characteristics would be able to fly nearly undetected and could be attacked only by weapons and systems not relying on radar. Although other detection measures existed, such as human observation, their short detection range allowed most aircraft to fly undetected at night. In 1974, DARPA requested information from U. S. aviation firms about the largest radar cross-section of an aircraft that would remain invisible to radars. Northrop and McDonnell Douglas were selected for further development. Lockheed had experience in this field due to developing the Lockheed A-12 and SR-71, which included a number of stealthy features, notably its canted vertical stabilizers, the use of composite materials in key locations, the overall surface finish in radar-absorbing paint.
A key improvement was the introduction of computer models used to predict the radar reflections from flat surfaces where collected data drove the design of a "faceted" aircraft. Development of the first such designs started in 1975 with "the hopeless diamond", a model Lockheed built to test the concept. Plans were well advanced by the summer of 1975, when DARPA started the Experimental Survivability Testbed project. Northrop and Lockheed were awarded contracts in the first round of testing. Lockheed received the sole award for the second test round in April 1976 leading to the Have Blue program and the F-117 stealth attack aircraft. Northrop had a classified technology demonstration aircraft, the Tacit Blue in development in 1979 at Area 51, it developed stealth technology, LO, fly-by-wire, curved surfaces, composite materials, electronic intelligence, Battlefield Surveillance Aircraft Experimental. "The stealth technology developed from the program was incorporated into other operational aircraft designs, including the B-2 stealth bomber".
By 1976, these programs had progressed to a position in which a long-range strategic stealth bomber appeared viable. President Carter became aware of these developments during 1977, it appears to have been one of the major reasons the B-1 was canceled. Further studies were ordered in early 1978, by which point the Have Blue platform had flown and proven the concepts. During the 1980 presidential election campaign in 1979, Ronald Reagan stated that Carter was weak on defense, used the B-1 as a prime example. In response, on 22 August 1980 the Carter administration publicly disclosed that the United States Department of Defense was working to develop stealth aircraft, including a bomber; the Advanced Technology Bomber program began in 1979. Full development of the black project followed, was funded under the code name "Aurora". After the evaluations of the companies' proposals, the ATB competition was narrowed to the Northrop/Boeing and Lockheed/Rockwell teams with each receiving a study contract for further work.
Both teams used flying wing designs. The Northrop proposal was code named "Seni
Nobel Prize in Physics
The Nobel Prize in Physics is a yearly award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions for humankind in the field of physics. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901; the first Nobel Prize in Physics was awarded to physicist Wilhelm Röntgen in recognition of the extraordinary services he rendered by the discovery of the remarkable rays. This award is administered by the Nobel Foundation and regarded as the most prestigious award that a scientist can receive in physics, it is presented in Stockholm at an annual ceremony on 10 December, the anniversary of Nobel's death. Through 2018, a total of 209 individuals have been awarded the prize. Only three women have won the Nobel Prize in Physics: Marie Curie in 1903, Maria Goeppert Mayer in 1963, Donna Strickland in 2018. Alfred Nobel, in his last will and testament, stated that his wealth be used to create a series of prizes for those who confer the "greatest benefit on mankind" in the fields of physics, peace, physiology or medicine, literature.
Though Nobel wrote several wills during his lifetime, the last one was written a year before he died and was signed at the Swedish-Norwegian Club in Paris on 27 November 1895. Nobel bequeathed 94% of his total assets, 31 million Swedish kronor, to establish and endow the five Nobel Prizes. Due to the level of skepticism surrounding the will, it was not until April 26, 1897 that it was approved by the Storting; the executors of his will were Ragnar Sohlman and Rudolf Lilljequist, who formed the Nobel Foundation to take care of Nobel's fortune and organise the prizes. The members of the Norwegian Nobel Committee who were to award the Peace Prize were appointed shortly after the will was approved; the prize-awarding organisations followed: the Karolinska Institutet on June 7, the Swedish Academy on June 9, the Royal Swedish Academy of Sciences on June 11. The Nobel Foundation reached an agreement on guidelines for how the Nobel Prize should be awarded. In 1900, the Nobel Foundation's newly created statutes were promulgated by King Oscar II.
According to Nobel's will, The Royal Swedish Academy of sciences were to award the Prize in Physics. A maximum of three Nobel laureates and two different works may be selected for the Nobel Prize in Physics. Compared with other Nobel Prizes, the nomination and selection process for the prize in Physics is long and rigorous; this is a key reason why it has grown in importance over the years to become the most important prize in Physics. The Nobel laureates are selected by the Nobel Committee for Physics, a Nobel Committee that consists of five members elected by The Royal Swedish Academy of Sciences. In the first stage that begins in September, around 3,000 people – selected university professors, Nobel Laureates in Physics and Chemistry, etc. – are sent confidential forms to nominate candidates. The completed nomination forms arrive at the Nobel Committee no than 31 January of the following year; these nominees are scrutinized and discussed by experts who narrow it to fifteen names. The committee submits a report with recommendations on the final candidates into the Academy, where, in the Physics Class, it is further discussed.
The Academy makes the final selection of the Laureates in Physics through a majority vote. The names of the nominees are never publicly announced, neither are they told that they have been considered for the prize. Nomination records are sealed for fifty years. While posthumous nominations are not permitted, awards can be made if the individual died in the months between the decision of the prize committee and the ceremony in December. Prior to 1974, posthumous awards were permitted; the rules for the Nobel Prize in Physics require that the significance of achievements being recognized has been "tested by time". In practice, it means that the lag between the discovery and the award is on the order of 20 years and can be much longer. For example, half of the 1983 Nobel Prize in Physics was awarded to Subrahmanyan Chandrasekhar for his work on stellar structure and evolution, done during the 1930s; as a downside of this approach, not all scientists live long enough for their work to be recognized.
Some important scientific discoveries are never considered for a prize, as the discoverers die by the time the impact of their work is appreciated. A Physics Nobel Prize laureate earns a gold medal, a diploma bearing a citation, a sum of money; the Nobel Prize medals, minted by Myntverket in Sweden and the Mint of Norway since 1902, are registered trademarks of the Nobel Foundation. Each medal has an image of Alfred Nobel in left profile on the obverse; the Nobel Prize medals for Physics, Physiology or Medicine, Literature have identical obverses, showing the image of Alfred Nobel and the years of his birth and death. Nobel's portrait appears on the obverse of the Nobel Peace Prize medal and the Medal for the Prize in Economics, but with a different design; the image on the reverse of a medal varies according to the institution awarding the prize. The reverse sides of the Nobel Prize medals for Chemistry and Physics share the same design of Nature, as a Goddess, whose veil is held up by the Genius of Science.
These medals and the ones for Physiology/Medicine and Literature were designed by Erik Lindberg in 1902. Nobel laureates receive a diploma directly from the hands of the
Deuterium is one of two stable isotopes of hydrogen. The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common protium has no neutron in the nucleus. Deuterium has a natural abundance in Earth's oceans of about one atom in 6420 of hydrogen, thus deuterium accounts for 0.0156% of all the occurring hydrogen in the oceans, while protium accounts for more than 99.98%. The abundance of deuterium changes from one kind of natural water to another; the deuterium isotope's name is formed from the Greek deuteros, meaning "second", to denote the two particles composing the nucleus. Deuterium was named in 1931 by Harold Urey; when the neutron was discovered in 1932, this made the nuclear structure of deuterium obvious, Urey won the Nobel Prize in 1934. Soon after deuterium's discovery and others produced samples of "heavy water" in which the deuterium content had been concentrated. Deuterium is destroyed in the interiors of stars faster. Other natural processes are thought to produce only an insignificant amount of deuterium.
Nearly all deuterium found in nature was produced in the Big Bang 13.8 billion years ago, as the basic or primordial ratio of hydrogen-1 to deuterium has its origin from that time. This is the ratio found in the gas giant planets, such as Jupiter. However, other astronomical bodies are found to have different ratios of deuterium to hydrogen-1; this is thought to be a result of natural isotope separation processes that occur from solar heating of ices in comets. Like the water cycle in Earth's weather, such heating processes may enrich deuterium with respect to protium; the analysis of deuterium/protium ratios in comets found results similar to the mean ratio in Earth's oceans. This reinforces theories; the deuterium/protium ratio of the comet 67P/Churyumov-Gerasimenko, as measured by the Rosetta space probe, is about three times that of earth water. This figure is the highest yet measured in a comet. Deuterium/protium ratios thus continue to be an active topic of research in both astronomy and climatology.
Deuterium is represented by the chemical symbol D. Since it is an isotope of hydrogen with mass number 2, it is represented by 2H. IUPAC allows 2H, although 2H is preferred. A distinct chemical symbol is used for convenience because of the isotope's common use in various scientific processes, its large mass difference with protium confers non-negligible chemical dissimilarities with protium-containing compounds, whereas the isotope weight ratios within other chemical elements are insignificant in this regard. In quantum mechanics the energy levels of electrons in atoms depend on the reduced mass of the system of electron and nucleus. For the hydrogen atom, the role of reduced mass is most seen in the Bohr model of the atom, where the reduced mass appears in a simple calculation of the Rydberg constant and Rydberg equation, but the reduced mass appears in the Schrödinger equation, the Dirac equation for calculating atomic energy levels; the reduced mass of the system in these equations is close to the mass of a single electron, but differs from it by a small amount about equal to the ratio of mass of the electron to the atomic nucleus.
For hydrogen, this amount is about 1837/1836, or 1.000545, for deuterium it is smaller: 3671/3670, or 1.0002725. The energies of spectroscopic lines for deuterium and light hydrogen therefore differ by the ratios of these two numbers, 1.000272. The wavelengths of all deuterium spectroscopic lines are shorter than the corresponding lines of light hydrogen, by a factor of 1.000272. In astronomical observation, this corresponds to a blue Doppler shift of 0.000272 times the speed of light, or 81.6 km/s. The differences are much more pronounced in vibrational spectroscopy such as infrared spectroscopy and Raman spectroscopy, in rotational spectra such as microwave spectroscopy because the reduced mass of the deuterium is markedly higher than that of protium. In nuclear magnetic resonance spectroscopy, deuterium has a different NMR frequency and is much less sensitive. Deuterated solvents are used in protium NMR to prevent the solvent from overlapping with the signal, although deuterium NMR on its own right is possible.
Deuterium is thought to have played an important role in setting the number and ratios of the elements that were formed in the Big Bang. Combining thermodynamics and the changes brought about by cosmic expansion, one can calculate the fraction of protons and neutrons based on the temperature at the point that the universe cooled enough to allow formation of nuclei; this calculation indicates seven protons for every neutron at the beginning of nucleogenesis, a ratio that would remain stable after nucleogenesis was over. This fraction was in favor of protons primarily because the lower mass of the proton favored their production; as the universe expanded, it cooled. Free neutrons and protons are less stable than helium nuclei, the protons and neutrons had a strong energetic reason to form helium-4. However, forming helium-4 requires the intermediate step of forming deuterium. Through much of the few minutes after the big bang during which nucleosynthesis could have occurred