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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20181106T123000
DTEND;TZID=Atlantic/Canary:20181106T133000
UID:iactalks-1210
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/1210
CREATED:2018-11-06T12:30:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:MOND, an introductory review
DESCRIPTION:MOND, an introductory review\nDr. Riccardo Scarpa\n\nBy the tim
 e, in 1937, the Zwicky measured the velocity dispersion of the Coma cluste
 r, astronomers somehow got acquainted with the idea that the universe is f
 illed by some kind of dark matter. After almost a century of investigation
 s, we have learned two things about it, (i) it has to be non-baryonic - th
 at is, made of something new that interact with normal matter only by grav
 itation- and, (ii) that its effects are observed in stellar systems when a
 nd only when their internal acceleration of gravity falls below a fix valu
 e a0=1.2×10-8 cm s-2. Being completely decoupled dark and norma
 l matter can mix in any ratio to form the objects we see in the Universe, 
 and indeed observations show the relative content of dark matter to vary d
 ramatically from object to object. This is in open contrast with point (ii
 ). In fact, there is no reason why normal and dark matter should conspire 
 to mix in just the right way for the mass discrepancy to appear always bel
 ow a fixed acceleration. This systematic, more than anything else, tells u
 s we might be facing a failure of the law of gravity in the weak field lim
 it rather then the effects of dark matter. Thus, in an attempt to avoid th
 e need for dark matter many modifications of the law of gravity have been 
 proposed in the past decades. The most successful - and the only one that 
 survived observational tests - is the Modified Newtonian Dynamics. MOND po
 sits a breakdown of Newton's law of gravity (or inertia) below a0, after w
 hich the dependence with distance became linear. Despite many attempts, MO
 ND resisted stubbornly to be falsified as an alternative to dark matter an
 d succeeds in explaining the properties of an impressively large number of
  objects without invoking the presence of non-baryonic dark matter. This s
 uggests MOND is telling us something important about gravity in the weak f
 ield limit. In this talk I will review the basics of MOND and its ability 
 to explain observations without the need of dark matter.
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