Bullet Cluster Two colliding clusters of galaxies in constellation Carina The object is of a particular note for astrophysicists, because gravitational lensing studies of the Bullet Cluster are claimed to provide the best evidence to date for the existence of dark matter.[3][4] Observations of other galaxy cluster collisions, such as MACS J0025.4-1222, similarly support the existence of dark matter. Overview[edit] The major components of the cluster pair—stars, gas and the putative dark matter—behave differently during collision, allowing them to be studied separately. The third component, the dark matter, was detected indirectly by the gravitational lensing of background objects. The Bullet Cluster is one of the hottest-known clusters of galaxies. Significance to dark matter[edit] According to Greg Madejski: Particularly compelling results were inferred from the Chandra observations of the 'bullet cluster' (1E0657-56; Fig. 2) by Markevitch et al. (2004) and Clowe et al. (2004). According to Eric Hayashi:
Theory of relativity The theory of relativity, or simply relativity in physics, usually encompasses two theories by Albert Einstein: special relativity and general relativity.[1] Concepts introduced by the theories of relativity include: Measurements of various quantities are relative to the velocities of observers. In particular, space contracts and time dilates.Spacetime: space and time should be considered together and in relation to each other.The speed of light is nonetheless invariant, the same for all observers. The term "theory of relativity" was based on the expression "relative theory" (German: Relativtheorie) used in 1906 by Max Planck, who emphasized how the theory uses the principle of relativity. In the discussion section of the same paper Alfred Bucherer used for the first time the expression "theory of relativity" (German: Relativitätstheorie).[2][3] Scope[edit] The theory of relativity transformed theoretical physics and astronomy during the 20th century. Two-theory view[edit] History[edit]
Einasto profile From Wikipedia, the free encyclopedia The Einasto profile (or Einasto model) is a mathematical function that describes how the density of a spherical stellar system varies with distance from its center. Jaan Einasto introduced his model at a 1963 conference in Alma-Ata, Kazakhstan.[1] The Einasto profile possesses a power law logarithmic slope of the form: which can be rearranged to give The parameter controls the degree of curvature of the profile. The larger , the more rapidly the slope varies with radius (see figure). , which has a constant slope on a log-log plot. Einasto's model has the same mathematical form as Sersic's law, which is used to describe the surface brightness (i.e. projected density) profile of galaxies. Einasto's model has been used to describe many types of system, including galaxies,[2] and dark matter halos.[3] See also[edit] NFW profile References[edit] External links[edit] Spherical galaxy models with power-law logarithmic slope.
Biocentrism (cosmology) Biocentric universe (from Greek: βίος, bios, "life"; and κέντρον, kentron, "center") — also known as biocentrism — is a concept proposed in 2007 by American doctor of medicine Robert Lanza, a scientist in the fields of regenerative medicine and biology,[1][2][3] which sees biology as the central driving science in the universe, and an understanding of the other sciences as reliant on a deeper understanding of biology. Biocentrism states that life and biology are central to being, reality, and the cosmos — life creates the universe rather than the other way around. It asserts that current theories of the physical world do not work, and can never be made to work, until they fully account for life and consciousness. Critics have questioned whether the theory is falsifiable. Hypothesis[edit] Lanza has said that he intends to publish aspects of biocentrism in peer-reviewed scientific journals.[17] Synopsis of Lanza's book Biocentrism[edit] Reception[edit] See also[edit] References[edit]
Dark-energy star Hypothetical object that potentially explains accelerating universal expansion A dark-energy star is a hypothetical compact astrophysical object, which a minority of physicists think might constitute an alternative explanation for observations of astronomical black hole candidates. The concept was proposed by physicist George Chapline. The theory states that infalling matter is converted into vacuum energy or dark energy, as the matter falls through the event horizon. The space within the event horizon would end up with a large value for the cosmological constant and have negative pressure to exert against gravity. There would be no information-destroying singularity.[1] Theory[edit] In March 2005, physicist George Chapline claimed that quantum mechanics makes it a "near certainty" that black holes do not exist and are instead dark-energy stars. In the dark-energy star hypothesis, infalling matter approaching the event horizon decays into successively lighter particles. See also[edit]
10 Awesome Online Classes You Can Take For Free Cool, but you need iTunes for nearly everything, and that gets an 'F.' Are there really no other places to get these lessons? I was sure there are some on Academic Earth. Flagged 1. 7 of them are available via YouTube. 2. iTunes is free. 1. 2. Don't worry, we're looking out for you! While I have no personal beef with iTunes, I know that many people share your sentiments — so I actually made a concerted effort to include relevant youtube links when possible.
Mészáros effect From Wikipedia, the free encyclopedia Evolution of Cold Dark Matter perturbations The Mészáros effect "is the main physical process that alters the shape of the initial power spectrum of fluctuations in the cold dark matter theory of cosmological structure formation".[1] It was introduced in 1974 by Péter Mészáros[2] considering the behavior of dark matter perturbations in the range around the radiation-matter equilibrium redshift and up to the radiation decoupling redshift . an additional distinct growth period which alters the initial fluctuation power spectrum, and allows sufficient time for the fluctuations to grow into galaxies and galaxy clusters by the present epoch. in which , the variable , and is the length scale parametrizing the expansion of the Universe. .
Signs of ageing halted in the lab 2 November 2011Last updated at 18:01 By James Gallagher Health reporter, BBC News Will it one day be possible to stop ageing? The onset of wrinkles, muscle wasting and cataracts has been delayed and even eliminated in mice, say researchers in the US. It was done by "flushing out" retired cells that had stopped dividing. The scientists believe their findings could eventually "really have an impact" in the care of the elderly. Experts said the results were "fascinating", but should be taken with a bit of caution. The study, published in Nature, focused on what are known as "senescent cells". These cells are cleared out by the immune system, but their numbers build up with time. Cleanup Scientists at the Mayo Clinic, in the US, devised a way to kill all senescent cells in genetically engineered mice. The animals would age far more quickly than normal, and when they were given a drug, the senescent cells would die. Eternal youth?
Dwarf galaxy problem From Wikipedia, the free encyclopedia Context[edit] For example, around 38 dwarf galaxies have been observed in the Local Group, and only around 11 orbiting the Milky Way,[2][a] yet dark matter simulations predict that there should be around 500 dwarf satellites for the Milky Way alone.[3][4] Prospective resolution[edit] There are two main alternatives which may resolve the dwarf galaxy problem: The smaller-sized clumps of dark matter may be unable to obtain or retain the baryonic matter needed to form stars in the first place; or, after they form, dwarf galaxies may be quickly “eaten” by the larger galaxies that they orbit. Baryonic matter too sparse[edit] One proposal is that the smaller halos do exist but that only a few of them end up becoming visible, because they are unable to acquire enough baryonic matter to form a visible dwarf galaxy. Early demise of young dwarfs[edit] See also[edit] [edit] References[edit] External links[edit]
Baryonic dark matter From Wikipedia, the free encyclopedia In astronomy and cosmology, baryonic dark matter is hypothetical dark matter composed of baryons. Only a small proportion of the dark matter in the universe is likely to be baryonic. Characteristics[edit] As "dark matter", baryonic dark matter is undetectable by its emitted radiation, but its presence can be inferred from gravitational effects on visible matter. Presence[edit] Baryonic dark matter may occur in non-luminous gas or in Massive Astrophysical Compact Halo Objects (MACHOs) – condensed objects such as black holes, neutron stars, white dwarfs, very faint stars, or non-luminous objects like planets and brown dwarfs. Estimates of quantity[edit] The total amount of baryonic dark matter can be inferred from models of Big Bang nucleosynthesis, and observations of the cosmic microwave background. Big Bang nucleosynthesis[edit] 0.001 M☉ (2×1027 kg) and do not burn anything, and white dwarfs.[1][2][clarification needed] See also[edit] Particle chauvinism
XMASS From Wikipedia, the free encyclopedia XMASS is a multipurpose physics experiment in Japan that monitors a large tank of xenon for flashes of light that might be caused by hypothetical dark matter particles.[1] In addition to searching for dark matter, XMASS is also studying neutrinoless double beta decay and solar neutrinos. Its results have not confirmed the annual variation seen in some earlier experiments.[2] History[edit] Construction started in April 2007. The detector was completed in September 2010. The XMASS-I experiment shut down and ceased data taking 20 February 2019. Results were published in 2021.[3] Detector[edit] The detector is located 1000m underground in the Kamioka Observatory in Japan. References[edit] External links[edit] Direct Dark Matter Search by Annual Modulation [Results from XMASS] Sept 2015
Euclid (spacecraft) European visible and near-infrared space observatory The objective of the Euclid mission is to better understand dark energy and dark matter by accurately measuring the accelerating expansion of the universe. To achieve this, the Korsch-type telescope will measure the shapes of galaxies at varying distances from Earth and investigate the relationship between distance and redshift. Dark energy is generally accepted as contributing to the increased acceleration of the expanding universe, so understanding this relationship will help to refine how physicists and astrophysicists understand it. Euclid's mission advances and complements ESA's Planck telescope (2009 to 2013). Scientific objectives and methods[edit] Spacecraft[edit] Instruments[edit] Spacecraft bus[edit] The telescope bus includes solar panels that provide power and stabilise the orientation and pointing of the telescope to better than 35 milliarcseconds (170 nrad). Milestones[edit] Mission execution and data[edit] Around the Earth