A Dark Universe
The universe is not as empty as we once thought
On December 1st, 2014, at the Planck 2014 conference in Italy, the distribution of the mass-energy of the Universe was announced. Given in the following proportions: Baryonic matter, that is to say the stuff that makes up literally everything you experience in everyday life, all living things, nonliving things, planets, and stars, make up approximately 4.9% of the total. Dark Matter accounts for another 26.8%. And the remaining 68.3% is Dark Energy.
Just take a moment to properly internalize that. Everything we experience in life, everything, accounts for less than 5% of the universe, and the remainder is dark matter and energy. One may then ask: What’s the difference between this mysterious material that makes up the majority of the universe, and the regular stuff? The simplest answer is: we have essentially no clue.
This is not to say that we know nothing about the stuff. For instance, we know that dark matter doesn’t interact with matter electromagnetically, and appears to only have gravitational effects. The same is true for dark energy. In either case, there really isn’t a good model for what it is, how it works, what it’s made of, or what else it can do. They both exist to fill glaring holes in experimental data. In the case of dark matter, the structure (and continued existence of galaxies necessitates a lot more mass than what is visually present. Dark matter is, in essence, pure mass that is used to account for discrepancies in certain measured quantities.
In the case of dark energy, it comes down to a simple thought experiment: what force is dominant on a cosmic scale? Gravity. And gravity pulls stuff back together. Ergo, after the initial outward explosion of the big bang, the universe should’ve started to be pulled back together. This is what the existing theory says. And yet, experimental data shows the dead opposite: not only is the expansion not slowing to a stop so that the universe may start contracting again, the expansion is actually accelerating. The most fundamental physics plainly states that acceleration doesn’t happen without energy. So, we have an energy that mathematically must exist, yet we know nothing about: dark energy.
And with that, we have 95.1% of the universe: completely unknown quantities that essentially exist only out of experimental necessity with next to no explanation of the why, what, or how. Such is the state of Cosmology at present time, the majority of that which exists is unknown. While this may seem hopeless, it is also a sign of proof that there is still a whole universe of discovery left out there for us to find. We are nowhere near finished learning about our world.
