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Currently Playing: Dark Matter, an Astrophysical Mystery – Physics Documentary

Dark matter accounts for more than 80% of all matter that populates the spacetime of our Universe. What is dark matter, is one of the most troubling mysteries in astrophysics and cosmology. But... how do we know that dark matter even exists? *=*=*=*=*=* Please support the channel, donate (see below) *=*=*=*=*=* Many cosmological observations show that there is more gravity than there should be if we only account for matter we can see directly. There must be some kind of invisible matter out there. its gravitational effect gives astronomers many opportunities to study it indirectly: The rotational dynamics of galaxies, the strength of gravitational lensing, The weak intensity of CMB fluctuations and many more, are phenomena that require dark matter… In this video, we create a model of a spiral galaxy, and from that predict its velocity curve (speed of stars vs the distance from the central supermassive black hole). Then, we compare this prediction to observations, and realise there is a serious glitch! A huge amount of mass appears to be missing: Dark Matter. Without it, out galaxy would evaporate, with a large fraction of its stars ejected into inter-galactic space! We stay open however to other explanations that do not require dark matter by briefly looking into the an alternative explanation, the MOND theory: it does work well in justifying the shape of galactic velocity curves without introducing any dark stuff, but it doesn’t match other astronomical observations. Now, enough reading: it is time for you to tighten you seat belts and join me for a ride in a Dark Universe! #astrophysics #cosmology #darkmatter = = = = = = = = = = Support the Channel : Donate ! = = = = = = = = = = You may have noticed… there were no ads in this video. That means that I am creating these videos entirely for free… If you enjoy them, please consider making a donation to support me. In addition to encouraging me, donation allow me to create new education videos on physics, that all can enjoy… To make a one-time donation, please visit: https://www.physics-made-easy.com/donate Thank you! = = = = = = = = = = The Presenter = = = = = = = = = = This video is produced and presented by Edouard Reny, Ph.D. in solid state chemistry and private tutor in Physical Sciences. For access to great resources that will help you with your studies of high school Physics, visit and subscribe to the "Physics Made Easy" website: https://www.physics-made-easy.com/ Edouard provides one-on-one private tuition in Physics (face to face or by Skype). If you wish to contact him, visit his website: https://www.physics-tutor.nl/ = = = = = = = = = = Footage and Image credits = = = = = = = = = = _ Picture of Galaxy in Intro and at 12:40, Star and Planet (Intro): by NASA/JPL-Caltech _ Artist view of Nebulae, Star in Space time, Galaxies flowing background (with CIL, Conceptual Image Lab), gravity lens animations, Dark matter pink-blue background, Galaxy background at 2:45, Sun in travelling in Milky Way (with CIL): all by NASA's Goddard Space Flight Center: _ Earth in spacetime grid by Mysid (CC BY-SA) _ Picture of NGC2835 by ESA, NASA and Hubble Team _ Traverse galaxy Background: by F. Summers, G. Bacon (STScI). Simulation by C Hummels, P. Hopkins (CalTech) and A. Wetzel (UC Davis) Plank image of the CMB: by ESA and the Planck Collaboration _ Picture of the Milky Way (without background stars) by NASA/JPL-Caltech_R.Hurt _ Picture of the Milky Way (with background stars): by Xing-Wu Zheng & Mark Reid BeSSeL/NJU/CFA _ Black Hole by NASA’s Goddard Space Flight Center/Jeremy Schnittman _ Andromeda Galaxy by Adam Evans (CC BY 2.0) _ Simulation of Galactic rotation by ESO / L. Calpada _ Infographic Matter-Dark Matter by NASA's Scientific Visualization Studio