Dark matter and dark energy – do you know the difference?

24 Mar 2024

Just when scientists think that they have reached the end, that they have listed all the important facts about the world and the entire universe in general, that they have discovered all the formulas that describe everything about nature that comes to mind – they actually find we don’t know almost anything because there is such a vast expanse of ignorance.

This has happened many times throughout history, from ancient Greece to the present day.

In the first half of the last century and after the period when physicists were convinced that they had discovered everything and that they possessed total and final knowledge – there were also those who gave up studying physics.

But science opened new chapters in the study of the micro and mega world, that is, from the tiniest of everything that exists to unimaginably large space structures.

It turned out that of the entire universe, almost 96 percent, is unknown to scientists. All those galaxies, stars, nebulae, clusters, planets, etc., they make up only a paltry 4% of what is available for study. About the rest, there is only guesswork that can be summed up in just a few sentences.

Of that 96%, there is about 69% of something we call dark energy, and 26% of what we call dark matter – and that is why we will point out the difference between these things.

Dark matter

So, what is dark matter? We don’t know, but we know that it is different from dark energy!

We know that dark matter exists by its gravitational influence on its surroundings. Even decades ago, scientists noticed the unusual movement of stars on the periphery of galaxies, but also the movement of galaxies in galactic clusters.

Stars at the edges of galaxies are moving much, much faster than they should, and galaxies in galaxy clusters are moving faster than scientists expected. In fact, both stars and galaxies are moving so fast that they should fly off into space. And yet that doesn’t happen. Why?

In short, there simply must be some form of matter that dictates the motion of both stars and galaxies with its gravity. It accelerates them, but at the same time prevents them from flying into space. We call that matter dark matter (dark because it does not emit or reflect any light).

It is not known what kind of matter it is, what it is made of.

Dark energy

Dark energy is an even bigger mystery than dark matter. The difference between these two things is primarily that dark energy is not matter at all.

Until 1998, it was not even known, and then astronomers concluded that the universe is rapidly expanding. Before that, there was a belief that the universe would expand more and more slowly and that it would finally begin to contract under the influence of the gravity of the matter that fills it, but then evidence was found that this will not happen because the universe is expanding faster and faster.

Why – it is not known, but astronomers generally agree that it is due to the influence of some mysterious force.

This force is called dark energy. So, there is some energy that fills all space and has repulsive gravity, pushing galaxies further and further away from each other.

The questions of dark matter and dark energy are not just idle intellectual distractions of physicists. The answer to these questions penetrates into the essence of nature and will have consequences for all scientific disciplines and for the whole of life – in one way or another.