If you're a space enthusiast, you've probably heard the term dark matter. But what about its lesser-known sibling, dark energy?
The universe is full of dark energy
For something as unknown as dark energy, there must be a huge amount of it. Of all the energy and mass in our universe, approximately five percent is made up of atoms, the molecules of which we, the Earth, and, for example, the Sun are made. So we know for sure what it is. Another roughly 23% is likely dark matter, a mysterious mass whose existence can only be proven indirectly, says astrophysics professor Ren van de Weegert of the University of Groningen. And the other 71 percent? “This is even more exotic. It's called dark energy.”
The difference between dark matter and energy
As with dark matter, no direct evidence has yet been found for what dark energy is. This is because scientists cannot detect it directly. That's why it got the name “Darkness”.
But that's where the comparison ends, van de Weegert says. “From the name you might think that dark energy is very similar to dark matter, but it's not at all. Dark matter attracts things like ordinary particles. But dark energy has the quite strange property of repulsive attraction.
What do we know about dark energy?
The idea behind dark energy came about in 1998, Van de Weegert explains. “Cosmologists believe that the expansion of the universe is slowing down.” This may be due to the attractive gravity of mass in our universe. “But measurements have shown that the universe is actually expanding faster than it was millions of years ago.” The explanation for this acceleration was repulsive dark energy. “As a result, the universe turned out to be older than initially thought. This immediately solved another problem: stars had previously been found that appeared to be older than the then estimated age of the universe.
Meanwhile, there have been about five to six independent, indirect observations of dark energy, the astronomer says. But it is much more mysterious than dark matter. We can still speculate about what the latter might be. But what is dark energy? Who do you know?.' They are also difficult to investigate because they are evenly distributed in the universe and therefore their density must be insanely low. As a result, there is no hope of being able to isolate and detect it in the laboratory.
However, scientists continue to search hard for answers. The European Euclid Space Telescope was launched in 2023. Its main mission? Define the nature of dark energy so we can learn more about our universe. This knowledge is urgently needed. Therefore, Van de Weijert always begins his lectures on this topic by saying: “Cosmologists think they know everything from their precise measurements, but we still have no idea what 95 percent of the universe is.”
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