October 31 - Dark Matter Day

Posted October 31, 2020

Key points

Tonight is all about Halloween – all manner of fun and tricks and treats in the dark – although the costumes and festivities have over the decades spilled into daytime fun, too – and one might argue all month long!

But today is also the day to celebrate the search for dark matter!

Dark matter is nothing to do with “dark magic” or “dark arts” or anything Halloween-y. Instead, it’s a topic astronomers and cosmologists are researching. You probably know that the universe is full of stars and planets, asteroids and comets, galaxies and nebulae – but most of the stuff in the universe is not all those familiar things (which we call ordinary matter). Instead, scientists believe that ordinary matter makes up only about 5 percent (around one-twentieth) of the total mass and energy of the universe.

So that means that we cannot see most – the other 95% – of the universe!

According to current theories, dark matter makes up around 27 percent of the universe (more than a fourth), and dark energy makes up MOST of the universe (68 percent – more than two-thirds)!

How do we come up with these ideas about dark matter and dark energy, if we can’t see them or measure them? Well, we see the effects of dark matter’s gravity, and we see the effects of dark energy in the acceleration of the galaxies’ movement away from one another.

Of course, further research, more evidence gathering, and new,
testable ideas about physics will give us a clearer picture and maybe revolutionize our current understanding…in the same way that relativity and quantum physics have revolutionized physics in modern times.

So…happy Dark Matter Day!