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SUMMARY:The Invention of Dark Matter and Dark Energy. - Craig Mackay
DTSTART:20210609T123000Z
DTEND:20210609T130000Z
UID:TALK158995@talks.cam.ac.uk
CONTACT:Emma Curtis Lake
DESCRIPTION:High quality photometry and spectroscopy of disk galaxies has 
 shown that the mass of a galaxy is the only parameter that determines the 
 dark matter attributed to a galaxy. Together with other results on ellipti
 cal galaxies we  look carefully at the fundamentals that led to the idea t
 hat Dark Matter was needed to account for the motions of stars and gas in 
 galaxies. It turns out that the problem is with the use of Newtonian dynam
 ics to explain motions in galaxies. Einstein showed that the field of the 
 gravitating object must not be neglected and that assumptions of homogenei
 ty\, isotropy and spherical symmetry are the root cause. Gravitational fie
 ld lines are affected by other masses in the same way that light is affect
 ed. This changes the way that gravitational forces act upon material orbit
 ing in the disk of a galaxy and are proportional to ~1/r as observed rathe
 r than ~1/r^2 predicted by Newton. This error led to the invention of Dark
  Matter. Gravitational field interaction also reduces gravitational forces
  outside an object\, reducing the forces between galaxies and giving effec
 ts that could be mistaken for Dark Energy. Dark Matter and Dark Energy wer
 e each introduced as concepts in order to make specific astronomical obser
 vations fit in with the then understanding of the physics involved. We dem
 onstrate that by replacing Newtonian dynamics which essentially forces sym
 metries on objects with Einstein's general relativistic dynamics is very l
 ikely to make the need for either Dark Matter or Dark Energy to go away.
LOCATION: Webinar  (via Zoom online)
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