Dark Matter #2: Gravitational Lensing

heic1506e.jpgA couple of months ago I talked about a piece of evidence supporting the existence of Dark Matter which is the fact that the stars in the outskirts of galaxies were seen to move at a similar pace as galaxies near the galactic core, defying the norm of the Keplerian Decline.

Recap: Dark Matter makes up roughly 25% of the Universe, so it is five times more prevalent than ordinary Baryonic Matter. Physicists gave it the name Dark Matter not because of it having some mysterious evil property or anything of that sort, but because it simply does not interact with Electromagnetic Radiation. I agree Physicists are a creative bunch.

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Dark Matter #1: Galactic Rotation Curves

After the death of pioneering astronomer Vera Rubin, I suspect many more people have become intrigued by the term Dark Matter. Something else that often accompanies this term is Dark Energy. Both probably sound like mysterious or perhaps evil forces of nature to an ordinary person – at least I thought so, but then I learned Dark simply implied that it doesn’t interact with light.

A friend’s sister, a frequent reader of Passion for STEM and also a physics lover herself suggested that I write something on dark matter. At first, I thought this may be a difficult task (and I still do) because of the amount of uncertainty regarding what it actually is within the scientific community.


Everything we know that exists: us, all living things, all nonliving things, all the stars, galaxies, asteroids and cosmic dust collectively gather under one title – Baryonic Matter, and it accounts for less than 5% of the known Universe. The rest of the Universe under current calculation predictions is dark matter and dark energy, making up roughly 25% and 70% of the stuff in the Universe. This is rather overwhelming as what we know and experience is only less than a tiny fraction of reality. Since dark matter cannot be observed because it doesn’t interact with light, or as we say the electromagnetic force, there is no direct way of detecting it so how do physicists know that so much of the Universe’s mass is dark matter and not just ordinary matter like dust? Continue reading