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Cosmic Background Radiation

Cosmic background radiation

In cosmology, the cosmic microwave background radiation (most often abbreviated CMB but occasionally CMBR, CBR or MBR) is a form of electromagnetic radiation discovered in 1965. It has a thermal black-body spectrum which peaks in the microwave range. Most cosmologists consider the cosmic microwave background radiation to be the best evidence for the hot big bang model of the universe.

Features

The cosmic microwave background is a 2.725 K thermal spectrum of black body radiation that fills the universe. It has a peak frequency of 160.4 GHz which corresponds to a wavelength of 1.9 mm. It is isotropic to roughly one part in 100,000: the root mean square variations are only 18 μK. The Far-Infrared Absolute Spectrophotometer (FIRAS) instrument on the NASA COsmic Background Explorer (COBE) satellite has carefully measured the spectrum of the cosmic microwave background, which has made it the most precisely measured black body spectrum ever. The cosmic microwave background is a prediction of the Big Bang. In the theory, the early universe is made up of a hot plasma of photons, electrons and baryons. The photons are constantly interacting with the plasma through Compton scattering. As the universe expands, the cosmological redshift causes the plasma to cool until it becomes favorable for electrons to combine with hydrogen and helium nuclei and form atoms. This happens at around 3000 K or when the universe is approximately 300,000 years old. At this point, the photons stop scattering off the neutral atoms and begin to travel freely through space. This process is called recombination or decoupling. The photons continue cooling until they reach their present 2.7 K temperature. The radiation we see on the sky today comes from a spherical surface, called the surface of last scattering, from which the photons that decoupled in the early universe, 13.7 billion years ago, are just now reaching observers on Earth. The big bang suggests that the cosmic microwave background fills all of observable space, and that most of the radiation energy in the universe is in the cosmic microwave background, which makes up a fraction of roughly 5×10-5 of the total density of the universe. Two of the greatest successes of the big bang are its prediction of the exactly thermal spectrum and detailed prediction of the anisotropies of the cosmic microwave background. The recent Wilkinson Microwave Anisotropy Probe has precisely measured these anisotropies over the whole sky down to angular scales of 0.2 degrees. These can be used to estimate the parameters of the standard Lambda-CDM model of the big bang. Some information, such as the shape of the Universe, can be obtained straightforwardly from the cosmic microwave background, while others, such as the Hubble constant, are not constrained and must be inferred from other measurements.

History

The cosmic microwave background was predicted by George Gamow, Ralph Alpher, and Robert Hermann in 1948. Moreover, Alpher and Herman were able to estimate the temperature of the cosmic microwave background to be 5 K. Although there were several previous estimates of the temperature of space (see timeline), these suffered from two flaws. First, they were measurements of the effective temperature of space, and did not suggest that space was filled with a thermal Planck spectrum: Second, they are dependent on our special place at the edge of the Milky Way galaxy and did not suggest the radiation is isotropic. Moreover, they would yield very different predictions if Earth happened to be located elsewhere in the universe. The results of Gamow were not widely discussed. However, they were rediscovered by Robert Dicke and Yakov Zel'dovich in the early 1960s. In 1964, this prompted David Todd Wilkinson and Peter Roll, Dicke's colleagues at Princeton University, to begin constructing a Dicke radiometer to measure the cosmic microwave background. In 1965, Arno Penzias and Robert Woodrow Wilson at Bell Telephone Laboratories in nearby Holmdel, New Jersey had built a Dicke radiometer that they intended to use for radio astronomy and satellite communication experiments. Their instrument had an excess 3.5 K antenna temperature which they could not account for. After receiving a telephone call from Holmdel, Dicke famously quipped: "Boys, we've been scooped." A meeting between the Princeton and Holmdel groups determined that the antenna temperature was indeed due to the microwave background. Penzias and Wilson received the 1978 Nobel Prize in Physics for their discovery. The interpretation of the cosmic microwave background was a controversial issue in the 1960s with some proponents of the steady state theory arguing that the microwave background was the result of scattered starlight from distant galaxies. Using this model, and based on the study of narrow absorption line features in the spectra of stars, the astronomer Andrew McKellar wrote in 1941: "It can be calculated that the 'rotational' temperature of interstellar space is 2 K." However, during the 1970s the consensus was established that the cosmic microwave background is a remnant of the big bang. This was largely because new measurements at a range of frequencies showed that the spectrum was a thermal, black-body spectrum, a result that the steady state model was unable to reproduce. Harrison, Peebles and Yu, and Zel'dovich realized that the early universe would have to have inhomogeneities at the level of 10−4 or 10−5. Rashid Sunyaev later calculated the observable imprint that these inhomogeneities would have on the cosmic microwave background. Increasingly stringent limits on the anisotropy of the cosmic microwave background were set by ground based experiments, but the anisotropy was first detected by the Differential Microwave Radiometer instrument on the COBE satellite. Inspired by the COBE results, a series of ground and balloon-based experiments measured cosmic microwave background anisotropies on smaller angular scales over the next decade. The primary goal of these experiments was to measure the scale of the first acoustic peak, which COBE did not have sufficient resolution to resolve. The first peak in the anisotropy was tentatively detected by the Toco experiment and the result was confirmed by the BOOMERanG and MAXIMA experiments.. These measurements demonstrated that the Universe is flat and were able to rule out cosmic strings as a theory of cosmic structure formation, and suggested cosmic inflation was the right theory of structure formation. The second peak was tentatively detected by several experiments before being definitively detected by WMAP, which has also tentatively detected the third peak. The polarization of the microwave background was first discovered by the Degree Angular Scale Interferometer (DASI).. Several experiments to improve measurements of the polarization and the microwave background on small angular scales are ongoing. These include DASI, WMAP, BOOMERanG and the Cosmic Background Imager. Forthcoming experiments include the Planck satellite, Atacama Cosmology Telescope and the South Pole Telescope.

Relationship to the Big Bang

South Pole TelescopeWMAP image of the CMB anisotropy,Cosmic microwave
background radiation. (June 2003))

2003 The power spectrum of the cosmic microwave background
radiation anisotropy interms of the angular scale (or
multipole moment) (top). Data from WMAP have extended
the accuracy of the spectrum at large angular scales
(i.e. on the left side of the plot) far beyond what was
known from earlier measurements.
The standard hot big bang model of the universe requires that the initial conditions for the universe are a Gaussian random field with a nearly scale invariant or Harrison-Zel'dovich spectrum. This is, for example, a prediction of the cosmic inflation model. This means that the initial state of the universe is random, but in a clearly specified way in which the amplitude of the primeval inhomogeneities is 10-5. Therefore, meaningful statements about the inhomogeneities in the universe need to be statistical in nature. This leads to cosmic variance in which the uncertainties in the variance of the largest scale fluctuations observed in the universe are difficult to accurately compare to theory.

Temperature

The cosmic microwave background radiation and the cosmological red shift are together regarded as the best available evidence for the Big Bang (BB) theory. The discovery of the CMB in the mid-1960s curtailed interest in alternatives such as the steady state theory. The CMB gives a snapshot of the Universe when, according to standard cosmology, the temperature dropped enough to allow electrons and protons to form hydrogen atoms, thus making the universe transparent to radiation. When it originated some 400,000 years after the Big Bang — this time period is generally known as the "time of last scattering" or the period of recombination or decoupling — the temperature of the Universe was about 3000 K. This corresponds to an energy of about 0.25 eV, which is much less than the 13.6 eV ionization energy of hydrogen. Since then the temperature of the radiation has dropped by a factor of roughly 1100 due to the expansion of the Universe. As the universe expands, the CMB photons are redshifted, making the radiation's temperature inversely proportional to the Universe's scale length. For details about the reasoning that the radiation is evidence for the Big Bang, see Cosmic background radiation of the Big Bang.

Primary anisotropy

The anisotropy of the cosmic microwave background is divided into two sorts: primary anisotropy – which is due to effects which occur at the last scattering surface and before – and secondary anisotropy – which is due to effects, such as interactions with hot gas or gravitational potentials, between the last scattering surface and the observer. The structure of the cosmic microwave background anisotropies is principally determined by two effects: acoustic oscillations and diffusion damping (also called collisionless damping or Silk damping). The acoustic oscillations arise because of a competition in the photon-baryon plasma in the early universe. The pressure of the photons tends to erase anisotropies, whereas the gravitational attraction of the baryons – which are moving at speeds much less than the speed of light – makes them tend to collapse to form dense haloes. These two effects compete to create acoustic oscillations which give the microwave background its characteristic peak structure. The peaks correspond, roughly, to resonances in which the photons decouple when a particular mode is at its peak amplitude. The peaks contain interesting physical signatures. The first peak determines the shape of the Universe. The second peak – truly the ratio of the odd peaks to the even peaks – determines the reduced baryon density. The third peak can be used to extract information about the dark matter density. Collisionless damping is caused by two effects, when the treatment of the primordial plasma as a fluid begins to break down:
- the increasing mean free path of the photons as the primordial plasma becomes increasingly rarefied in an expanding universe
- the finite thickness of the last scattering surface, which causes the mean free path to increase rapidly during decoupling, even while some Compton scattering is still occurring. These effects contribute about equally to the supression of anisotropies on small scales, and give rise to the characteristic exponential damping tail seen in the very small angular scale anisotropies.

Polarization

The cosmic microwave background is polarized at the level of a few microkelvin. There are two types of polarization, called E-modes and B-modes. This is in analogy to electrodynamics, in which the electric field (E-field) has a vanishing divergence and the magnetic field (B-field) has a vanishing curl. The E-modes arise naturally from Thomson scattering in an inhomogeneous plasma. The B-modes, which have not been measured and are thought to have an amplitude of at most a 0.1 μK, are not produced from the plasma physics alone. They are a signal from cosmic inflation and are determined by the density of primordial gravitational waves.

Secondary anisotropy

After the creation of the CMB, there are a number of important events. After the emission of the CMB, ordinary matter in the universe was mostly in the form of neutral hydrogen and helium atoms, but from observations of galaxies, it seems that most of the volume of the intergalactic medium (IGM) today consists of ionized material (since there are few absorption lines due to hydrogen atoms). This implies a period of reionization in which the material of the universe breaks down into hydrogen ions. The CMB photons scatter off free charges such as electrons not bound in atoms. In an ionized universe, such electrons have been liberated from neutral atoms by ionizing (ultraviolet) radiation. Today these free charges are at sufficiently low density in most of the volume of the Universe that they do not measurably affect the CMB. However, if the IGM was ionized at very early times when the universe was still denser, then there are two main effects on the CMB: # Small scale anisotropies are erased (just as when looking at an object through fog, details of the object appear fuzzy). # The physics of how photons scatter off of free electrons (Thomson scattering) induce polarization anisotropies on large angular scales. This large angle polarization is correlated with the large angle temperature perturbation. Both of these effects have been observed by the WMAP satellite, providing evidence that the universe was ionized at very early times, at a redshift of larger than 17. The detailed provenance of this early ionizing radiation is still a matter of scientific debate. It may have included starlight from the very first population of stars (population III stars), supernovae when these first stars reached the end of their lives, or the ionizing radiation produced by the accretion disks of massive black holes. The period after the emission of the cosmic microwave background and the observation of the first stars is semi-humorously referred to by cosmologists as the dark age, and is a period which is under intense study by astronomers. See 21 centimeter radiation. Other anisotropies due to effects that occur between reionization and our observation of the cosmic microwave background include the Sunyaev-Zel'dovich effect, in which a cloud of high energy electrons scatters the radiation, transferring some energy to the CMB photons, and the Sachs-Wolfe effect, which causes photons from the cosmic microwave background to be gravitationally redshifted.

Microwave background observations

The design of cosmic microwave background experiments is a very challenging task. The greatest problems are:
- Detectors The challenge of observing differences of a few microkelvin on top of a 2.7 K signal is difficult. Many improved microwave detector technologies have been designed for microwave background applications. Some technologies used are HEMT, MMIC, SIS (Superconductor-Insulator-Superconductor) and bolometers. Experiments generally use elaborate cryogenic systems to keep the detectors cool. Often, experiments are interferometers which only measure the difference in signals on two parts of the sky, thus subtracting out the 2.7 K background. Another problem is the 1/f noise intrinsic to all detectors. Usually the experimental scan strategy is designed to minimize the effect of such noise.
- Optics Microwave optics are designed to minimize side lobes and minimize . For this reason, elaborate lenses and feed horns are usually used.
- Water vapor Because water absorbs microwave radiation, a fact that is used to build microwave ovens, it is rather difficult to observe the microwave background with ground-based instruments. CMB research therefore makes increasing use of air and space-borne experiments. Ground-based observations are usually made from high altitude locations such as the Chilean Andes and the South Pole.

Analyses

The analysis of cosmic microwave background data to produce maps, an angular power spectrum and ultimately cosmological parameters is a complicated, computationally difficult problem. Although computing a power spectrum from a map is in principle a simple Fourier transform, decomposing the map of the sky into spherical harmonics, in practice it is hard to take the effects of noise and foregrounds into account. In general, it is not possible to solve these problems by brute force, and instead optimization techniques such as Markov Chain Monte Carlo simulations must be used.

Low multipoles

With the increasingly precise data provided by WMAP, there have been a number of claims that the CMB suffers from anomalies, such as non-Gaussianity. The most longstanding of these is the low-l multipole controversy. Even in the COBE map, it was observed that the quadrupole (l = 2 spherical harmonic) has a low amplitude compared to the predictions of the big bang. Some observers have pointed out that the anisotropies in the WMAP data did not appear to be consistent with the big bang picture. In particular, the quadrupole and octopole (l = 3) modes appear to have an unexplained alignment with each other and with the ecliptic plane. While a number of groups have suggested that this could be the signature of new physics at the largest observable scales. Ultimately, due to the foregrounds and the cosmic variance problem, the largest modes will never be as well measured as the small angular scale modes. The analyses were performed on two maps that have had the foregrounds removed as best as is possible: the "internal linear combination" map of the WMAP collaboration and a similar map prepared by Max Tegmark and others. Later analyses have argued that as the modes most susceptible to foreground contamination from synchrotron, dust and free-free emission, and from experimental uncertainty in the monopole and dipole. While the low quadrupole does appear to be robust (the measured value has a likelihood of roughly 2–4% in the Lambda-CDM model), removing the parts of the data that are most contaminated by foregrounds removes the alignment, which suggests that it is due to foreground contamination.

References

# This ignores the dipole anisotropy, which is due to the Doppler shift of the microwave background radiation due to our peculiar velocity relative to the comoving cosmic rest frame. This feature is consistent with the Earth moving at some 600 km/s towards the constellation Virgo. # D. J. Fixen et al., "The Cosmic Microwave Background Spectrum from the full COBE FIRAS data set", Astrophysical Journal 473, 576–587 (1996). # The energy density of a black-body spectrum is \pi k_B^2T^4/15(\hbar c)^3, where T is the temperature, kB is the Boltzmann constant, \hbar is the Planck constant and c is the speed of light. This can be related to the critical density of the universe using the parameters of the Lambda-CDM model. # Astrophysical Journal Supplement, 148 (2003). In particular, G. Hinshaw et al. "First-year Wilkinson Microwave Anisotropy Probe (WMAP) observations: the angular power spectrum", 135–159. # D. N. Spergel et al., "First-year Wilkinson Microwave Anisotropy Probe (WMAP) observations: determination of cosmological parameters", Astrophysical Journal Supplement 148, 175–194 (2003). # G. Gamow, "The Origin of Elements and the Separation of Galaxies," Physical Review 74 (1948), 505. G. Gamow, "The evolution of the universe", Nature 162 (1948), 680. R. A. Alpher and R. Herman, "On the Relative Abundance of the Elements," Physical Review 74 (1948), 1577. # A. K. T. Assis, M. C. D. Neves, "History of the 2.7 K Temperature Prior to Penzias and Wilson," (1995, [http://redshift.vif.com/JournalFiles/Pre2001/V02NO3PDF/V02N3ASS.PDF PDF] | [http://www.dfi.uem.br/~macedane/history_of_2.7k.html HTML]) but see also N. Wright, "Eddington did not predict the CMB", [http://www.astro.ucla.edu/~wright/Eddington-T0.html HTML]. # R. H. Dicke, "The measurement of thermal radiation at microwave frequencies", Rev. Sci. Instrum. 17, 268 (1946). This basic design for a radiometer has been used in most subsequent cosmic microwave background experiments. # A. A. Penzias and R. W. Wilson, "A Measurement of Excess Antenna Temperature at 4080 Mc/s," Astrophysical Journal 142 (1965), 419. R. H. Dicke, P. J. E. Peebles, P. G. Roll and D. T. Wilkinson, "Cosmic Black-Body Radiation," Astrophysical Journal 142 (1965), 414. The history is given in P. J. E. Peebles, Principles of physical cosmology (Princeton Univ. Pr., Princeton 1993). # A. McKellar, Publ. Dominion Astrophys. Obs. 7, 251. # E. R. Harrison, "Fluctuations at the threshold of classical cosmology," Phys. Rev. D1 (1970), 2726. P. J. E. Peebles and J. T. Yu, "Primeval adiabatic perturbation in an expanding universe," Astrophysical Journal 162 (1970), 815. Ya. B. Zel'dovich, "A hypothesis, unifying the structure and entropy of the universe," Monthly Notices of the Royal Astronomical Society 160 (1972). # R. A. Sunyaev, "Fluctuations of the microwave background radiation," in Large Scale Structure of the Universe ed. M. S. Longair and J. Einasto, 393. Dordrecht: Reidel 1978. While this is the first paper to discuss the detailed observational imprint of density inhomogeneities as anisotropies in the cosmic microwave background, some of the groundwork was laid in Peebles and Yu, above. # G. F. Smoot et al. "Stucture in the COBE DMR first year maps", Astrophysical Journal 396 L1–L5 (1992). C. L. Bennett et al. "Four year COBE DMR cosmic microwave background observations: maps and basic results.", Astrophysical Journal 464 L1–L4 (1996). # A. D. Miller et al., "A measurement of the angular power spectrum of the cosmic microwave background from l = 100 to 400", Astrophysical Journal 524, L1–L4 (1999). A. E. Lange et al., "Cosmological parameters from the first results of Boomerang". P. de Bernardis et al., "A flat universe from high-resolution maps of the cosmic microwave background", Nature 404, 955 (2000). S. Hanany et al. "MAXIMA-1: A measurement of the cosmic microwave background anisotropy on angular scales of 10'-5°", Astrophysical Journal 545 L5–L9 (2000). # J. Kovac et al., "Detection of polarization in the cosmic microwave background using DASI", Nature 420, 772-787 (2002). # A. de Oliveira-Costa, M. Tegmark, M. Zaldarriga and A. Hamilton, "The significance of the largest scale CMB fluctuations in WMAP", Phys. Rev. D69 (2004) 063516 . D. J. Schwarz, G. D. Starkman, D. Huterer and C. J. Copi, "Is the low-l microwave background cosmic?", Phys. Rev. Lett. 93 (2004) 221301 . # C. L. Bennett et al., "First-year Wilkinson Microwave Anisotropy Probe (WMAP) observations: preliminary maps and basic results", Astrophysical Journal Supplement 148, 1 (2003). M. Tegmark, A. de Oliveira-Costa and A. Hamilton, "A high resolution foreground cleaned CMB map from WMAP", Phys. Rev. D68, 123523 (2003). The WMAP paper warns: "the statistics of this internal linear combination map are complex and inappropriate for most CMB analyses." # A. Slosar and U. Seljak, "Assessing the effects of foregrounds and sky removal in WMAP", Phys. Rev. D70, 083002 (2004). . C. J. Copi, D. Hueterer, D. J. Schwarz and G. D. Starkman, "On the large-angle anomalies of the microwave sky", .

Further reading and external links


- Seife, Charles (2003). Breakthrough of the Year: Illuminating the Dark Universe. Science 302 2038–2039.
- Partridge, R. B. (1995). 3K: The Cosmic Microwave Background Radiation. New York: Cambridge University Press.
- [http://lambda.gsfc.nasa.gov/ NASA's Legacy Archive for Microwave Background Data Analysis (LAMBDA)]
- Wayne Hu's [http://background.uchicago.edu/ The Physics of Microwave Background Anisotropies]. An extensive collection of cosmic microwave background tutorials, animations and reviews describing the physics behind the microwave background. The materials range in detail from popular introductions to technical discussions.
- Cosmology textbooks Category:Radio astronomy Category:Cosmology ja:宇宙背景放射

Physical cosmology

Cosmology, as a branch of astrophysics, is the study of the large-scale structure of the universe and is concerned with fundamental questions about its formation and evolution. Cosmology involves itself with studying the motions of the celestial bodies and the first cause. For most of human history, it has been a branch of metaphysics. Cosmology as a science originates with the Copernican principle, which implies that celestial bodies obey identical physical laws to those on earth, and Newtonian mechanics, which first allowed us to understand those motions. This is now called celestial mechanics. Physical cosmology, as it is now understood, began with the twentieth century development of Albert Einstein's theory of general relativity and better astronomical observations of extremely distant objects. The twentieth century advances made it possible to speculate about the origins of the universe and allowed scientists to establish the big bang as the leading cosmological theory, which most cosmologists now accept as the basis for their theory and observations. (Some people still advocate alternative cosmologies such as the plasma cosmology and steady state theory, although professional cosmologists generally agree that the big bang best explains observations.) Physical cosmology, roughly speaking, deals with the very largest objects in the universe (galaxies, clusters and superclusters), the very earliest distinct objects to form (quasars) and the very early universe, when it was nearly homogeneous (hot big bang, cosmic inflation and the cosmic microwave background radiation). Cosmology is unusual in physics for drawing heavily on the work of particle physicists' experiments, and research into phenomenology and even string theory; from astrophysicists; from general relativity research; and from plasma physics.

History of physical cosmology

Modern cosmology developed along tandem observational and theoretical tracks. In 1915, Albert Einstein developed his theory of general relativity. At the time, physicists were prejudiced to believe in a perfectly static universe without beginning or end. Einstein added a cosmological constant to his theory to try to force it to allow for a static universe with matter in it. The so-called Einstein universe is, however, unstable. It is bound to eventually start expanding or contracting. The cosmological solutions of general relativity were found by Alexander Friedmann, whose equations describe the Friedmann-Lemaître-Robertson-Walker universe, which may expand or contract. In the 1910s, Vesto Slipher and later Carl Wilhelm Wirtz interpreted the red shift of spiral nebulae as a Doppler shift that indicated they were receding from Earth. However, it is notoriously difficult to determine the distance to astronomical objects: even if it is possible to measure their angular size it is usually impossible to know their actual size or luminosity. They did not realize that the nebulae were actually galaxies outside our own Milky Way, nor did they speculate about the cosmological implications. In 1927, the Belgian catholic priest Georges Lemaître independently derived the Friedmann-Lemaître-Robertson-Walker equations and proposed, on the basis of the recession of spiral nebulae, that the universe began with the "explosion" of a "primeval atom"—what was later called the big bang. In 1929, Edwin Hubble provided an observational basis for Lemaître's theory. Hubble proved that the spiral nebulae were galaxies and measured their distances by observing Cepheid variable stars. He discovered a relationship between the redshift of a galaxy and its luminosity. He interpreted this as evidence that the galaxies are receding in every direction at speeds (relative to the Earth) directly proportional to their distance. This fact is known as Hubble's law. The relationship between distance and speed, however, was accurately ascertained only relatively recently: Hubble was off by a factor of ten. Given the cosmological principle, Hubble's law suggested that the universe was expanding. This idea allowed for two opposing possibilities. One was Lemaître's Big Bang theory, advocated and developed by George Gamow. The other possibility was Fred Hoyle's steady state model in which new matter would be created as the galaxies moved away from each other. In this model, the universe is roughly the same at any point in time. For a number of years the support for these theories was evenly divided. However, the observational evidence began to support the idea that the universe evolved from a hot dense state. Since the discovery of the cosmic microwave background in 1965 it has been regarded as the best theory of the origin and evolution of the cosmos. Before the late 1960s, many cosmologists thought the infinitely dense singularity at the starting time of Friedmann's cosmological model was a mathematical over-idealization, and that the universe was contracting before entering the hot dense state and starting to expand again. This is Richard Tolman's oscillatory universe. In the sixties, Stephen Hawking and Roger Penrose [http://www.maths.soton.ac.uk/relativity/GRExplorer/singularities/singtheorems.htm] demonstrated that this idea was unworkable, and the singularity is an essential feature of Einstein's gravity. This led the majority of cosmologists to accept the Big Bang, in which the universe we observe began a finite time ago.

Areas of study

Below, some of the most active areas of inquiry in cosmology are described, in roughly chronological order. This does not include all of the big bang cosmology, which is presented in cosmological timeline.

The very early universe

While the early, hot universe appears to be well explained by the big bang from roughly 10-33 seconds onwards, there are several problems. One is that there is no compelling reason, using current particle physics, to expect the universe to be flat, homogeneous and isotropic (see the cosmological principle). Moreover, grand unified theories of particle physics suggest that there should be magnetic monopoles in the universe, which have not been found. These problems are resolved by a brief period of cosmic inflation, which drives the universe to flatness; smooths out anisotropies and inhomogeneities to the observed level; and exponentially dilutes the monopoles. The physical model behind cosmic inflation is extremely simple, however it has not yet been confirmed by particle physics, and there are difficult problems reconciling inflation and quantum field theory. Some cosmologists think that string theory and brane cosmology will provide an alternative to inflation. Another major problem in cosmology is what has caused the universe to contain more particles than antiparticles. Cosmologists can use X-ray observations to deduce that the universe is not split into regions of matter and antimatter, but rather is predominantly made of matter. This problem is called the baryon asymmetry, and the theory to describe the resolution is called baryogenesis. The theory of baryogenesis was worked out by Andrei Sakharov in 1967, and requires a violation of the particle physics symmetry, called CP-symmetry, between matter and antimatter. Particle accelerators, however, measure too small a violation of CP-symmetry to account for the baryon asymmetry. Cosmologists and particle physicists are trying to find additional violations of the CP-symmetry in the early universe that might account for the baryon asymmetry. Both the problems of baryogenesis and cosmic inflation of these problems are very closely related to particle physics, and their resolution might come from high energy theory and experiment, rather than through observations of the universe.

Big bang nucleosynthesis

Big Bang Nucleosynthesis is the theory of the formation of the elements in the early universe. It finished when the universe was about three minutes old and its temperature fell enough that nuclear fusion ceased. Because the time in which big bang nucleosynthesis occured was so short, only the very lightest elements were produced, unlike in stellar nucleosynthesis. Starting from hydrogen ions (protons), it principally produced deuterium, helium-4 and lithium. Other elements were produced in only trace abundances. While the basic theory of nucleosynthesis has been understood for decades (it was developed in 1948 by George Gamow, Ralph Asher Alpher and Robert Herman) it is an extremely sensitive probe of physics at the time of the big bang, as the theory of big bang nucleosynthesis connects the abundances of primordial light elements with the features of the early universe. Specifically, it can be used to test the equivalence principle, to probe dark matter and test neutrino physics. Some cosmologists have proposed that big bang nucleosynthesis suggests there is a fourth "sterile" species of neutrino.

Cosmic microwave background

The cosmic microwave background is radiation left over from decoupling, when atoms first formed, and the radiation produced in the big bang stopped Thomson scattering from charged ions. The radiation, first observed in 1965 by Arno Penzias and Robert Woodrow Wilson, has a perfect thermal black-body spectrum. It has a temperature of 2.7 Kelvin today and is isotropic to one part in 105. Cosmological perturbation theory, which describes the evolution of slight inhomogeneities in the early universe, has allowed cosmologists to precisely calculate the angular power spectrum of the radiation, and it has been measured by the recent satellite experiments (COBE and WMAP) and many ground and balloon-based experiments (such as Degree Angular Scale Interferometer, Cosmic Background Imager, and Boomerang). One of the goals of these efforts is to measure the basic parameters of the Lambda-CDM model with increasing accuracy, as well as to test the predictions of the big bang model and look for new physics. The recent measurements made by WMAP, for example, have placed limits on the neutrino masses. Newer experiments are trying to measure the polarization of the cosmic microwave background, which will provide further confirmation of the theory as well as information about cosmic inflation, and the so-called secondary anisotropies, such as the Sunyaev-Zel'dovich effect and Sachs-Wolfe effect, which are caused by interaction between galaxies and galaxy clusters with the cosmic microwave background.

Formation and evolution of large-scale structure

, Galaxy formation and evolution Understanding the formation and evolution of the largest and earliest structures (ie, quasars, galaxies, galaxy clusters and superclusters) is one of the largest efforts in cosmology. Cosmologists study a model of hierarchical structure formation in which structures form from the bottom up, with smaller objects forming first, while the largest objects, such as superclusters, are still assembling. The most straightforward way to study structure in the universe is to survey the visible galaxies, in order to construct a three-dimensional picture of the galaxies in the universe and measure the matter power spectrum. This is the approach of the Sloan Digital Sky Survey and the 2dF Galaxy Redshift Survey. An important tool for understanding these structure formation is simulations, which cosmologists use to study the gravitational aggregation of matter in the universe, as it clusters into filaments, superclusters and voids. Most simulations contain only non-baryonic cold dark matter, which should suffice to understand the universe on the largest scales, as there is much more dark matter in the universe than visible, baryonic matter. More advanced simulations are starting to include baryons and study the formation of individual galaxies. Cosmologists study these simulations to see if they agree with the galaxy surveys, and to understand any discrepancy. Other, complementary techniques will allow cosmologists to measure the distribution of matter in the distant universe and to probe reionization. These include:
- The Lyman alpha forest, which allows cosmologists to measure the distribution of neutral atomic hydrogen gas in the early universe, by measuring the absorption of light from distant quasars by the gas.
- The 21 centimeter adsorption line of neutral atomic hydrogen also provides a sensitive test of cosmology
- Weak lensing, the distortion of a distant image by gravitational lensing due to dark matter. These will help cosmologists settle the question of when the first quasars formed.

Dark matter

Evidence from big bang nucleosynthesis, the cosmic microwave background and structure formation suggests that about 25% of the mass of the universe is made up of non-baryonic dark matter, whereas only 4% is made up of visible, baryonic matter. The gravitational effects of dark matter are well understood, as it behaves like cold, non-radiative dust which forms around haloes around galaxies. Dark matter has never been detected in the laboratory: the particle physics nature of dark matter is completely unknown. However, there are a number of candidates, such as a stable supersymmetric particle, a weakly interacting massive particle, an axion, a massive compact halo object or even a modification of gravity at small accelerations (MOND) or an effect from brane cosmology. The physics at the center of galaxies (see active galactic nuclei, supermassive black hole) may give some clues about the nature of dark matter.

Dark energy

If the universe is to be flat, there must be an additional component making up 71% (in addition to the 25% dark matter and 4% baryons) of the density of the universe. This is called dark energy. In order not to interfere with big bang nucleosynthesis and the cosmic microwave background, it must not cluster in haloes like baryons and dark matter. There is strong observational evidence for dark energy, as the total mass of the universe is known, since it is measured to be flat, but the amount of clustering matter is tightly measured, and is much less than this. The case for dark energy was strengthened in 1999, when measurements demonstrated that the expansion of the universe is accelerating, much like the more rapid acceleration during cosmic inflation. However, apart from its density and its clustering properties, nothing is known about dark energy. Quantum field theory predicts a cosmological constant much like dark energy, but 120 orders of magnitude too large. Steven Weinberg and a number of string theorists (see string landscape) have used this as evidence for the anthropic principle, which suggests that the cosmological constant is so small because life (and thus physicists, to make observations) cannot exist in a universe with a large cosmological constant, but many people find this an unsatisfying explantion. Other possible explanations for dark energy include quintessence or a modification of gravity on the largest scales. The effect on cosmology of the dark energy that these models describe is given by the dark energy's equation of state, which varies depending upon the theory. The nature of dark energy is one of the most challenging problems in cosmology. A better understanding of dark energy is likely to solve the problem of the ultimate fate of the universe. In the current cosmological epoch, the accelerated expansion due to dark energy is preventing structures larger than superclusters from forming. It is not known whether the acceleration will continue indefinitely, perhaps even increasing and cause a big rip, or whether it will eventually reverse.

Other areas of inquiry

Cosmologists also study:
- whether primordial black holes were formed in our universe, and what happened to them.
- the GZK cutoff for high-energy cosmic rays, and whether it signals a failure of special relativity at high energies
- the equivalence principle, and whether Einstein's general theory of relativity is the correct theory of gravity, and if the fundamental laws of physics are the same everywhere in the universe

See also


- Timeline of cosmology
- List of cosmologists.

References

Popular reading


-
-
- Simon Singh, Big bang: the origins of the universe, (Fourth Estate, 2005).
- Steven Weinberg, The first three minutes, (Basic Books, 1993).
- Brian Greene, The fabric of the cosmos, (Vintage, 2005).

Textbooks


- S. Dodelson, Modern Cosmology, Academic Press (2003). Released slightly before the WMAP results, this is the most modern introductory textbook.
- E. Harrison, Cosmology: the science of the universe, Cambridge University Press (2000). A relatively unmathematical textbook.
- An introductory astronomy textbook.
- E. W. Kolb and M. S. Turner, The Early Universe, Addison-Wesley (1990). This is the classic reference for cosmologists.
- A. Liddle, An Introduction to Modern Cosmology, John Wiley (2003).
- A. R. Liddle and D. H. Lyth, Cosmological Inflation and Large-Scale Structure, Cambridge (2000). An introduction to cosmology with a thorough discussion of inflation.
- T. Padmanabhan, Structure formation in the universe, Cambridge University Press (1993). Describes the formation of large-scale structures in detail.
- J. Peacock, Cosmological Physics, Cambridge University Press (1998). An introduction with more background on general relativity and quantum field theory than most.
- P. J. E. Peebles, Principles of Physical Cosmology, Princeton University Press (1993). Peebles' book has a strong historical focus.
- P. J. E. Peebles, The Large-Scale Structure of the Universe, Princeton University Press (1980). The classic work on large scale structure, in particular the discussion of correlation functions.
- M. Rees, New Perspectives in Astrophysical Cosmology, Cambridge University Press (2002).
- S. Weinberg, Gravitation and Cosmology, John Wiley (1971). An older book, but still a standard reference for a lot of the mathematical formalism.

External references

From groups


- [http://www.damtp.cam.ac.uk/user/gr/public/cos_home.html]-from the Cambridge University(Public Home Page)
- [http://map.gsfc.nasa.gov/m_uni.html Cosmology 101] - from the NASA WMAP group
- [http://www.pbs.org/wgbh/nova/origins/ Origins, Nova Online] - Provided by PBS.
- [http://dhost.info/cosmology/ Cosmology] -- Cosmology Of The Universe.
- [http://cfcp.uchicago.edu/ Center for Cosmological Physics]. University of Chicago, Chicago, Illinois.
- Dictionary of the History of Ideas:
  - [http://etext.lib.virginia.edu/cgi-local/DHI/dhi.cgi?id=dv1-64 Cosmic Images]
  - [http://etext.lib.virginia.edu/cgi-local/DHI/dhi.cgi?id=dv1-66 Cosmology from Antiquity to 1850]
  - [http://etext.lib.virginia.edu/cgi-local/DHI/dhi.cgi?id=dv1-67 Cosmology since 1850]
- [http://www.shekpvar.net/~dennis/Elib/Astronomicon/Astronomicon/Cosmos/cosmos.html Cosmos - an Illustrated Dimensional Journey from microcosmos to macrocosmos] - from DNA Digital Nature Agency

From individuals


- Gale, George, "[http://plato.stanford.edu/entries/cosmology-30s/ Cosmology: Methodological Debates in the 1930s and 1940s]", The Stanford Encyclopedia of Philosophy, Edward N. Zalta (ed.)
- Hoiland, Paul, "[http://cosmology.bravehost.com/ Modern Cosmology Examined]"[http://tprints.ecs.soton.ac.uk/archive/00000033/01/MUSINGS_ON_THE_EVOLUTION_OF_A_COSMOS.pdf Musing on the Evolution of a Cosmos] Gouldsboro, Maine.
- Jordan, Thomas F., "[http://arxiv.org/abs/astro-ph/0309756 Cosmology calculations almost without general relativity]". (arXiv.org)
- Madore, Barry F., "[http://nedwww.ipac.caltech.edu/level5/ Level 5] : A Knowledgebase for Extragalactic Astronomy and Cosmology". Caltech and Carnegie. Pasadena, California, USA.
- Smith, Tony, "[http://www.innerx.net/personal/tsmith/cosm.html Cosmology] -- At the Millennium, Experimental Observations tell us a lot about Cosmology".
- Tyler, Pat, and Phil Newman "[http://universe.gsfc.nasa.gov/ Beyond Einstein]". Laboratory for High Energy Astrophysics (LHEA) NASA Goddard Space Flight Center.
- Wright, Ned. "[http://www.astro.ucla.edu/~wright/cosmolog.htm Cosmology tutorial and FAQ]". Division of Astronomy & Astrophysics, UCLA. Category:Astrophysics Category:Cosmology ja:宇宙論 simple:Cosmology

1965

1965 (MCMLXV) was a common year starting on Friday (link goes to calendar).

Events

January-February

common year starting on Friday
- January 4 - United States President Lyndon Johnson proclaims his "Great Society" during his State of the Union address.
- January 12 - Bodies of two 15 year olds - Christine Sharrock and Marrine Schmidt - found at Wanda Beach, Sydney (Wanda Beach Murders)
- January 14 - Prime Ministers of Northern Ireland and the Republic of Ireland meet for the first time in 43 years
- January 24 - Winston Churchill dies at the age of 90.
- January 26 - Hindi becomes the official language of India.
- January 30 - Winston Churchill's funeral is held in London.
- February 6 - Sir Stanley Matthews plays his final First Division game, at the record age of 50 years and 5 days
- February 7 - US begins regular bombing of North Vietnamese towns and villages
- February 9 - Vietnam War: The first United States combat troops are sent to South Vietnam
- February 15 - A new red and white maple leaf design is adopted as the flag of Canada replacing the Union Flag and the Canadian Red Ensign.
- February 18 - The Gambia becomes independent from the United Kingdom
- February 20 - Ranger 8 crashes into the Moon after a successful mission of photographing possible landing sites for the Apollo program astronauts.
- February 21 - Malcolm X is assassinated on the first day of National Brotherhood Week at the Audubon Ballroom in New York City by Black Muslims

March


- March 7 - Bloody Sunday in Selma, Alabama
- March 8 - Vietnam War: 3,500 United States Marines arrive in South Vietnam becoming the first American combat troops in Vietnam
- March 8 - First US combat forces arrive in Vietnam
- March 9 - Second march from Selma to Montgomery under the leadership of Martin Luther King, Jr. stops at the bridge that was the site of Bloody Sunday to hold a prayer service and return to Selma in obedience to a court restraining order. White supremacists beat up white Unitarian Universalist minister James J. Reeb later that day in Selma, Alabama.
- March 10 - Goldie, a London Zoo golden eagle is recaptured after 13 days of freedom
- March 11 - White Unitarian Universalist minister James J. Reeb, beaten by White Supremacists in Selma, Alabama on March 9 following the second march from Selma, dies in a hospital in Birmingham, Alabama.
- March 18 - Cosmonaut Aleksei Leonov, leaving his spacecraft Voskhod 2 for 12 minutes, becomes the first person to walk in space
- March 21 - Ranger program: NASA launches Ranger 9 which is the last in a series of unmanned lunar space probes
- March 21 - Civil rights activists led by Martin Luther King, Jr. begin march from Selma to the capitol in Montgomery
- March 23 - NASA launches Gemini III with the United States' first two-person crew into earth orbit (Gus Grissom and John Young).
- March 24- Mark "The Undertaker" Callaway, Professional Wrestler March 25 - Civil rights activists led by Martin Luther King, Jr. successfully end march from Selma, arriving at the capitol in Montgomery

April


- April 6 - Launch of Early Bird communications satellite. It becomes operational May 2 and is placed in commercial service in June.
- April 9 - The West German parliament extends the statute of limitations on Nazi war crimes. Also, in Houston, Texas, the Harris County Domed Stadium (or commonly known as Astrodome) was opened.
- April 11 - The Palm Sunday Tornado Outbreak: An estimated fifty-one tornadoes (forty-seven confirmed) hit in six Midwestern states killing anywhere from 256 to 271 people and injuring some 1,500 more.
- April 14 - In Cold Blood killers Richard Hickock and Perry Smith, convicted of murdering four members of the Herbert Clutter family of Holcomb, Kansas, are executed by hanging at the Kansas State Penitentiary For Men in Lansing, Kansas.
- April 21 - NY World's Fair in Flushing Meadows, NY, reopens.
- April 23 - The Pennine Way officially opened.
- April 24 - Bodies of Portuguese opposition politician Humberto Delgado and his secretary Arajaris Campos are found in a forest near Villanueva del Fresno, Spain. They were killed February 12.
- April 24 - Fighting breaks out in the Dominican Republic as officers loyal to deposed President Juan Bosch lead a mutiny against the right wing junta running the country. US troops are later sent by President Lyndon B. Johnson "for the stated purpose of protecting US citizens and preventing an alleged Communist takeover of the country", thus thwarting the possibilty of "another Cuba".
- April 28 - Vietnam War: Australian Prime Minister Robert Menzies announces that the country will substantially increase its number of troops in South Vietnam, supposedly at the request of the Saigon government, although it is later revealed that Menzies had asked the leadership in Saigon to send the request at the behest of the Americans.
- April 29 - Australia announces that it is sending an infantry battalion to support the South Vietnam government.

May-June


- May 1 - Bob (later Sir Robert) Askin replaces Jack Renshaw as Premier of New South Wales.
- May 2 - US president Johnson sends troops to the Dominican Republic.
- May 13 - West German court of appeals condemns behavior of ex-defense minister Franz Joseph Strauss during the Spiegel scandal.
- May 19 - Tui Malila, the oldest tortoise or living animal ever, dies of natural causes.
- May 29 - A mining accident in Dhambas, India kills 274.
- May 31 - Racing driver Jim Clark wins the Indianapolis 500, and later wins the Formula One world driving championship in the same year.
- June 2 - Vietnam War: The first contingent of Australian combat troops arrives in South Vietnam.
- June 3 - US astronaut Edward White makes first US space walk during Gemini IV.
- June 7 - A mining accident in Kakanji, Bosnia results in 128 deaths.
- June 10 - Vietnam War: Battle of Dong Xoai begins - About 1,500 Vietcong mount a mortar attack on Dong Xoai and then overrun its military headquarters and adjoining militia compound.
- June 19 - Houari Boumedienne's Revolutionary Council ousts Ahmed Ben Bella in a bloodless coup in Algeria.
- June 20 - Police in Algiers break up demonstrations by people who have taken to the streets chanting slogans in support of deposed President Ben Bella.
- June 22 - Treaty on Basic Relations between Japan and the Republic of Korea.
- June 24 - Freddie Mills, former British boxing champion, is found shot in his car in Soho.

July


- July 14 - US spacecraft Mariner 4 flies by Mars, becoming the first spacecraft to return images from the red planet
- July 16 - The Mont Blanc Tunnel is used for the first time
- July 22 - Sir Alec Douglas-Home suddenly resigns as a head of the British Conservative Party
- July 24 - Vietnam War: Four F-4C Phantoms escorting a bombing raid at Kang Chi are the targets of antiaircraft missiles in the first such attack against American planes in the war. One is shot down and the other three sustain damage
- July 27 - Edward Heath becomes Leader of the British Conservative Party
- July 28 - Vietnam War: US President Lyndon B. Johnson announces his order to increase the number of United States troops in South Vietnam from 75,000 to 125,000
- July 29 - Vietnam War: The first 4,000 101st Airborne Division paratroopers arrive in Vietnam, landing at Cam Ranh Bay
- July 30 - War on Poverty: US President Lyndon B. Johnson signs the Social Security Act of 1965 into law, establishing Medicare and Medicaid

August


- August 1 - Cigarette advertising banned in British television
- August 6 - US President Lyndon B. Johnson signs the Voting Rights Act of 1965 into United States law
- August 7 - Singapore is expelled and separated from the Federation of Malaysia.
- August 9 - Singapore proclaims its independence from Malaysia
- August 9 - An explosion at a missile plant in Arkansas kills 53
- August 9 – Indonesian president Sukarno collapses in public
- August 11 - Watts Riots begin in Los Angeles, California
- August 13 - Jefferson Airplane debut at the Matrix in San Francisco, California and begin to appear there regularly.
- August 18 - Vietnam War: Operation Starlite begins as 5,500 United States Marines destroy a Viet Cong stronghold on the Van Tuong peninsula in Quang Ngai Province, in the first major American ground battle of the war. The Marines were tipped-off by a Viet Cong deserter who said that there was an attack planned against the US base at Chu Lai
- August 19 - At the Auschwitz trial in Frankfurt, 66 ex-SS personnel receive life sentences, 15 others smaller ones

September


- September 2 - Pakistani troops enter the Indian sector of Kashmir
- September 6 - Indian troops march on Lahore
- September 7 - China announces that it will reinforce its troops in the Indian border
- September 7 - Vietnam War: In a follow-up to August's Operation Starlite, United States Marines and South Vietnamese forces initiate Operation Piranha on the Batangan Peninsula, 23 miles south of the Chu Lai Marine base
- September 8 - India opens two additional fronts against Pakistan
- September 9 - UN secretary general U Thant negotiates with Pakistani president Ayub Khan
- September 9 - U Thant recommends China for UN membership
- September 13 - Congress of Arab countries begins in Casablanca - Habib Bourgiba boycotts the meeting
- September 14 - Opening of fourth and final period of Second Vatican Council
- September 16 - China protests against Indian provocations in its border region
- September 16 - In Iraq, Prime Minister Razzak's attempted coup fails
- September 17 - Stefan Stafanopoulos forms a new government in Greece and ends a two-year old political crisis
- September 18 - China claims that US troops have used poison gas in South Vietnam
- September 18 - In Denmark, Palle Sörensen shoots four policemen in pursuit - apprehended the same day
- September 19 - Soviet prime minister Alexei Kosygin invites the leaders of India and Pakistan to meet in Soviet Union to negotiate
- September 20 - End of term for Tuanku Syed Putra ibni Almarhum Syed Hassan Jamalullail as the 3rd Yang di-Pertuan Agong of Malaysia.
- September 21 - Commander of US troops in Vietnam, general William Westmoreland, pleads Washington to cancel the ban to use mustard gas
- September 21 - Ismail Nasiruddin Shah ibni Almarhum Sultan Zainal Abidin III, Sultan of Terengganu becomes the 4th Yang di-Pertuan Agong of Malaysia.
- September 22 - Radio Peking announces that Indian troops have dismantled their equipment on the Chinese side of the border
- September 24 - Fighting between Indian and Pakistani troops erupts again
- September 24 - British governor of Aden cancels the Aden constitution and takes direct control of the protectorate because of the bad security situation
- September 27 - Largest tanker ship at the time, Tokyo Maru, launched in Yokohama
- September 28 - Fidel Castro announces that everybody who wants can immigrate to USA
- September 28 - Taal Volcano in Luzon, Philippines, erupts - hundreds dead
- September 30 – Attempted communist coup in Indonesia. Indonesian army crushes it with the lead of general Suharto

October


- October 3 - Fidel Castro announces that Che Guevara has resigned and left the country
- October 4 - Prime minister Ian Smith of Rhodesia and Arthur Bottomley of British Commonwealth begin negotiations in London - they end on October 8 without results
- October 5 - Pakistan sever diplomatic relations with Malaysia because of the disagreement in UN
- October 5 - The Beatles are set to release their song 'Love Me Do' on Parlophone
- October 6 - Ian Brady and Myra Hindley, the Moors Murderers, arrested.
- October 8 - Indonesian army arrests and executes communists
- October 8 - Olympic Committee admits East Germany as a member
- October 8 - The Post Office Tower opens in London
- October 9 - Yale University presents the "Vinland map"
- October 9 - Brigade of South Korean soldiers arrive in South Vietnam
- October 10 - First group of Cuban refugees travels to USA
- October 12 - Per Borten forms a government in Norway
- October 12 - UN general council recommends that United Kingdom try everything to stop a rebellion in Rhodesia
- October 13 - President of Congo, Joseph Kasavubu, fires Prime Minister Moise Tsombe and forms a provisional government with Evariste Kimba in a lead
- October 15 - Vietnam War: The anti-war student-run National Coordinating Committee to End the War in Vietnam stages the first public burning of a draft card in the United States
- October 16 - Suharto takes power in Indonesia
- October 17 - NY World's Fair at Flushing Meadows, NY, closes. Due to financial losses, some of the projected improvements on the park on the site fail to materialize.
- October 18 - Indonesian government declares communist party illegal
- October 20 - Ludwig Erhard elected as Chancellor in West Germany
- October 21 - Ikeja-Seki comet
- October 21 - OAU meeting begins in Accra
- October 22 - French authors André Figueras and Jacques Laurent are fined for their comments against Charles De Gaulle
- October 22 - African countries demand that the United Kingdom use force to prevent Rhodesia from declaring unilateral independence
- October 24 - British Prime Minister Harold Wilson and Arthur Bottomley travel to Rhodesia for negotiations
- October 25 - Soviet Union declares its support of African countries in case Rhodesia unilaterally declares independence
- October 26
  - Anti-government demonstrations in the Dominican Republic
  - The body of Sylvia Likens discovered by authorities in Indianapolis, Indiana, USA.
- October 27 - Brazilian president Branco removes power of parliament, legal courts and opposition parties
- October 28 - French foreign minister Couve de Murville travels to Moscow
- October 28 - Pope Paul VI announces that ecumenical council has decided that Jews are not collectively responsible for the killing of Christ
- October 28 - In St. Louis, Missouri, the 630-foot-tall parabolic steel Gateway Arch is completed
- October 29 - Kidnapping of Mehdi Ben Barka
- October 30 - Vietnam War: Just miles from Da Nang, United States Marines repel an intense attack by wave after wave of Viet Cong forces, killing 56 guerrillas. Among the dead, a sketch of Marine positions was found on the body of a 13-year-old Vietnamese boy who sold drinks to the Marines the day before.
- October 31 - Indonesian army announces that it is fighting with communist guerillas in Java

November


- November 2 - Republican John V. Lindsay elected mayor of New York City
- November 3 - Charles De Gaulle announces that he will stand in next presidential election
- November 5 - Martial law announced in Rhodesia. UN General Assembly accepts British intent to use force against Rhodesia if necessary with a vote of 82-9.
- November 6 - Freedom Flights begin: Cuba and the United States formally agree to start an airlift for Cubans who want to go to the United States (by 1971 250,000 Cubans take advantage of this program).
- November 8 - The British Indian Ocean Territory is created, consisting of Chagos Archipelago, Aldabra, Farquhar and Des Roches islands (on June 23, 1976 Aldabra, Farquhar and Des Roches were returned to Seychelles).
- November 9 - Northeast Blackout of 1965: Several U.S. states (VT, NH, MA, CT, RI, NY and portions of NJ) and parts of Canada are hit by a series of blackouts lasting up to 13 1/2 hours.
- November 9 - Vietnam War: In New York City, 22-year old Catholic Worker Movement member Roger Allen LaPorte sets himself on fire in front of the United Nations building in protest of the war in Vietnam (this was the second such incident in a week; on November 2 32-year-old Quaker member Norman Morrison did the same thing in front of The Pentagon)
- November 11 - In Rhodesia (modern-day Zimbabwe), the white minority regime of Ian Smith unilaterally declares independence
- November 12 - UN Security Council resolution (voted 10-0) recommends that other countries would not recognize independent Rhodesia
- November 13 - The SS Yarmouth Castle burns and sinks 60 miles off Nassau with the loss of 90 lives.
- November 14 - Vietnam War: Battle of the Ia Drang begins - In the Ia Drang Valley of the Central Highlands in Vietnam, the first major engagement of the war between regular American and North Vietnamese forces begins
- November 15 - US racer Craig Breedlove sets a new land speed record of 600.601 mph
- November 16 - Venera program: The Soviet Union launches the Venera 3 space probe from Baikonur, Kazakhstan toward Venus (on March 1, 1966 it became the first spacecraft to reach the surface of another planet)
- November 16 - Disney launches Epcot Center
- November 20 - UN Security Council recommends that all states stop trading with Rhodesia
- November 23 - Soviet general Mikhail Kazakov becomes commander of Warsaw Pact
- November 24 - Queen Elizabeth of Belgium dies
- November 24 - Congolese lieutenant general Mobutu ousts Joseph Kasavubu and declares himself president
- November 26 - At the Hammaguira launch facility in the Sahara Desert, France launches a Diamant-A rocket with its first satellite, Asterix-1 on board, becoming the third country to enter space.
- November 27 - Vietnam War: The Pentagon tells US President Lyndon B. Johnson that if planned major sweep operations needed to neutralize Viet Cong forces during the next year were to succeed, the number of American troops in Vietnam has to be increased from 120,000 to 400,000
- November 28 - Vietnam War: In response to US President Lyndon B. Johnson's call for "more flags" in Vietnam, Philippines President Elect Ferdinand Marcos announces he will send troops to help fight in South Vietnam.
- November 29 - Canadian satellite Alouette 2 is launched.

December


- December 1 - The Border Security Force is established in India as a special force to guard the borders.
- December 3 - First British aid flight arrive in Lusaka - Zambia has asked for British help against Rhodesia
- December 3 - Members of OAU decide to sever diplomatic relations with United Kingdom unless the British government ends rebellion of Rhodesia by mid-December
- December 5 – Charles De Gaulle re-elected as French president with 10,828,421 votes
- December 8 - Rhodesian prime minister warns that Rhodesia would resist trade embargo by neighboring countries with force
- December 8 - Closing of Second Vatican Council
- December 12 - In baseball, Roy Hofheinz fires manager Lum Harris (record of 65-97). Grady Hatton takes over the Astros.
- December 15 - Tanzania and Guinea sever diplomatic relations with United Kingdom
- December 15 - Gemini 6 and Gemini 7 perform the first controlled rendezvous in Earth orbit
- December 17 - British government begins oil embargo against Rhodesia - USA joins the effort
- December 21 - Soviet Unions announces that it has shipped rockets to North Vietnam
- December 21 - Soviet scientists condemn Trofim Lysenko
- December 21 - Konrad Adenauer resigns from the post of chairman of the Christian Democratic party
- December 22 - Military coup on Dahomey
- December 22 - 70 mph speed limit imposed on British roads
- December 27 - British oil platform Sea Gem collapses in the North Sea
- December 28 - Italian foreign minister Mintore Fanfani resigns
- December 30 - President Kenneth Kaunda of Zambia announces that Zambia and United Kingdom have agreed to a deadline before which the Rhodesian white government should be ousted
- December 30 - Ferdinand Marcos becomes President of the Philippines

Unknown dates


- The Council for National Academic Awards is established in the UK
- TAT-4 cable goes into operation.
- Mont Blanc tunnel between France and Italy completed.
- Desteldonk becomes a part of Ghent (East Flanders, Flanders, Belgium)
- California City, California incorporated.

Births

January-February


- January 9 - Joely Richardson, British actress
- January 11 - Matthew Maxwell Taylor Kennedy, son of Robert F. Kennedy and Ethel Skakel Kennedy and nephew of U.S president John F Kennedy and Edward M Kennedy
- January 14 - Marc Delissen, Dutch field hockey player
- January 15 - Adam Jones, American musician (Tool)
- January 18 - Dave Attell, American comedian
- January 20 - Sophie, Countess of Wessex
- January 20 - John Michael Montgomery, American singer
- January 22 - DJ Jazzy Jeff, American rapper and actor
- January 22 - Diane Lane, American actress
- January 27 - Alan Cumming, Scottish actor
- January 29 - Dominik Hasek, Czech hockey player
- February 1 - Sherilyn Fenn, American actress
- February 1 - Brandon Lee, American actor (d. 1993)
- February 1 - Princess Stéphanie of Monaco
- February 11 - Stephen Gregory, American actor
- February 18 - Dr. Dre, American rapper and music producer
- February 22 - Scott Lowell, American actor
- February 23 - Michael Dell, American computer manufacturer

March-April


- March 1 - Stewart Elliott, Canadian jockey
- March 4 - Gary Helms, American kick-boxer
- March 7 - Jesper Parnevik, Swedish golfer
- March 9 - Benito Santiago, baseball player
- March 10 - Rod Woodson, American football player
- March 11 - Lawrence Llewelyn-Bowen, British television presenter
- March 12 - Steve Finley, baseball player
- March 14 - Kevin Brown, baseball player
- March 24 - Mark Calaway, American professional wrestler
- March 25 - Sarah Jessica Parker, American actress
- March 25 - Stefka Kostadinova, Bulgarian high jumper and president of the Bulgarian olympic committee
- April 1 - Robert Steadman, English composer
- April 4 - Robert Downey Jr., American actor
- April 7 - Bill Bellamy, American actor and comedian
- April 15 - Linda Perry, American musician
- April 16 - Martin Lawrence, American actor, comedian, and producer
- April 21 - Ed Belfour, Canadian hockey player
- April 26 - Kevin James, American comedian and actor
- April 28 - Steven Blum, American voice actor

May-June


- May 7 - Owen Hart, Canadian professional wrestler (d. 1999)
- May 9 - Steve Yzerman, Canadian hockey player
- May 14 - Eoin Colfer, Irish writer
- May 16 - Krist Novoselic, American bassist (Nirvana)
- May 17 - Trent Reznor, American musician (Nine Inch Nails)
- May 28 - Chris Ballew, American musician
- May 31 - Brooke Shields, American actress
- June 1 - Nigel Short, English chess player
- June 4 - Mick Doohan, Australian motorcycle racer
- June 7 - Mick Foley, American professional wrestler and author
- June 10 - Elizabeth Hurley, English actress
- June 15 - Bernard Hopkins, American boxer
- June 16 - Charika Corea, Sri Lankan autism campaigner

July-August


- July 1 - Harald Zwart, Norwegian film director
- July 11 - Ernesto Hoost, Dutch kickboxer
- July 17 - Craig Morgan, American singer
- July 18 - Michael Sharrett, American actor
- July 19 - Stuart Scott, American sports reporter
- July 20 - Anthony Paul Kennedy Shriver nephew of John F Kennedy and son of Sargent Shriver and Eunice Mary Kennedy
- July 21 - Guðni Bergsson, Icelandic footballer
- July 22 - Shawn Michaels, American professional wrestler
- July 23 - Slash, American musician, guitar ledgend, Guns N' Roses
- July 26 - Sandra Bullock, American actress
- July 28 - Lori Loughlin, American actress
- July 31 - J. K. Rowling, English author
- August 10 - Mike Smith, American jockey
- August 10 - John Starks, American basketball player
- August 14 - Emmanuelle Béart, French actress
- August 18 - Koji Kikkawa, Japanese singer
- August 24 - Reggie Miller, American basketball player
- August 28 - Shania Twain, American singer and songwriter

Se