Matter as we know it are atoms, stars, planets, trees, rocks and us account for less than 5% of the total volume of known universe. The rest remains somewhat of a mystery which is called “Dark Matter”
Dark matter is called “Dark” and mysterious because it’s invisible to our eyes, it doesn’t interact with light it does not appear to interact with the Electromagnetic Spectrum (EM), which means it does not absorb, reflect, or emit electromagnetic radiation and is difficult to detect. Its existence is inferred only through its gravitational effects on visible matter, making it difficult to directly observe or study.
The electromagnetic (EM) spectrum is the range of all types of EM radiation. Radiation is energy that travels and spreads out as it goes the visible light that comes from a lamp in your house and the radio waves that come from a radio station are two types of electromagnetic radiation.
Unlike normal matter, dark matter does not interact with the electromagnetic force. This means it does not absorb, reflect or emit light, making it extremely hard to spot. In fact, researchers have been able to infer the existence of dark matter only from the gravitational effect it seems to have on visible matter.
Astronomers and Cosmologists think that around 25% of our total universe is made of something called Dark Matter, and the remainder around 70% is what’s known as Dark Energy.
Essentially, the gravity exerted by the visible mass of galaxies and clusters is insufficient to hold them together so there should be some additional mass to create the extra gravity needed to hold it. Without dark matter, stars would likely be scattered all throughout the universe. Galaxies, including our Milky Way, and therefore us, would not exist.
Why we donot see Dark Matter?
The works of many astronomers contributed to our current understanding of dark matter. In 1933, the astronomer Fritz Zwicky observed that galaxies within the Coma cluster were moving faster than expected. The speeds which should have caused them to leave the cluster rather than being held in by its gravitational pull.
After some year, Australian astronomer Ken Freeman noticed gas was moving around galaxies at greater and greater distances at the same speed, despite there being little material at these large distances. telescope, Vera Rubin, saw the same thing with stars on the edges of many galaxies.
These observations indicated that the gravitational fields in the galaxies were greater than expected based on their amount of visible mass. The large gravitational pull they were exerting could only be explained by the presence of some sort of additional mass. The best guess as to where this mass comes from is that it’s some sort of strange exotic particle.
No one knows much about this particle, except to be pretty sure it’s something we’ve never encountered here on Earth. It doesn’t interact with light, hence the name is ‘dark’ matter, which means that it’s neutral, with no electrical charge. It’s also slow moving, being concentrated in galaxies and clusters rather than dispersed evenly throughout space.
Even though we don’t know what it is and we can’t see it, we do know that dark matter really matters.