DARK MATTER

WHEN IT COMES TO UNIVERSE, WE SERIOUSLY DON’T KNOW MUCH ABOUT IT (THOUGH WE HAVE SOME IDEAS).LET’S TAKE A LOOK AT THE COMPOSITION OF THE UNIVERSE ~ 68 %=DARK  ENERGY ,~27% DARK MATTER AND ROUGHLY 5% NORMAL(BARYONIC) MATTER. 

LET’S TALK ABOUT DARK MATTER FIRST. THE EFFECT OF DARK MATTER WAS FIRST NOTICED IN 1933 WHEN FRITZ ZWICKY NOTICED THAT THE GALAXIES IN THE COMA CLUSTER WERE MOVING WAY TOO FAST TO BE GRAVITATIONALLY BOUND WITHIN THE CLUSTER. IT WAS CALLED ‘DUNKIE MATERIE’ THEN.

AS PER NEWTON’S LAW OF GRAVITATION, BECAUSE OF WEAKENING OF THE FORCE OF GRAVITY ON INCREASING THE DISTANCE, THE GRAPH OF VELOCITY VS DISTANCE FROM THE CENTRE OF ROTATION SHOULD INCREASE LINEARLY TO A VALUE AND THEN DECREASE. BUT WHAT WE OBSERVE IS THE LINEAR INCREASE AND THEN THE CONSTANCY  IN THE RELATION. V=root(GM/R) ;IT MEANT THAT THERE IS MAJORITY OF MASS RESENT IN THE HALO OF THE GALAXY.WE CALL IT ‘DARK MATTER’.

LETS TAKE A LOOK AT VARIOUS POSSIBILITIES ABOUT WHAT IT CAN BE--

1. IT IS A FORM OF PARTICLE THAT IS VERY DIFFICULT TO DETECT.

- IF DARK MATTER HAS FORMED FROM THE BARYONIC MATERIAL, IT SHOULD BE DETECTABLE BY THE GRAVITATIONAL LENSING. IT SHOULD BE A MACHO- I.E. MASSIVE COMPACT HALO OBJECT (INCL. FAILED STARS, BLACK HOLES).THE SAD STORY IS EVEN IF WE TAKE ACCOUNT OF  THEIR MASSES BY GRAVITATIONAL LENSING , WE COULD NOT ACCOUNT FOR THE MASS NEEDED.

2. GRAVITY BEHAVES DIFFERNTLY ON LARGE GALACTIC SCALES (F VARIES AS 1/R)

THIS IS CALLED MOND (MODIFIED VERSION OF NEWTONIAN DYNAMICS).ACCORDING TO THIS, BARYONS AND DARK MATTER ARE ESSENTIALLY THE SAME. LET’S TAKE A LOOK AT THIS ARGUMENT VIA BULLET CLUSTER- THESE ARE THE PAIR OF GALAXIES WHOSE COLLISION LOOKED LIKED THE SHAPE OF A BULLET.WHEN COLLISION HAPPENED , THE STARS OF THE GALAXIES PASSED RIGHT THROUGH AND THE GAS WAS IN THE MIDDLE .IF DARK MATTER CONSISTED OF BARYONS, THE MOST MASS SHOULD BE CONCENTRATED IN THE GASEOUS REGION. BUT THE MASS WAS CONCENTRATED IN THE REGION OF GALAXIES. THIS SHOWED THAT THE DARK MATTER IS A PARTICLE THING.

3. PARALLEL UNIVERSE THEORY- 

IT STATES THAT THE EXTRA  GRAVITATION IS ATTRIBUTED TO A PARALLEL UNIVERSE, WHICH CAN INTERACT TO US ONLY BY GRAVITATIONAL EFFECTS.

4.EXTENSION/MODIFICATION TO PARTICLE PHYSICS-

 THESE PARTICLES MAYBE WIMPS- (WEAKLY INTERACTING MASSIVE PARTICLES) THAT EMERGE FROM FANCY MATHEMATICS  AND SUPERSYMMETRY. THE POSSIBLE CANDIDATES ALSO INCLUDE HEXAQUARKS* (I.E THE PARTICLE OBTAINED BY THE COMBINATION OF 6 QUARKS-IT IS HYPOTHESIZED THAT THEY HAVE VERY LARGE  DECAY PERIOD ).

TILL NOW, FROM WHAT ALL WE KNOW , ALL THE COMPUTER SIMULATIONS THAT THE SCIENTISTS HAVE RUN, IT’S SURE THAT WE NEED DARK MATTER FOR THE EVOLUTION OF THE UNIVERSE FROM THE HOT PLASMA TO THE BEAUTIFUL STRUCTURE WE SEE TODAY. AND THAT IT SHOULD BE COLD  (I.E IT SHOULD NOT BE MOVING AT VERY HIGH RELATIVISTIC SPEEDS) AND POSSIBLY A PARTICLE. WE NEED MORE INFORMATION ABOUT THE FORMATION OF GALAXIES AND THEIR BEHAVIOUR AT THE EARLY STAGE OF UNIVERSE. JAMES WEBB TELESCOPE- WE ALL ARE WAITING FOR YOU!

Refrences-

-https://www.space.com/hexaquarks-big-bang-form-universe-dark-matter.html

Dr. Physics - https://www.youtube.com/user/DrPhysicsA
PBS Space Time-https://www.youtube.com/channel/UC7_gcs09iThXybpVgjHZ_7g
NASA Science Article - https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy