What Is Background Radiation?

Cosmic microwave background (English: CMB, cosmic microwave background, also known as 3K background radiation) is the thermal radiation left over from the "Big Bang" in cosmology. In the early literature, the "cosmic microwave background" was called "cosmic microwave background radiation" (CMBR) or "legacy radiation", which is a type of electromagnetic radiation that fills the entire universe.

Background radiation

Cosmic microwave background (English: CMB, cosmic microwave background, also known as 3K background radiation) is a cosmological "

The anisotropy of the cosmic microwave background is divided into two types: the first-order anisotropy, which is derived from the influence that occurred before and at the last scattering surface; and the second-order anisotropy, which is derived from the interaction with the background hot gas radiation. Effect or gravity potential energy, the latter occurs between the final scattering surface and the observer.

The anisotropic structure of the cosmic microwave background radiation is mainly due to two effects: acoustic oscillation diffusion damping (also known as collision damping). Acoustic oscillations result from photon-baryon collisions in the plasma of the early universe. The pressure of photons tends to eliminate anisotropy, and gravity attracts baryons--moving much slower than photons--making them often collapse into dense quasars. These two effects compete to create an acoustic oscillation that gives a peak structure of microwave background radiation characteristics. These peaks roughly correspond and resonate with a mode in which the photon decoupling was then peak amplitude.

These peaks contain interesting physical characteristics. The angular scale of the first peak determines the curvature of the universe (but not the topology of the universe). The next peakthe odd peak to even peak ratiodetermines the third peak of the constricted baryon density, which can be used to obtain information about the density of dark matter. ^[11]

The cosmic microwave background is polarized at several micro-absolute temperatures. There are two types of polarization, E-mode and B-mode. This situation is analogous to electrostatics. In electrostatics, the rotation of the electric field ("E" field) is zero, and the divergence of the magnetic field ("B" field) is zero. In a heterogeneous plasma, E-modes are naturally generated by Thomson scattering. The B mode has not been measured, and it is considered that the maximum amplitude should be 0.1 K, which is not generated by plasma physics. The B-mode does not come from a standard scalar perturbation, but from two mechanisms. The first is from the E mode behind the gravitational lens, which was measured by the Antarctic Observatory in 2013. ^[12]

In 1934, Tolman discovered that in the evolution of radiant temperature in the universe, temperature will change with time; and the frequency of photons will change with time (that is, cosmological redshift). But when the two are considered together, that is, when discussing the spectrum (a function of frequency and temperature), the changes of both will be offset, that is, the form of blackbody radiation will be retained.

In 1948, American physicists Gamow, Alfie, and Herman estimated that if the initial temperature of the universe was about one billion degrees, there would be about 5 to 10k of black body radiation left. However, this work has not received much attention. In 1964, research by Zeldovich in the Soviet Union, Hoyle in the United Kingdom, Taylor, and Peebles in the United States predicted that the universe should have background radiation with a temperature of a few K, and the centimeter It should be observable on the band, which has regained the attention of academic circles on background radiation. American Dicke, Roll, Wilkinson and others also started to make a low-noise antenna to detect this radiation, but American radio astronomers Penzias and Robert Wilson are in Inadvertently before they found background radiation.

Before the 1980s, there was still a problem related to background radiation that was confusing. Radiation from all directions in space has exactly the same temperature, which is too smooth and perfect.

Has now been proven reliably

The theory claims that the result of these irregularities is that there should be ripples in the background radiation, that is, the temperature should be slightly different when the instrument is pointed at different parts of the sky. The difference in prophecy is very small and can only rise from the higher

The satellite's original cosmic microwave background data (such as WMAP) contains foreground effects and will completely obscure the fine-scale structure of the cosmic microwave background. The fine-scale structure is superimposed on the original cosmic microwave background data, which is too small to appear from the original data at that scale. The most prominent foreground effect is the dipole anisotropy caused by the movement of the sun relative to the cosmic microwave background. Due to the dipole anisotropy and the earth's relative to the sun, many microwave sources on the plane of the Milky Way, and other annual motions and others must be subtracted to reveal ultra-fine changes and depict the fine-scale structural characteristics of the cosmic microwave background.

The whole-sky map, angular power spectrum, and detailed analysis of the final cosmological parameters made by the cosmic microwave background data are a complex and difficult to calculate problem. Although the calculation of the power spectrum from the diagram is in principle a simple Fourier transform that decomposes the whole-sky map into a spherical harmonic function, in practice, it is difficult to take noise and foreground sources into consideration. In particular, these prospects are dominated by galaxy rays such as braking radiation, synchrotron radiation, and interstellar dust in microwave emission bands. In practice, galaxies have been deleted, resulting in the universe microwave background image not being a full-sky image. In addition, point light sources such as galaxy clusters represent additional sources of foreground, which must be removed to avoid distorting the small-scale structure in the cosmic microwave background energy spectrum.

The limits on many cosmological parameters can be obtained by their effects on the energy spectrum, and the results are often calculated by Markov Monte Carlo sampling technology.

(COBE) Background Radiation Cosmic Background Explorer (COBE)

According to the results measured by the Cosmic Background Explorer (COBE) lifted off in November 1989, the cosmic microwave background radiation spectrum fits the black body radiation spectrum with a temperature of 2.726 ± 0.010K very accurately, confirming that the Milky Way is relative to the background Radiation has a relative speed of movement, and it has also been verified that after deducting the effect of this speed on the measurement results and the interference of matter radiation in the Milky Way, the background radiation of the universe is highly isotropic, and the amplitude of temperature fluctuations is only about one million Five percent. Currently accepted theories believe that this temperature fluctuation originates from the quantum fluctuations on the minimum scale of the universe in the early stage of its formation. It expands to the cosmological scale with the inflation of the universe, and it is precisely because of the temperature fluctuations. The inhomogeneity of the material distribution of the material universe resulted in the formation of large-scale structures such as galaxy clusters.

In 2006, American scientists John Mather and George Smoot, who were in charge of the COBE project, won the Nobel Prize in Physics for their "black body form and anisotropy of cosmic microwave background radiation."

(WMAP) Background radiation Wilkinson microwave anisotropy detector (WMAP)

In 2003, the Wilkinson microwave anisotropy detector launched by the United States measured the rise and fall of the cosmic microwave background in different directions. The age of the universe is 137 ± 100 million years. Of the composition of the universe, 4% is general matter 23% is dark matter and 73% is dark energy. The current expansion speed of the universe is a gap of 71 kilometers per second per million seconds. The space of the universe is almost flat. It has experienced the process of inflation and will continue to expand.

Background radiation from Planck satellite results

Planck Sky Surveyor is the third medium-sized scientific program of the European Space Agency in Vision 2000. Her design goal is to obtain anisotropic maps of cosmic microwave background radiation across the sky with unprecedentedly high angular resolution. The Planck Sky Surveyor will provide several major cosmological and astrophysics messages, such as testing the theory of the early universe and the origin of the structure of the universe. Before the plan was approved, the name of the project was CosmicBackground Radiation Anisotropy Satellite and Background Anisotropy Measurement (CosmicBackgroundRadiationAnisotropySatellite and Satellite forMeasurement ofBackgroundAnisotropies., Abbreviated as COBRAS / SAMBA). After the mission was approved, it was changed to its current name to commemorate the 1918 German scientist Max Planck (1858-1947) who won the Nobel Prize in Physics in 1937. Planck Sky Surveyor was launched by the Aryan V rocket and Herschel Space Observatory on May 14, 2009. This is a plan in cooperation with NASA to complement the shortcomings of WMAP detectors in measuring large-scale Lianyi. ^[14]