The symbol crops up on cave walls in Europe and North America, across Africa and India, in Southeast Asia and as far away as Australia. These great filaments are made largely of dark matter. In this video I explain just what physicists mean when they speak about 'dark matter' and what reasons we have to think that dark matter exists.
- Symbol For Dark Matter
- Dark Matter Ben 10
- The Symbol For Dark Matter
- Dark Matter Equation
- Dark Matter In The Universe
FAQ | Age | Distances | Bibliography | Relativity
absolute magnitude: the magnitude an objectwould have at the standard distance of 10 parsecs.
absorption line: a more or less narrow range of wavelengths in aspectrum that is darker than neighboring wavelengths.Absorption lines are seen in stars. Slotomania status points.
baryon: a massive elementary particle made up of three quarks.Neutrons and protons are baryons.
Cepheid: a type of pulsating variable starwith a luminosity that can be determined from the period of its variation: Cepheids with longpulsation periods are bigger and thus more luminous than short periodCepheids.
cold dark matter: a type of dark matter that was moving at much less than the speed of light 10,000 years after the Big Bang. (see dark matter)
continuum: a smooth spectrum without emission or absorptionlines. Some sources like tungsten lamps or blackbodies are purelycontinuum sources, while in sources with lines the continuum is a smoothspectrum drawn through the points between the lines.
CMB: Cosmic Microwave Backgroundradiation, also CMBR, CBR andthe '3 K blackbody radiation'. Radiation left over from the hot BigBang which has cooled by expansion to a temperature slightly less than 3degrees above absolute zero.
Symbol For Dark Matter
cosmological constant: a term in Einstein's general relativity equations that leads to an acceleration of the expansion of the Universe.Usually denoted by Λ, the capital Greek letter Lambda when expressedwith units of inverse length squared, or by ΩΛor the lower-case Greek lambda (λ) when normalized to the critical density like Ω.
dark energy: a more general form of the vacuum energy densitythan the cosmological constant.
distance modulus: the difference between the magnitude andthe absolute magnitude, so DM = 5 log10(D/[10 pc]).
Doppler: 19th century physicist who discovered the variation in the wavelength of waves caused by motion of the source.
emission line: a more or less narrow range of wavelengths in aspectrum that is brighter than neighboring wavelengths.Emission lines are seen in quasars. Apple only software.
equation of state: the ratio of the pressure to the energy densityin the dark energy or vacuum energy. Usually denoted by w.For the cosmological constantw = -1.
Casino slots for android. flux: power per unit area. The flux from the Sun at the Earth is 1367 Watts per square meter. This total power is often divided up into different frequency or wavelength bands, giving for example Watts per square meter per Hertz or ergs per square cm per second per micron. 1Janskyis 10-26 Multi game video poker. Casino titan mobile. Watts per square meter per Hertz.
Gyr: gigayear, or one billion years. See for atable of all the metric prefixes from yocto (10-24)to yotta (1024).
hot dark matter: a type of dark matter that was moving at close tothe speed of light 10,000 years after the Big Bang. (see dark matter)
isotropic: the same in all directions. Anisotropic - notisotropic. Anisotropy - difference between different directions.In the standard color scheme for CMB anisotropy maps measured by theCOBE DMR, red shows areasof the sky that are warmer, while blue shows the cooler regions.
Dark Matter Ben 10
Lambda: the upper case Greek Lambda is usually used to denoteEinstein's cosmological constant. A non-zero Lambdaindicates a non-zero vacuum energy densityand causes a long-range repulsive effect which leads to the acceleratingexpansion of the Universe.
The Symbol For Dark Matter
cosmological constant: a term in Einstein's general relativity equations that leads to an acceleration of the expansion of the Universe.Usually denoted by Λ, the capital Greek letter Lambda when expressedwith units of inverse length squared, or by ΩΛor the lower-case Greek lambda (λ) when normalized to the critical density like Ω.
dark energy: a more general form of the vacuum energy densitythan the cosmological constant.
distance modulus: the difference between the magnitude andthe absolute magnitude, so DM = 5 log10(D/[10 pc]).
Doppler: 19th century physicist who discovered the variation in the wavelength of waves caused by motion of the source.
emission line: a more or less narrow range of wavelengths in aspectrum that is brighter than neighboring wavelengths.Emission lines are seen in quasars. Apple only software.
equation of state: the ratio of the pressure to the energy densityin the dark energy or vacuum energy. Usually denoted by w.For the cosmological constantw = -1.
Casino slots for android. flux: power per unit area. The flux from the Sun at the Earth is 1367 Watts per square meter. This total power is often divided up into different frequency or wavelength bands, giving for example Watts per square meter per Hertz or ergs per square cm per second per micron. 1Janskyis 10-26 Multi game video poker. Casino titan mobile. Watts per square meter per Hertz.
Gyr: gigayear, or one billion years. See for atable of all the metric prefixes from yocto (10-24)to yotta (1024).
hot dark matter: a type of dark matter that was moving at close tothe speed of light 10,000 years after the Big Bang. (see dark matter)
isotropic: the same in all directions. Anisotropic - notisotropic. Anisotropy - difference between different directions.In the standard color scheme for CMB anisotropy maps measured by theCOBE DMR, red shows areasof the sky that are warmer, while blue shows the cooler regions.
Dark Matter Ben 10
Lambda: the upper case Greek Lambda is usually used to denoteEinstein's cosmological constant. A non-zero Lambdaindicates a non-zero vacuum energy densityand causes a long-range repulsive effect which leads to the acceleratingexpansion of the Universe.
The Symbol For Dark Matter
Lyman alpha line: the strongest line in the spectrum of the most commonatom in the Universe, hydrogen. It is emitted at a wavelength of 122 nm.The general formula for the wavelength of hydrogen lines iswhere n = 1, 2, 3, . is the lower state quantum number and m = n+1, n+2, . is the upper state quantum number.When n = 1, these lines with m = 2, 3, . are calledLyman alpha, Lyman beta, . and form the Lyman series.When n = 2, these lines with m = 3, 4, . are calledH-alpha, H-beta, . and form the Balmer series.
MACHO: MAssive Compact Halo Object, and also one of projectssearching for MACHOs by looking for gravitational microlensing: theother projects are EROS and OGLE.A MACHO is an object with a massfrom about 10 billion tons to solar masses. If it is made out neutronsand protons then it is baryonic dark matter, but primordial black holesare a non-baryonic dark matter version of MACHOs.
magnitude: a scale used by astronomers to measure flux. Each 5 units on the magnitudescale corresponds to a 100-fold decrease in the flux.The Sun has magnitude -26.5. Sirius, the brightest star in the night sky, has magnitude -1.6. The faintest stars visible with the naked eye havemagnitude 6.
Dark Matter Equation
neutralino: a particle predicted by supersymmetry models of the forces of nature. These models predict that each type of known particle will have a supersymmetric partner. The neutralino is the lightest electrically neutral supersymmetric partner, and it is a candidate for cold dark matter. As of 1999, no supersymmetric partner particles of any kind have been observed experimentally. A neutralino is one type ofWIMP.
Omega or Ω: the ratio of the density of the Universe to thecritical density.
omega: the lower case Greek ω is often used to denoteΩh2 (or Omega*h^2), where h=Ho/[100 km/sec/Mpc].Since Ω is the density divided by the critical density, and the critical density is 3Ho2/[8πG], this combinationis just proportional to the physical density. ω=1 corresponds to19*10-30 gm/cc, or in SI: 19 yoctograms per cubic meter.
QSO: quasi-stellar object. The first discovered QSO's were radiosources, leading to the name quasi-stellar radio sources, or QSRS, orquasars. These objects look like stars on an image of the sky, buttheir spectra show strong emission lines at high redshift. The redshiftmeans that quasars are very far away, and are thus the most luminousobjects in the Universe.
redshift: the Doppler shift for objects receding from the Earth causes the wavelengths of light to get longer,and hence shift into the red part of the spectrum. Because of the expansionof the Universe, objects with high redshift are far away, and we see themas they were a long time ago.
spectrum: result of spreading out light by wavelengths. Arainbow is a natural spectrum. The eye is sensitive to waves fromviolet at 380 nm wavelength to red at 700 nm wavelength, but astronomersnow study electromagnetic radiation from gamma rays through X-rays,ultraviolet, violet, blue, green, yellow, orange, red, infrared and radiowaves.
vacuum energy density: Quantum theory requires empty space to be filled with particles and anti-particles being continually created andannihilated. This could lead to a net density of the vacuum, which ifpresent, would behave like a cosmological constant.
WIMP: a Weakly Interacting Massive Particle, a possible form forcold dark matter.
z: z is the symbol used for the redshift. The formula is where a line is emitted at one wavelength but observed at a different wavelength.
Ned Wright's home pageDark Matter In The Universe
Tutorial: Part 1 | Part 2 | Part 3 | Part 4
FAQ | Age | Distances | Bibliography | Relativity
© 1996-2012 EdwardL. Wright. Last modified 27 Dec 2012
