Our Universe — Part 2
Original post date: December 24, 2018
This is the second part of Our Universe. To read the first part, click here.
"Look up at the stars and not down at your feet. Try to make sense of what you see, and wonder about what makes the universe exist. Be curious." — Stephen Hawking
When you look up at the night sky, you see stars, wandering planets, falling meteors, and travelling comets. All of it visible to the bare eye. But our universe is far more than what we can see. Beyond the matter we can observe, there are invisible bodies that actually run the universe.
One of the first invisible bodies that comes to mind is a black hole. It is invisible because it absorbs everything in its path, including light. You may have seen illustrations of black holes as dark round objects pulling in light like a whirlpool. Reality may be different. Black holes have never been directly seen. They are predicted and detected entirely through their effects on surrounding matter and space.
The universe is expanding, and that expansion is accelerating. To increase the rate of expansion, energy is required, much like blowing air into a balloon faster requires more effort. Where does that energy come from? Everything we know to exist is matter and energy, but calculations show that visible matter and energy alone cannot drive the acceleration. There must be something else. Something invisible. Something not yet found.
Scientists call it dark energy. It is considered the most dominant constituent of the universe, so dominant that it is gradually diminishing the relative influence of ordinary matter and energy. Dark energy has not been directly detected or studied. What we have are theoretical predictions. Dark energy makes up roughly 68% of the universe. Dark matter accounts for another 27%. The visible universe we observe is only about 5% of everything that exists. If we could ever detect and harness dark energy, the implications for civilization would be staggering. But that is a conversation for another day.
Everything that is born is destined to die. The universe is no exception. There are three major theories for how it ends.
The first is called the Big Rip. As dark energy grows more dominant, the rate of expansion eventually overwhelms gravity. When gravity can no longer hold the universe together, reality itself breaks apart. Every structure, every force, every particle. If this happens, you and I will not be around to witness it.
The second is heat death. Rooted in thermodynamics, this theory holds that the universe gradually exhausts all usable energy. Stars burn out one by one. For a time, the universe contains nothing but black holes. Eventually, even black holes collapse. What remains is absolute nothing. Cold, still, and silent.
The third theory suggests the universe will eventually stop expanding and begin contracting. According to some scientists, the universe may have gone through many such cycles. As it contracts, heat builds. At maximum compression, temperatures climb so high that atoms cease to exist. The universe becomes an infinitely dense, infinitely hot point. And then, perhaps, it explodes again. A new Big Bang. A new universe.
None of these endings are anywhere near our time. But consider this: what if we live inside a universe that is itself a balloon being inflated? What if that balloon is part of something larger? What if it pops?
Are we truly alone in all of this?
Originally posted on thedopplerdude.blogspot.com.