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Euthanasia

Euthanasia (from εὐθανασία: εὖ + θάνατος) is the practice of intentionally ending life to eliminate pain and suffering.

Different countries have different euthanasia laws. The British House of Lords select committee on medical ethics defines euthanasia as "a deliberate intervention undertaken with the express intention of ending a life to relieve intractable suffering". In the Netherlands and Belgium, euthanasia is understood as "termination of life by a doctor at the request of a patient". The Dutch law, however, does not use the term 'euthanasia' but includes the concept under the broader definition of "assisted suicide and termination of life on request".

Euthanasia is categorised in different ways, which include voluntary, non-voluntary, and involuntary. Voluntary euthanasia is when a person wishes to have their life ended and is legal in a growing number of countries. Non-voluntary euthanasia occurs when a patient's consent is unavailable and is legal in some countries under certain limited conditions, in both active and passive forms. Involuntary euthanasia, which is done without asking for consent or against the patient's will, is illegal in all countries and is usually considered murder.

, euthanasia had become the most active area of research in bioethics. In some countries, divisive public controversy occurs over the moral, ethical, and legal issues associated with euthanasia. Passive euthanasia (known as "pulling the plug") is legal under some circumstances in many countries. Active euthanasia, however, is legal or de facto legal in only a handful of countries (for example, Belgium, Canada, and Switzerland), which limit it to specific circumstances and require the approval of counsellors, doctors, or other specialists. In some countries—such as Nigeria, Saudi Arabia, and Pakistan—support for active euthanasia is almost nonexistent.

Definition
Like other terms borrowed from history, "euthanasia" has had different meanings depending on usage. The first apparent usage of the term "euthanasia" belongs to the historian Suetonius, who described how the Emperor Augustus, "dying quickly and without suffering in the arms of his wife, Livia, experienced the 'euthanasia' he had wished for." The word "euthanasia" was first used in a medical context by Francis Bacon in the 17th century to refer to an easy, painless, happy death, during which it was a "physician's responsibility to alleviate the 'physical sufferings' of the body." Bacon referred to an "outward euthanasia"—the term "outward" he used to distinguish from a spiritual concept—the euthanasia "which regards the preparation of the soul."

In current usage, euthanasia has been defined as the "painless inducement of a quick death". However, it is argued that this approach fails to properly define euthanasia, as it leaves open a number of possible actions that would meet the requirements of the definition but would not be seen as euthanasia. In particular, these include situations where a person kills another, painlessly, but for no reason beyond that of personal gain, or accidental deaths that are quick and painless but not intentional.

Another approach incorporates the notion of suffering into the definition. The definition offered by the Oxford English Dictionary incorporates suffering as a necessary condition with "the painless killing of a patient suffering from an incurable and painful disease or in an irreversible coma", This approach is included in Marvin Khol and Paul Kurtz's definition of it as "a mode or act of inducing or permitting death painlessly as a relief from suffering". Counterexamples can be given: such definitions may encompass killing a person suffering from an incurable disease for personal gain (such as to claim an inheritance), and commentators such as Tom Beauchamp and Arnold Davidson have argued that doing so would constitute "murder simpliciter" rather than euthanasia.

The third element incorporated into many definitions is that of intentionality: the death must be intended rather than accidental, and the intent of the action must be a "merciful death". Michael Wreen argued that "the principal thing that distinguishes euthanasia from intentional killing simpliciter is the agent's motive: it must be a good motive insofar as the good of the person killed is concerned." Similarly, Heather Draper speaks to the importance of motive, arguing that "the motive forms a crucial part of arguments for euthanasia, because it must be in the best interests of the person on the receiving end." Definitions such as those offered by the House of Lords Select committee on Medical Ethics take this path, where euthanasia is defined as "a deliberate intervention undertaken with the express intention of ending a life, to relieve intractable suffering." Beauchamp and Davidson also highlight Baruch Brody's "an act of euthanasia is one in which one person ... (A) kills another person (B) for the benefit of the second person, who actually does benefit from being killed".

Draper argued that any definition of euthanasia must incorporate four elements: an agent and a subject; an intention; causal proximity, such that the actions of the agent lead to the outcome; and an outcome. Based on this, she offered a definition incorporating those elements, stating that euthanasia "must be defined as death that results from the intention of one person to kill another person, using the most gentle and painless means possible, that is motivated solely by the best interests of the person who dies." Prior to Draper, Beauchamp and Davidson had also offered a definition that included these elements. Their definition specifically discounts fetuses to distinguish between abortions and euthanasia:

"In summary, we have argued ... that the death of a human being, A, is an instance of euthanasia if and only if (1) A's death is intended by at least one other human being, B, where B is either the cause of death or a causally relevant feature of the event resulting in death (whether by action or by omission); (2) there is either sufficient current evidence for B to believe that A is acutely suffering or irreversibly comatose, or there is sufficient current evidence related to A's present condition such that one or more known causal laws supports B's belief that A will be in a condition of acute suffering or irreversible comatoseness; (3) (a) B's primary reason for intending A's death is cessation of A's (actual or predicted future) suffering or irreversible comatoseness, where B does not intend A's death for a different primary reason, though there may be other relevant reasons, and (b) there is sufficient current evidence for either A or B that causal means to A's death will not produce any more suffering than would be produced for A if B were not to intervene; (4) the causal means to the event of A's death are chosen by A or B to be as painless as possible, unless either A or B has an overriding reason for a more painful causal means, where the reason for choosing the latter causal means does not conflict with the evidence in 3b; (5) A is a nonfetal organism."

Wreen, in part responding to Beauchamp and Davidson, offered a six-part definition:

"Person A committed an act of euthanasia if and only if (1) A killed B or let her die; (2) A intended to kill B; (3) the intention specified in (2) was at least partial cause of the action specified in (1); (4) the causal journey from the intention specified in (2) to the action specified in (1) is more or less in accordance with A's plan of action; (5) A's killing of B is a voluntary action; (6) the motive for the action specified in (1), the motive standing behind the intention specified in (2), is the good of the person killed."

Wreen also considered a seventh requirement: "(7) The good specified in (6) is, or at least includes, the avoidance of evil", although, as Wreen noted in the paper, he was not convinced that the restriction was required.

In discussing his definition, Wreen noted the difficulty of justifying euthanasia when faced with the notion of the subject's "right to life". In response, Wreen argued that euthanasia has to be voluntary and that "involuntary euthanasia is, as such, a great wrong". Other commentators incorporate consent more directly into their definitions. For example, in a discussion of euthanasia presented in 2003 by the European Association of Palliative Care (EPAC) Ethics Task Force, the authors offered: "Medicalized killing of a person without the person's consent, whether nonvoluntary (where the person is unable to consent) or involuntary (against the person's will), is not euthanasia: it is murder. Hence, euthanasia can be voluntary only." Although the EPAC Ethics Task Force argued that both non-voluntary and involuntary euthanasia could not be included in the definition of euthanasia, there is discussion in the literature about excluding one but not the other.

Classification
Euthanasia may be classified into three types, according to whether a person gives informed consent: voluntary, non-voluntary and involuntary.

There is a debate within the medical and bioethics literature about whether or not the non-voluntary (and by extension, involuntary) killing of patients can be regarded as euthanasia, irrespective of intent or the patient's circumstances. In the definitions offered by Beauchamp and Davidson and, later, by Wreen, consent on the part of the patient was not considered one of their criteria, although it may have been required to justify euthanasia. However, others see consent as essential.

Voluntary euthanasia
Voluntary euthanasia is conducted with the consent of the patient. Active voluntary euthanasia is legal in Belgium, Luxembourg and the Netherlands. Passive voluntary euthanasia is legal throughout the US per Cruzan v. Director, Missouri Department of Health. When the patient brings about their own death with the assistance of a physician, the term assisted suicide is often used instead. Assisted suicide is legal in Switzerland and the U.S. states of California, Oregon, Washington, Montana and Vermont.

Non-voluntary euthanasia
Non-voluntary euthanasia is conducted when the consent of the patient is unavailable. Examples include child euthanasia, which is illegal worldwide but decriminalised under certain specific circumstances in the Netherlands under the Groningen Protocol. Passive forms of non-voluntary euthanasia (i.e. withholding treatment) are legal in a number of countries under specified conditions.

Involuntary euthanasia
Involuntary euthanasia is conducted against the will of the patient.

Passive and active euthanasia
Voluntary, non-voluntary and involuntary types can be further divided into passive or active variants. Passive euthanasia entails the withholding treatment necessary for the continuance of life. Active euthanasia entails the use of lethal substances or forces (such as administering a lethal injection), and is more controversial. While some authors consider these terms to be misleading and unhelpful, they are nonetheless commonly used. In some cases, such as the administration of increasingly necessary, but toxic doses of painkillers, there is a debate whether or not to regard the practice as active or passive.

History
Euthanasia was practiced in Ancient Greece and Rome: for example, hemlock was employed as a means of hastening death on the island of Kea, a technique also employed in Massalia. Euthanasia, in the sense of the deliberate hastening of a person's death, was supported by Socrates, Plato and Seneca the Elder in the ancient world, although Hippocrates appears to have spoken against the practice, writing "I will not prescribe a deadly drug to please someone, nor give advice that may cause his death" (noting there is some debate in the literature about whether or not this was intended to encompass euthanasia).

Early modern period
The term euthanasia, in the earlier sense of supporting someone as they died, was used for the first time by Francis Bacon. In his work, Euthanasia medica, he chose this ancient Greek word and, in doing so, distinguished between euthanasia interior, the preparation of the soul for death, and euthanasia exterior, which was intended to make the end of life easier and painless, in exceptional circumstances by shortening life. That the ancient meaning of an easy death came to the fore again in the early modern period can be seen from its definition in the 18th century Zedlers Universallexikon:

"Euthanasia: a very gentle and quiet death, which happens without painful convulsions. The word comes from ευ, bene, well, and θανατος, mors, death."

The concept of euthanasia in the sense of alleviating the process of death goes back to the medical historian Karl Friedrich Heinrich Marx, who drew on Bacon's philosophical ideas. According to Marx, a doctor had a moral duty to ease the suffering of death through encouragement, support and mitigation using medication. Such an "alleviation of death" reflected the contemporary zeitgeist, but was brought into the medical canon of responsibility for the first time by Marx. Marx also stressed the distinction of the theological care of the soul of sick people from the physical care and medical treatment by doctors.

Euthanasia in its modern sense has always been strongly opposed in the Judeo-Christian tradition. Thomas Aquinas opposed both and argued that the practice of euthanasia contradicted our natural human instincts of survival, as did Francois Ranchin (1565–1641), a French physician and professor of medicine, and Michael Boudewijns (1601–1681), a physician and teacher. Other voices argued for euthanasia, such as John Donne in 1624, and euthanasia continued to be practised. In 1678, the publication of Caspar Questel's De pulvinari morientibus non-subtrahend, ("On the pillow of which the dying should not be deprived"), initiated debate on the topic. Questel described various customs which were employed at the time to hasten the death of the dying, (including the sudden removal of a pillow, which was believed to accelerate death), and argued against their use, as doing so was "against the laws of God and Nature". This view was shared by others who followed, including Philipp Jakob Spener, Veit Riedlin and Johann Georg Krünitz. Despite opposition, euthanasia continued to be practised, involving techniques such as bleeding, suffocation, and removing people from their beds to be placed on the cold ground.

Suicide and euthanasia became more accepted during the Age of Enlightenment. Thomas More wrote of euthanasia in Utopia, although it is not clear if More was intending to endorse the practice. Other cultures have taken different approaches: for example, in Japan suicide has not traditionally been viewed as a sin, as it is used in cases of honor, and accordingly, the perceptions of euthanasia are different from those in other parts of the world.

Beginnings of the contemporary euthanasia debate
In the mid-1800s, the use of morphine to treat "the pains of death" emerged, with John Warren recommending its use in 1848. A similar use of chloroform was revealed by Joseph Bullar in 1866. However, in neither case was it recommended that the use should be to hasten death. In 1870 Samuel Williams, a schoolteacher, initiated the contemporary euthanasia debate through a speech given at the Birmingham Speculative Club in England, which was subsequently published in a one-off publication entitled Essays of the Birmingham Speculative Club, the collected works of a number of members of an amateur philosophical society. Williams' proposal was to use chloroform to deliberately hasten the death of terminally ill patients:

"That in all cases of hopeless and painful illness, it should be the recognized duty of the medical attendant, whenever so desired by the patient, to administer chloroform or such other anaesthetic as may by-and-bye supersede chloroform – so as to destroy consciousness at once, and put the sufferer to a quick and painless death; all needful precautions being adopted to prevent any possible abuse of such duty; and means being taken to establish, beyond the possibility of doubt or question, that the remedy was applied at the express wish of the patient."

The essay was favourably reviewed in The Saturday Review, but an editorial against the essay appeared in The Spectator. From there it proved to be influential, and other writers came out in support of such views: Lionel Tollemache wrote in favour of euthanasia, as did Annie Besant, the essayist and reformer who later became involved with the National Secular Society, considering it a duty to society to "die voluntarily and painlessly" when one reaches the point of becoming a 'burden'. Popular Science analyzed the issue in May 1873, assessing both sides of the argument. Kemp notes that at the time, medical doctors did not participate in the discussion; it was "essentially a philosophical enterprise ... tied inextricably to a number of objections to the Christian doctrine of the sanctity of human life".

Early euthanasia movement in the United States
The rise of the euthanasia movement in the United States coincided with the so-called Gilded Age, a time of social and technological change that encompassed an "individualistic conservatism that praised laissez-faire economics, scientific method, and rationalism", along with major depressions, industrialisation and conflict between corporations and labour unions. It was also the period in which the modern hospital system was developed, which has been seen as a factor in the emergence of the euthanasia debate.

Robert Ingersoll argued for euthanasia, stating in 1894 that where someone is suffering from a terminal illness, such as terminal cancer, they should have a right to end their pain through suicide. Felix Adler offered a similar approach, although, unlike Ingersoll, Adler did not reject religion. In fact, he argued from an Ethical Culture framework. In 1891, Adler argued that those suffering from overwhelming pain should have the right to commit suicide, and, furthermore, that it should be permissible for a doctor to assist – thus making Adler the first "prominent American" to argue for suicide in cases where people were suffering from chronic illness. Both Ingersoll and Adler argued for voluntary euthanasia of adults suffering from terminal ailments. Dowbiggin argues that by breaking down prior moral objections to euthanasia and suicide, Ingersoll and Adler enabled others to stretch the definition of euthanasia.

The first attempt to legalise euthanasia took place in the United States, when Henry Hunt introduced legislation into the General Assembly of Ohio in 1906. Hunt did so at the behest of Anna Sophina Hall, a wealthy heiress who was a major figure in the euthanasia movement during the early 20th century in the United States. Hall had watched her mother die after an extended battle with liver cancer, and had dedicated herself to ensuring that others would not have to endure the same suffering. Towards this end she engaged in an extensive letter writing campaign, recruited Lurana Sheldon and Maud Ballington Booth, and organised a debate on euthanasia at the annual meeting of the American Humane Association in 1905 – described by Jacob Appel as the first significant public debate on the topic in the 20th century.

Hunt's bill called for the administration of an anesthetic to bring about a patient's death, so long as the person is of lawful age and sound mind, and was suffering from a fatal injury, an irrevocable illness, or great physical pain. It also required that the case be heard by a physician, required informed consent in front of three witnesses, and required the attendance of three physicians who had to agree that the patient's recovery was impossible. A motion to reject the bill outright was voted down, but the bill failed to pass, 79 to 23.

Along with the Ohio euthanasia proposal, in 1906 Assemblyman Ross Gregory introduced a proposal to permit euthanasia to the Iowa legislature. However, the Iowa legislation was broader in scope than that offered in Ohio. It allowed for the death of any person of at least ten years of age who suffered from an ailment that would prove fatal and cause extreme pain, should they be of sound mind and express a desire to artificially hasten their death. In addition, it allowed for infants to be euthanised if they were sufficiently deformed, and permitted guardians to request euthanasia on behalf of their wards. The proposed legislation also imposed penalties on physicians who refused to perform euthanasia when requested: a 6–12-month prison term and a fine of between $200 and $1,000. The proposal proved to be controversial. It engendered considerable debate and failed to pass, having been withdrawn from consideration after being passed to the Committee on Public Health.

After 1906 the euthanasia debate reduced in intensity, resurfacing periodically, but not returning to the same level of debate until the 1930s in the United Kingdom.

Euthanasia opponent Ian Dowbiggin argues that the early membership of the Euthanasia Society of America (ESA) reflected how many perceived euthanasia at the time, often seeing it as a eugenics matter rather than an issue concerning individual rights. Dowbiggin argues that not every eugenist joined the ESA "solely for eugenic reasons", but he postulates that there were clear ideological connections between the eugenics and euthanasia movements.

1930s in Britain
The Voluntary Euthanasia Legalisation Society was founded in 1935 by Charles Killick Millard (now called Dignity in Dying). The movement campaigned for the legalisation of euthanasia in Great Britain.

In January 1936, King George V was given a fatal dose of morphine and cocaine to hasten his death. At the time he was suffering from cardio-respiratory failure, and the decision to end his life was made by his physician, Lord Dawson. Although this event was kept a secret for over 50 years, the death of George V coincided with proposed legislation in the House of Lords to legalise euthanasia.

Nazi Euthanasia Program
A 24 July 1939 killing of a severely disabled infant in Nazi Germany was described in a BBC "Genocide Under the Nazis Timeline" as the first "state-sponsored euthanasia". Parties that consented to the killing included Hitler's office, the parents, and the Reich Committee for the Scientific Registration of Serious and Congenitally Based Illnesses. The Telegraph noted that the killing of the disabled infant—whose name was Gerhard Kretschmar, born blind, with missing limbs, subject to convulsions, and reportedly "an idiot"— provided "the rationale for a secret Nazi decree that led to 'mercy killings' of almost 300,000 mentally and physically handicapped people". While Kretchmar's killing received parental consent, most of the 5,000 to 8,000 children killed afterwards were forcibly taken from their parents.

The "euthanasia campaign" of mass murder gathered momentum on 14 January 1940 when the "handicapped" were killed with gas vans and at killing centres, eventually leading to the deaths of 70,000 adult Germans. Professor Robert Jay Lifton, author of The Nazi Doctors and a leading authority on the T4 program, contrasts this program with what he considers to be a genuine euthanasia. He explains that the Nazi version of "euthanasia" was based on the work of Adolf Jost, who published The Right to Death (Das Recht auf den Tod) in 1895. Lifton writes:

"Jost argued that control over the death of the individual must ultimately belong to the social organism, the state. This concept is in direct opposition to the Anglo-American concept of euthanasia, which emphasizes the individual's 'right to die' or 'right to death' or 'right to his or her own death,' as the ultimate human claim. In contrast, Jost was pointing to the state's right to kill. ... Ultimately the argument was biological: 'The rights to death [are] the key to the fitness of life.' The state must own death—must kill—in order to keep the social organism alive and healthy."

In modern terms, the use of "euthanasia" in the context of Action T4 is seen to be a euphemism to disguise a program of genocide, in which people were killed on the grounds of "disabilities, religious beliefs, and discordant individual values". Compared to the discussions of euthanasia that emerged post-war, the Nazi program may have been worded in terms that appear similar to the modern use of "euthanasia", but there was no "mercy" and the patients were not necessarily terminally ill. Despite these differences, historian and euthanasia opponent Ian Dowbiggin writes that "the origins of Nazi euthanasia, like those of the American euthanasia movement, predate the Third Reich and were intertwined with the history of eugenics and Social Darwinism, and with efforts to discredit traditional morality and ethics."

1949 New York State Petition for Euthanasia and Catholic opposition
On 6 January 1949, the Euthanasia Society of America presented to the New York State Legislature a petition to legalize euthanasia, signed by 379 leading Protestant and Jewish ministers, the largest group of religious leaders ever to have taken this stance. A similar petition had been sent to the New York Legislature in 1947, signed by approximately 1,000 New York physicians. Roman Catholic religious leaders criticized the petition, saying that such a bill would "legalize a suicide-murder pact" and a "rationalization of the fifth commandment of God, 'Thou Shalt Not Kill. The Right Reverend Robert E. McCormick stated that: "The ultimate object of the Euthanasia Society is based on the Totalitarian principle that the state is supreme and that the individual does not have the right to live if his continuance in life is a burden or hindrance to the state. The Nazis followed this principle and compulsory Euthanasia was practiced as a part of their program during the recent war. We American citizens of New York State must ask ourselves this question: 'Are we going to finish Hitler's job?'" The petition brought tensions between the American Euthanasia Society and the Catholic Church to a head that contributed to a climate of anti-Catholic sentiment generally, regarding issues such as birth control, eugenics, and population control. However, the petition did not result in any legal changes.

Debate
Historically, the euthanasia debate has tended to focus on a number of key concerns. According to euthanasia opponent Ezekiel Emanuel, proponents of euthanasia have presented four main arguments: a) that people have a right to self-determination, and thus should be allowed to choose their own fate; b) assisting a subject to die might be a better choice than requiring that they continue to suffer; c) the distinction between passive euthanasia, which is often permitted, and active euthanasia, which is not substantive (or that the underlying principle–the doctrine of double effect–is unreasonable or unsound); and d) permitting euthanasia will not necessarily lead to unacceptable consequences. Pro-euthanasia activists often point to countries like the Netherlands and Belgium, and states like Oregon, where euthanasia has been legalized, to argue that it is mostly unproblematic.

Similarly, Emanuel argues that there are four major arguments presented by opponents of euthanasia: a) not all deaths are painful; b) alternatives, such as cessation of active treatment, combined with the use of effective pain relief, are available; c) the distinction between active and passive euthanasia is morally significant; and d) legalising euthanasia will place society on a slippery slope, which will lead to unacceptable consequences. In fact, in Oregon, in 2013, pain was not one of the top five reasons people sought euthanasia. Top reasons were a loss of dignity, and a fear of burdening others.

In the United States in 2013, 47% nationwide supported doctor-assisted suicide. This included 32% of Latinos, 29% of African-Americans. Some U.S. disability rights organizations have also opposed bills legalizing assisted suicide.

A 2015 Populus poll in the United Kingdom found broad public support for assisted dying. 82% of people supported the introduction of assisted dying laws, including 86% of people with disabilities.

An alternative approach to the question is seen in the hospice movement which promotes palliative care for the dying and terminally ill. This has pioneered the use of pain-relieving drugs in a holistic atmosphere in which the patient's spiritual care ranks alongside physical care. It 'intends neither to hasten nor postpone death'.

Legal status
Eligibility for euthanasia varies across jurisdictions where it is legal. Some countries such as Belgium and the Netherlands allow euthanasia for mental illness.

West's Encyclopedia of American Law states that "a 'mercy killing' or euthanasia is generally considered to be a criminal homicide" and is normally used as a synonym of homicide committed at a request made by the patient.

The judicial sense of the term "homicide" includes any intervention undertaken with the express intention of ending a life, even to relieve intractable suffering. Not all homicide is unlawful. Two designations of homicide that carry no criminal punishment are justifiable and excusable homicide. In most countries this is not the status of euthanasia. The term "euthanasia" is usually confined to the active variety; the University of Washington website states that "euthanasia generally means that the physician would act directly, for instance by giving a lethal injection, to end the patient's life". Physician-assisted suicide is thus not classified as euthanasia by the US State of Oregon, where it is legal under the Oregon Death with Dignity Act, and despite its name, it is not legally classified as suicide either. Unlike physician-assisted suicide, withholding or withdrawing life-sustaining treatments with patient consent (voluntary) is almost unanimously considered, at least in the United States, to be legal. The use of pain medication to relieve suffering, even if it hastens death, has been held as legal in several court decisions.

Some governments around the world have legalized voluntary euthanasia but most commonly it is still considered to be criminal homicide. In the Netherlands and Belgium, where euthanasia has been legalized, it still remains homicide although it is not prosecuted and not punishable if the perpetrator (the doctor) meets certain legal conditions.

In a historic judgment, the Supreme Court of India legalized passive euthanasia. The apex court remarked in the judgement that the Constitution of India values liberty, dignity, autonomy, and privacy. A bench headed by Chief Justice Dipak Misra delivered a unanimous judgment.

Health professionals' sentiment
A 2010 survey in the United States of more than 10,000 physicians found that 16.3% of physicians would consider halting life-sustaining therapy because the family demanded it, even if they believed that it was premature. Approximately 54.5% would not, and the remaining 29.2% responded "it depends". The study also found that 45.8% of physicians agreed that physician-assisted suicide should be allowed in some cases; 40.7% did not, and the remaining 13.5% felt it depended.

In the United Kingdom, the assisted dying campaign group Dignity in Dying cites research in which 54% of general practitioners support or are neutral towards a law change on assisted dying. Similarly, a 2017 Doctors.net.uk poll reported in the British Medical Journal stated that 55% of doctors believe assisted dying, in defined circumstances, should be legalised in the UK.

In 2019, the World Medical Association issued a statement during its 70th Assembly declaring itself opposed to euthanasia and assisted suicide.

Broadly against
The Roman Catholic Church condemns euthanasia and assisted suicide as morally wrong. As paragraph 2324 of the Catechism of the Catholic Church states, "Intentional euthanasia, whatever its forms or motives, is murder. It is gravely contrary to the dignity of the human person and to the respect due to the living God, his Creator". Because of this, per the Declaration on Euthanasia, the practice is unacceptable within the Church. The Orthodox Church in America, along with other Eastern Orthodox Churches, also opposes euthanasia stating that "euthanasia is the deliberate cessation of human life, and, as such, must be condemned as murder."

Many non-Catholic churches in the United States take a stance against euthanasia. Among Protestant denominations, the Episcopal Church passed a resolution in 1991 opposing euthanasia and assisted suicide stating that it is "morally wrong and unacceptable to take a human life to relieve the suffering caused by incurable illnesses." Protestant and other non-Catholic churches which oppose euthanasia include:

 * Assemblies of God
 * The Church of Jesus Christ of Latter-day Saints
 * Church of the Nazarene
 * Evangelical Lutheran Church in America
 * Presbyterian Church in America
 * Lutheran Church–Missouri Synod
 * Reformed Church in America
 * Salvation Army
 * Seventh-day Adventist Church
 * Southern Baptist Convention
 * United Methodist Church

Partially in favor of
The Church of England accepts passive euthanasia under some circumstances, but is strongly against active euthanasia, and has led opposition against recent attempts to legalise it. The United Church of Canada accepts passive euthanasia under some circumstances, but is in general against active euthanasia, with growing acceptance now that active euthanasia has been partly legalised in Canada. The Waldensians take a liberal stance on Euthanasia and allow the decision to lie with individuals.

Islam
Euthanasia is a complex issue in Islamic theology; however, in general it is considered contrary to Islamic law and holy texts. Among interpretations of the Qur'an and Hadith, the early termination of life is a crime, be it by suicide or helping one commit suicide. The various positions on the cessation of medical treatment are mixed and considered a different class of action than direct termination of life, especially if the patient is suffering. Suicide and euthanasia are both crimes in almost all Muslim majority countries.

Judaism
There is much debate on the topic of euthanasia in Judaic theology, ethics, and general opinion (especially in Israel and the United States). Passive euthanasia was declared legal by Israel's highest court under certain conditions and has reached some level of acceptance. Active euthanasia remains illegal; however, the topic is actively under debate with no clear consensus through legal, ethical, theological and spiritual perspectives.

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title: Euthanasia


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Extraterrestrial life

Extraterrestrial life, alien life, or colloquially simply aliens, is life which does not originate from Earth. No extraterrestrial life has yet been conclusively detected. Such life might range from simple forms such as prokaryotes to intelligent beings, possibly bringing forth civilizations that might be far more advanced than the human species. The Drake equation speculates about the existence of sapient life elsewhere in the universe. The science of extraterrestrial life is known as astrobiology.

Speculation about the possibility of inhabited worlds beyond Earth dates back to antiquity. Early Christian writers discussed the idea of a "plurality of worlds" as proposed by earlier thinkers such as Democritus; Augustine references Epicurus's idea of innumerable worlds "throughout the boundless immensity of space" (originally expressed in his Letter to Herodotus) in The City of God.

Pre-modern writers typically assumed extraterrestrial "worlds" are inhabited by living beings. William Vorilong, in the 15th century, acknowledged the possibility that Jesus could have visited extraterrestrial worlds to redeem their inhabitants. Nicholas of Cusa wrote in 1440 that Earth is "a brilliant star" like other celestial objects visible in space; which would appear similar to the Sun from an exterior perspective due to a layer of "fiery brightness" in the outer layer of the atmosphere. He theorised all extraterrestrial bodies could be inhabited by men, plants, and animals, including the Sun. Descartes wrote that there was no means to prove that the stars were not inhabited by "intelligent creatures", but their existence was a matter of speculation.

Furthermore, when considering the atmospheric composition and ecosystems hosted by these extraterrestrial bodies, the matter of extraterrestrial life seems more of a speculation than reality due to the harsh conditions and disparate chemical composition of the atmospheres when compared to the life-abundant Earth. However, there are many extreme and chemically harsh ecosystems on Earth that do support forms of life and are often hypothesized to be the origin of life on Earth. Hydrothermal vents, acidic hot springs, and volcanic lakes are all prime examples of life forming under difficult circumstances, and could provide parallels to the extreme environments on other planets and give hope to the possibility of extraterrestrial life.

Since the mid-20th century, active research has taken place to look for signs of extraterrestrial life, encompassing searches for current and historic extraterrestrial life, and a narrower search for extraterrestrial intelligent life. Depending on the category of search, methods range from the analysis of telescope and specimen data to radios used to detect and transmit communications.

The concept of extraterrestrial life, and particularly extraterrestrial intelligence, has had a major cultural impact, especially extraterrestrials in fiction. Science fiction has communicated scientific ideas, imagined a wide range of possibilities, and influenced public interest in and perspectives on extraterrestrial life. One shared space is the debate over the wisdom of attempting communication with extraterrestrial intelligence. Some encourage aggressive methods to try to contact intelligent extraterrestrial life. Others – citing the tendency of technologically advanced human societies to enslave or destroy less advanced societies – argue it may be dangerous to actively draw attention to Earth.

Context
If extraterrestrial life exists, it could range from simple microorganisms and multicellular organisms similar to animals or plants, to complex alien intelligences akin to humans. When scientists talk about extraterrestrial life, they consider all those types. Although it is possible that extraterrestrial life may have other configurations, scientists use the hierarchy of lifeforms from Earth for simplicity, as it is the only one known to exist.

According to the Big Bang interpretations, the universe as a whole was initially too hot to allow life. 15 million years later, it cooled to temperate levels, but the elements that make up living things did not exist yet. The only freely available elements at that point were hydrogen and helium. Carbon and oxygen (and later, water) would not appear until 50 million years later, created through stellar fusion. At that point, the difficulty for life to appear was not the temperature, but the scarcity of free heavy elements. Planetary systems emerged, and the first organic compounds may have formed in the protoplanetary disk of dust grains that would eventually create rocky planets like Earth. Although Earth was in a molten state after its birth and may have burned any organics that fell in it, it would have been more receptive once it cooled down. Once the right conditions on Earth were met, life started by a chemical process known as abiogenesis. Alternatively, life may have formed less frequently, then spread – by meteoroids, for example – between habitable planets in a process called panspermia.

There is an area around a star, the circumstellar habitable zone or "Goldilocks zone", where water may be at the right temperature to exist in liquid form at a planetary surface. This area is neither too close to the star, where water would become steam, nor too far away, where water would be frozen as a rock. However, although useful as an approximation, planetary habitability is complex and defined by several factors. Being in the habitable zone is not enough for a planet to be habitable, not even to actually have such liquid water. Venus is located in the habitable zone of the Solar System but does not have liquid water because of the conditions of its atmosphere. Jovian planets or Gas Giants are not considered habitable even if they orbit close enough to their stars as hot Jupiters, due to crushing atmospheric pressures. The actual distances for the habitable zones vary according to the type of star, and even the solar activity of each specific star influences the local habitability. The type of star also defines the time the habitable zone will exist, as its presence and limits will change along with the star's stellar evolution.

Life on Earth is quite ubiquitous across the planet and has adapted over time to almost all the available environments in it, even the most hostile ones. As a result, it is inferred that life in other celestial bodies may be equally adaptive. However, the origin of life is unrelated to its ease of adaptation, and may have stricter requirements. A planet or moon may not have any life on it, even if it was habitable.

Likelihood of existence
It is unclear if life and intelligent life are ubiquitous in the cosmos or rare. The hypothesis of ubiquitous extraterrestrial life relies on three main ideas. The first one, the size of the universe allows for plenty of planets to have a similar habitability to Earth, and the age of the universe gives enough time for a long process analog to the history of Earth to happen there. The second is that the chemical elements that make up life, such as carbon and water, are ubiquitous in the universe. The third one is that the physical laws are universal, which means that the forces that would facilitate or prevent the existence of life would be the same ones as on Earth. According to this argument, made by scientists such as Carl Sagan and Stephen Hawking, it would be improbable for life not to exist somewhere else other than Earth. This argument is embodied in the Copernican principle, which states that Earth does not occupy a unique position in the Universe, and the mediocrity principle, which states that there is nothing special about life on Earth.

Other authors consider instead that life in the cosmos, or at least multicellular life, may be actually rare. The Rare Earth hypothesis maintains that life on Earth is possible because of a series of factors that range from the location in the galaxy and the configuration of the Solar System to local characteristics of the planet, and that it is unlikely that all such requirements are simultaneously met by another planet. The proponents of this hypothesis consider that very little evidence suggests the existence of extraterrestrial life, and that at this point it is just a desired result and not a reasonable scientific explanation for any gathered data.

In 1961, astronomer and astrophysicist Frank Drake devised the Drake equation as a way to stimulate scientific dialogue at a meeting on the search for extraterrestrial intelligence (SETI). The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilisations in the Milky Way galaxy. The Drake equation is:
 * $$N = R_{\ast} \cdot f_p \cdot n_e \cdot f_{\ell} \cdot f_i \cdot f_c \cdot L$$

where:
 * N = the number of Milky Way galaxy civilisations already capable of communicating across interplanetary space

and
 * R* = the average rate of star formation in our galaxy
 * fp = the fraction of those stars that have planets
 * ne = the average number of planets that can potentially support life
 * fl = the fraction of planets that actually support life
 * fi = the fraction of planets with life that evolves to become intelligent life (civilisations)
 * fc = the fraction of civilisations that develop a technology to broadcast detectable signs of their existence into space
 * L = the length of time over which such civilisations broadcast detectable signals into space

Drake's proposed estimates are as follows, but numbers on the right side of the equation are agreed as speculative and open to substitution:

$$10{,}000 = 5 \cdot 0.5 \cdot 2 \cdot 1 \cdot 0.2 \cdot 1 \cdot 10{,}000$$

The Drake equation has proved controversial since, although it is written as a math equation, none of its values were known at the time. Although some values may eventually be measured, others are based on social sciences and are not knowable by their very nature. This does not allow one to make noteworthy conclusions from the equation.

Based on observations from the Hubble Space Telescope, there are nearly 2 trillion galaxies in the observable universe. It is estimated that at least ten per cent of all Sun-like stars have a system of planets, i.e. there are $6.25$ stars with planets orbiting them in the observable universe. Even if it is assumed that only one out of a billion of these stars has planets supporting life, there would be some 6.25 billion life-supporting planetary systems in the observable universe. A 2013 study based on results from the Kepler spacecraft estimated that the Milky Way contains at least as many planets as it does stars, resulting in 100–400 billion exoplanets.

The apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilisations and the lack of evidence for such civilisations is known as the Fermi paradox. Dennis W. Sciama claimed that life's existence in the universe depends on various fundamental constants. Zhi-Wei Wang and Samuel L. Braunstein suggest that a random universe capable of supporting life is likely to be just barely able to do so, giving a potential explanation to the Fermi paradox.

Biochemical basis
The first basic requirement for life is an environment with non-equilibrium thermodynamics, which means that the thermodynamic equilibrium must be broken by a source of energy. The traditional sources of energy in the cosmos are the stars, such as for life on Earth, which depends on the energy of the sun. However, there are other alternative energy sources, such as volcanos, plate tectonics, and hydrothermal vents. There are ecosystems on Earth in deep areas of the ocean that do not receive sunlight, and take energy from black smokers instead. Magnetic fields and radioactivity have also been proposed as sources of energy, although they would be less efficient ones.

Life on Earth requires water in a liquid state as a solvent in which biochemical reactions take place. It is highly unlikely that an abiogenesis process can start within a gaseous or solid medium: the atom speeds, either too fast or too slow, make it difficult for specific ones to meet and start chemical reactions. A liquid medium also allows the transport of nutrients and substances required for metabolism. Sufficient quantities of carbon and other elements, along with water, might enable the formation of living organisms on terrestrial planets with a chemical make-up and temperature range similar to that of Earth. Life based on ammonia rather than water has been suggested as an alternative, though this solvent appears less suitable than water. It is also conceivable that there are forms of life whose solvent is a liquid hydrocarbon, such as methane, ethane or propane.

Another unknown aspect of potential extraterrestrial life would be the chemical elements that would compose it. Life on Earth is largely composed of carbon, but there could be other hypothetical types of biochemistry. A potential replacement for carbon should be able to create complex molecules, store information required for evolution, and be freely available in the medium. To create DNA, RNA, or a close analog, such an element should be able to bind its atoms with many others, creating complex and stable molecules. It should be able to create at least three covalent bonds; two for making long strings and at least a third to add new links and allow for diverse information. Only nine elements meet this requirement: boron, nitrogen, phosphorus, arsenic, antimony (three bonds), carbon, silicon, germanium and tin (four bonds). As for abundance, carbon, nitrogen, and silicon are the most abundant ones in the universe, far more than the others. On Earth's crust the most abundant of those elements is silicon, in the Hydrosphere it is carbon and in the atmosphere, it is carbon and nitrogen. Silicon, however, has disadvantages over carbon. The molecules formed with silicon atoms are less stable, and more vulnerable to acids, oxygen, and light. An ecosystem of silicon-based lifeforms would require very low temperatures, high atmospheric pressure, an atmosphere devoid of oxygen, and a solvent other than water. The low temperatures required would add an extra problem, the difficulty to kickstart a process of abiogenesis to create life in the first place.

Even if extraterrestrial life is based on carbon and uses water as a solvent, like Earth life, it may still have a radically different biochemistry. Life on Earth started with an RNA world and later evolved to its current form, where some of the RNA tasks were transferred to the DNA and proteins. Extraterrestrial life may still be stuck on the RNA world, or evolve into other configurations. It is unclear if our biochemistry is the most efficient one that could be generated, or which elements would follow a similar pattern. However, it is likely that, even if cells had a different composition to those from Earth, they would still have a cell membrane. Life on Earth jumped from prokaryotes to eukaryotes and from unicellular organisms to multicellular organisms through evolution. So far no alternative process to achieve such a result has been conceived, even if hypothetical. Evolution requires life to be divided into individual organisms, and no alternative organisation has been satisfactorily proposed either. At the basic level, membranes define the limit of a cell, between it and its environment, while remaining partially open to exchange energy and resources with it.

The evolution from simple cells to eukaryotes, and from them to multicellular lifeforms, is not guaranteed. The Cambrian explosion took place thousands of millions of years after the origin of life, and its causes are not fully known yet. On the other hand, the jump to multicellularity took place several times, which suggests that it could be a case of convergent evolution, and so likely to take place on other planets as well. Palaeontologist Simon Conway Morris considers that convergent evolution would lead to kingdoms similar to our plants and animals, and that many features are likely to develop in alien animals as well, such as bilateral symmetry, limbs, digestive systems and heads with sensory organs. Scientists from the University of Oxford analysed it from the perspective of evolutionary theory and wrote in a study in the International Journal of Astrobiology that aliens may be similar to humans. The planetary context would also have an influence: a planet with higher gravity would have smaller animals, and other types of stars can lead to non-green photosynthesisers. The amount of energy available would also affect biodiversity, as an ecosystem sustained by black smokers or hydrothermal vents would have less energy available than those sustained by a star's light and heat, and so its lifeforms would not grow beyond a certain complexity. There is also research in assessing the capacity of life for developing intelligence. It has been suggested that this capacity arises with the number of potential niches a planet contains, and that the complexity of life itself is reflected in the information density of planetary environments, which in turn can be computed from its niches.

Harsh environmental conditions on Earth harboring life
It is common knowledge that the conditions on other planets in the solar system, in addition to the many galaxies outside of the Milky Way galaxy, are very harsh and seem to be too extreme to harbor any life. The environmental conditions on these planets can have intense UV radiation paired with extreme temperatures, lack of water, and much more that can lead to conditions that don't seem to favor the creation or maintenance of extraterrestrial life. However, there has been much historical evidence that some of the earliest and most basic forms of life on Earth originated in some extreme environments that seem unlikely to have harbored life at least at one point in Earth's history. Fossil evidence as well as many historical theories backed up by years of research and studies have marked environments like hydrothermal vents or acidic hot springs as some of the first places that life could have originated on Earth. These environments can be considered extreme when compared to the typical ecosystems that the majority of life on Earth now inhabit, as hydrothermal vents are scorching hot due to the magma escaping from the Earth's mantle and meeting the much colder oceanic water. Even in today's world, there can be a diverse population of bacteria found inhabiting the area surrounding these hydrothermal vents which can suggest that some form of life can be supported even in the harshest of environments like the other planets in the solar system.

The aspects of these harsh environments that make them ideal for the origin of life on Earth, as well as the possibility of creation of life on other planets, is the chemical reactions forming spontaneously. For example, the hydrothermal vents found on the ocean floor are known to support many chemosynthetic processes which allow organisms to utilize energy through reduced chemical compounds that fix carbon. In return, these reactions will allow for organisms to live in relatively low oxygenated environments while maintaining enough energy to support themselves. The early Earth environment was reducing and therefore, these carbon fixing compounds were necessary for the survival and possible origin of life on Earth. With the little amount of information that scientists have found regarding the atmosphere on other planets in the Milky Way galaxy and beyond, the atmospheres are most likely reducing or with very low oxygen levels, especially when compared with Earth's atmosphere. If there were the necessary elements and ions on these planets, the same carbon fixing, reduced chemical compounds occurring around hydrothermal vents could also occur on these planets' surfaces and possibly result in the origin of extraterrestrial life.

Planetary habitability in the Solar System
The Solar System has a wide variety of planets, dwarf planets, and moons, and each one is studied for its potential to host life. Each one has its own specific conditions that may benefit or harm life. So far, the only lifeforms found are those from Earth. No extraterrestrial intelligence other than humans exists or has ever existed within the Solar System. Astrobiologist Mary Voytek points out that it would be unlikely to find large ecosystems, as they would have already been detected by now.

The inner Solar System is likely devoid of life. However, Venus is still of interest to astrobiologists, as it is a terrestrial planet that was likely similar to Earth in its early stages and developed in a different way. There is a greenhouse effect, the surface is the hottest in the Solar System, sulfuric acid clouds, all surface liquid water is lost, and it has a thick carbon-dioxide atmosphere with huge pressure. Comparing both helps to understand the precise differences that lead to beneficial or harmful conditions for life. And despite the conditions against life on Venus, there are suspicions that microbial lifeforms may still survive in high-altitude clouds.

Mars is a cold and almost airless desert, inhospitable to life. However, recent studies revealed that water on Mars used to be quite abundant, forming rivers, lakes, and perhaps even oceans. Mars may have been habitable back then, and life on Mars may have been possible. But when the planetary core ceased to generate a magnetic field, solar winds removed the atmosphere and the planet became vulnerable to solar radiation. Ancient lifeforms may still have left fossilised remains, and microbes may still survive deep underground.

As mentioned, the gas giants and ice giants are unlikely to contain life. The most distant solar system bodies, found in the Kuiper Belt and outwards, are locked in permanent deep-freeze, but cannot be ruled out completely.

Although the giant planets themselves are highly unlikely to have life, there is much hope to find it on moons orbiting these planets. Europa, from the Jovian system, has a subsurface ocean below a thick layer of ice. Ganymede and Callisto also have subsurface oceans, but life is less likely in them because water is sandwiched between layers of solid ice. Europa would have contact between the ocean and the rocky surface, which helps the chemical reactions. It may be difficult to dig so deep in order to study those oceans, though. Enceladus, a tiny moon of Saturn with another subsurface ocean, may not need to be dug, as it releases water to space in eruption columns. The space probe Cassini flew inside one of these, but could not make a full study because NASA did not expect this phenomenon and did not equip the probe to study ocean water. Still, Cassini detected complex organic molecules, salts, evidence of hydrothermal activity, hydrogen, and methane.

Titan is the only celestial body in the Solar System besides Earth that has liquid bodies on the surface. It has rivers, lakes, and rain of hydrocarbons, methane, and ethane, and even a cycle similar to Earth's water cycle. This special context encourages speculations about lifeforms with different biochemistry, but the cold temperatures would make such chemistry take place at a very slow pace. Water is rock-solid on the surface, but Titan does have subsurface water ocean like several other moons. However, it is of such a great depth that it would be very difficult to access it for study.

Scientific search
The science that searches and studies life in the universe, both on Earth and elsewhere, is called astrobiology. With the study of Earth's life, the only known form of life, astrobiology seeks to study how life starts and evolves and the requirements for its continuous existence. This helps to determine what to look for when searching for life in other celestial bodies. This is a complex area of study, and uses the combined perspectives of several scientific disciplines, such as astronomy, biology, chemistry, geology, oceanography, and atmospheric sciences.

The scientific search for extraterrestrial life is being carried out both directly and indirectly. , 3,667 exoplanets in 2,747 systems have been identified, and other planets and moons in the Solar System hold the potential for hosting primitive life such as microorganisms. As of 8 February 2021, an updated status of studies considering the possible detection of lifeforms on Venus (via phosphine) and Mars (via methane) was reported.

Search for basic life

Scientists search for biosignatures within the Solar System by studying planetary surfaces and examining meteorites. Some claim to have identified evidence that microbial life has existed on Mars. In 1996, a controversial report stated that structures resembling nanobacteria were discovered in a meteorite, ALH84001, formed of rock ejected from Mars. Although all the unusual properties of the meteorite were eventually explained as the result of inorganic processes, the controversy over its discovery laid the groundwork for the development of astrobiology.

An experiment on the two Viking Mars landers reported gas emissions from heated Martian soil samples that some scientists argue are consistent with the presence of living microorganisms. Lack of corroborating evidence from other experiments on the same samples suggests that a non-biological reaction is a more likely hypothesis.

In February 2005 NASA scientists reported they may have found some evidence of extraterrestrial life on Mars. The two scientists, Carol Stoker and Larry Lemke of NASA's Ames Research Center, based their claim on methane signatures found in Mars's atmosphere resembling the methane production of some forms of primitive life on Earth, as well as on their own study of primitive life near the Rio Tinto river in Spain. NASA officials soon distanced NASA from the scientists' claims, and Stoker herself backed off from her initial assertions.

In November 2011, NASA launched the Mars Science Laboratory that landed the Curiosity rover on Mars. It is designed to assess the past and present habitability on Mars using a variety of scientific instruments. The rover landed on Mars at Gale Crater in August 2012.

A group of scientists at Cornell University started a catalog of microorganisms, with the way each one reacts to sunlight. The goal is to help with the search for similar organisms in exoplanets, as the starlight reflected by planets rich in such organisms would have a specific spectrum, unlike that of starlight reflected from lifeless planets. If Earth was studied from afar with this system, it would reveal a shade of green, as a result of the abundance of plants with photosynthesis.

In August 2011, NASA studied meteorites found on Antarctica, finding adenine, guanine, hypoxanthine and xanthine. Adenine and guanine are components of DNA, and the others are used in other biological processes. The studies ruled out pollution of the meteorites on Earth, as those components would not be freely available the way they were found in the samples. This discovery suggests that several organic molecules that serve as building blocks of life may be generated within asteroids and comets. In October 2011, scientists reported that cosmic dust contains complex organic compounds ("amorphous organic solids with a mixed aromatic-aliphatic structure") that could be created naturally, and rapidly, by stars. It is still unclear if those compounds played a role in the creation of life on Earth, but Sun Kwok, of the University of Hong Kong, thinks so. "If this is the case, life on Earth may have had an easier time getting started as these organics can serve as basic ingredients for life."

In August 2012, and in a world first, astronomers at Copenhagen University reported the detection of a specific sugar molecule, glycolaldehyde, in a distant star system. The molecule was found around the protostellar binary IRAS 16293-2422, which is located 400 light years from Earth. Glycolaldehyde is needed to form ribonucleic acid, or RNA, which is similar in function to DNA. This finding suggests that complex organic molecules may form in stellar systems prior to the formation of planets, eventually arriving on young planets early in their formation.

In December 2023, astronomers reported the first time discovery, in the plumes of Enceladus, moon of the planet Saturn, of hydrogen cyanide, a possible chemical essential for life as we know it, as well as other organic molecules, some of which are yet to be better identified and understood. According to the researchers, "these [newly discovered] compounds could potentially support extant microbial communities or drive complex organic synthesis leading to the origin of life."

Search for extraterrestrial intelligences
Although most searches are focused on the biology of extraterrestrial life, an extraterrestrial intelligence capable enough to develop a civilization may be detectable by other means as well. Technology may generate technosignatures, effects on the native planet that may not be caused by natural causes. There are three main types of technosignatures considered: interstellar communications, effects on the atmosphere, and planetary-sized structures such as Dyson spheres.

Organizations such as the SETI Institute search the cosmos for potential forms of communication. They started with radio waves, and now search for laser pulses as well. The challenge for this search is that there are natural sources of such signals as well, such as gamma-ray bursts and supernovae, and the difference between a natural signal and an artificial one would be in its specific patterns. Astronomers intend to use artificial intelligence for this, as it can manage large amounts of data and is devoid of biases and preconceptions. Besides, even if there is an advanced extraterrestrial civilization, there is no guarantee that it is transmitting radio communications in the direction of Earth. The length of time required for a signal to travel across space means that a potential answer may arrive decades or centuries after the initial message.

The atmosphere of Earth is rich in nitrogen dioxide as a result of air pollution, which can be detectable. The natural abundance of carbon, which is also relatively reactive, makes it likely to be a basic component of the development of a potential extraterrestrial technological civilization, as it is on Earth. Fossil fuels may likely be generated and used on such worlds as well. The abundance of chlorofluorocarbons in the atmosphere can also be a clear technosignature, considering their role in ozone depletion. Light pollution may be another technosignature, as multiple lights on the night side of a rocky planet can be a sign of advanced technological development. However, modern telescopes are not strong enough to study exoplanets with the required level of detail to perceive it.

The Kardashev scale proposes that a civilization may eventually start consuming energy directly from its local star. This would require giant structures built next to it, called Dyson spheres. Those speculative structures would cause an excess infrared radiation, that telescopes may notice. The infrared radiation is typical of young stars, surrounded by dusty protoplanetary disks that will eventually form planets. An older star such as the Sun would have no natural reason to have excess infrared radiation. The presence of heavy elements in a star's light-spectrum is another potential biosignature; such elements would (in theory) be found if the star were being used as an incinerator/repository for nuclear waste products.

Extrasolar planets
Some astronomers search for extrasolar planets that may be conducive to life, narrowing the search to terrestrial planets within the habitable zones of their stars. Since 1992, over four thousand exoplanets have been discovered ( planets in planetary systems including  multiple planetary systems as of ).

The extrasolar planets so far discovered range in size from that of terrestrial planets similar to Earth's size to that of gas giants larger than Jupiter. The number of observed exoplanets is expected to increase greatly in the coming years. The Kepler space telescope has also detected a few thousand candidate planets, of which about 11% may be false positives.

There is at least one planet on average per star. About 1 in 5 Sun-like stars have an "Earth-sized" planet in the habitable zone, with the nearest expected to be within 12 light-years distance from Earth. Assuming 200 billion stars in the Milky Way, that would be 11 billion potentially habitable Earth-sized planets in the Milky Way, rising to 40 billion if red dwarfs are included. The rogue planets in the Milky Way possibly number in the trillions.

The nearest known exoplanet is Proxima Centauri b, located 4.2 ly from Earth in the southern constellation of Centaurus.

, the least massive exoplanet known is PSR B1257+12 A, which is about twice the mass of the Moon. The most massive planet listed on the NASA Exoplanet Archive is DENIS-P J082303.1−491201 b, about 29 times the mass of Jupiter, although according to most definitions of a planet, it is too massive to be a planet and may be a brown dwarf instead. Almost all of the planets detected so far are within the Milky Way, but there have also been a few possible detections of extragalactic planets. The study of planetary habitability also considers a wide range of other factors in determining the suitability of a planet for hosting life.

One sign that a planet probably already contains life is the presence of an atmosphere with significant amounts of oxygen, since that gas is highly reactive and generally would not last long without constant replenishment. This replenishment occurs on Earth through photosynthetic organisms. One way to analyse the atmosphere of an exoplanet is through spectrography when it transits its star, though this might only be feasible with dim stars like white dwarfs.

Cosmic pluralism

The modern concept of extraterrestrial life is based on assumptions that were not commonplace during the early days of astronomy. The first explanations for the celestial objects seen in the night sky were based on mythology. Scholars from Ancient Greece were the first to consider that the universe is inherently understandable and rejected explanations based on supernatural incomprehensible forces, such as the myth of the Sun being pulled across the sky in the chariot of Apollo. They had not developed the scientific method yet and based their ideas on pure thought and speculation, but they developed precursor ideas to it, such as that explanations had to be discarded if they contradict observable facts. The discussions of those Greek scholars established many of the pillars that would eventually lead to the idea of extraterrestrial life, such as Earth being round and not flat. The cosmos was first structured in a geocentric model that considered that the sun and all other celestial bodies revolve around Earth. However, they did not consider them as worlds. In Greek understanding, the world was composed by both Earth and the celestial objects with noticeable movements. Anaximander thought that the cosmos was made from apeiron, a substance that created the world, and that the world would eventually return to the cosmos.

Eventually two groups emerged, the atomists that thought that matter at both Earth and the cosmos was equally made of small atoms of the classical elements (earth, water, fire and air), and the Aristotelians who thought that those elements were exclusive of Earth and that the cosmos was made of a fifth one, the aether. Atomist Epicurus thought that the processes that created the world, its animals and plants should have created other worlds elsewhere, along with their own animals and plants. Aristotle thought instead that all the earth element naturally fell towards the center of the universe, and that would made it impossible for other planets to exist elsewhere. Under that reasoning, Earth was not only in the center, it was also the only planet in the universe.

Cosmic pluralism, the plurality of worlds, or simply pluralism, describes the philosophical belief in numerous "worlds" in addition to Earth, which might harbor extraterrestrial life. The earliest recorded assertion of extraterrestrial human life is found in ancient scriptures of Jainism. There are multiple "worlds" mentioned in Jain scriptures that support human life. These include, among others, Bharat Kshetra, Mahavideh Kshetra, Airavat Kshetra, and Hari kshetra. Medieval Muslim writers like Fakhr al-Din al-Razi and Muhammad al-Baqir supported cosmic pluralism on the basis of the Qur'an. Chaucer's poem The House of Fame engaged in medieval thought experiments that postulated the plurality of worlds. However, those ideas about other worlds were different from the current knowledge about the structure of the universe, and did not postulate the existence of planetary systems other than the Solar System. When those authors talk about other worlds, they talk about places located at the center of their own systems, and with their own stellar vaults and cosmos surrounding them.

The Greek ideas and the disputes between atomists and Aristotelians outlived the fall of the Greek empire. The Great Library of Alexandria compiled information about it, part of which was translated by Islamic scholars and thus survived the end of the Library. Baghdad combined the knowledge of the Greeks, the Indians, the Chinese and its own scholars, and the knowledge expanded through the Byzantine Empire. From there it eventually returned to Europe by the time of the Middle Ages. However, as the Greek atomist doctrine held that the world was created by random movements of atoms, with no need for a creator deity, it became associated with atheism, and the dispute intertwined with religious ones. Still, the Church did not react to those topics in a homogeneous way, and there were stricter and more permissive views within the church itself.

The first known mention of the term 'panspermia' was in the writings of the 5th-century BC Greek philosopher Anaxagoras. He proposed the idea that life exists everywhere.

Early modern period
By the time of the late Middle Ages there were many known inaccuracies in the geocentric model, but it was kept in use because naked eye observations provided limited data. Nicolaus Copernicus started the Copernican Revolution by proposing that the planets spin around the sun rather than Earth. His proposal had little acceptance at first because, as he kept the assumption that orbits were perfect circles, his model led to as many inaccuracies as the geocentric one. Tycho Brahe improved the available data with naked-eye observatories, which worked with highly complex sextants and quadrants. Tycho could not make sense of his observations, but Johannes Kepler did: orbits were not perfect circles, but ellipses. This knowledge benefited the Copernican model, which worked now almost perfectly. The invention of the telescope a short time later, perfected by Galileo Galilei, clarified the final doubts, and the paradigm shift was completed. Under this new understanding, the notion of extraterrestrial life became feasible: if Earth is but just a planet orbiting around a star, there may be planets similar to Earth elsewhere. The astronomical study of distant bodies also proved that physical laws are the same elsewhere in the universe as on Earth, with nothing making the planet truly special.

The new ideas were met with resistance from the Catholic church. Galileo was trialed for the heliocentric model, which was considered heretical, and forced to recant it. The best-known early-modern proponent of ideas of extraterrestrial life was the Italian philosopher Giordano Bruno, who argued in the 16th century for an infinite universe in which every star is surrounded by its own planetary system. Bruno wrote that other worlds "have no less virtue nor a nature different to that of our earth" and, like Earth, "contain animals and inhabitants". Bruno's belief in the plurality of worlds was one of the charges leveled against him by the Venetian Holy Inquisition, which trialed and executed him.

The heliocentric model was further strengthened by the postulation of the theory of gravity by Sir Isaac Newton. This theory provided the mathematics that explains the motions of all things in the universe, including planetary orbits. By this point, the geocentric model was definitely discarded. By this time, the use of the scientific method had become a standard, and new discoveries were expected to provide evidence and rigorous mathematical explanations. Science also took a deeper interest in the mechanics of natural phenomena, trying to explain not just the way nature works but also the reasons for working that way.

There was very little actual discussion about extraterrestrial life before this point, as the Aristotlean ideas remained influential while geocentrism was still accepted. When it was finally proved wrong, it not only meant that Earth was not the center of the universe, but also that the lights seen in the sky were not just lights, but physical objects. The notion that life may exist in them as well soon became an ongoing topic of discussion, although one with no practical ways to investigate.

The possibility of extraterrestrials remained a widespread speculation as scientific discovery accelerated. William Herschel, the discoverer of Uranus, was one of many 18th–19th-century astronomers who believed that the Solar System is populated by alien life. Other scholars of the period who championed "cosmic pluralism" included Immanuel Kant and Benjamin Franklin. At the height of the Enlightenment, even the Sun and Moon were considered candidates for extraterrestrial inhabitants.

19th century
Speculation about life on Mars increased in the late 19th century, following telescopic observation of apparent Martian canals – which soon, however, turned out to be optical illusions. Despite this, in 1895, American astronomer Percival Lowell published his book Mars, followed by Mars and its Canals in 1906, proposing that the canals were the work of a long-gone civilisation.

Spectroscopic analysis of Mars's atmosphere began in earnest in 1894, when U.S. astronomer William Wallace Campbell showed that neither water nor oxygen was present in the Martian atmosphere. By 1909 better telescopes and the best perihelic opposition of Mars since 1877 conclusively put an end to the canal hypothesis.

As a consequence of the belief in the spontaneous generation there was little thought about the conditions of each celestial body: it was simply assumed that life would thrive anywhere. This theory was disproved by Louis Pasteur in the 19th century. Popular belief in thriving alien civilisations elsewhere in the solar system still remained strong until Mariner 4 and Mariner 9 provided close images of Mars, which debunked forever the idea of the existence of Martians and decreased the previous expectations of finding alien life in general. The end of the spontaneous generation belief forced to investigate the origin of life. Although abiogenesis is the more accepted theory, a number of authors reclaimed the term "panspermia" and proposed that life was brought to Earth from elsewhere. Some of those authors are Jöns Jacob Berzelius (1834), Kelvin (1871), Hermann von Helmholtz (1879) and, somewhat later, by Svante Arrhenius (1903).

The science fiction genre, although not so named during the time, developed during the late 19th century. The expansion of the genre of extraterrestrials in fiction influenced the popular perception over the real-life topic, making people eager to jump to conclusions about the discovery of aliens. Science marched at a slower pace, some discoveries fueled expectations and others dashed excessive hopes. For example, with the advent of telescopes, most structures seen on the Moon or Mars were immediately attributed to Selenites or Martians, and later ones (such as more powerful telescopes) revealed that all such discoveries were natural features. A famous case is the Cydonia region of Mars, first imagined by the Viking 1 orbiter. The low-resolution photos showed a rock formation that resembled a human face, but later spacecraft took photos in higher detail that showed that there was nothing special about the site.

Recent history
The search and study of extraterrestrial life became a science of its own, astrobiology. Also known as exobiology, this discipline is studied by the NASA, the ESA, the INAF, and others. Astrobiology studies life from Earth as well, but with a cosmic perspective. For example, abiogenesis is of interest to astrobiology, not because of the origin of life on Earth, but for the chances of a similar process taking place in other celestial bodies. Many aspects of life, from its definition to its chemistry, are analyzed as either likely to be similar in all forms of life across the cosmos or only native to Earth. Astrobiology, however, remains constrained by the current lack of extraterrestrial lifeforms to study, as all life on Earth comes from the same ancestor, and it is hard to infer general characteristics from a group with a single example to analyse.

The 20th century came with great technological advances, speculations about future hypothetical technologies, and an increased basic knowledge of science by the general population thanks to science divulgation through the mass media. The public interest in extraterrestrial life and the lack of discoveries by mainstream science led to the emergence of pseudosciences that provided affirmative, if questionable, answers to the existence of aliens. Ufology claims that many unidentified flying objects (UFOs) would be spaceships from alien species, and ancient astronauts hypothesis claim that aliens would have visited Earth in antiquity and prehistoric times but people would have failed to understand it by then. Most UFOs or UFO sightings can be readily explained as sightings of Earth-based aircraft (including top-secret aircraft), known astronomical objects or weather phenomenons, or as hoaxes.

By the 21st century, it was accepted that multicellular life in the Solar System can only exist on Earth, but the interest in extraterrestrial life increased regardless. This is a result of the advances in several sciences. The knowledge of planetary habitability allows to consider on scientific terms the likelihood of finding life at each specific celestial body, as it is known which features are beneficial and harmful for life. Astronomy and telescopes also improved to the point exoplanets can be confirmed and even studied, increasing the number of search places. Life may still exist elsewhere in the Solar System in unicellular form, but the advances in spacecraft allow to send robots to study samples in situ, with tools of growing complexity and reliability. Although no extraterrestrial life has been found and life may still be just a rarity from Earth, there are scientific reasons to suspect that it can exist elsewhere, and technological advances that may detect it if it does.

Many scientists are optimistic about the chances of finding alien life. In the words of SETI's Frank Drake, "All we know for sure is that the sky is not littered with powerful microwave transmitters". Drake noted that it is entirely possible that advanced technology results in communication being carried out in some way other than conventional radio transmission. At the same time, the data returned by space probes, and giant strides in detection methods, have allowed science to begin delineating habitability criteria on other worlds, and to confirm that at least other planets are plentiful, though aliens remain a question mark. The Wow! signal, detected in 1977 by a SETI project, remains a subject of speculative debate.

On the other hand, other scientists are pessimistic. Jacques Monod wrote that "Man knows at last that he is alone in the indifferent immensity of the universe, whence which he has emerged by chance". In 2000, geologist and paleontologist Peter Ward and astrobiologist Donald Brownlee published a book entitled Rare Earth: Why Complex Life is Uncommon in the Universe. In it, they discussed the Rare Earth hypothesis, in which they claim that Earth-like life is rare in the universe, whereas microbial life is common. Ward and Brownlee are open to the idea of evolution on other planets that is not based on essential Earth-like characteristics such as DNA and carbon.

As for the possible risks, theoretical physicist Stephen Hawking warned in 2010 that humans should not try to contact alien life forms. He warned that aliens might pillage Earth for resources. "If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans", he said. Jared Diamond had earlier expressed similar concerns. On 20 July 2015, Hawking and Russian billionaire Yuri Milner, along with the SETI Institute, announced a well-funded effort, called the Breakthrough Initiatives, to expand efforts to search for extraterrestrial life. The group contracted the services of the 100-meter Robert C. Byrd Green Bank Telescope in West Virginia in the United States and the 64-meter Parkes Telescope in New South Wales, Australia. On 13 February 2015, scientists (including Geoffrey Marcy, Seth Shostak, Frank Drake and David Brin) at a convention of the American Association for the Advancement of Science, discussed Active SETI and whether transmitting a message to possible intelligent extraterrestrials in the Cosmos was a good idea; one result was a statement, signed by many, that a "worldwide scientific, political and humanitarian discussion must occur before any message is sent".

In fiction
Although the idea of extraterrestrial peoples became feasible once astronomy developed enough to understand the nature of planets, they were not thought of as being any different from humans. Having no scientific explanation for the origin of mankind and its relation to other species, there was no reason to expect them to be any other way. This was changed by the 1859 book On the Origin of Species by Charles Darwin, which proposed the theory of evolution. Now with the notion that evolution on other planets may take other directions, science fiction authors created bizarre aliens, clearly distinct from humans. A usual way to do that was to add body features from other animals, such as insects or octopuses. Budget reasons forced to tone down the fantasy in films and TV series, as actor costuming and special effects placed limits on their feasibility. Bizarre aliens became feasible since the 1990s with the advent of computer-generated imagery (CGI), and later on as CGI became more effective and less expensive.

Real-life events sometimes captivate people's imagination and this influences the works of fiction. For example, during the Barney and Betty Hill incident, the first recorded claim of an alien abduction, the couple reported that they were abducted and experimented on by aliens with oversized heads, big eyes, pale grey skin, and small noses, a description that eventually became the grey alien archetype once used in works of fiction.

Government responses
The 1967 Outer Space Treaty and the 1979 Moon Agreement define rules of planetary protection against potentially hazardous extraterrestrial life. COSPAR also provides guidelines for planetary protection. A committee of the United Nations Office for Outer Space Affairs had in 1977 discussed for a year strategies for interacting with extraterrestrial life or intelligence. The discussion ended without any conclusions. As of 2010, the UN lacks response mechanisms for the case of an extraterrestrial contact.

One of the NASA divisions is the Office of Safety and Mission Assurance (OSMA), also known as the Planetary Protection Office. A part of its mission is to "rigorously preclude backward contamination of Earth by extraterrestrial life."

In 2016, the Chinese Government released a white paper detailing its space program. According to the document, one of the research objectives of the program is the search for extraterrestrial life. It is also one of the objectives of the Chinese Five-hundred-meter Aperture Spherical Telescope (FAST) program.

In 2020, Dmitry Rogozin, the head of the Russian space agency, said the search for extraterrestrial life is one of the main goals of deep space research. He also acknowledged the possibility of existence of primitive life on other planets of the Solar System.

The French space agency has an office for the study of "non-identified aero spatial phenomena". The agency is maintaining a publicly accessible database of such phenomena, with over 1600 detailed entries. According to the head of the office, the vast majority of entries have a mundane explanation; but for 25% of entries, their extraterrestrial origin can neither be confirmed nor denied.

In 2020, chairman of the Israel Space Agency Isaac Ben-Israel stated that the probability of detecting life in outer space is "quite large". But he disagrees with his former colleague Haim Eshed who stated that there are contacts between an advanced alien civilisation and some of Earth's governments.

title: Extraterrestrial life


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European Strategic Programme on Research in Information Technology

European Strategic Programme on Research in Information Technology (ESPRIT) was a series of integrated programmes of information technology research and development projects and industrial technology transfer measures. It was a European Union initiative managed by the Directorate General for Industry (DG III) of the European Commission.

Programmes
Five ESPRIT programmes (ESPRIT 0 to ESPRIT 4) ran consecutively from 1983 to 1998. ESPRIT 4 was succeeded by the Information Society Technologies (IST) programme in 1999.

Projects
Some of the projects and products supported by ESPRIT were:

 * BBC Domesday Project, a partnership between Acorn Computers Ltd, Philips, Logica and the BBC with some funding from the European Commission's ESPRIT programme, to mark the 900th anniversary of the original Domesday Book, an 11th-century census of England. It is frequently cited as an example of digital obsolescence on account of the physical medium used for data storage.
 * CGAL, the Computational Geometry Algorithms Library (CGAL) is a software library that aims to provide easy access to efficient and reliable algorithms in computational geometry. While primarily written in C++, Python bindings are also available. The original funding for the project came from the ESPRIT project.
 * Eurocoop & Eurocode: ESPRIT III projects to develop systems for supporting distributed collaborative working.
 * Open Document Architecture, a free and open international standard document file format maintained by the ITU-T to replace all proprietary document file formats. In 1985 ESPRIT financed a pilot implementation of the ODA concept, involving, among others, Bull corporation, Olivetti, ICL and Siemens AG.
 * Paradise: A sub-project of the ESPRIT I project, COSINE which established a pan-European computer-based network infrastructure that enabled research workers to communicate with each other using OSI.  Paradise implemented a distributed X.500 directory across the academic community.
 * Password: Part of the ESPRIT III VALUE project, developed secure applications based on the X.509 standard for use in the academic community.
 * ProCoS I Project (1989–1991), ProCoS II Project (1992–1995), and ProCoS-WG Working Group (1994–1997) on Provably Correct Systems, under ESPRIT II.
 * REDO Project (1989–1992) on software maintenance, under ESPRIT II.
 * RAISE, Rigorous Approach to Industrial Software Engineering, was developed as part of the European ESPRIT II LaCoS project in the 1990s, led by Dines Bjørner.
 * REMORA methodology is an event-driven approach for designing information systems, developed by Colette Rolland. This methodology integrates behavioral and temporal aspects with concepts for modelling the structural aspects of an information system. In the ESPRIT I project TODOS, which has led to the development of an integrated environment for the design of office information systems (OISs),
 * SAMPA: The Speech Assessment Methods Phonetic Alphabet (SAMPA) is a computer-readable phonetic script originally developed in the late 1980s.
 * SCOPES: The Systematic Concurrent design of Products, Equipments and Control Systems project was a 3-year project launched in July, 1992, with the aim of specifying integrated computer-aided (CAD) tools for design and control of flexible assembly lines.
 * SIP (Advanced Algorithms and Architectures for Speech and Image Processing), a partnership between Thomson-CSF, AEG, CSELT and ENSPS (ESPRIT P26), to develop the algorithmic and architectural techniques required for recognizing and understanding spoken or visual signals and to demonstrate these techniques in suitable applications.
 * StatLog: "ESPRIT project 5170. Comparative testing and evaluation of statistical and logical learning algorithms on large-scale applications to classification, prediction and control"
 * SUNDIAL (Speech UNderstanding DIALgue) started in September 1988 with Logica Ltd. as prime contractor, together with Erlangen University, CSELT, Daimler-Benz, Capgemini, Politecnico di Torino. Followed the Esprit P.26 to implement and evaluate dialogue systems to be used in telephone industry. The final results were 4 prototypes in 4 languages, involving speech and understanding technologies, and some criteria for evaluation were also reported.
 * Web for Schools, an ESPRIT IV project that introduced the World Wide Web in secondary schools in Europe. Teachers created more than 70 international collaborative educational projects that resulted in an exponential growth of teacher communities and educational activities using the World Wide Web
 * AGENT: A project led by IGN-France aiming at developing an operational automated map generalisation software based on multi-agent system paradigm.