HOW DOES GRAVITATIONAL LENSING PROVE DARK MATTER

Gravitational lensing occurs when a lot of mass, for example, a cluster of galaxies is between us(an observer) and a source background galaxy, that is behind the cluster. The cluster of galaxies acts like a lens and magnifies and distorts the image of source galaxy. The cosmologists can determine the mass of the cluster of galaxies by measuring how much their gravitational fields distorts light that passes through them. The mass of a gravitational lens (the cluster of galaxies) is not enough to produce the observing lensing effect, but does. Thetefore there might be dark matter that is causing it.

Originally known as "the missing mass", Dark Matter's existence was first inferred by Swiss American astronomer Fritz Zwicky, who in 1933 discovered that the mass of all stars in the COMA cluster of galaxies provided about 1% of the mass needed to keep the galaxies from escaping from cluster's gravity pull. The reality of this missing mass remained in question for decades. The most common view is that Dark Matter is not baryonic at all, it is made up of exotic matter like axions or WIMP (Weakly Interacting Massive Particles), i. e. is made of heavy slow moving particles.

Baryonic matter is all matter that encountered or experienced in everyday life : protons, neutrons, electrons. Dark matter do not emit light, do not interact with light and with baryonic matter, yet has a mass and is inferred to exist because we observe its gravitational influence on visible matter. Mostra meno 

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