When we look into space, the laws of physics sometimes fail to explain what we see. So either we abandon these laws, or call on some new, unseen agents to explain what we observe.
What exactly is holding the Pinwheel Galaxy together?
There must be invisible 'stuff' in the galaxy, but what is it? Whatever Dark Matter is, it provides the attractive force that helps gravity hold galaxies together.
For all of the amazement we feel looking out into space, perhaps the most incredible thing is that the universe we experience may only be a tiny fraction of everything out there. Stars, planets, nebulas, supernovas, galaxies -- all of this normal matter, the stuff with mass, is only five percent of the entire universe.
All these worlds and wonders: only five percent
The remaining ninety-five percent of the universe is as exotic as anything we can imagine. We cannot see it, cannot touch it, and it doesn’t work the way normal matter does. Most of the universe exists beyond our senses, as Dark Matter and Dark Energy. These unknown entities contradict the immutable laws, and beg us to try and understand them. Dark Matter and Dark Energy are like invisible hands, interacting with normal matter in strange and wonderful ways, constantly shaping our universe.
This may sound rather unscientific, but there is solid evidence that both exist. Some of this evidence is close to home.
The galaxy rotation problem
Galaxies are great swirling masses of stars, gas and dust. Through careful surveys, we can map everything in a galaxy, where it is and how it moves. The frustrating conclusion is that there is not enough mass here to explain how a galaxy spins. If they are made only of the matter we can see, they should not exist!
There must be invisible ‘stuff’ in the galaxy, but what is it? It could be massive, non-glowing objects that we do not yet have the technology to see … or some strange, new particle that permeates the galaxy in colossal numbers. Or something else. Whatever Dark Matter is, it provides the attractive force that helps gravity hold galaxies together, and it accounts for one quarter of the total matter in the universe.
Dark Matter is definitely strange
But at least Dark Matter behaves like something we understand – a matter that is pulled by gravity. Dark Energy, on the other hand, is the opposite. Dark Energy is a repulsive force, pushing objects apart.
It is a sobering thought that we have no clue what most of our cosmos is made of.
We discovered Dark Energy at the most distant reaches of the universe. As our telescopes showed us ever more distant galaxies, we learned a surprising thing: they were all moving apart, fast. Way too fast.
A phantom energy, the opposite of gravity, must be actively working to drive the universe apart, an invisible agent with an unreal strength. This is Dark Energy, this is the quintessence, a fantastic power that propels the very expansion of the universe! And if Dark Energy can overcome gravity, there may be no stopping it. Our end state may be one of unthinkable violence, in which every galaxy, star, planet, and atom is ripped apart and reduced to pure oblivion.
It is a sobering thought that we have no clue what most of our cosmos is made of. With the ultimate fate of the universe at stake, we can only imagine how these strange forces will reveal themselves in the years to come.
And alter our perception of reality forever.