Since ancient times, our ancestors have studied the stars in wonder. They started out with simple charts that mapped out the sky and progressed into building telescopes to view celestial objects. Before long, giant ships were invented and blasted off into space with satellites protectively orbiting around our planet. For hundreds of thousands of years, humanity has progressed as our knowledge has expanded. But even after all this time, we barely know anything about the universe. Its complex secrets and mysteries have been hidden from our view, and when we look at the bigger picture, there is still much to be understood. 

After centuries of exploration, we only understand about 5% of what makes up our universe (and it’s mass). The other 95% is composed of two puzzling forces: dark energy and dark matter. Simply put, dark energy speeds up the expansion of the universe while dark matter counteracts it (slows it down).

Dark energy is the more powerful force of the two as it accounts for about 68 percent of the universe’s mass. Dark energy is the only thing (that we know of) that can explain why the expansion of the universe is speeding up. If we take the Big Bang theory, we know that the universe expanded from singularity. This explosion resulted in an expanding universe, but the expansion should have slowed down by a measurable amount by now. This problem stumped scientists for years, until the addition of dark energy. This force alone can explain exactly how the universe has continued to grow at a more rapid pace.

Dark matter on the other hand only makes up about 27 percent of the mass of our universe. Because it doesn’t interact with gravity or light in any way, it’s the glue that holds the universe together. The idea of dark energy was first proposed by astronomer Fritz Zwicky. He noticed that certain galaxies were moving so fast that they should have been pulled apart by the overwhelming centrifugal force created. Instead, there was something holding them together. This same problem was viewed in many different galaxies and led to the idea that a force (dark mater) was keeping them from falling apart. Scientists have also noticed that the extreme amount of gravity created by galaxies warps light at a degree that would not be possible to attain without factoring in dark matter. 

Combined, these two forces would solve a lot of different cosmological problems, but because we know next to nothing about them (or even if they exist at all,) there is nothing we can do but continue to study that night sky like our ancestors did centuries before us.

Resources

DISCOVERY MAGAZINE, ASTRONOMY.COM