1.3: An Inter-national System
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The early modern state was a coercive machinery designed to make war and to extract resources from society. Yet at the end of the eighteenth century, this machinery came to be radically transformed. Or rather, the ‘state’ was combined with a ‘nation’ forming a compound noun – the ‘nation-state’ – which was organised differently and pursued different goals. A nation, in contrast to a state, constitutes a community of people joined by a shared identity and by common social practices. Communities of various kinds have always existed but they now became, for the first time, a political concern. As a new breed of nationalist leaders came to argue, the nation should take over the state and make use of its institutional structures to further the nation’s ends. In one country after another the nationalists were successful in these aims. The nation added an interior life to the state, we might perhaps say; the nation was a soul added to the body of the early modern state machinery.
The revolutions that took place in Britain’s North American colonies in 1776, and in France in 1789, provided models for other nationalists to follow. ‘We the People of the United States’ – the first words of the Preamble to the US Constitution – was a phrase which itself would have been literally unthinkable in an earlier era. In France, the king was officially the only legitimate political actor and the people as a whole were excluded from politics. In addition, the power of the aristocracy and the church remained strong, above all in the countryside where they were the largest landowners. In the revolution of 1789, the old regime was overthrown and with it the entire social order. The French nation was from now on to be governed by the people, the nation, and in accordance with the principles of liberté , égalité et fraternité – liberty, equality and brotherhood.
Already in 1792, confrontation began between the revolutionary French nation and the kings of the rest of Europe. The wars were to go on for close to 25 years, most ferociously during the Napoleonic Wars of the early nineteenth century named after the French general, Napoleon Bonaparte, who made himself emperor of France. In contrast to the kings of the old regimes, the revolutionary French government could rely on the whole people to make contributions to the war due to the power of patriotism. This allowed first the revolutionaries, and later Napoleon, to create a formidable fighting machine which set about conquering Europe. Germany was quickly overrun and its sudden and complete defeat was a source of considerable embarrassment to all Germans. The Holy Roman Empire, by now in tatters, was finally dissolved in 1806 in the wake of Napoleon’s conquest. Yet, since there was no German state around which prospective nationalists could rally, the initial response was formulated in cultural rather than in military terms. Nationalist sentiment focused on the German language, German traditions and a shared sense of history. Before long a strong German nation began looking around for a unified German state. The goal was eventually achieved in 1871, after Germany – appropriately enough, perhaps – had defeated France in a war.
The Congress of Vienna of 1815, where a settlement was reached at the end of the Napoleonic Wars, was supposed to have returned Europe to its prerevolutionary ways. Yet, nationalist sentiments were growing across the continent and they constantly threatened to undermine the settlement. All over Europe national communities demanded to be included into the politics of their respective countries. Nationalism in the first part of the nineteenth century was a liberal sentiment concerning self-determination – the right of a people to determine its own fate. This programme had far-reaching implications for the way politics was organised domestically, but it also had profound ramifications for international politics. Most obviously, the idea of self-determination undermined the political legitimacy of Europe’s empires. If all the different peoples that these empires contained gained the right to determine their own fates, the map of Europe would have to be radically redrawn. In 1848 this prospect seemed to become a reality as nationalist uprisings quickly spread across the continent. Everywhere the people demanded the right to rule themselves.
Although the nationalist revolutions of 1848 were defeated by the political establishment, the sentiments themselves were impossible to control. Across Europe an increasingly prosperous middle-class demanded inclusion in the political system and their demands were increasingly expressed through the language of nationalism. The Finns wanted an independent Finland; the Bulgarians an independent Bulgaria; the Serbs an independent Serbia, and so on. In 1861 Italy too – long divided into separate city-states and dominated by the Church – became a unified country and an independent nation. Yet it was only with the conclusion of the First World War in 1918 that selfdetermination was acknowledged as a right. After the First World War most people in Europe formed their own nation-states.
As a result of the nationalist revolutions, the European international system became for the first time truly ‘inter-national’. That is, while the Westphalian system concerned relations between states, world affairs in the nineteenth century increasingly came to concern relations between nation-states. In fact, the word ‘international’ itself was coined only in 1783, by the British philosopher Jeremy Bentham. In most respects, however, the inter-national system continued to operate in much the same fashion as the Westphalian inter-state system. Nation-states claimed the same right to sovereignty which meant that they were formally equal to each other. Together, they interacted in an anarchical system in which power was decentralised and wars were a constant threat. Yet, the addition of the nation changed the nature of the interaction in crucial ways. For one thing, leaders who ruled their countries without at least the tacit support of their national communities were increasingly seen as illegitimate. This also meant that newly created nationstates such as Italy and Germany were automatically regarded as legitimate members of the European community of nations. They were legitimate since the people, in theory at least, were in charge.
There were also new hopes for world peace. While kings wage war for the sake of glory or personal gain, a people is believed to be more attuned to the aspirations of another people. Inspired by such hopes, liberal philosophers devised plans for how a ‘perpetual peace’ could be established. For some considerable time, these assumptions seemed quite feasible. The nineteenth century – or, more accurately, the period from 1815 to 1914 – was indeed an uncharacteristically peaceful period in European history. At the time, great hopes were associated with the increase in trade. As Adam Smith pointed out in The Wealth of Nations (1776), a nation is rich not because it has a lot of natural resources but because it has the capacity to manufacture things that others want. In order to capitalise on this capacity, you need to trade and the more you trade the wealthier you are likely to become. Once the quest for profits and market shares has become more important than the quest for a neighbouring state’s territory, world peace would naturally follow. In a world in which everyone is busy trading with each other, no one can afford to go to war.
By the twentieth century most of these liberal hopes were dashed. As the First World War demonstrated, nation-states could be as violent as the earlymodern states. In fact, nation-states were far more lethal, not least since they were able to involve their entire population in the war effort together with the entirety of its shared resources. The peaceful quest for profits and market shares had not replaced the anxious quest for security or the aggressive quest for pre-eminence. In the Second World War, the industrial might of the world’s most developed nations was employed for military ends with aerial bombardments of civilian populations, including the dropping of two atomic bombs on Japan. Between 1939 and 1945 over 60 million people were killed – around 2.5 per cent of the world’s population. This figure included the six million Jews exterminated by Germany in the Holocaust, which was one of the worst genocides in recorded history. After the Second World War, the military competition continued between the United States and the Soviet Union. This was known as a ‘cold war’ since the two superpowers never engaged each other in direct warfare, but they fought several wars by proxy such as those in Korea and Vietnam.


8: Central Asia
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- 8.3: Introduction
- Central Asia displayed a remarkable ability to embrace foreign influences, such as the Turkic migrations, expansion of Islam, and Mongol conquest, internalizing them and making them its own. Situated at the crossroads of many empires, Central Asia was tucked in between the Chinese, Europeans, Arabs, and Indians. There, just along the Great Silk Road, the region connected the Orient to the Occident and shaped the course of its history.
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- 8.5: Turkic Migrations
- Nomadic migration was the first major external influence that would be integrated into the culture of the region. Beginning with the Xiongnu (209 BCE – 93 CE), a long-term exodus of steppe peoples spread out of Mongolia and into Central Asia. Over time, they slowly Turkified the area, endowing it with a more nomadic character.
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- 8.6: Islam
- Islam was not the first foreign religion to arrive in Central Asia. In fact, the region had already been exposed to many foreign systems of belief prior to the coming of Islam in the seventh century. Local merchants conducting long-distance trade along the Silk Road came into contact with many different religious doctrines; the trade route served as a conveyor of not only goods but also concepts.
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- 8.7: The Mongol Era
- During the 13th Century, the Mongols reunited with the Turkic groups who had been expelled from the Orkhon Steppe over the course of a millennia. The Mongols created the largest empire in history. Perhaps the greatest obstacle was their own divisiveness. Inter-tribal strife was commonplace. But once they united, the Mongols expanded deep into Russia, China, India, and the Middle East.
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- 8.8: The Khanate of Chagatai
- Chagatai (1226 – 1241) was the second son of Genghis and his wife Börte. In 1227, he claimed his patrimonial territory designated as between the Caspian Sea and the Tarim Basin. The origins of the Chagatai Khanate shaped its political and demographic character. Chagatai obtained the core of Central Asia, pastureland located along the Kazakh steppe, as well as settled lands to the south in modern-day Uzbekistan. Instead of personal ambition for the position of great khan; he helped his brother Ög
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- 8.9: The Khanate of the Ilkhans (1265-1335)
- Hülegü Khan (1256 – 1265) was the grandson of Genghis Khan and son of Tolui. He served his brother Khan Möngke (1251 – 1259), and campaigned through the Middle East. While there, he whipped out the Assassins, a secret order of Shia entrenched in the mountains of Gilan province. He also destroyed the Abbasid capital of Baghdad in 1258, putting an end to the Caliphate. By 1260, Hülegü controlled parts of Armenia, Iraq, Anatolia, all of Azerbaijan, and all of Iran. Kublai Khan (1250 – 1294) had awa
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- 8.10: Timur
- Under Timur (1370 – 1405), Central Asia moved to the fore of world events. He developed a political arrangement that could harness the best attributes of each society, without the dangerous side effect of communal violence. The new political and military system was deeply ingrained in the political background of the Chagatai Khanate, and eliminated the Inju practice. Timur provided a framework for both societies to live in harmony.
Expansion of the Mongol Empire 1206–1294 superimposed on a modern political map of Eurasia. (CC BY-SA 2.5 Generic; Astrokey44 and Sting via Wikipedia).


3.4: Cultural Competence
The freedom to express one’s cultural beliefs is a fundamental right of all people. Nurses realize that people speak, behave, and act in many different ways due to the influential role that culture plays in their lives and their view of the world. Cultural competence is a lifelong process of applying evidence-based nursing in agreement with the cultural values, beliefs, worldview, and practices of patients to produce improved patient outcomes. [1] , [2] , [3]
Culturally-competent care requires nurses to combine their knowledge and skills with awareness, curiosity, and sensitivity about their patients’ cultural beliefs. It takes motivation, time, and practice to develop cultural competence, and it will evolve throughout your nursing career. Culturally competent nurses have the power to improve the quality of care leading to better health outcomes for culturally diverse patients. Nurses who accept and uphold the cultural values and beliefs of their patients are more likely to develop supportive and trusting relationships with their patients. In turn, this opens the way for optimal disease and injury prevention and leads towards positive health outcomes for all patients .
The roots of providing culturally-competent care are based on the original transcultural nursing theory developed by Dr. Madeleine Leininger. Transcultural nursing incorporates cultural beliefs and practices of individuals to help them maintain and regain health or to face death in a meaningful way. [4] See Figure 3.4 [5] for an image of Dr. Leininger. Read more about transcultural nursing theory in the following box.
Dr. Madeleine Leininger (1925-2012) founded the transcultural nursing theory. She was the first professional nurse to obtain a PhD in anthropology. She combined the “culture” concept from anthropology with the “care” concept from nursing and reformulated these concepts into “culture care.”
In the mid-1950s, no cultural knowledge base existed to guide nursing decisions or understand cultural behaviors as a way of providing therapeutic care. Leininger wrote the first books in the field and coined the term “culturally congruent care.” She developed and taught the first transcultural nursing course in 1966, and master’s and doctoral programs in transcultural nursing were launched shortly after. Dr. Leininger was honored as a Living Legend of the American Academy of Nursing in 1998.
Nurses have an ethical and moral obligation to provide culturally competent care to the patients they serve. [7] The “Respectful and Equitable Practice” Standard of Professional Performance set by the American Nurses Association (ANA) states that nurses must practice with cultural humility and inclusiveness. The ANA Code of Ethics also states that the nurse should collaborate with other health professionals, as well as the public, to protect human rights, fight discriminatory practices, and reduce disparities. [8] Additionally, the ANA Code of Ethics also states that nurses “are expected to be aware of their own cultural identifications in order to control their personal biases that may interfere with the therapeutic relationship. Self-awareness involves not only examining one’s culture but also examining perceptions and assumptions about the patient’s culture…nurses should possess knowledge and understanding how oppression, racism, discrimination, and stereotyping affect them personally and in their work.” [9]
Developing cultural competence begins in nursing school. [10] , [11] Culture is an integral part of life, but its impact is often implicit. It is easy to assume that others share the same cultural values that you do, but each individual has their own beliefs, values, and preferences. Begin the examination of your own cultural beliefs and feelings by answering the questions below. [12]
Reflect on the following questions carefully and contemplate your responses as you begin your journey of providing culturally responsive care as a nurse. (Questions are adapted from the Anti Defamation League’s “Imagine a World Without Hate” Personal Self-Assessment Anti-Bias Behavior). [13]
- Who are you? With what cultural group or subgroups do you identify?
- When you meet someone from another culture/country/place, do you try to learn more about them?
- Do you notice instances of bias, prejudice, discrimination, and stereotyping against people of other groups or cultures in your environment (home, school, work, TV programs or movies, restaurants, places where you shop)?
- Have you reflected on your own upbringing and childhood to better understand your own implicit biases and the ways you have internalized messages you received?
- Do you ever consider your use of language to avoid terms or phrases that may be degrading or hurtful to other groups?
- When other people use biased language and behavior, do you feel comfortable speaking up and asking them to refrain?

The Process of Developing Cultural Competence
Dr. Josephine Campinha-Bacote is an influential nursing theorist and researcher who developed a model of cultural competence. The model asserts there are specific characteristics that a nurse becoming culturally competent possesses, including cultural awareness, cultural knowledge, cultural skill, and cultural encounters. [14]
Cultural awareness is a deliberate, cognitive process in which health care providers become appreciative and sensitive to the values, beliefs, attitudes, practices, and problem-solving strategies of a patient’s culture. To become culturally aware, the nurse must undergo reflective exploration of personal cultural values while also becoming conscious of the cultural practices of others. In addition to reflecting on one’s own cultural values, the culturally competent nurse seeks to reverse harmful prejudices, ethnocentric views, and attitudes they have. Cultural awareness goes beyond a simple awareness of the existence of other cultures and involves an interest, curiosity, and appreciation of other cultures. Although cultural diversity training is typically a requirement for health care professionals, cultural desire refers to the intrinsic motivation and commitment on the part of a nurse to develop cultural awareness and cultural competency. [15]
Acquiring cultural knowledge is another important step towards becoming a culturally competent nurse. Cultural knowledge refers to seeking information about cultural health beliefs and values to understand patients’ world views. To acquire cultural knowledge, the nurse actively seeks information about other cultures, including common practices, beliefs, values, and customs, particularly for those cultures that are prevalent within the communities they serve. [16] Cultural knowledge also includes understanding the historical backgrounds of culturally diverse groups in society, as well as physiological variations and the incidence of certain health conditions in culturally diverse groups. Cultural knowledge is best obtained through cultural encounters with patients from diverse backgrounds to learn about individual variations that occur within cultural groups and to prevent stereotyping.
While obtaining cultural knowledge, it is important to demonstrate cultural sensitivity. Cultural sensitivity means being tolerant and accepting of cultural practices and beliefs of people. Cultural sensitivity is demonstrated when the nurse conveys nonjudgmental interest and respect through words and action and an understanding that some health care treatments may conflict with a person’s cultural beliefs. [17] Cultural sensitivity also implies a consciousness of the damaging effects of stereotyping, prejudice, or biases on patients and their well-being. Nurses who fail to act with cultural sensitivity may be viewed as uncaring or inconsiderate, causing a breakdown in trust for the patient and their family members. When a patient experiences nursing care that contradicts with their cultural beliefs, they may experience moral or ethical conflict, nonadherence, or emotional distress.
Cultural desire, awareness, sensitivity, and knowledge are the building blocks for developing cultural skill. Cultural skill is reflected by the nurse’s ability to gather and synthesize relevant cultural information about their patients while planning care and using culturally sensitive communication skills. Nurses with cultural skill provide care consistent with their patients’ cultural needs and deliberately take steps to secure a safe health care environment that is free of discrimination or intolerance. For example, a culturally skilled nurse will make space and seating available within a patient’s hospital room for accompanying family members when this support is valued by the patient. [18]
Cultural encounters is a process where the nurse directly engages in face-to-face cultural interactions and other types of encounters with clients from culturally diverse backgrounds in order to modify existing beliefs about a cultural group and to prevent possible stereotyping.
By developing the characteristics of cultural awareness, cultural knowledge, cultural skill, and cultural encounters, a nurse develops cultural competence.
- Centers for Disease Control and Prevention. (2020, October 21). Cultural competence in health and human services . https://npin.cdc.gov/pages/cultural-competence ↵
- Curtis, E., Jones, R., Tipene-Leach, D., Walker, C., Loring, B., Paine, S.-J., & Reid, P. (2019). Why cultural safety rather than cultural competency is required to achieve health equity: A literature review and recommended definition. International Journal for Equity in Health, 18, 174. https://doi.org/10.1186/s12939-019-1082-3 ↵
- Young, S., & Guo, K. (2016). Cultural diversity training: The necessity for cultural competence for healthcare providers and in nursing practice. The Health Care Manager, 35 (2), 94-102. https://doi.org/10.1097/hcm.0000000000000100 ↵
- Murphy, S. C. (2006). Mapping the literature of transcultural nursing. Journal of the Medical Library Association: JMLA, 94(2 Suppl), e143–e151. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1463039/ ↵
- “ Leininger.jpg ” by Juda712 is licensed under CC BY-SA 3.0 ↵
- Murphy, S. C. (2006). Mapping the literature of transcultural nursing. Journal of the Medical Library Association: JMLA , 94(2 Suppl), e143–e151. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1463039/ ↵
- Young, S., & Guo, K. (2016). Cultural diversity training: The necessity for cultural competence for healthcare providers and in nursing practice. The Health Care Manager, 35 (2), 94-102. https://doi.org/10.1097/hcm.0000000000000100 ↵
- American Nurses Association. (2015). Code of ethics for nurses with interpretive statements . American Nurses Association. https://www.nursingworld.org/practice-policy/nursing-excellence/ethics/code-of-ethics-for-nurses/coe-view-only / ↵
- American Nurses Association. (2015). Code of ethics for nurses with interpretive statements. American Nurses Association. https://www.nursingworld.org/practice-policy/nursing-excellence/ethics/code-of-ethics-for-nurses/coe-view-only/ ↵
- Gillson, S., & Cherian, N. (2019). The importance of teaching cultural diversity in baccalaureate nursing education. Journal of Cultural Diversity, 26 (3), 85–88. ↵
- Gavin-Knecht, J., Fontana, J. S., Fischer, B., Spitz, K. R., & Tetreault, J. N. (2018). An investigation of the development of cultural competence in baccalaureate nursing students: A mixed methods study. Journal of Cultural Diversity, 26 (3), 89-95. ↵
- Zeran, V. (2016). Cultural competency and safety in nursing education: A case study. Northern Review, 43 , 105–115. https://thenorthernreview.ca/index.php/nr/article/view/591 ↵
- Anti-Defamation League. (2013). Imagine a world without hate: Anti-Defamation League 2012 Annual Report . https://www.adl.org/media/4528/download . ↵
- Transcultural C.A.R.E. Associates. (2020). The Process of Cultural Competemility. http://transculturalcare.net/the-process-of-cultural-competence-in-the-delivery-of-healthcare-services/ ↵
- Anti-Defamation League. (2013). Imagine a world without hate: Anti-Defamation League 2012 Annual Report . https://www.adl.org/media/4528/download . ↵
- Gillson, S., & Cherian, N. (2019). The importance of teaching cultural diversity in baccalaureate nursing education. Journal of Cultural Diversity, 26 (3), 85–88. ↵
- Curtis, E., Jones, R., Tipene-Leach, D., Walker, C., Loring, B., Paine, S.-J., & Reid, P. (2019). Why cultural safety rather than cultural competency is required to achieve health equity: A literature review and recommended definition. International Journal for Equity in Health, 18 , 174. https://doi.org/10.1186/s12939-019-1082-3 ↵
- Brooks, L., Manias, E., & Bloomer, M. (2019). Culturally sensitive communication in healthcare: A concept analysis. Collegian, 26 (3), 383-391. https://doi.org/10.1016/j.colegn.2018.09.007 ↵


1.21: Hot and Cold Relics of the Big Bang
In the previous chapter we worked out the abundance of a massive fermionic particles species, \(\chi\) and antiparticle \(\bar \chi\) under a particular set of assumptions including kinetic equilibrium as well as chemical equilibrium maintained by reactions that set the chemical potentials \(\mu_\chi = \mu_{\bar \chi} = 0\). We saw that, given these assumptions, if we artificially set the initial values of \(n_\chi\) and \(n_{\bar \chi}\) to zero we would, at early times when \(m_\chi c^2 \ll k_B T\), rapidly evolve to an abundance of them very similar to that of the photons -- only differing by the number of degrees of freedom, \(g\), and the slight difference that arises due to the small difference in the form of \(f\) for fermionic and bosonic species. As long as all our assumptions remain valid, the abundance of the species would eventually start to decrease as \(k_B T\) dropped below \(m_\chi c^2\), suppressed by the Boltzmann factor \(\exp(-m_\chi c^2/(k_BT))\). In this scenario, assuming that today \(m_\chi c^2 \gg k_B T\), we would have negligible amounts of these particles still around today.
Particles that at one time were driven to kinetic and chemical equilibrium abundances in the big bang, and survive to today are called "thermal relics." Survival to today sometimes require a departure from the equilibrium abundances worked out in the previous chapter. These departures, in some cases, occur because the reactions that maintained chemical equilibrium become too slow to continue to do so as the temperature drops and the equilibrium abundance changes. We refer to the process of the reactions becoming slow as "freeze-out." If freeze-out happens when the particles are still relativistic we call them "hot relics," if it occurs when they are non-relativistic we call them "cold relics." In this chapter we discuss hot and cold relics of the big bang.
Freeze-out
Calculation of reaction rates, and a complete treatment of non-equilibrium abundance evolution, is beyond the scope of this course. Here we summarize some important results:
- When per-particle reaction rates, \(\Gamma\), are much greater than the expansion rate, \(H\), then the abundance is rapidly driven to an equilibrium amount with chemical potentials governed by the reactions in question.
- The ratio \(\Gamma/H\) in general decreases over time as the universe expands and therefore temperature and density drops. Thus reactions tend to go from being "fast" (able to maintain equilibrium) to being "slow" (not able to maintain equilibrium). Note that both \(H\) and \(\Gamma\) drop with time, but \(\Gamma\) usually drops more rapidly.
- When \(\Gamma << H\) for reactions that create and destroy \(\chi\) and \(\bar \chi\) particles then it is a good approximation to ignore these processes and assume their numbers just dilute with the expansion. We therefore have \(n_\chi \propto a^{-3}\) and \(n_{\bar \chi} \propto a^{-3}\).
- In fact, a fairly good approximation is to define a freeze-out temperature \(T_{\rm F}\) to be the temperature at which \(\Gamma = H\) and then assume the equilibrium abundance for \(T > T_{\rm F}\) and \(n_\chi \propto a^{-3}\) for \(T < T_{\rm F}\), with the proportionality constant chosen so as to have a continuous abundance curve at \(T=T_{\rm F}\).
| Solid curve: Equilibrium abundance for a massive fermionic species with \(g=2\) and zero chemical potential relative to massless bosonic species with \(g=2\). This is very similar to what you were asked to sketch in the previous chapter since \(n_\gamma \propto a^{-3}\). Dashed curves: the same ratio for two cold relics over time, with differing values of \(T_{\rm F}\). These are considered cold relics since they freeze out at \(m_\chi c^2 > k_B T\). Note that the later the occurrence of freeze-out, the lower the relic abundance. Not shown: hot relics, which would freeze out at \(T < T_{\rm F}\). Note that for hot relics the relic abundance is independent of when freeze-out occurs since the equilibrium curve is flat there. |
Hot Relics: Photons and Neutrinos
At \(z > 10^7\) or so, corresponding to temperatures greater than about \(k_B T = 4\) keV reactions such as
\[e^-+p^+ \leftarrow \rightarrow e^-+p^+ + \gamma\]
that create or destroy photons become slow. Since this happens while photons are relativistic (since photons are always relativistic), photons qualify as hot relics. This is the relic background predicted by Alpher and Herman in the 1940s and serendipitously discovered by Penzias and Wilson in 1964. We know it today as the cosmic microwave background (CMB). With a temperature of about 2.73\(^\circ\)K the intensity of this light peaks in the microwave region of the spectrum. The spectrum has been measured with high precision and found to be consistent with a black body.
Various different types of distortion away from black body have been constrained by these measurements, including a non-zero chemical potential. Using data from the FIRAS instrument on the COBE satellite, cosmologists have placed a limit of \(\mu/(k_BT) < 10^{-5}\). This level of consistency with a black body spectrum places constraints on possible scenarios in which energy is injected into the plasma of the big bang, for example from some particle species that decays while out of equilibrium into two photons. Such injection of energy would heat up the plasma. If the energy injection occurred at \(z > 10^7\), the photon-number-changing reactions would ensure that the chemical potential remained zero, with the result that we would see no evidence in the spectrum of the CMB today. If the energy injection occurred at lower redshifts then the lack of photon-number-changing reactions would lead to a non-zero chemical potential. With a sufficient amount of energy injected, this distortion of the spectrum away from that of a black body would be discernible with current data.
Neutrinos are subatomic particles first inferred from examination of radioactive decay products. For example, a free neutron will decay to an electron, a proton and a neutrino. If one measures the momentum of the electron and proton from a neutron decaying at rest, one finds that either energy and momentum conservation is violated, or there must be an unseen additional decay product: the neutrino. There are three types of neutrinos in the standard model of particle physics, one paired with each of the three charged leptons in the standard model. Together these are the electron and the electron neutrino, the muon and the muon neutrino, and the tauon and the tau neutrino.
Unlike the charged leptons, which interact with other particles via both the weak and electromagnetic forces, neutrinos only interact via the weak force. This force is appropriately named: the weak interactions are very weak. Neutrinos produced in nuclear reactions in the sun stream straight out of the sun hardly interacting at all, whereas photons produced in nuclear reactions scatter around the plasma of the sun for millions of years before finally making it to the surface. Despite the weakness of the interactions, at sufficiently early times the universe was hot and dense enough that reactions that produce and destroy neutrinos were occurring rapidly, as well as neutrino scattering reactions that exchange kinetic energy. The universe was in this state at temperatures \(k_B T > 0.8\) MeV. Neutrinos were highly relativistic at this time, and thus they qualify as hot relics.
We have strong indirect indications of the existence of a relic background of cosmic neutrinos. Due to the weakness of their interactions, their low energy today (having been cooled by the expansion), and the drop in reaction rates with energy, it is exceedingly difficult, and perhaps practically impossible, to directly detect the cosmic neutrino background.
When we study Big Bang Nucleosynthesis (BBN) we will see some of the indirect evidence for the neutrino background. The energy density of the cosmic neutrino background, \(\epsilon_\nu\), contributes to the total energy density and thus, via the Friedmann equation, to the expansion rate. The existence of the neutrinos means that, at a given temperature, the expansion rate is faster than it would be otherwise. We will see that this increased expansion rate affects the abundances of light elements. We will study the case of helium-4 in particular.
I have a particular interest in neutrinos and the cosmic neutrino background. The neutrinos have a somewhat-unique influence on the oscillations of standing waves in the plasma of the big bang, which follows from the fact that they can stream through the plasma at the speed of light, unlike the photons that readily scatter off of free electrons. A result of this free-streaming is that gravitational potentials that drive the standing wave oscillations decay more rapidly than they would otherwise, fast enough that they alter the temporal phases of the oscillations, an effect that is observable in the statistical properties of the cosmic microwave background. My graduate students and I were the first to isolate this effect in the data. The paper is in Physical Review Letters. There is a popular account in Scientific American, and in some blog posts including this one , and this one which is somewhat overblown about the significance, but provides, as background material, a nice summary of our historical progress on understanding the big bang. The work also led to an article about me and my research and teaching in the Sacramento Bee.
Box \(\PageIndex{1}\)
Exercise 21.1.1 : At \(z \simeq 10^7 \) some reactions involving photons became slow, and at \(z \simeq 10^3\) some other reactions involving photons became slow. Which epoch corresponds to freeze-out for photons? What is the significance of the later epoch?
Exercise 21.1.2: A weaker interaction (slower production and annihilation rates) usually means freeze-out happens earlier or later?
Exercise 21.1.3: For hot relics, why is the abundance today relatively insensitive to freeze-out temperature?
Exercise 21.1.4: Why do additional species of light particles potentially lead to a faster expansion rate in the early universe at a given temperature?
Cold Relics: The WIMP Miracle (or Misleading Coincidence?)
We've learned so far that photons and neutrinos are produced thermally in the big bang. Potentially there are also particles produced in the big bang that are not in the standard model of particle physics. The cold dark matter that seems to dominate the mass density of the universe might be such a particle. Here we consider a general class of models of dark matter in which it is a Weakly Interacting Massive Particle (WIMP).
WIMPs have received a lot of attention. There are major experimental efforts underway to detect WIMPs indirectly (by seeing evidence of their annihilation into standard model decay products in regions of dense dark matter such as the galactic center or centers of dwarf galaxies) to detect them directly (via rare interactions of dark matter with baryonic matter in a sensitive detector), and to produce them in particle colliders such as the Large Hadron Collider in Europe.
This attention follows, at least in part, from a theoretical result called the "WIMP Miracle." The miracle is as follows. An idea in particle physics called "supersymmetry," which is attractive to particle physics because of problems it solves having nothing to do with cosmological observations, leads to a collection of new particles, one of which could quite naturally turn out to be the dark matter. If one works out reaction rates for these supersymmetric particles, and when freeze-out occurs for the lightest one (which is the only stable one), the lightest one can easily have (depending on choices of free parameters) the right relic abundance today. More generally, supersymmetry offers a solution to the "hierarchy" problem of particle physics, a problem associated with the weak interaction scale. Weak interaction particle cross sections are about what one needs in order to end up with relic abundances today roughly consistent with the mass density of dark matter as inferred from cosmological observations.
What is the relationship between particle cross sections and their relic abundance? Particle interaction cross sections control reaction rates. The smaller the cross sections, the slower the reaction rates. The slower the reaction rates, the earlier freeze-out occurs. The earlier freeze-out occurs (not in terms of time itself, but in terms of the time-like variable \(m_\chi c^2/(k_BT)\)), the higher the resulting abundance. A weak interaction level of cross section (which the supersymmetric particles generally have) turns out to be just right for getting the right density of dark matter today. This is the WIMP miracle.
Or... it could be just a coincidence that has thrown us off the right path toward finding out what the dark matter really is. So far, searches for supersymmmetric dark matter, after decades of searching and improving sensitivity, have resulted in upper limits. There are some claimed detections, but none of these have yet been reproduced by other experiments.
Box \(\PageIndex{2}\)
Exercise 21.21 : For cold relics, why are weaker interactions associated with higher relic abundances?
Exercise 21.2.2: If there is a new particle physics theory that has in it new particles, or new interactions, or both, why is it important to consider cosmological consequences? What might they be?
Homework
21.1: Starting when \(k_BT \simeq 0.511\) MeV, (so that \(m_ec^2/(k_BT) = 1\) ) the number density of electrons and positrons, relative to photons, begins to drop. Eventually, almost all the positrons and electrons are gone. This whole process occurs after the neutrinos have decoupled (at \(k_BT = 0.8\) MeV) so the annihilations of the electrons and positrons all goes into heating up the photons (some goes into the remaining electrons and nuclei, but their number densities and kinetic energy densities are tiny compared to photon number an energy densities). Assuming that the process does not change the entropy in a comoving region, show that the end result is that neutrinos are cooler relative to photons by an amount
\[T_\nu/T_\gamma = \left(\frac{4}{11}\right)^{1/3}.\]
You'll need to use the fact that the entropy density (physical density, not comoving density) for a relativistic species is
\[s=\frac{2\pi^2}{45}g k_B \left(\frac{k_BT}{\hbar c}\right)^3\]
for bosons and
\[s=\frac{7}{8}\frac{2\pi^2}{45}g k_B \left(\frac{k_BT}{\hbar c}\right)^3\]
for fermions.
Some hints:
1) You have a conserved quantity. Evaluate it at a time when electrons and positrons are relativistic and at a later time when the electrons and positrons have all disappeared. Use this to figure out how the early temperature is related to the later temperature.
2) Since the neutrinos stop interacting with themselves and with electrons, positrons, and photons, their entropy is conserved separately from the electrons, positrons, and photons. The entropy of the electron, positron, and photon system is also conserved.
3) Electrons are spin 1/2 so have \(g=2\). Same for positrons.
4) Initially neutrinos, electrons, positrons, and photons are exchanging kinetic energy and so their initial temperatures (prior to the electrons and positrons starting to disappear) are equal.
21.2: From atmospheric neutrino oscillations, we know that the lightest that the most massive neutrino can be is 0.048 eV/\(c^2\). Assuming it's as light as possible, what is a typical speed for the most massive neutrinos in the cosmic neutrino background today? (I'm looking for something correct to within a factor of 2 or so). Keep in mind that neutrinos freeze out while still relativistic so they keep \(f = [\exp(pc/k_BT)+1]^{-1}\) even though that is not equal to \([\exp(E/(k_BT)) +1]^{-1}\). For such a distribution a typical value of \(pc\) is \(k_B T\).
21.3: The number density of cosmic microwave background photons today is about 400/cm\(^{-3}\). Assuming there are 3 species of neutrino, each with \(g=2\), and that their temperature is reduced relative to photons as described in problem 22.1, what is the number density of cosmic neutrinos today?
21.4: Combining results from 22.2 and 22.3, give an estimate of the number of highest-mass cosmic neutrinos flowing through you per second.
21.5: The baryon-to-photon ratio \(n_b/n_\gamma\) is about \(6 \times 10^{-10}\). Assuming, for simplicity, that all the baryons are protons, calculate the temperature at which there is one photon with energy above 13.6 eV for every baryon. You may use this result (which you could obtain by integrating over the photon energy distribution): the fraction of photons with energy above \(E\) is
\[\frac{n(>E)}{n} \simeq \left(\frac{E}{k_BT}\right)^2\exp\left(\frac{-E}{k_BT}\right) \]
for \(E >> k_BT\).


6.5: Sample problems and solutions
Katie, an amateur snowboarder, rests at the top of hill inclined by an angle of \(\theta=50^{\circ}\) with respect to the horizontal, as shown in Figure \(\PageIndex{1}\). She gracefully slides down the hill until she face-plants into a large pile of snow at the bottom, \(40\text{m}\) from where she started. If the coefficient of kinetic friction between Katie’s snowboard and the hill is \(\mu_k=0.45\) , how long elapses between when she starts to glide and when she face plants?
- Answer
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Before trying to solve the problem, we should think of the strategy that will allow us to model the time that it takes to arrive at the bottom. We know that Newton’s Second Law relates the forces on Katie to her acceleration. If we build a model of the forces on Katie, we can then determine her acceleration. Once we know her acceleration, we can use kinematics to determine how long it takes for her to cover the distance of \(40\text{m}\) .
The forces exerted on Katie are:
- \(\vec F_g\) , her weight.
- \(\vec N\) , a normal force exerted by the slope.
- \(\vec f_k\) , a force of kinetic friction exerted by the slope, with magnitude \(f_k=\mu_kN\)
First, we write Newton's Second Law of motion for this situation:
\[\begin{aligned} \sum \vec{F}_{\text{external}} = \vec{N}+\vec{F}_g+\vec{f}_k=m \vec{a}\end{aligned}\]
This allows us to build a free-body diagram for the forces on Katie, as shown in the Figure below. Since Katie will glide down the slope, her acceleration will be parallel to the slope and downwards, which we showed with a thicker arrow on the free-body diagram. Our free-body diagram also shows the coordinate system that we chose, with the \(x\) axis pointing parallel to the acceleration.
With a free-body diagram, we can write the \(x\) and \(y\) components of Newton’s Second Law. In the \(x\) direction, both the force of friction and the weight have components. The force of friction is in the negative \(x\) direction, whereas the component of gravity in the \(x\) direction is \(F_g\sin\theta\) . The acceleration vector is also in the \(x\) direction. Putting this altogether into Newton’s Second Law: \[\begin{aligned} \sum F_x = F_g\sin\theta - f_k &= ma\\ \therefore mg\sin\theta -\mu_k N &= ma\end{aligned}\] where we used the fact that the weight is given by \(mg\) ( \(m\) is Katie’s mass) and the magnitude of the force of friction is given by \(f_k=\mu_kN\) .
Next, we write out the \(y\) component of Newton’s Second Law. The normal force is in the positive \(y\) direction, whereas the component of gravity in the \(y\) direction is \(-F_g\cos\theta\) . The acceleration has no component in the \(y\) direction. Putting this into Newton’s Second Law: \[\begin{aligned} \sum F_y = N-F_g\cos\theta &=0\\ \therefore N-mg\cos\theta &=0\end{aligned}\]
We now have two equations that describe Katie’s motion: \[\begin{aligned} mg\sin\theta -\mu_k N &= ma\\ N-mg\cos\theta &=0\end{aligned}\] We have three unknowns, \(m\) , \(N\) , and \(a\) , but only two equations! Hopefully, one of these will cancel out! At this point, all of the physics for the problem is done! We can now proceed to solve these equations to find the acceleration. The second equation allows us to solve for the normal force, \(N=mg\cos\theta\) , which we substitute into the first equation: \[\begin{aligned} mg\sin\theta -\mu_k N &= ma\\ \therefore mg\sin\theta -\mu_k mg\cos\theta &= ma\\\end{aligned}\] As you can see, the mass \(m\) can be canceled out of this equation, and we can find the acceleration:
\(\begin{aligned} a&=g\sin\theta-\mu_{k}g\cos\theta \\ &=g(\sin\theta -\mu_{k}\cos\theta ) \\ &=(9.8\text{N/kg})(\sin (50^{\circ})-(0.45)\cos (50^{\circ})) \\ &=4.67\text{N/kg}=4.67\text{m/s}^2 \end{aligned}\)
Knowing that Katie’s initial velocity is \(v_{0x}=0\text{m/s}\) , her acceleration is \(a_x=a=4.67\text{m/s}^{2}\) in the \(x\) direction (the same direction as the slope), and the distance that she must travel is \(x=40\text{m}\) , we can find the time it takes for her to face-plant. If we set the origin of the \(x\) axis where she starts (so that her initial position along the \(x\) axis, \(x_0=0\) ), the distance that she covered in the time, \(t\) , is given by: \[\begin{aligned} x(t)&=x_0+v_{0x}t+\frac{1}{2}at^2\\ 40\text{m}&=(0)+(0)t+\frac{1}{2}(1.31\text{m/s}^{2})t^2\\ \therefore t&=\sqrt{\frac{2(40\text{m})}{(4.67\text{m/s}^{2})}}=4.14\text{s}\end{aligned}\] Katie has \(4.14\text{s}\) of gliding bliss before face-planting into the large pile of snow.
Two boxes with masses, \(m_1\) and \(m_2\) , respectively, are placed on top of one another, as shown in Figure \(\PageIndex{3}\) . The coefficient of static friction between the two boxes and between the boxes and the ground is \(\mu_s=0.3\) . A constant force, \(\vec F\) , is exerted on box 2, as shown. Show that it is impossible for box 1 to accelerate.
- Answer
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The only way for box 1 to accelerate is if box 2 “drags” box 1 along with it through a force of friction exerted at the interface between box 1 and box 2. We need to show that the force of (static) friction exerted by the ground on box 1 will always be at least as large as the force of friction exerted by box 2 on box 1. The largest force of friction that box 2 can exert on box 1 is a force of static friction, so we model all forces between surfaces as forces of static friction.
The forces on box 2 are:
- \(\vec F_{2g}\) , its weight.
- \(\vec N_2\) , a normal exerted by box 1.
- \(\vec f_{2s}\) , a force of static friction exerted by box 1.
- \(\vec F\) , the applied force.
The forces on box 1 are:
- \(\vec F_{1g}\) , its weight.
- \(-\vec N_2\) , a normal force exerted by box 2 (downwards).
- \(-\vec f_{2s}\) , a force of static friction exerted by box 2.
- \(\vec N_1\) , a normal force exerted by the ground.
- \(\vec f_{1s}\) , a force of static friction exerted by the ground.
The are illustrated in the free-body diagram in Figure \(\PageIndex{4}\) .
Considering the \(y\) component of Newton’s Second Law for box 2 (the top box), we can find the value of the normal force exerted by box 1: \[\begin{aligned} \sum F_y &= N_2 - F_{2g} = 0\\ \therefore N_2 &= m_2 g\end{aligned}\] The maximal magnitude of the force of static friction, \(f_{2s}\) , between the two boxes is given by: \[\begin{aligned} f_{2s} = \mu_sN_2 = \mu_s m_2g\end{aligned}\] This is the maximal magnitude of the force that can accelerate box 1. Considering the \(y\) component of Newton’s Second Law applied to box 1, we can find \(N_1\) , the normal force exerted by the ground: \[\begin{aligned} \sum F_y = N_1 - F_{1g} - N_2 = 0\\ \therefore N_1 = F_{1g}+N_2 = (m_1+m_2)g\end{aligned}\] The force of static friction exerted by the ground on box 1 will be in the opposite direction as the force of static friction exerted by box 2. The maximal magnitude of the force of static friction exerted by the ground is given by: \[\begin{aligned} f_{1s} = \mu_sN_1 = \mu_s (m_1+m_2)g\end{aligned}\] We can see that the maximal force of static friction exerted by the ground will always exceed the magnitude of the force of static friction exerted by box 2. It is thus impossible to push on box 2 to make box 1 move (as long as the force of static friction between the two boxes and the box and the ground are the same).


3.1.7: Old Age and Death
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In Western culture most people seem to focus on youth. Old age and death are to be avoided, even feared. And yet, both are inevitable, unless we die young, something that is even less desirable than eventually dying of old age. What is most curious, however, is that there is nothing in our culture to suggest that death is something bad. Most people believe in life after death, and that good people go to Heaven. So why would we want to avoid that? In many other cultures, death is not viewed with the same finality as it is in Western culture, and ancestors are revered, and even worshipped. Even within Western culture, there are those who embrace the later years in life, and who do not fear death. These are the perspectives we will examine here.
Growing Old: Or Older and Growing?
The title for this section was taken from an essay written by Carl Rogers (1980). Rogers was 75 years old at the time, and he was looking back on the previous 10 years of his life. Rogers was experiencing a number of physical problems associated with the natural deterioration of his body due to advanced age, such as some loss of vision and arthritis in his right shoulder (making it impossible to enjoy playing Frisbee), but he still enjoyed 4 mile walks on the beach and felt physically strong in many ways. As for his career, from the age of 65 to 75 years old he had been very productive, publishing numerous books and articles. He also led many workshops and encounter groups, including some that required him to travel around the world. Professionally he began to take many risks, experimenting with his theories and workshops in ways he might never have considered earlier in his career. As it became necessary for him to rely on others for help, due to his slowing down with age, he also found that he was able to form far more intimate relationships with those colleague/friends who helped him. Even as his wife approached death during those years, he found that the struggle and pain led him to realize just how much he had loved her. Ten years later, as he turned 85 years old, Rogers wrote another essay, On Reaching 85 (Rogers, 1989). Once again, he had been very productive during the 10 years between being 75 and 85 years old, most notably leading a number of peace conferences that led to his nomination for a Nobel Peace Prize. He felt deeply privileged to have lived long enough to see the great international influence of his work. There can be little doubt that when his life ended, which was actually before this essay was published (he wrote the essay, turned 85, and died 1 month later), he had experienced integrity and wisdom:
I hope it is clear that my life at eighty-five is better than anything I could have planned, dreamed of, or expected. And I cannot close without at least mentioning the love relationships that nurture me, enrich my being, and invigorate my life. I do not know when I will die, but I do know that I will have lived a full and exciting eighty-five years! (pg. 58; Rogers, 1989)
Erikson, in contrast, knew something of the despair that contrasts the integrity one hopes for in old age. Never having known his own father, which resulted in an unending identity crisis, he struggled with feelings of having been an inadequate father himself. As famous as he was, he desired the ultimate recognition of a Nobel Prize, and was disappointed that Ghandi’s Truth only won a Pulitzer Prize. He was also very sensitive to criticism in any form. As his own daughter pointed out, it is a tragic irony that individuals such as Erikson do not accept the vast majority of approval as commentary on their real self, but they do experience every shred of criticism as being very real (Bloland, 2005). Erikson himself said that even when a person developed a clear identity following adolescence, significant life events later on can precipitate a renewal of the identity crisis. One can only imagine the terrible psychological burden of sending away their baby Neil to die alone and secretly in a hospital, only to have him live for 21 years. Under such circumstances, Erikson described the search for a new identity as frantic (Evans, 1964).
One of the most interesting, important, and potentially enjoyable consequences of old age is the likelihood that one has grandchildren. All too often in American culture there are challenges to the relationships between grandparents and grandchildren. Families move across the country, they are broken apart by divorce, and, in general, our culture does not place value on the experiences of the elderly. However, only the elderly can provide generational continuity, which can be an important aspect of one’s identity. For the grandparents, they can play a vital role in supporting the emotional development of their grandchildren, especially following a traumatic event such as divorce. They can provide adolescents with hope for continued development and purpose throughout life, a prospect that might seem quite difficult for an adolescent to comprehend on their own. And perhaps most importantly, they can simply spend quality time with their grandchildren, without the burden of being responsible for the day-to-day raising of the child (Erikson, 1959; Erikson & Erikson, 1997; Erikson, Erikson, & Kivnick, 1986). As shared by Joan Erikson, a grandmother and her grandchild can congratulate themselves for doing a marvelous job picking blueberries, while experiencing the reality of the life cycle:
After a while I did need to sit down on a rock and rest a bit, but not he. He continued for a moment or so and then stood up very straight in front of me to clarify essentials. “Nama,” he said, “you are old and I am new” - an unchallengeable pronouncement. (pg. 115; Erikson & Erikson, 1997)
Figure \(\PageIndex{1}\)
Healthy relationships between grandparents and their grandchildren can benefit everyone in the family. In particular, grandparents provide a generational link that can help young people form their own identities.
While Carl Rogers and Joan Erikson seemed to accept old age and achieve integrity, Erik Erikson struggled with despair, despite his international acclaim and many obvious accomplishments. Thus, it should become clear that an individual’s point of view is an important aspect of one’s identity. In Still Here (Ram Dass, 2000), Ram Dass, a former Harvard University psychologist turned renowned guru of Bhakti Yoga and Kirtan (see Chapter 17), acknowledges the challenges of old age: physical problems, illness, loneliness, embarrassment, powerlessness, loss of role/meaning, depression, and even senility. The suffering associated with these conditions is, however, self-induced, and one can choose mindfully to not suffer. Whether or not one suffers, therefore, and whether or not one approaches the end of life with relative integrity or despair, is in many ways a choice. And that choice will have a dramatic effect on the final stage of life: death.
Death and Dying
It is important to begin by distinguishing between death and dying . Death is the end of life, and as far as scientific psychology is concerned, no one alive has been able to study death itself. Dying is a process that occurs when death is imminent, but does not come immediately. The dying process begins either with old age or the diagnosis of a terminal illness. Elisabeth Kubler-Ross is well-known for her research on the dying process, as are the five stages that she described in On Death and Dying (1969): Denial and Isolation; Anger; Bargaining; Depression; and Acceptance. When diagnosed with a terminal illness, most people naturally respond with the common defense mechanism of denial, but there is more to it. Many psychology textbooks do not address the second aspect of this first stage: isolation. Denial is usually temporary, but the dying person may still not be ready or even able to talk about their death, so they isolate themselves psychologically. Unfortunately, hospital staff members often foster this isolation, because of their own fears and discomfort regarding death. Kubler-Ross and her colleagues found it quite difficult to stop hospital staff members from encouraging the isolation of patients clinging to denial, including such simple tasks as keeping the patient’s door open so that people passing by could look in and vice versa. The final stage of acceptance, according to Kubler-Ross, is one that many patients do not achieve. Many people fear death, and Western culture, due in part to its emphasis on science and medicine, and its movement away from religion, encourages people to challenge death. But for those who fight, struggle, and hope to the very end, even they eventually “just cannot make it anymore” (Kubler-Ross, 1969).
There are, however, many people who do come to accept the inevitability of death, either as a result of illness or old age. Erikson seemed to finally be at peace at the very end of his life, smiling whenever he recognized his wife or daughter:
I was deeply touched on one visit to Dad when a flash of pleasure crossed his face as I entered the room, and he said faintly to himself, Meine Tochter (“my daughter” in his native tongue). (pg. 204; Bloland, 2005)
Carl Rogers was largely unconcerned about death, he seldom thought about it. He was, however, quite interested in the work of Kubler-Ross, particularly after he experienced his wife’s dying process. One night, when his wife was near death, he told her that she should not feel obligated to live, all was well with her family, and that she should feel free to live or die, as she wished. After Rogers left that evening, his wife called for the nurses, thanked them for all they had done, and told them she was going to die. By the next morning she was in a coma, and by the next day she was dead (Rogers, 1980). This experience was profoundly moving for Rogers, and awakened a deep spirituality in him, but with a decidedly unscientific aspect to it. Kubler-Ross joined Carl Jung in believing in synchronicity and the possibility of out-of-body experiences, life after death, and the like (see Kubler-Ross, 1983, 1997). Rogers also came to believe in such possibilities. Helen Rogers reported seeing evil figures and the Devil by her hospital bed, as well as a white light that would come and begin to lift her from the bed. Earlier the two of them had attended sessions with a medium who claimed to be able to contact the dead. Rogers was thoroughly convinced that the medium’s abilities were real, and that she had contacted Helen’s deceased sister, and later Helen Rogers herself. According to Rogers, each event was “an incredible, and certainly non-fraudulent experience” (Rogers, 1980).
For the individual who is, indeed, about to die, what remains of life? Kubler-Ross, Joan Erikson, and Ram Dass all see death itself as a final stage of growth. For Joan Erikson, when hope and trust can no longer sustain the individual, “to face down despair with faith and appropriate humility is perhaps the wisest course,” and one may then strive for gerotranscendence. Indeed, the ninth stage of development proposed by Joan Erikson seems quite similar to the stage of acceptance proposed by Kubler-Ross (Erikson & Erikson, 1997). Ram Dass talks about the different perspective on death in India, and how it helped him to believe that although the body and the mind, as well as their reflection in the ego/self, could die, the soul was something that would exist forever. Accordingly, it is more common in India, and in many other cultures, to prepare for death. The failure to do so in America can have painful consequences:
When I was in my 30s, my mother was diagnosed with a terminal blood disorder. I went to visit her in the hospital, and all the people around her were saying things like, “You look great!” “You’ll be home in no time!” But she looked terrible, and it was likely she’d never come home again. No one - not my father, her sister or the rabbi - would tell her the truth. In that moment I saw just how isolated she was. She was dying and no one would talk to her about death. We spoke about it, Soul to Soul, and she began to relax. (pg. 149; Ram Dass, 2000)
Kubler-Ross examined a variety of cultural perspectives on death, in a collection of essays entitled Death: The Final Stage of Growth (Kubler-Ross, 1975). Among Alaskan Indians the time of death was a choice. As death approaches, if it does not come suddenly, the dying person would call together relatives and friends for a time of storytelling and prayer. The dying person’s life would be celebrated, and their death would be accepted as an inevitable matter of fact (Trelease, 1975). In the Jewish faith, tradition holds that the dying process should be met with efforts to alleviate distress as much as possible, but that death must also be accepted as the decree of human mortality by the Eternal and Righteous Judge (Rabbi Heller, 1975). In Hindu and Buddhist traditions, there is no death, but rather a common belief in rebirth. The circumstances of one’s rebirth, however, are determined by how one lived their most recent life (based on karma). So, one’s life, as well as the preparations preceding the death of one’s body in this life, is an important factor in determining the nature of the next life. Of course, one can transcend this cycle of death and rebirth by attaining enlightenment. Thus, it is common in countries like India and China to practice Yoga or Buddhist meditation, as well as other spiritual practices, in order to either attain nirvana or, at least, a more favorable circumstance in the next life (Long, 1975). Each of these traditions, as well as others, considers death to be an important transition between this life and something beyond. It is in anticipation of something beyond that death and dying should be approached, both in terms of one’s actions and one’s state of mind. In conclusion:
There is no need to be afraid of death. It is not the end of the physical body that should worry us. Rather, our concern must be to live while we’re alive - to release our inner selves from the spiritual death that comes with living behind a façade designed to conform to external definitions of who and what we are. …when you fully understand that each day you awaken could be the last you have, you take the time that day to grow, to become more of who you really are, to reach out to other human beings. (pg. 164; Kubler-Ross, 1975)
discussion question \(\PageIndex{1}\)
People who have experienced the dying process often report strange occurrences, such as out-of-body experiences, visions of spirits (including angels and demons), or white lights shining down from above and beyond. Do you believe in any of these phenomena? Why do you think they only seem to occur with people who are, indeed, close to death?


4.10: Behavioral Considerations
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- Cindy Stephens, Gina Peterson, Sharon Eyrich, & Jennifer Paris
- College of the Canyons via College of the Canyons
Guiding the behavior of children is another important role that early childhood professionals possess. There are a plethora of programs designed to provide parents and early childhood professionals with the skills and tools that effectively help children navigate their emotions and the behaviors that they may exhibit at different developmental ages. Chapter 6 (Curriculum) has more extensive information on this topic. Below is a chart that provides some ideas about how to approach guidance positively.
| Ages/Stages | Developmental Factors | Examples of a Positive Approach to developmental factors to manage behavior |
|---|---|---|
| Infant/Toddler |
Children this age:
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Children in this stage tend to dump and run, so plan games to enhance this behavior in a positive way. Have large wide-mouth bins for children to practice “dumping items” into and out of. This strategy redirects the behavior of creating a mess into a structured activity to match the development. |
| Older Toddlers |
Children this age:
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Teachers of this age often find children trying to climb up on tables, chairs, and shelves. Incorporate developmentally climbing equipment and create obstacle courses to redirect activity into positive behaviors. Avoid using the word “no” and create expressions that teach what to do instead of what not to do. |
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Young Preschool (3-4 years) |
Children this age:
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Young preschoolers become curious and create many misconceptions as they create new schemas for understanding concepts. Listen to ideas sensitively address them quickly and honestly. Model exploration and engagement in new activities (especially ones they may be fearful of engaging in) |
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Older Preschool (4-5 years) |
Children this age:
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Ask the children to create new silly, but appropriate words to represent emotions rather than focusing on the “bad” words they use. |
| Young School-Age |
Children this age:
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Fairness is a big issue for this group so working with this age group, a teacher should sit with children to develop “rules” and “consequences” so they can take ownership of behavioral expectations |
Pause to Reflect
What makes the most sense to you about guiding children’s behavior? What seems confusing to you?


7.3: DNA Structure and Sequencing
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- Ying Liu
- City College of San Francisco
Learning Objectives
By the end of this section, you will be able to do the following:
- Describe the structure of DNA
- Explain the Sanger method of DNA sequencing
- Discuss the similarities and differences between eukaryotic and prokaryotic DNA
The building blocks of DNA are nucleotides. The important components of the nucleotide are a nitrogenous (nitrogen-bearing) base, a 5-carbon sugar (pentose), and a phosphate group (Figure 14.5). The nucleotide is named depending on the nitrogenous base. The nitrogenous base can be a purine such as adenine (A) and guanine (G), or a pyrimidine such as cytosine (C) and thymine (T).
Visual Connection
Visual Connection
The images above illustrate the five bases of DNA and RNA. Examine the images and explain why these are called “nitrogenous bases.” How are the purines different from the pyrimidines? How is one purine or pyrimidine different from another, e.g., adenine from guanine? How is a nucleoside different from a nucleotide?
The purines have a double ring structure with a six-membered ring fused to a five-membered ring. Pyrimidines are smaller in size; they have a single six-membered ring structure.
The sugar is deoxyribose in DNA and ribose in RNA. The carbon atoms of the five-carbon sugar are numbered 1', 2', 3', 4', and 5' (1' is read as “one prime”). The phosphate, which makes DNA and RNA acidic, is connected to the 5' carbon of the sugar by the formation of an ester linkage between phosphoric acid and the 5'-OH group (an ester is an acid + an alcohol). In DNA nucleotides, the 3' carbon of the sugar deoxyribose is attached to a hydroxyl (OH) group. In RNA nucleotides, the 2' carbon of the sugar ribose also contains a hydroxyl group. The base is attached to the 1'carbon of the sugar.
The nucleotides combine with each other to produce phosphodiester bonds. The phosphate residue attached to the 5' carbon of the sugar of one nucleotide forms a second ester linkage with the hydroxyl group of the 3' carbon of the sugar of the next nucleotide, thereby forming a 5'-3' phosphodiester bond. In a polynucleotide, one end of the chain has a free 5' phosphate, and the other end has a free 3'-OH. These are called the 5' and 3' ends of the chain.
In the 1950s, Francis Crick and James Watson worked together to determine the structure of DNA at the University of Cambridge, England. Other scientists like Linus Pauling and Maurice Wilkins were also actively exploring this field. Pauling previously had discovered the secondary structure of proteins using X-ray crystallography. In Wilkins’ lab, researcher Rosalind Franklin was using X-ray diffraction methods to understand the structure of DNA. Watson and Crick were able to piece together the puzzle of the DNA molecule on the basis of Franklin's data because Crick had also studied X-ray diffraction (Figure 14.6). In 1962, James Watson, Francis Crick, and Maurice Wilkins were awarded the Nobel Prize in Medicine. Unfortunately, by then Franklin had died, and Nobel prizes are not awarded posthumously.
Watson and Crick proposed that DNA is made up of two strands that are twisted around each other to form a right-handed helix. Base pairing takes place between a purine and pyrimidine on opposite strands, so that A pairs with T, and G pairs with C (suggested by Chargaff's Rules). Thus, adenine and thymine are complementary base pairs, and cytosine and guanine are also complementary base pairs. The base pairs are stabilized by hydrogen bonds: adenine and thymine form two hydrogen bonds and cytosine and guanine form three hydrogen bonds. The two strands are anti-parallel in nature; that is, the 3' end of one strand faces the 5' end of the other strand. The sugar and phosphate of the nucleotides form the backbone of the structure, whereas the nitrogenous bases are stacked inside, like the rungs of a ladder. Each base pair is separated from the next base pair by a distance of 0.34 nm, and each turn of the helix measures 3.4 nm. Therefore, 10 base pairs are present per turn of the helix. The diameter of the DNA double-helix is 2 nm, and it is uniform throughout. Only the pairing between a purine and pyrimidine and the antiparallel orientation of the two DNA strands can explain the uniform diameter. The twisting of the two strands around each other results in the formation of uniformly spaced major and minor grooves (Figure 14.7).
DNA Sequencing Techniques
Until the 1990s, the sequencing of DNA (reading the sequence of DNA) was a relatively expensive and long process. Using radiolabeled nucleotides also compounded the problem through safety concerns. With currently available technology and automated machines, the process is cheaper, safer, and can be completed in a matter of hours. Fred Sanger developed the sequencing method used for the human genome sequencing project, which is widely used today (Figure 14.8).
Link to Learning
Link to Learning
Visit this site to watch a video explaining the DNA sequence-reading technique that resulted from Sanger’s work.
The sequencing method is known as the dideoxy chain termination method. The method is based on the use of chain terminators, the dideoxynucleotides (ddNTPs). The ddNTPSs differ from the deoxynucleotides by the lack of a free 3' OH group on the five-carbon sugar. If a ddNTP is added to a growing DNA strand, the chain cannot be extended any further because the free 3' OH group needed to add another nucleotide is not available. By using a predetermined ratio of deoxynucleotides to dideoxynucleotides, it is possible to generate DNA fragments of different sizes.
The DNA sample to be sequenced is denatured (separated into two strands by heating it to high temperatures). The DNA is divided into four tubes in which a primer, DNA polymerase, and all four nucleoside triphosphates (A, T, G, and C) are added. In addition, limited quantities of one of the four dideoxynucleoside triphosphates (ddCTP, ddATP, ddGTP, and ddTTP) are added to each tube respectively. The tubes are labeled as A, T, G, and C according to the ddNTP added. For detection purposes, each of the four dideoxynucleotides carries a different fluorescent label. Chain elongation continues until a fluorescent dideoxy nucleotide is incorporated, after which no further elongation takes place. After the reaction is over, electrophoresis is performed. Even a difference in length of a single base can be detected. The sequence is read from a laser scanner that detects the fluorescent marker of each fragment. For his work on DNA sequencing, Sanger received a Nobel Prize in Chemistry in 1980.
Link to Learning
Link to Learning
Sanger’s genome sequencing has led to a race to sequence human genomes at rapid speed and low cost. Learn more by viewing the animation here .
Gel electrophoresis is a technique used to separate DNA fragments of different sizes. Usually the gel is made of a chemical called agarose (a polysaccharide polymer extracted from seaweed that is high in galactose residues). Agarose powder is added to a buffer and heated. After cooling, the gel solution is poured into a casting tray. Once the gel has solidified, the DNA is loaded on the gel and electric current is applied. The DNA has a net negative charge and moves from the negative electrode toward the positive electrode. The electric current is applied for sufficient time to let the DNA separate according to size; the smallest fragments will be farthest from the well (where the DNA was loaded), and the heavier molecular weight fragments will be closest to the well. Once the DNA is separated, the gel is stained with a DNA-specific dye for viewing it (Figure 14.9).
Evolution Connection
Evolution Connection
Neanderthal Genome: How Are We Related? The first draft sequence of the Neanderthal genome was recently published by Richard E. Green et al. in 2010. 1 Neanderthals are the closest ancestors of present-day humans. They were known to have lived in Europe and Western Asia (and now, perhaps, in Northern Africa) before they disappeared from fossil records approximately 30,000 years ago. Green’s team studied almost 40,000-year-old fossil remains that were selected from sites across the world. Extremely sophisticated means of sample preparation and DNA sequencing were employed because of the fragile nature of the bones and heavy microbial contamination. In their study, the scientists were able to sequence some four billion base pairs. The Neanderthal sequence was compared with that of present-day humans from across the world. After comparing the sequences, the researchers found that the Neanderthal genome had 2 to 3 percent greater similarity to people living outside Africa than to people in Africa. While current theories have suggested that all present-day humans can be traced to a small ancestral population in Africa, the data from the Neanderthal genome suggest some interbreeding between Neanderthals and early modern humans.
Green and his colleagues also discovered DNA segments among people in Europe and Asia that are more similar to Neanderthal sequences than to other contemporary human sequences. Another interesting observation was that Neanderthals are as closely related to people from Papua New Guinea as to those from China or France. This is surprising because Neanderthal fossil remains have been located only in Europe and West Asia. Most likely, genetic exchange took place between Neanderthals and modern humans as modern humans emerged out of Africa, before the divergence of Europeans, East Asians, and Papua New Guineans.
Several genes seem to have undergone changes from Neanderthals during the evolution of present-day humans. These genes are involved in cranial structure, metabolism, skin morphology, and cognitive development. One of the genes that is of particular interest is RUNX2 , which is different in modern day humans and Neanderthals. This gene is responsible for the prominent frontal bone, bell-shaped rib cage, and dental differences seen in Neanderthals. It is speculated that an evolutionary change in RUNX2 was important in the origin of modern-day humans, and this affected the cranium and the upper body.
Link to Learning
Link to Learning
Watch Svante Pääbo’s talk explaining the Neanderthal genome research at the 2011 annual TED (Technology, Entertainment, Design) conference.
DNA Packaging in Cells
Prokaryotes are much simpler than eukaryotes in many of their features (Figure 14.10). Most prokaryotes contain a single, circular chromosome that is found in an area of the cytoplasm called the nucleoid region .
Visual Connection
Visual Connection
In eukaryotic cells, DNA and RNA synthesis occur in a separate compartment from protein synthesis. In prokaryotic cells, both processes occur together. What advantages might there be to separating the processes? What advantages might there be to having them occur together?
The size of the genome in one of the most well-studied prokaryotes, E.coli, is 4.6 million base pairs (approximately 1.1 mm, if cut and stretched out). So how does this fit inside a small bacterial cell? The DNA is twisted by what is known as supercoiling. Supercoiling suggests that DNA is either “under-wound” (less than one turn of the helix per 10 base pairs) or “over-wound” (more than 1 turn per 10 base pairs) from its normal relaxed state. Some proteins are known to be involved in the supercoiling; other proteins and enzymes such as DNA gyrase help in maintaining the supercoiled structure.
Eukaryotes, whose chromosomes each consist of a linear DNA molecule, employ a different type of packing strategy to fit their DNA inside the nucleus (Figure 14.11). At the most basic level, DNA is wrapped around proteins known as histones to form structures called nucleosomes. The histones are evolutionarily conserved proteins that are rich in basic amino acids and form an octamer composed of two molecules of each of four different histones. Their composition and properties are important to understanding gene expression, and were partially uncovered based on research by Marie M. Daly and Alfred E. Mirsky in the early 1950s. The DNA (remember, it is negatively charged because of the phosphate groups) is wrapped tightly around the histone core. This nucleosome is linked to the next one with the help of a linker DNA . This is also known as the “beads on a string” structure. With the help of a fifth histone, a string of nucleosomes is further compacted into a 30-nm fiber, which is the diameter of the structure. Metaphase chromosomes are even further condensed by association with scaffolding proteins. At the metaphase stage, the chromosomes are at their most compact, approximately 700 nm in width.
In interphase, eukaryotic chromosomes have two distinct regions that can be distinguished by staining. The tightly packaged region is known as heterochromatin, and the less dense region is known as euchromatin. Heterochromatin usually contains genes that are not expressed, and is found in the regions of the centromere and telomeres. The euchromatin usually contains genes that are transcribed, with DNA packaged around nucleosomes but not further compacted.
Footnotes
- 1 Richard E. Green et al., “A Draft Sequence of the Neandertal Genome,” Science 328 (2010): 710-22.


9: Alkynes - An Introduction to Organic Synthesis
After you have completed Chapter 9, you should be able to
- fulfillall of the detailed objectives listed under each individual section.
- solve road-map problems involving any of the reactions introduced to this point.
- design multistep syntheses using any of the reactions introduced to this point, and determine the viability of a given synthesis.
- define, and use in context, the key terms introduced.
Addition reactions not only dominate the chemistry of alkenes, they are also the major class of reaction you will encounter. This chapter discusses an important difference between (terminal) alkynes and alkenes, that is, the acidity of the former; it also addresses the problem of devising organic syntheses. Once you have completed this chapter you will have increased the number of organic reactions in your repertoire, and should be able to design much more elaborate multistep syntheses. As you work through Chapter 9, you should notice the many similarities among the reactions described here and those in Chapters 7 and 8.
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- 9.1: Naming Alkynes
- Alkynes are organic molecules made of the functional group carbon-carbon triple bonds and are written in the empirical formula of CnH2n−2 . They are unsaturated hydrocarbons. Like alkenes have the suffix –ene, alkynes use the ending –yne; this suffix is used when there is only one alkyne in the molecule.
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- 9.3: Reactions of Alkynes - Addition of HX and X₂
- Reactions of alkynes, a class of hydrocarbons containing carbon-carbon triple bonds, exhibit various chemical transformations due to the presence of the highly reactive π-bonds. These reactions can be broadly categorized into addition reactions and substitution reactions.
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- 9.4: Hydration of Alkynes
- As with alkenes, hydration (addition of water) to alkynes requires a strong acid, usually sulfuric acid, and is facilitated by mercuric sulfate. However, unlike the additions to double bonds which give alcohol products, addition of water to alkynes gives ketone products ( except for acetylene which yields acetaldehyde ). The explanation for this deviation lies in enol-keto tautomerization.
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- 9.5: Reduction of Alkynes
- Reactions between alkynes and catalysts are a common source of alkene formation. Because alkynes differ from alkenes on account of their two procurable π bonds, alkynes are more susceptible to additions. Aside from turning them into alkenes, these catalysts affect the arrangement of substituents on the newly formed alkene molecule. Depending on which catalyst is used, the catalysts cause anti- or syn-addition of hydrogens. Alkynes can readily undergo additions because of their availability of tw
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- 9.7: Alkyne Acidity - Formation of Acetylide Anions
- Terminal alkynes are much more acidic than most other hydrocarbons. Removal of the proton leads to the formation of an acetylide anion, RC=C:-. The origin of the enhanced acidity can be attributed to the stability of the acetylide anion, which has the unpaired electrons in an sp hybridized orbital. The stability results from occupying an orbital with a high degree of s-orbital character.