Cosmic noise, also known as galactic radio noise, is not actually sound, but a physical phenomenon derived from outside of the Earth's atmosphere. It can be detected through a radio receiver, which is an electronic device that receives radio waves and converts the information given by them to a audible form. Its characteristics are comparable to those of thermal noise. Cosmic noise occurs at frequencies above about 15 MHz when highly directional antennas are pointed toward the sun or other regions of the sky, such as the center of the Milky Way Galaxy. Celestial objects like quasars, which are super dense objects far from Earth, emit electromagnetic waves in their full spectrum, including radio waves. The fall of a meteorite can also be heard through a radio receiver; the falling object burns from friction with the Earth's atmosphere, ionizing surrounding gases and producing radio waves. Cosmic microwave background radiation (CMBR) from outer space is also a form of cosmic noise. CMBR is thought to be a relic of the Big Bang, and pervades the space almost homogeneously over the entire celestial sphere. The bandwidth of the CMBR is wide, though the peak is in the microwave range.
Karl Jansky, an American physicist and radio engineer, first discovered radio waves from the Milky Way in August, 1931. At Bell Telephone Laboratories in 1932, Jansky built an antenna designed to receive radio waves at a frequency of 20.5 MHz, which is a wavelength of approximately 14.6 meters.
After recording signals with this antenna for several months, Jansky categorized them into three types: nearby thunderstorms, distant thunderstorms, and a faint steady hiss of an unknown origin. He discovered the location of maximum intensity rose and fell once a day, which led him to believe he was detecting radiation from the Sun.
A few months went by following this signal thought to be from the Sun, and Jansky found that the brightest point moved away from the Sun and concluded the cycle repeated every 23 hours and 56 minutes. After this discovery, Jansky concluded the radiation was coming from the Milky Way and was strongest in the direction of the center of the galaxy.
Jansky's work helped to distinguish between the radio sky and the optical sky. The optical sky is what is seen by the human eye, whereas the radio sky consists of daytime meteors, solar bursts, quasars, and gravitational waves.
Later in 1963, American physicist and radio astronomer Arno Allan Penzias (born April 26, 1933) discovered cosmic microwave background radiation. Penzias's discovery of cosmic microwave background radiation helped establish the Big Bang theory of cosmology. Penzias and his partner, Robert Woodrow Wilson worked together on ultra-sensitive cryogenic microwave receivers, originally intended for radio astronomy observations. In 1964, upon creating their most sensitive antenna/receiver system, the Holmdel Horn Antenna, the two discovered a radio noise they could not explain. After further investigation, Penzias contacted Robert Dicke, who suggested it could be the background radiation predicted by cosmological theories, a radio remnant of the Big Bang. Penzias and Wilson won the Nobel Prize in Physics in 1978.
The Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE) is a device designed to observe the transition out of the "cosmic dark ages" as the first stars ignite in nuclear fusion and the universe begins to resemble its current form.
ARCADE consists of 7 precision radiometers carried to an altitude of over 35 km (21 miles) by a scientific research balloon. The device measures the tiny heating of the early universe by the first generation of stars and galaxies to form after the Big Bang.
Cosmic noise refers to the background radio frequency radiation from galactic sources, which have constant intensity during geomagnetically quiet periods.
Cosmic noise can be traced from solar flares, which are sudden explosive releases of stored magnetic energy in the atmosphere of the Sun, causing sudden brightening of the photosphere. Solar flares can last from a few minutes to several hours.
During solar flare events, particles and electromagnetic emissions can affect Earth's atmosphere by fluctuating the level of ionization in the Earth's ionosphere. Increased ionization results in absorption of the cosmic radio noise as it passes through the ionosphere.
Solar wind is a flux of particles, protons and electrons together with nuclei of heavier elements in smaller numbers, that are accelerated by the high temperatures of the solar corona to velocities large enough to allow them to escape from the Sun's gravitational field.
Solar wind causes sudden bursts of cosmic noise absorption in the Earth's ionosphere. These bursts can only be detected only if the magnitude of the geomagnetic field perturbation caused by the solar wind shock is large enough.
The cosmic microwave background, in Big Bang cosmology, is electromagnetic radiation which is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all space. It is an important source of data on the early universe because it is the oldest electromagnetic radiation in the universe, dating to the epoch of recombination. With a traditional optical telescope, the space between stars and galaxies is completely dark. However, a sufficiently sensitive radio telescope shows a faint background noise, or glow, almost isotropic, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum. The accidental discovery of the CMB in 1965 by American radio astronomers Arno Penzias and Robert Wilson was the culmination of work initiated in the 1940s, and earned the discoverers the 1978 Nobel Prize in Physics.
The ionosphere is the ionized part of Earth's upper atmosphere, from about 48 km (30 mi) to 965 km (600 mi) altitude, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an important role in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth.
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF bands. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz. In all cases, microwaves include the entire SHF band at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations.
A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency portion of the electromagnetic spectrum emitted by astronomical objects, just as optical telescopes are the main observing instrument used in traditional optical astronomy which studies the light wave portion of the spectrum coming from astronomical objects. Unlike optical telescopes, radio telescopes can be used in the daytime as well as at night.
Astronomy is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates outside Earth's atmosphere. Cosmology is a branch of astronomy that studies the universe as a whole.
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1932, when Karl Jansky at Bell Telephone Laboratories observed radiation coming from the Milky Way. Subsequent observations have identified a number of different sources of radio emission. These include stars and galaxies, as well as entirely new classes of objects, such as radio galaxies, quasars, pulsars, and masers. The discovery of the cosmic microwave background radiation, regarded as evidence for the Big Bang theory, was made through radio astronomy.
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies as high as 300 gigahertz (GHz) to as low as 30 hertz (Hz). At 300 GHz, the corresponding wavelength is 1 mm ; at 30 Hz the corresponding wavelength is 10,000 km. Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a close, but slightly lower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects.
Karl Guthe Jansky was an American physicist and radio engineer who in August 1931 first discovered radio waves emanating from the Milky Way. He is considered one of the founding figures of radio astronomy.
The Wilkinson Microwave Anisotropy Probe (WMAP), originally known as the Microwave Anisotropy Probe (MAP), is an inactive uncrewed spacecraft operating from 2001 to 2010 which measured temperature differences across the sky in the cosmic microwave background (CMB) – the radiant heat remaining from the Big Bang. Headed by Professor Charles L. Bennett of Johns Hopkins University, the mission was developed in a joint partnership between the NASA Goddard Space Flight Center and Princeton University. The WMAP spacecraft was launched on June 30, 2001 from Florida. The WMAP mission succeeded the COBE space mission and was the second medium-class (MIDEX) spacecraft in the NASA Explorers program. In 2003, MAP was renamed WMAP in honor of cosmologist David Todd Wilkinson (1935–2002), who had been a member of the mission's science team. After nine years of operations, WMAP was switched off in 2010, following the launch of the more advanced Planck spacecraft by European Space Agency in 2009.
A microwave radiometer (MWR) is a radiometer that measures energy emitted at millimetre-to-centimetre wavelengths known as microwaves. Microwave radiometers are very sensitive receivers designed to measure thermally-emitted electromagnetic radiation. They are usually equipped with multiple receiving channels in order to derive the characteristic emission spectrum of planetary atmospheres, surfaces or extraterrestrial objects. Microwave radiometers are utilized in a variety of environmental and engineering applications, including remote sensing, weather forecasting, climate monitoring, radio astronomy and radio propagation studies.
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems.
Arno Allan Penzias is an American physicist, radio astronomer and Nobel laureate in physics. Along with Robert Woodrow Wilson, he discovered the cosmic microwave background radiation, which helped establish the Big Bang theory of cosmology.
Grote Reber was an American pioneer of radio astronomy, which combined his interests in amateur radio and amateur astronomy. He was instrumental in investigating and extending Karl Jansky's pioneering work, and conducted the first sky survey in the radio frequencies.
Astrophysics is a science that employs the methods and principles of physics in the study of astronomical objects and phenomena. Among the subjects studied are the Sun, other stars, galaxies, extrasolar planets, the interstellar medium and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum, and the properties examined include luminosity, density, temperature, and chemical composition. Because astrophysics is a very broad subject, astrophysicists apply concepts and methods from many disciplines of physics, including classical mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic and molecular physics.
The Holmdel Horn Antenna is a large microwave horn antenna that was used as a satellite communication antenna and radio telescope during the 1960s at Bell Telephone Laboratories in Holmdel Township, New Jersey, United States. It was designated a National Historic Landmark in 1988 because of its association with the research work of two radio astronomers, Arno Penzias and Robert Wilson. In 1965 while using this antenna, Penzias and Wilson discovered the cosmic microwave background radiation (CMBR) that permeates the universe. This was one of the most important discoveries in physical cosmology since Edwin Hubble demonstrated in the 1920s that the universe was expanding. It provided the evidence that confirmed George Gamow's and Georges Lemaître's "Big Bang" theory of the creation of the universe. This helped change the science of cosmology, the study of the history of the universe, from a field for unlimited theoretical speculation into a discipline of direct observation. In 1978 Penzias and Wilson received the Nobel Prize for Physics for their discovery.
The discovery of cosmic microwave background radiation constitutes a major development in modern physical cosmology. The cosmic background radiation (CMB) was measured by Andrew McKellar in 1941 at an effective temperature of 2.3 K using CN stellar absorption lines observed by W. S. Adams. Theoretical work around 1950 showed the need for a CMB for consistency with the simplest relativistic universe models. In 1964, US physicist Arno Penzias and radio-astronomer Robert Woodrow Wilson rediscovered the CMB, estimating its temperature as 3.5 K, as they experimented with the Holmdel Horn Antenna. The new measurements were accepted as important evidence for a hot early Universe and as evidence against the rival steady state theory. In 1978, Penzias and Wilson were awarded the Nobel Prize for Physics for their joint measurement.
Observational cosmology is the study of the structure, the evolution and the origin of the universe through observation, using instruments such as telescopes and cosmic ray detectors.
Robert Henry Dicke was an American astronomer and physicist who made important contributions to the fields of astrophysics, atomic physics, cosmology and gravity. He was the Albert Einstein Professor in Science at Princeton University.
In physical cosmology, the age of the universe is the time elapsed since the Big Bang. Today, astronomers have derived two different measurements of the age of the universe: a measurement based on the observations of a distant, infant state of the universe, whose results are an age of around 13.77 billion years, 13.772±0.040 billion years within the Lambda-CDM concordance model as of 2018; and a measurement based on the observations of the local, modern universe which suggest a younger universe. The uncertainty of the first kind of measurement has been narrowed down to 20 million years, based on a number of studies which all gave extremely similar figures for the age. These include studies of the microwave background radiation by the Planck spacecraft, the Wilkinson Microwave Anisotropy Probe and other space probes. Measurements of the cosmic background radiation give the cooling time of the universe since the Big Bang, and measurements of the expansion rate of the universe can be used to calculate its approximate age by extrapolating backwards in time. The range of the estimate is also within the range of the estimate for the oldest observed star in the universe.
Charles L. Bennett is an American observational astrophysicist. He is a Bloomberg Distinguished Professor, the Alumni Centennial Professor of Physics and Astronomy and a Gilman Scholar at Johns Hopkins University. He is the Principal Investigator of NASA's highly successful Wilkinson Microwave Anisotropy Probe (WMAP).