document_title: Redshift

question_text: who was the first to notice that distant galaxies were red shifted with respect to closer stars

text: Redshift

text: History[edit]

text: The history of the subject began with the development in the 19th century of wave mechanics and the exploration of phenomena associated with the Doppler effect. The effect is named after Christian Doppler, who offered the first known physical explanation for the phenomenon in 1842.[4] The hypothesis was tested and confirmed for sound waves by the Dutch scientist Christophorus Buys Ballot in 1845.[5] Doppler correctly predicted that the phenomenon should apply to all waves, and in particular suggested that the varying colors of stars could be attributed to their motion with respect to the Earth.[6] Before this was verified, however, it was found that stellar colors were primarily due to a star's temperature, not motion. Only later was Doppler vindicated by verified redshift observations.

text: The first Doppler redshift was described by French physicist Hippolyte Fizeau in 1848, who pointed to the shift in spectral lines seen in stars as being due to the Doppler effect. The effect is sometimes called the "Doppler–Fizeau effect". In 1868, British astronomer William Huggins was the first to determine the velocity of a star moving away from the Earth by this method.[7] In 1871, optical redshift was confirmed when the phenomenon was observed in Fraunhofer lines using solar rotation, about 0.1 Å in the red.[8] In 1887, Vogel and Scheiner discovered the annual Doppler effect, the yearly change in the Doppler shift of stars located near the ecliptic due to the orbital velocity of the Earth.[9] In 1901, Aristarkh Belopolsky verified optical redshift in the laboratory using a system of rotating mirrors.[10]

text: The earliest occurrence of the term "red-shift" in print (in this hyphenated form) appears to be by American astronomer Walter S. Adams in 1908, in which he mentions "Two methods of investigating that nature of the nebular red-shift".[11] The word does not appear unhyphenated until about 1934 by Willem de Sitter, perhaps indicating that up to that point its German equivalent, Rotverschiebung, was more commonly used.[12]

text: Beginning with observations in 1912, Vesto Slipher discovered that most spiral galaxies, then mostly thought to be spiral nebulae, had considerable redshifts. Slipher first reports on his measurement in the inaugural volume of the Lowell Observatory Bulletin.[13] Three years later, he wrote a review in the journal Popular Astronomy.[14] In it he states, "[...] the early discovery that the great Andromeda spiral had the quite exceptional velocity of –300 km(/s) showed the means then available, capable of investigating not only the spectra of the spirals but their velocities as well."[15] Slipher reported the velocities for 15 spiral nebulae spread across the entire celestial sphere, all but three having observable "positive" (that is recessional) velocities. Subsequently, Edwin Hubble discovered an approximate relationship between the redshifts of such "nebulae" and the distances to them with the formulation of his eponymous Hubble's law.[16] These observations corroborated Alexander Friedmann's 1922 work, in which he derived the Friedmann-Lemaître equations.[17] They are today considered strong evidence for an expanding universe and the Big Bang theory.[18]

text: Measurement, characterization, and interpretation[edit]

text: The spectrum of light that comes from a single source (see idealized spectrum illustration top-right) can be measured. To determine the redshift, one searches for features in the spectrum such as absorption lines, emission lines, or other variations in light intensity. If found, these features can be compared with known features in the spectrum of various chemical compounds found in experiments where that compound is located on Earth. A very common atomic element in space is hydrogen. The spectrum of originally featureless light shone through hydrogen will show a signature spectrum specific to hydrogen that has features at regular intervals. If restricted to absorption lines it would look similar to the illustration (top right). If the same pattern of intervals is seen in an observed spectrum from a distant source but occurring at shifted wavelengths, it can be identified as hydrogen too. If the same spectral line is identified in both spectra—but at different wavelengths—then the redshift can be calculated using the table below. Determining the redshift of an object in this way requires a frequency- or wavelength-range. In order to calculate the redshift one has to know the wavelength of the emitted light in the rest frame of the source, in other words, the wavelength that would be measured by an observer located adjacent to and comoving with the source. Since in astronomical applications this measurement cannot be done directly, because that would require travelling to the distant star of interest, the method using spectral lines described here is used instead. Redshifts cannot be calculated by looking at unidentified features whose rest-frame frequency is unknown, or with a spectrum that is featureless or white noise (random fluctuations in a spectrum).[20]

text: Redshift (and blueshift) may be characterized by the relative difference between the observed and emitted wavelengths (or frequency) of an object. In astronomy, it is customary to refer to this change using a dimensionless quantity called z. If λ represents wavelength and f represents frequency (note, λf = c where c is the speed of light), then z is defined by the equations:[21]

text:
Calculation of redshift,

z

{\displaystyle z}

Based on wavelength
Based on frequency

z
=

λ

o
b
s
v

−

λ

e
m
i
t

λ

e
m
i
t

{\displaystyle z={\frac {\lambda _{\mathrm {obsv} }-\lambda _{\mathrm {emit} }}{\lambda _{\mathrm {emit} }}}}

z
=

f

e
m
i
t

−

f

o
b
s
v

f

o
b
s
v

{\displaystyle z={\frac {f_{\mathrm {emit} }-f_{\mathrm {obsv} }}{f_{\mathrm {obsv} }}}}

1
+
z
=

λ

o
b
s
v

λ

e
m
i
t

{\displaystyle 1+z={\frac {\lambda _{\mathrm {obsv} }}{\lambda _{\mathrm {emit} }}}}

1
+
z
=

f

e
m
i
t

f

o
b
s
v

{\displaystyle 1+z={\frac {f_{\mathrm {emit} }}{f_{\mathrm {obsv} }}}}

tag: table

text: After z is measured, the distinction between redshift and blueshift is simply a matter of whether z is positive or negative. See the formula section below for some basic interpretations that follow when either a redshift or blueshift is observed. For example, Doppler effect blueshifts (z < 0) are associated with objects approaching (moving closer to) the observer with the light shifting to greater energies. Conversely, Doppler effect redshifts (z > 0) are associated with objects receding (moving away) from the observer with the light shifting to lower energies. Likewise, gravitational blueshifts are associated with light emitted from a source residing within a weaker gravitational field as observed from within a stronger gravitational field, while gravitational redshifting implies the opposite conditions.

text: Redshift formulae[edit]

text: In general relativity one can derive several important special-case formulae for redshift in certain special spacetime geometries, as summarized in the following table. In all cases the magnitude of the shift (the value of z) is independent of the wavelength.[2]

text:
Redshift summary

Redshift type
Geometry
Formula[22]

Relativistic Doppler
Minkowski space (flat spacetime)

1
+
z
=
γ

(
1
+

v

∥

c

)

{\displaystyle 1+z=\gamma \left(1+{\frac {v_{\parallel }}{c}}\right)}

z
≈

v

∥

c

{\displaystyle z\approx {\frac {v_{\parallel }}{c}}}

 for small

v

{\displaystyle v}

1
+
z
=

1
+

v
c

1
−

v
c

{\displaystyle 1+z={\sqrt {\frac {1+{\frac {v}{c}}}{1-{\frac {v}{c}}}}}}

 for motion completely in the radial direction.

1
+
z
=

1

1
−

v

2

c

2

{\displaystyle 1+z={\frac {1}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}}

 for motion completely in the transverse direction.

Cosmological redshift
FLRW spacetime (expanding Big Bang universe)

1
+
z
=

a

n
o
w

a

t
h
e
n

{\displaystyle 1+z={\frac {a_{\mathrm {now} }}{a_{\mathrm {then} }}}}

Gravitational redshift
any stationary spacetime (e.g. the Schwarzschild geometry)

1
+
z
=

g

t
t

(

receiver

)

g

t
t

(

source

)

{\displaystyle 1+z={\sqrt {\frac {g_{tt}({\text{receiver}})}{g_{tt}({\text{source}})}}}}

(for the Schwarzschild geometry,

1
+
z
=

1
−

2
G
M

c

2

r

receiver

1
−

2
G
M

c

2

r

source

{\displaystyle 1+z={\sqrt {\frac {1-{\frac {2GM}{c^{2}r_{\text{receiver}}}}}{1-{\frac {2GM}{c^{2}r_{\text{source}}}}}}}}

text: Doppler effect[edit]

text: If a source of the light is moving away from an observer, then redshift (z > 0) occurs; if the source moves towards the observer, then blueshift (z < 0) occurs. This is true for all electromagnetic waves and is explained by the Doppler effect. Consequently, this type of redshift is called the Doppler redshift. If the source moves away from the observer with velocity v, which is much less than the speed of light (v ≪ c), the redshift is given by

text: where c is the speed of light. In the classical Doppler effect, the frequency of the source is not modified, but the recessional motion causes the illusion of a lower frequency.

text: A more complete treatment of the Doppler redshift requires considering relativistic effects associated with motion of sources close to the speed of light. A complete derivation of the effect can be found in the article on the relativistic Doppler effect. In brief, objects moving close to the speed of light will experience deviations from the above formula due to the time dilation of special relativity which can be corrected for by introducing the Lorentz factor γ into the classical Doppler formula as follows (for motion solely in the line of sight):

text: This phenomenon was first observed in a 1938 experiment performed by Herbert E. Ives and G.R. Stilwell, called the Ives–Stilwell experiment.[23]

text: Since the Lorentz factor is dependent only on the magnitude of the velocity, this causes the redshift associated with the relativistic correction to be independent of the orientation of the source movement. In contrast, the classical part of the formula is dependent on the projection of the movement of the source into the line-of-sight which yields different results for different orientations. If θ is the angle between the direction of relative motion and the direction of emission in the observer's frame[24] (zero angle is directly away from the observer), the full form for the relativistic Doppler effect becomes:

text: and for motion solely in the line of sight (θ = 0°), this equation reduces to:

text: For the special case that the light is approaching at right angles (θ = 90°) to the direction of relative motion in the observer's frame,[25] the relativistic redshift is known as the transverse redshift, and a redshift:

text: is measured, even though the object is not moving away from the observer. Even when the source is moving towards the observer, if there is a transverse component to the motion then there is some speed at which the dilation just cancels the expected blueshift and at higher speed the approaching source will be redshifted.[26]

text: Expansion of space[edit]

text: In the early part of the twentieth century, Slipher, Hubble and others made the first measurements of the redshifts and blueshifts of galaxies beyond the Milky Way. They initially interpreted these redshifts and blueshifts as due to random motions, but later Hubble discovered a rough correlation between the increasing redshifts and the increasing distance of galaxies. Theorists almost immediately realized that these observations could be explained by a mechanism for producing redshifts seen in certain cosmological solutions to Einstein's equations of general relativity. Hubble's law of the correlation between redshifts and distances is required by all such models that have a metric expansion of space.[18] As a result, the wavelength of photons propagating through the expanding space is stretched, creating the cosmological redshift.

text: There is a distinction between a redshift in cosmological context as compared to that witnessed when nearby objects exhibit a local Doppler-effect redshift. Rather than cosmological redshifts being a consequence of the relative velocities that are subject to the laws of special relativity (and thus subject to the rule that no two locally separated objects can have relative velocities with respect to each other faster than the speed of light), the photons instead increase in wavelength and redshift because of a global feature of the spacetime metric through which they are traveling. One interpretation of this effect is the idea that space itself is expanding.[27] Due to the expansion increasing as distances increase, the distance between two remote galaxies can increase at more than 3×108 m/s, but this does not imply that the galaxies move faster than the speed of light at their present location (which is forbidden by Lorentz covariance).

text: Mathematical derivation[edit]

text: The observational consequences of this effect can be derived using the equations from general relativity that describe a homogeneous and isotropic universe.

text: To derive the redshift effect, use the geodesic equation for a light wave, which is

text: where

text:
ds is the spacetime interval
dt is the time interval
dr is the spatial interval
c is the speed of light
a is the time-dependent cosmic scale factor
k is the curvature per unit area.

text: For an observer observing the crest of a light wave at a position r = 0 and time t = tnow, the crest of the light wave was emitted at a time t = tthen in the past and a distant position r = R. Integrating over the path in both space and time that the light wave travels yields:

text: In general, the wavelength of light is not the same for the two positions and times considered due to the changing properties of the metric. When the wave was emitted, it had a wavelength λthen. The next crest of the light wave was emitted at a time

text: The observer sees the next crest of the observed light wave with a wavelength λnow to arrive at a time

text: Since the subsequent crest is again emitted from r = R and is observed at r = 0, the following equation can be written:

text: The right-hand side of the two integral equations above are identical which means

text: Using the following manipulation:

text: we find that:

text: For very small variations in time (over the period of one cycle of a light wave) the scale factor is essentially a constant (a = anow today and a = athen previously). This yields

text: which can be rewritten as

text: Using the definition of redshift provided above, the equation

text: is obtained. In an expanding universe such as the one we inhabit, the scale factor is monotonically increasing as time passes, thus, z is positive and distant galaxies appear redshifted.

text: Using a model of the expansion of the Universe, redshift can be related to the age of an observed object, the so-called cosmic time–redshift relation. Denote a density ratio as Ω0:

text: with ρcrit the critical density demarcating a universe that eventually crunches from one that simply expands. This density is about three hydrogen atoms per thousand liters of space.[28] At large redshifts one finds:

text: where H0 is the present-day Hubble constant, and z is the redshift.[29][30][31]

text: Distinguishing between cosmological and local effects[edit]

text: For cosmological redshifts of z < 0.01 additional Doppler redshifts and blueshifts due to the peculiar motions of the galaxies relative to one another cause a wide scatter from the standard Hubble Law.[32] The resulting situation can be illustrated by the Expanding Rubber Sheet Universe, a common cosmological analogy used to describe the expansion of space. If two objects are represented by ball bearings and spacetime by a stretching rubber sheet, the Doppler effect is caused by rolling the balls across the sheet to create peculiar motion. The cosmological redshift occurs when the ball bearings are stuck to the sheet and the sheet is stretched.[33][34][35]

text: The redshifts of galaxies include both a component related to recessional velocity from expansion of the Universe, and a component related to peculiar motion (Doppler shift).[36] The redshift due to expansion of the Universe depends upon the recessional velocity in a fashion determined by the cosmological model chosen to describe the expansion of the Universe, which is very different from how Doppler redshift depends upon local velocity.[37] Describing the cosmological expansion origin of redshift, cosmologist Edward Robert Harrison said, "Light leaves a galaxy, which is stationary in its local region of space, and is eventually received by observers who are stationary in their own local region of space. Between the galaxy and the observer, light travels through vast regions of expanding space. As a result, all wavelengths of the light are stretched by the expansion of space. It is as simple as that..."[38] Steven Weinberg clarified, "The increase of wavelength from emission to absorption of light does not depend on the rate of change of a(t) [here a(t) is the Robertson-Walker scale factor] at the times of emission or absorption, but on the increase of a(t) in the whole period from emission to absorption."[39]

text: Popular literature often uses the expression "Doppler redshift" instead of "cosmological redshift" to describe the redshift of galaxies dominated by the expansion of spacetime, but the cosmological redshift is not found using the relativistic Doppler equation[40] which is instead characterized by special relativity; thus v > c is impossible while, in contrast, v > c is possible for cosmological redshifts because the space which separates the objects (for example, a quasar from the Earth) can expand faster than the speed of light.[41] More mathematically, the viewpoint that "distant galaxies are receding" and the viewpoint that "the space between galaxies is expanding" are related by changing coordinate systems. Expressing this precisely requires working with the mathematics of the Friedmann-Robertson-Walker metric.[42]

text: If the Universe were contracting instead of expanding, we would see distant galaxies blueshifted by an amount proportional to their distance instead of redshifted.[43]

text: Gravitational redshift[edit]

text: In the theory of general relativity, there is time dilation within a gravitational well. This is known as the gravitational redshift or Einstein Shift.[44] The theoretical derivation of this effect follows from the Schwarzschild solution of the Einstein equations which yields the following formula for redshift associated with a photon traveling in the gravitational field of an uncharged, nonrotating, spherically symmetric mass:

text: where

text:
G is the gravitational constant,
M is the mass of the object creating the gravitational field,
r is the radial coordinate of the source (which is analogous to the classical distance from the center of the object, but is actually a Schwarzschild coordinate), and
c is the speed of light.

text: This gravitational redshift result can be derived from the assumptions of special relativity and the equivalence principle; the full theory of general relativity is not required.[45]

text: The effect is very small but measurable on Earth using the Mössbauer effect and was first observed in the Pound–Rebka experiment.[46] However, it is significant near a black hole, and as an object approaches the event horizon the red shift becomes infinite. It is also the dominant cause of large angular-scale temperature fluctuations in the cosmic microwave background radiation (see Sachs-Wolfe effect).[47][48]

text: Observations in astronomy[edit]

text: The redshift observed in astronomy can be measured because the emission and absorption spectra for atoms are distinctive and well known, calibrated from spectroscopic experiments in laboratories on Earth. When the redshift of various absorption and emission lines from a single astronomical object is measured, z is found to be remarkably constant. Although distant objects may be slightly blurred and lines broadened, it is by no more than can be explained by thermal or mechanical motion of the source. For these reasons and others, the consensus among astronomers is that the redshifts they observe are due to some combination of the three established forms of Doppler-like redshifts. Alternative hypotheses and explanations for redshift such as tired light are not generally considered plausible.[49]

text: Spectroscopy, as a measurement, is considerably more difficult than simple photometry, which measures the brightness of astronomical objects through certain filters.[50] When photometric data is all that is available (for example, the Hubble Deep Field and the Hubble Ultra Deep Field), astronomers rely on a technique for measuring photometric redshifts.[51] Due to the broad wavelength ranges in photometric filters and the necessary assumptions about the nature of the spectrum at the light-source, errors for these sorts of measurements can range up to δz = 0.5, and are much less reliable than spectroscopic determinations.[52] However, photometry does at least allow a qualitative characterization of a redshift. For example, if a Sun-like spectrum had a redshift of z = 1, it would be brightest in the infrared rather than at the yellow-green color associated with the peak of its blackbody spectrum, and the light intensity will be reduced in the filter by a factor of four, (1 + z)2. Both the photon count rate and the photon energy are redshifted. (See K correction for more details on the photometric consequences of redshift.)[53]

text: Local observations[edit]

text: In nearby objects (within our Milky Way galaxy) observed redshifts are almost always related to the line-of-sight velocities associated with the objects being observed. Observations of such redshifts and blueshifts have enabled astronomers to measure velocities and parametrize the masses of the orbiting stars in spectroscopic binaries, a method first employed in 1868 by British astronomer William Huggins.[7] Similarly, small redshifts and blueshifts detected in the spectroscopic measurements of individual stars are one way astronomers have been able to diagnose and measure the presence and characteristics of planetary systems around other stars and have even made very detailed differential measurements of redshifts during planetary transits to determine precise orbital parameters.[54] Finely detailed measurements of redshifts are used in helioseismology to determine the precise movements of the photosphere of the Sun.[55] Redshifts have also been used to make the first measurements of the rotation rates of planets,[56] velocities of interstellar clouds,[57] the rotation of galaxies,[2] and the dynamics of accretion onto neutron stars and black holes which exhibit both Doppler and gravitational redshifts.[58] Additionally, the temperatures of various emitting and absorbing objects can be obtained by measuring Doppler broadening – effectively redshifts and blueshifts over a single emission or absorption line.[59] By measuring the broadening and shifts of the 21-centimeter hydrogen line in different directions, astronomers have been able to measure the recessional velocities of interstellar gas, which in turn reveals the rotation curve of our Milky Way.[2] Similar measurements have been performed on other galaxies, such as Andromeda.[2] As a diagnostic tool, redshift measurements are one of the most important spectroscopic measurements made in astronomy.

text: Extragalactic observations[edit]

text: The most distant objects exhibit larger redshifts corresponding to the Hubble flow of the Universe. The largest observed redshift, corresponding to the greatest distance and furthest back in time, is that of the cosmic microwave background radiation; the numerical value of its redshift is about z = 1089 (z = 0 corresponds to present time), and it shows the state of the Universe about 13.8 billion years ago,[60] and 379,000 years after the initial moments of the Big Bang.[61]

text: The luminous point-like cores of quasars were the first "high-redshift" (z > 0.1) objects discovered before the improvement of telescopes allowed for the discovery of other high-redshift galaxies.

text: For galaxies more distant than the Local Group and the nearby Virgo Cluster, but within a thousand megaparsecs or so, the redshift is approximately proportional to the galaxy's distance. This correlation was first observed by Edwin Hubble and has come to be known as Hubble's law. Vesto Slipher was the first to discover galactic redshifts, in about the year 1912, while Hubble correlated Slipher's measurements with distances he measured by other means to formulate his Law. In the widely accepted cosmological model based on general relativity, redshift is mainly a result of the expansion of space: this means that the farther away a galaxy is from us, the more the space has expanded in the time since the light left that galaxy, so the more the light has been stretched, the more redshifted the light is, and so the faster it appears to be moving away from us. Hubble's law follows in part from the Copernican principle.[62] Because it is usually not known how luminous objects are, measuring the redshift is easier than more direct distance measurements, so redshift is sometimes in practice converted to a crude distance measurement using Hubble's law.

text: Gravitational interactions of galaxies with each other and clusters cause a significant scatter in the normal plot of the Hubble diagram. The peculiar velocities associated with galaxies superimpose a rough trace of the mass of virialized objects in the Universe. This effect leads to such phenomena as nearby galaxies (such as the Andromeda Galaxy) exhibiting blueshifts as we fall towards a common barycenter, and redshift maps of clusters showing a Fingers of God effect due to the scatter of peculiar velocities in a roughly spherical distribution.[62] This added component gives cosmologists a chance to measure the masses of objects independent of the mass to light ratio (the ratio of a galaxy's mass in solar masses to its brightness in solar luminosities), an important tool for measuring dark matter.[63]

text: The Hubble law's linear relationship between distance and redshift assumes that the rate of expansion of the Universe is constant. However, when the Universe was much younger, the expansion rate, and thus the Hubble "constant", was larger than it is today. For more distant galaxies, then, whose light has been travelling to us for much longer times, the approximation of constant expansion rate fails, and the Hubble law becomes a non-linear integral relationship and dependent on the history of the expansion rate since the emission of the light from the galaxy in question. Observations of the redshift-distance relationship can be used, then, to determine the expansion history of the Universe and thus the matter and energy content.

text: While it was long believed that the expansion rate has been continuously decreasing since the Big Bang, recent observations of the redshift-distance relationship using Type Ia supernovae have suggested that in comparatively recent times the expansion rate of the Universe has begun to accelerate.

text: Highest redshifts[edit]

text: Currently, the objects with the highest known redshifts are galaxies and the objects producing gamma ray bursts. The most reliable redshifts are from spectroscopic data, and the highest confirmed spectroscopic redshift of a galaxy is that of GN-z11,[64] with a redshift of z = 11.1, corresponding to 400 million years after the Big Bang. The previous record was held by UDFy-38135539[65] at a redshift of z = 8.6, corresponding to 600 million years after the Big Bang. Slightly less reliable are Lyman-break redshifts, the highest of which is the lensed galaxy A1689-zD1 at a redshift z = 7.5[66][67] and the next highest being z = 7.0.[68] The most distant observed gamma-ray burst with a spectroscopic redshift measurement was GRB 090423, which had a redshift of z = 8.2.[69] The most distant known quasar, ULAS J1120+0641, is at z = 7.1.[70][71] The highest known redshift radio galaxy (TN J0924-2201) is at a redshift z = 5.2[72] and the highest known redshift molecular material is the detection of emission from the CO molecule from the quasar SDSS J1148+5251 at z = 6.42[73]

text: Extremely red objects (EROs) are astronomical sources of radiation that radiate energy in the red and near infrared part of the electromagnetic spectrum. These may be starburst galaxies that have a high redshift accompanied by reddening from intervening dust, or they could be highly redshifted elliptical galaxies with an older (and therefore redder) stellar population.[74] Objects that are even redder than EROs are termed hyper extremely red objects (HEROs).[75]

text: The cosmic microwave background has a redshift of z = 1089, corresponding to an age of approximately 379,000 years after the Big Bang and a comoving distance of more than 46 billion light years.[76] The yet-to-be-observed first light from the oldest Population III stars, not long after atoms first formed and the CMB ceased to be absorbed almost completely, may have redshifts in the range of 20 < z < 100.[77] Other high-redshift events predicted by physics but not presently observable are the cosmic neutrino background from about two seconds after the Big Bang (and a redshift in excess of z > 1010)[78] and the cosmic gravitational wave background emitted directly from inflation at a redshift in excess of z > 1025.[79]

text: In June 2015, astronomers reported evidence for Population III stars in the Cosmos Redshift 7 galaxy at z = 6.60. Such stars are likely to have existed in the very early universe (i.e., at high redshift), and may have started the production of chemical elements heavier than hydrogen that are needed for the later formation of planets and life as we know it.[80][81]

text: Redshift surveys[edit]

text: With advent of automated telescopes and improvements in spectroscopes, a number of collaborations have been made to map the Universe in redshift space. By combining redshift with angular position data, a redshift survey maps the 3D distribution of matter within a field of the sky. These observations are used to measure properties of the large-scale structure of the Universe. The Great Wall, a vast supercluster of galaxies over 500 million light-years wide, provides a dramatic example of a large-scale structure that redshift surveys can detect.[82]

text: The first redshift survey was the CfA Redshift Survey, started in 1977 with the initial data collection completed in 1982.[83] More recently, the 2dF Galaxy Redshift Survey determined the large-scale structure of one section of the Universe, measuring redshifts for over 220,000 galaxies; data collection was completed in 2002, and the final data set was released 30 June 2003.[84] The Sloan Digital Sky Survey (SDSS), is ongoing as of 2013 and aims to measure the redshifts of around 3 million objects.[85] SDSS has recorded redshifts for galaxies as high as 0.8, and has been involved in the detection of quasars beyond z = 6. The DEEP2 Redshift Survey uses the Keck telescopes with the new "DEIMOS" spectrograph; a follow-up to the pilot program DEEP1, DEEP2 is designed to measure faint galaxies with redshifts 0.7 and above, and it is therefore planned to provide a high redshift complement to SDSS and 2dF.[86]

text: Effects from physical optics or radiative transfer[edit]

text: The interactions and phenomena summarized in the subjects of radiative transfer and physical optics can result in shifts in the wavelength and frequency of electromagnetic radiation. In such cases, the shifts correspond to a physical energy transfer to matter or other photons rather than being by a transformation between reference frames. Such shifts can be from such physical phenomena as coherence effects or the scattering of electromagnetic radiation whether from charged elementary particles, from particulates, or from fluctuations of the index of refraction in a dielectric medium as occurs in the radio phenomenon of radio whistlers.[2] While such phenomena are sometimes referred to as "redshifts" and "blueshifts", in astrophysics light-matter interactions that result in energy shifts in the radiation field are generally referred to as "reddening" rather than "redshifting" which, as a term, is normally reserved for the effects discussed above.[2]

text: In many circumstances scattering causes radiation to redden because entropy results in the predominance of many low-energy photons over few high-energy ones (while conserving total energy).[2] Except possibly under carefully controlled conditions, scattering does not produce the same relative change in wavelength across the whole spectrum; that is, any calculated z is generally a function of wavelength. Furthermore, scattering from random media generally occurs at many angles, and z is a function of the scattering angle. If multiple scattering occurs, or the scattering particles have relative motion, then there is generally distortion of spectral lines as well.[2]

text: In interstellar astronomy, visible spectra can appear redder due to scattering processes in a phenomenon referred to as interstellar reddening[2] – similarly Rayleigh scattering causes the atmospheric reddening of the Sun seen in the sunrise or sunset and causes the rest of the sky to have a blue color. This phenomenon is distinct from redshifting because the spectroscopic lines are not shifted to other wavelengths in reddened objects and there is an additional dimming and distortion associated with the phenomenon due to photons being scattered in and out of the line-of-sight.

text: For a list of scattering processes, see Scattering.


document_title: Renunciation of citizenship

question_text: how much is it to renounce us citizenship

root

text: Renunciation of citizenship

text: Historic practices[edit]

text: This section needs expansion. You can help by adding to it. (May 2012)

text: The common law doctrine of perpetual allegiance denied an individual the right to renounce obligations to his sovereign. The bonds of subjecthood were conceived in principle to be both singular and immutable. These practices held on in varying ways until the late 19th century.[1][2]

tag: p

text: The refusal of many states to recognize expatriation became problematic for the United States, which had a large immigrant population. The War of 1812 was caused partly by Britain's impressment of U.S. citizens born in the UK into the British Royal Navy. Immigrants to the U.S. were sometimes held to the obligations of their foreign citizenship when they visited their home countries. In response, the U.S. government passed the Expatriation Act of 1868 and concluded various treaties, the Bancroft Treaties, recognizing the right to renounce one's citizenship.[3][4]

text: The Universal Declaration of Human Rights lists both the right to leave any country, including one's own (Article 13(2)) and the right to change one's nationality (Article 15(2)), which implicitly recognizes the right to renounce citizenship.[citation needed]

text: In modern law[edit]

text: Renunciation of citizenship is particularly relevant in cases of multiple citizenship, given that additional citizenships may be acquired automatically and may be undesirable. Many countries have pragmatic policies that recognize the often arbitrary nature of citizenship claims of other countries and negative consequences, such as loss of security clearance, can mostly be expected only for actively exercising foreign citizenship, for instance by obtaining a foreign passport. People from some countries renounce their citizenship to avoid compulsory military service. However, some people may wish to be free even of the purely theoretical obligations and appearance of dual loyalty that another citizenship implies. Even in countries that allow dual citizenship, such as Australia, Jamaica and Pakistan, electoral laws demand that politicians not be under an obligation of allegiance to any foreign country, and so when politicians have been found to be violating such laws, they stepped down and renounced their other citizenships in response to the public controversy.[5][6][7] Another example may be political refugees who would wish to renounce allegiance to the country from which they escaped.[citation needed]

text: Renunciation law in specific countries[edit]

text: Each country sets its own policies for formal renunciation of citizenship. There is a common concern that individuals about to relinquish their citizenship do not become a stateless person and many countries require evidence of another citizenship or an official promise to grant citizenship before they release that person from citizenship. Some countries may not allow or do not recognize renunciation of citizenship or establish administrative procedures that are essentially impossible to complete.[example needed]

text: Mexico requires renunciation of all other citizenships as a condition of naturalization.[8]

text: Israel allows dual citizenship upon naturalization through the Law of Return, but Knesset (Israeli parliament) members are required to renounce all foreign citizenships.[9][10]

text: Renunciation of citizenship is most straightforward in those countries which recognize and strictly enforce a single citizenship. Thus, voluntary naturalization in another country is considered as "giving up" of one's previous citizenship or implicit renunciation. For practical reasons, such an automatic renunciation cannot officially take place until the authorities of the original country are informed about the naturalization. In Japan, a formal report is required from the renouncing person to be submitted at an embassy. Germany actively investigates whether its citizens living abroad have naturalized there when they apply for a passport; for instance in Canada, German passport applicants have to submit a search of citizenship record.[11] Canada and Australia are signatories to the United Nations Convention on the Reduction of Statelessness, and renunciation is possible only if it will not result in statelessness.[12][13] Applications for renunciation of citizenship need to be submitted in those countries with a waiting time of several months until approval.

text: Nigeria[edit]

text: The right to renounce Nigerian citizenship is established in § 29 of the 1999 Constitution of Nigeria, which states that "any citizen of Nigeria of full age who wishes to renounce his/her Nigerian citizenship shall make a declaration in the prescribed manner for the renunciation", which the government is obliged to register except when Nigeria is physically involved in a war or when the President of Nigeria is of the opinion that the renunciation is contrary to public policy. Under § 29(4)(a), a person of either gender becomes "of full age" at eighteen years, while under § 29(4)(b) a girl younger than that is still deemed to be "of full age" if she is married.[14]

text: In 2013, the Senate of Nigeria proposed a constitutional amendment to delete § 29(4)(b), which would have the effect that girls could only renounce Nigerian citizenship at the age of eighteen or older regardless of their marital status; the amendment passed by a vote of 75–14, two votes greater than the two-thirds supermajority required for the passage of constitutional amendments. However, after the vote, a point of order was raised against the amendment by Senate Deputy Minority Leader Ahmad Sani Yerima (ANPP-Zamfara), who stated that Schedule 2 of the Constitution prohibited the National Assembly of Nigeria from legislating on any matters relating to customary or Islamic law.[15] Some sources suggested that the amendment would have the effect of outlawing child marriage, a matter of personal concern to Yerima due to his 2009 marriage to an Egyptian girl then only 13 years old. Senate President David Mark was initially disinclined to permit a second vote on the matter, but relented after an argument. Yerima's arguments were sufficient to convince enough erstwhile supporters and non-voters to oppose the amendment; with a vote of 60–35, it was deprived of its supermajority and failed to pass.[16][17]

text: Singapore[edit]

text: Citizens of Singapore can only renounce Singaporean citizenship if they have acquired citizenship of another country. At the time of renunciation, renunciants must submit their Singaporean passports and National Registration Identity Cards for cancellation.[18] Male Singaporeans generally cannot renounce citizenship until completing military service, though there are exceptions for those who emigrated at a young age (generally those who were not educated in Singapore).[19] In 2012, a Hong Kong-born man who had acquired Singaporean citizenship by registration while a minor filed a lawsuit regarding this requirement.[20]

text: About 1,200 Singaporean citizens renounce their citizenship every year, a quarter of them naturalised citizens. Singapore does not permit multiple citizenship for adults.[21] The total number of renunciants from 2001 to 2011 was roughly 10,900. Of these, roughly half were Chinese Singaporeans (who comprise about three-quarters of the population), while the rest were of other ethnicities such as Malay or Indians (who comprise about one-quarter of the population).[22]

text: United States[edit]

text: Overview[edit]

text: Although renunciation may be the most commonly used term when referring to loss of U.S. nationality, renunciation is only one of the seven expatriating acts that may be performed voluntarily and with the intent to relinquish U.S. nationality stated in Section 349 of the Immigration and Nationality Act of 1952 (8 U.S.C. § 1481).[23]

text: United States law requires that an individual appear in person before a consular officer at a U.S. embassy or consulate outside the United States and sign an oath or affirmation that the individual intends to renounce U.S. citizenship. Exceptions to this rule are permitted in times of war and under special circumstances.[24][25] During the expatriation procedure, the individual must complete several documents and demonstrate in an interview with a consular officer that the renunciation is voluntary and intentional. Depending on the embassy or consulate, the individual is often required to appear in person two times and conduct two separate interviews with consular officers over the course of several months.[26]

text: There were 235 renunciants in 2008,[27] between 731 and 743 in 2009, and about 1485 in 2010;[28][29] In 2011, there were 1781 renunciants.[30] A total of 2,999 Americans renounced their citizenship in 2012-2013;[31] in 2014, 3415 have renounced their USA citizenship or long term residency.[32] The State Department estimates 5986 renunciants and 559 relinquishers during FY2015.[33]

text: Since 1998, the Federal Bureau of Investigation has also maintained its own list of people who have renounced citizenship under 8 U.S.C. § 1481(a)(5). This is one of the categories of people who are prohibited from purchasing firearms under the Gun Control Act of 1968, and whose names must be entered in the National Instant Criminal Background Check System (NICS) under the Brady Handgun Violence Prevention Act of 1993.[34][35] The names are not made public, but each month the FBI issues a report on the number of entries added in each category. NICS covers a different population than the Federal Register expatriate list: the former includes only those who renounce U.S. citizenship, while the latter should include those who voluntarily lose citizenship by any means, and possibly certain former permanent residents as well.[36][37]

text: In fiscal year 2015, the State Department estimated there were 5,986 applications for renunciation of nationality, and forecast an additional 559 citizenship relinquishments. The discrepancy between this total of 6,545 compared to the 4,279 announced by the Treasury Department is speculated to be at least partly due to different counting of long-term green card holders, but no department of the government has released an official explanation.[38]

text: In 2016, the Treasury Department published 1,151 names of people who expatriated in Q1 FY2016.[39] For all of the year 2016, the published number of renunciants was 5,411, a 26% increase from 4,279 in 2015—a record high.[40]

text: A summary of the difference between the NICS database of renunciants and the Federal Register of the mentioned renunciants and relinquishers of long-term residence status is summarized below.[41]

text:
Year
NICS
Federal Register

2011
658
1,819

2012
4,385
1,247

2013
3,128
2,414

2014
8,781
2,984

2015*
13,110
5,986

text: Certificate of Loss of Nationality[edit]

text: Formal confirmation of the loss of U.S. citizenship is provided by the Certificate of Loss of Nationality (CLN) and is received by the renunciant a number of months later.

text: As recently as November 2014, individuals renouncing US citizenship waited up to 6 months for the official certificate of renunciation, while many renunciants, particularly those who renounced in consulates not located in the most common European cities such as London and Zurich, were never provided with a CLN and were told that the statement signed at the oath of renunciation is the only form given. Unofficial statements by the US State Department ascribe the problems to the fact that before 2010, the system was not efficiently designed and consular officers often improvised their own procedures based on the rough guidelines in their instructions. Since the passage of FATCA, the large increase in renunciations led the Department of State to re-organize the process so it is clear and follows the same steps in all consulates, although as of 2016, a backlog of several months still exists in many consulates.[42]

text: Statelessness[edit]

text: Although many countries require citizenship of another nation before allowing renunciation, the United States does not, and an individual may legally renounce U.S. citizenship and become stateless. Nonetheless, the United States Department of State warns renunciants that, unless they already possess a foreign nationality or are assured of acquiring another nationality shortly after completing their renunciation, they would become stateless and without the protection of any government.[43][44]

text: In one case, Vincent Cate, an encryption expert living in Anguilla, chose to renounce his US citizenship to avoid the possibility of violating US laws that may have prohibited US citizens from "exporting" encryption software.[45]

text: Renunciation fee[edit]

text: Renunciation of U.S. citizenship was free until July 2010, at which time a fee of $450 was established.[46] An increase to $2,350, effective September 12, 2014, was justified as "reflective of the true cost" of processing.[47][48] This followed a fee increase of approximately 220% in 2013.[49] The increase took effect in January 2015.[citation needed][50]

text: On October 26, 2015 Forbes reported that during 2014, American dual citizens in Canada who were trying to renounce their U.S. citizenship created a backlog at the U.S. Consulate in Toronto.[51]

text: Taxation[edit]

text: People giving up U.S. citizenship may be subject to an expatriation tax. Originally, under the Foreign Investors Tax Act of 1966, people determined to be giving up citizenship for the purpose of avoiding U.S. taxation were subject to 10 years of continued taxation on their U.S.-source income, to prevent ex-citizens from taking advantage of special tax incentives offered to foreigners investing in the United States.[52]

text: In 1996, the Health Insurance Portability and Accountability Act included various changes to the tax treatment of people who give up U.S. citizenship. First, it defined concrete criteria to determine whether an ex-citizen or ex-permanent resident was a "covered expatriate" presumed to have given up U.S. status for tax reasons, based on the person's income and assets, or inability to certify compliance with their tax filing and payment obligations for the past five years (26 U.S.C. § 877(a)(2)). Second, it required the Department of the Treasury to "name and shame" people who give up U.S. citizenship by listing their names in the Quarterly Publication of Individuals Who Have Chosen to Expatriate in the Federal Register (26 U.S.C. § 6039G(d).[53] The list does not appear to contain the names of all people who give up U.S. citizenship. though tax lawyers disagree whether that is because the list is only required to contain "covered expatriates", or due to bureaucratic errors or other reasons. Names of those renouncing in the last months of the year will mostly appear on the list before they have filed IRS form 8854 establishing covered or non-covered status, so it does not seem possible that the list is only required to contain covered expatriates. [54][55][56][57]

text: Additionally, the Illegal Immigration Reform and Immigrant Responsibility Act of 1996 included a provision, the Reed Amendment (8 U.S.C. § 1182(a)(10)(E)), to bar entry to any individual "who officially renounces United States citizenship and who is determined by the Attorney General to have renounced United States citizenship for the purpose of avoiding taxation by the United States". However, former IRS lawyers, as well as the Department of Homeland Security, have indicated that the provision is unenforceable because there is no authority for the IRS to share tax return information to enforce it.[58][59] DHS stated that they can only enforce the Reed Amendment when former U.S. citizens "affirmatively admit to renouncing their U.S. citizenship for the purpose of avoiding U.S. taxation", and between 2002 and 2015 they denied entry to only two former U.S. citizens on the basis of the amendment.[59]

text: In 2008, Congress enacted the Heroes Earnings Assistance and Relief Act, which changed the expatriation tax to a one-time mark-to-market worldwide capital gains tax rather than ten years of taxation on U.S.-source income.[60] Effective June 2008, U.S. citizens who renounce their citizenship are subject under certain circumstances to an expatriation tax, which is meant to extract, from the expatriate, taxes that would have been paid had he or she remained a citizen. All property of a covered expatriate is deemed sold for its fair market value on the day before the expatriation date, which usually results in a capital gain, which is taxable income.[61] Eduardo Saverin, a Brazilian-born co-founder of Facebook, renounced his U.S. citizenship just before the company's expected initial public offering. The timing prompted media speculation that the act was motivated by potential U.S. tax obligations.[30]

text: Since the enactment of the Foreign Account Tax Compliance Act (FATCA) of 2010, the numbers of people renouncing US citizenship have broken new records each year, increasing from a few hundred per year before FATCA to 5,411 in 2016. In the first two quarters of 2017 alone, 3,072 people renounced, which exceeds the full year total for 2013.[62][63][64] In 2016, there were about 18 times more renunciations than in 2008, and the 2017 quarter 2 total (1,759) is more than 76 times that of quarter 2 in 2008 (23).[65][66] Renunciants have reported that they feel forced to renounce under duress caused by FATCA but are prevented from saying this when renouncing.[67][not in citation given][68][verification needed]


document_title: Maslow's hierarchy of needs

question_text: what are the basic needs at the lowest level of maslow motivational hierarchy

text: Maslow's hierarchy of needs

text: Hierarchy[edit]

text: Maslow's hierarchy of needs is often portrayed in the shape of a pyramid with the largest, most fundamental needs at the bottom and the need for self-actualization and self-transcendence at the top.[1][7]

text: The most fundamental and basic four layers of the pyramid contain what Maslow called "deficiency needs" or "d-needs": esteem, friendship and love, security, and physical needs. If these "deficiency needs" are not met – with the exception of the most fundamental (physiological) need – there may not be a physical indication, but the individual will feel anxious and tense. Maslow's theory suggests that the most basic level of needs must be met before the individual will strongly desire (or focus motivation upon) the secondary or higher level needs. Maslow also coined the term "metamotivation" to describe the motivation of people who go beyond the scope of the basic needs and strive for constant betterment.[8]

text: The human brain is a complex system and has parallel processes running at the same time, thus many different motivations from various levels of Maslow's hierarchy can occur at the same time. Maslow spoke clearly about these levels and their satisfaction in terms such as "relative", "general", and "primarily". Instead of stating that the individual focuses on a certain need at any given time, Maslow stated that a certain need "dominates" the human organism.[4] Thus Maslow acknowledged the likelihood that the different levels of motivation could occur at any time in the human mind, but he focused on identifying the basic types of motivation and the order in which they would tend to be met.

text: Physiological needs[edit]

text: Physiological needs are the physical requirements for human survival. If these requirements are not met, the human body cannot function properly and will ultimately fail. Physiological needs are thought to be the most important; they should be met first.

text: Physiological needs include:

text:
Air (Breathing)
Water
Food
Sexual instinct
Sleep
Clothing
Shelter

tag: ul

text: Safety needs[edit]

text: Once a person's physiological needs are relatively satisfied, their safety needs take precedence and dominate behavior. In the absence of physical safety – due to war, natural disaster, family violence, childhood abuse, etc. – people may (re-)experience post-traumatic stress disorder or transgenerational trauma. In the absence of economic safety – due to economic crisis and lack of work opportunities – these safety needs manifest themselves in ways such as a preference for job security, grievance procedures for protecting the individual from unilateral authority, savings accounts, insurance policies, disability accommodations, etc. This level is more likely to predominate in children as they generally have a greater need to feel safe.

text: Safety and Security needs include:

text:
Personal security
Financial security
Health and well-being
Safety needs against accidents/illness and their adverse impacts

text: Social belonging[edit]

text: After physiological and safety needs are fulfilled, the third level of human needs is interpersonal and involves feelings of belongingness. This need is especially strong in childhood and it can override the need for safety as witnessed in children who cling to abusive parents. Deficiencies within this level of Maslow's hierarchy – due to hospitalism, neglect, shunning, ostracism, etc. – can adversely affect the individual's ability to form and maintain emotionally significant relationships in general.

text: Social Belonging needs include:

text:
Friendships
Intimacy
Family

text: According to Maslow, humans need to feel a sense of belonging and acceptance among social groups, regardless whether these groups are large or small. For example, some large social groups may include clubs, co-workers, religious groups, professional organizations, sports teams, gangs, and online communities. Some examples of small social connections include family members, intimate partners, mentors, colleagues, and confidants. Humans need to love and be loved – both sexually and non-sexually – by others.[2] Many people become susceptible to loneliness, social anxiety, and clinical depression in the absence of this love or belonging element. This need for belonging may overcome the physiological and security needs, depending on the strength of the peer pressure.

text: Esteem[edit]

text: Esteem needs are ego needs or status needs develop a concern with getting recognition, status, importance, and respect from others. All humans have a need to feel respected; this includes the need to have self-esteem and self-respect. Esteem presents the typical human desire to be accepted and valued by others. People often engage in a profession or hobby to gain recognition. These activities give the person a sense of contribution or value. Low self-esteem or an inferiority complex may result from imbalances during this level in the hierarchy. People with low self-esteem often need respect from others; they may feel the need to seek fame or glory. However, fame or glory will not help the person to build their self-esteem until they accept who they are internally. Psychological imbalances such as depression can hinder the person from obtaining a higher level of self-esteem or self-respect.

text: Most people have a need for stable self-respect and self-esteem. Maslow noted two versions of esteem needs: a "lower" version and a "higher" version. The "lower" version of esteem is the need for respect from others. This may include a need for status, recognition, fame, prestige, and attention. The "higher" version manifests itself as the need for self-respect. For example, the person may have a need for strength, competence, mastery, self-confidence, independence, and freedom. This "higher" version takes precedence over the "lower" version because it relies on an inner competence established through experience. Deprivation of these needs may lead to an inferiority complex, weakness, helplessness etc. .

text: Maslow states that while he originally thought the needs of humans had strict guidelines, the "hierarchies are interrelated rather than sharply separated".[4] This means that esteem and the subsequent levels are not strictly separated; instead, the levels are closely related.

text: Self-actualization[edit]

text: "What a man can be, he must be."[4]:91 This quotation forms the basis of the perceived need for self-actualization. This level of need refers to what a person's full potential is and the realization of that potential. Maslow describes this level as the desire to accomplish everything that one can, to become the most that one can be.[4]:92 Individuals may perceive or focus on this need very specifically. For example, one individual may have the strong desire to become an ideal parent. In another, the desire may be expressed athletically. For others, it may be expressed in paintings, pictures, or inventions.[4]:93 As previously mentioned, Maslow believed that to understand this level of need, the person must not only achieve the previous needs, but master them.

text: Self-transcendence[edit]

text: In his later years, Abraham Maslow explored a further dimension of needs, while criticizing his own vision on self-actualization.[9] By this later theory, the self only finds its actualization in giving itself to some higher outside goal, in altruism and spirituality. He equated this with the desire to reach the infinite.[10] "Transcendence refers to the very highest and most inclusive or holistic levels of human consciousness, behaving and relating, as ends rather than means, to oneself, to significant others, to human beings in general, to other species, to nature, and to the cosmos" (Farther Reaches of Human Nature, New York 1971, p. 269).

text: Application to Nursing[edit]

text: Nurses can apply Maslow’s hierarchy of basic needs in the assessment, planning, implementation, and evaluation of patient care. It helps the nurse identify unmet needs as they become health care needs, and allows the nurse to locate the patient on the health-illness continuum and to incorporate the human dimensions and health models into meeting needs.

text: The Human Dimensions and Basic Human Needs[edit]

text:
Physical dimension
Physiologic needs
Breathing, circulation, temperature, intake of food and fluids, elimination of wastes, movement.

Environmental dimension
Safety and security needs
Housing, community, climate.

Sociocultural dimension
Love and belonging needs
Relationships with others, communications with others, support systems, being part of community, feeling loved by others.

Emotional dimension
Self-esteem needs
Hope, joy, curiosity, happiness, accepting Self.

Intellectual and spiritual dimensions
Self-actualization needs
Thinking, learning, decision making, values, beliefs, fulfillment, helping others.

text: All basic human needs are interrelated and may require nursing actions at more than one level at a given time. For example, in caring for a person coming into the emergency department with a heart attack, the nurse’s immediate concern in the patient’s physiologic needs (e.g., oxygen and pain relief). At the same time, safety needs (e.g., for ensuring that the person does not fall off the examining table) and love and belonging needs (e.g., for having a family member nearby if possible) are still major considerations.[11]

text: Research[edit]

text: Recent research appears to validate the existence of universal human needs, although the hierarchy proposed by Maslow is called into question.[12][13]

text: Following World War II, the unmet needs of homeless and orphaned children presented difficulties that were often addressed with the help of attachment theory, which was initially based on Maslow and others' developmental psychology work by John Bowlby.[14] Originally dealing primarily with maternal deprivation and concordant losses of essential and primal needs, attachment theory has since been extended to provide explanations of nearly all the human needs in Maslow's hierarchy, from sustenance and mating to group membership and justice.[15]

text: Criticism[edit]

text: Ranking[edit]

text: Global ranking[edit]

text: In their extensive review of research based on Maslow's theory, Wahba and Bridwell found little evidence for the ranking of needs that Maslow described or for the existence of a definite hierarchy at all.[16]

text: The order in which the hierarchy is arranged has been criticized as being ethnocentric by Geert Hofstede.[17] Maslow's hierarchy of needs fails to illustrate and expand upon the difference between the social and intellectual needs of those raised in individualistic societies and those raised in collectivist societies. The needs and drives of those in individualistic societies tend to be more self-centered than those in collectivist societies, focusing on improvement of the self, with self-actualization being the apex of self-improvement. In collectivist societies, the needs of acceptance and community will outweigh the needs for freedom and individuality.[18]

text: Ranking of sex[edit]

text: The position and value of sex on the pyramid has also been a source of criticism regarding Maslow's hierarchy. Maslow's hierarchy places sex in the physiological needs category along with food and breathing; it lists sex solely from an individualistic perspective. For example, sex is placed with other physiological needs which must be satisfied before a person considers "higher" levels of motivation. Some critics feel this placement of sex neglects the emotional, familial, and evolutionary implications of sex within the community, although others point out that this is true of all of the basic needs.[19][20]

text: Changes to the hierarchy by circumstance[edit]

text: The higher-order (self-esteem and self-actualization) and lower-order (physiological, safety, and love) needs classification of Maslow's hierarchy of needs is not universal and may vary across cultures due to individual differences and availability of resources in the region or geopolitical entity/country.

text: In one study,[21] exploratory factor analysis (EFA) of a thirteen item scale showed there were two particularly important levels of needs in the US during the peacetime of 1993 to 1994: survival (physiological and safety) and psychological (love, self-esteem, and self-actualization). In 1991, a retrospective peacetime measure was established and collected during the Persian Gulf War and US citizens were asked to recall the importance of needs from the previous year. Once again, only two levels of needs were identified; therefore, people have the ability and competence to recall and estimate the importance of needs. For citizens in the Middle East (Egypt and Saudi Arabia), three levels of needs regarding importance and satisfaction surfaced during the 1990 retrospective peacetime. These three levels were completely different from those of the US citizens.

text: Changes regarding the importance and satisfaction of needs from the retrospective peacetime to the wartime due to stress varied significantly across cultures (the US vs. the Middle East). For the US citizens, there was only one level of needs since all needs were considered equally important. With regards to satisfaction of needs during the war, in the US there were three levels: physiological needs, safety needs, and psychological needs (social, self-esteem, and self-actualization). During the war, the satisfaction of physiological needs and safety needs were separated into two independent needs while during peacetime, they were combined as one. For the people of the Middle East, the satisfaction of needs changed from three levels to two during wartime.[22][23]

text: A 1981 study looked at how Maslow's hierarchy might vary across age groups.[24] A survey asked participants of varying ages to rate a set number of statements from most important to least important. The researchers found that children had higher physical need scores than the other groups, the love need emerged from childhood to young adulthood, the esteem need was highest among the adolescent group, young adults had the highest self-actualization level, and old age had the highest level of security, it was needed across all levels comparably. The authors argued that this suggested Maslow's hierarchy may be limited as a theory for developmental sequence since the sequence of the love need and the self-esteem need should be reversed according to age.

text: Definition of terms[edit]

text: Self-actualization[edit]

text: The term "self-actualization" may not universally convey Maslow's observations; this motivation refers to focusing on becoming the best person that one can possibly strive for in the service of both the self and others.[4] Maslow's term of self-actualization might not properly portray the full extent of this level; quite often, when a person is at the level of self-actualization, much of what they accomplish in general may benefit others, or "the greater good".