Dark matter | Wikipedia audio article
Channel: wikipedia tts
Date: 08/12/2018

This is an audio version of the Wikipedia Article:
Dark matter


00:02:55 1 History
00:03:04 1.1 Early history
00:05:56 1.2 1970s
00:08:53 2 Technical definition
00:10:10 3 Observational evidence
00:10:19 3.1 Galaxy rotation curves
00:11:19 3.2 Velocity dispersions
00:12:02 3.3 Galaxy clusters
00:12:55 3.4 Gravitational lensing
00:14:37 3.5 Cosmic microwave background
00:16:48 3.6 Structure formation
00:18:00 3.7 Bullet Cluster
00:18:42 3.8 Type Ia supernova distance measurements
00:19:22 3.9 Sky surveys and baryon acoustic oscillations
00:19:47 3.10 Redshift-space distortions
00:19:57 3.11 Lyman-alpha forest
00:20:09 4 Composition of dark matter: baryonic vs. nonbaryonic
00:21:23 4.1 Baryonic matter
00:22:49 4.2 Non-baryonic matter
00:23:19 4.3 Dark matter aggregation and dense dark matter objects
00:24:03 5 Classification of dark matter: cold, warm or hot
00:25:48 5.1 Alternative definitions
00:26:55 5.2 Cold dark matter
00:29:11 5.3 Warm dark matter
00:30:34 5.4 Hot dark matter
00:33:27 6 Detection of dark matter particles
00:35:09 6.1 Direct detection
00:36:15 6.2 Indirect detection
00:38:03 6.3 Collider searches for dark matter
00:38:56 7 Alternative hypotheses
00:42:02 8 In philosophy of science
00:44:50 9 In popular culture
00:45:53 10 See also
00:47:22 11 Notes
00:47:55 12 References
00:48:21 12.1 Bibliography



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SUMMARY
=======
Dark matter is a hypothetical form of matter that is thought to account for approximately 85% of the matter in the universe, and about a quarter of its total energy density. The majority of dark matter is thought to be non-baryonic in nature, possibly being composed of some as-yet undiscovered subatomic particles. Its presence is implied in a variety of astrophysical observations, including gravitational effects that cannot be explained unless more matter is present than can be seen. For this reason, most experts think dark matter to be ubiquitous in the universe and to have had a strong influence on its structure and evolution. The name dark matter refers to the fact that it does not appear to interact with observable electromagnetic radiation, such as light, and is thus invisible (or 'dark') to the entire electromagnetic spectrum, making it extremely difficult to detect using usual astronomical equipment.The primary evidence for dark matter is that calculations show that many galaxies would fly apart instead of rotating, or would not have formed or move as they do, if they did not contain a large amount of unseen matter. Other lines of evidence include observations in gravitational lensing, from the cosmic microwave background, from astronomical observations of the observable universe's current structure, from the formation and evolution of galaxies, from mass location during galactic collisions, and from the motion of galaxies within galaxy clusters. In the standard Lambda-CDM model of cosmology, the total mass–energy of the universe contains 5% ordinary matter and energy, 27% dark matter and 68% of an unknown form of energy known as dark energy. Thus, dark matter constitutes 85% of total mass, while dark energy plus dark matter constitute 95% of total mass–energy content.Because dark matter has not yet been observed directly, it must barely interact with ordinary baryonic matter and radiation. The primary candidate for dark matter is some new kind of elementary particle that has not yet been discovered, in particular, weakly-interacting massive particles (WIMPs), or gravitationally-interacting massive particles (GIMPs). Many experiments to directly detect and study dark matter particles are being actively undertaken, but none has yet succeeded. Dark matter is classified as cold, warm, or hot according to its velocity (more precisely, its free streaming length). Current models favor a cold dark matter scenario, in which structures emerge by gradual accumulation of particles.
Although the existence of dark matter is generally accepted by the scientific community, some astrophysicists, intrigued by certain ...