Throughout history, scientists have attempted to understand the past and present, most recently, by bringing together the last couple of centuries major schools of thought. Now, they have discovered that the lifecycle of the Universe expands over five eras.
Currently, we are somewhere near the middle, which places Earth in the Universe's Stelliferous era. Here, on a moonless night, a gorgeous space-scape of stars treat us to a mind-bogglingly dense backdrop of countless specks of light absolutely everywhere.
Scientists have found many ways to consider and discuss the past, present, and future of the Universe. However, one particular method has caught the fancy of many astronomers.
In 1999, the book The Five Ages of the Universe: Inside the Physics of Eternity, was published by Fred Adams and Gregory Laughlin, where they divided the Universe's life story into five eras: Primordial era, Stellferous era, Degenerate era, Black Hole Era and Dark era. In 2013, the book was last updated – according to current scientific understandings – but many astronomers find the method a useful way of discussing such an extraordinarily vast amount of time.
In the book, they explain the five stages, starting with The Primordial era. The book explains that this is where the Universe begins, dating all the way back to the Big Bang about 13.8 billion years ago. However, though what came before it and where it came from are still up for discussion.
The authors state; "For the first little, and we mean very little, bit of time, spacetime and the laws of physics are thought not yet to have existed. That weird, unknowable interval is the Planck Epoch that lasted for 10-44 seconds – or 10 million of a trillion, of a trillion of a trillionth of a second. Much of what we currently believe about the Planck Epoch eras is theoretical, based largely on a hybrid of general-relativity and quantum theories called quantum gravity. And it's all subject to revision.
"Within a second after the Big Bang happened – inflation began. Within minutes, the plasma began cooling, and subatomic particles began to form and stick together. In the 20 minutes after the Big Bang, atoms started forming in the super-hot, fusion-fired Universe. Cooling proceeded apace, leaving us with a Universe containing mostly 75% hydrogen and 25% helium, similar to that we see in the Sun today. Electrons gobbled up photons, leaving the Universe opaque."
380,000 years after the Big Bang event, it is believed that the Universe had cooled enough that the first stable atoms capable of surviving began to form. "With electrons thus occupied in atoms, photons were released as the background glow that astronomers detect today as cosmic background radiation," says the book.
Due to the remarkable overall consistency astronomers measure in cosmic background radiation, it is believed that inflation happened.
"A star is formed when a gas pocket becomes denser and denser until it, and matter nearby, collapse in on itself, producing enough heat to trigger nuclear fusion in its core – the source of most of the universe's energy now. The first stars were immense, eventually exploding as supernovas, forming many more, smaller stars. These coalesced, thanks to gravity, into galaxies.
"One axiom of the Stelliferous era is that the bigger the star, the more quickly it burns through its energy, and then dies, typically in just a couple of million years. Smaller stars that consume energy more slowly stay active longer. In any event, stars – and galaxies – are coming and going all the time in this era, burning out and colliding."
In further studies, scientists predicted that in about four billion years, our Milky Way galaxy will crash into – and combine with – the neighbouring Andromeda galaxy. This will form a new one astronomers are calling the Milkomeda galaxy.
Scientists predict that our solar system will survive the merge. A billion years later, the Sun will start running out of hydrogen and begin enlarging into its red giant phase. This is when the Sun will subsume Earth and its companions.
The third era is known as The Degenerate era, which will begin about one quintillion years after the Big Bang, and last until one Duodecillion later.
In this period, the remains of stars we see today will dominate the Universe. There will only be much darker sky with just a handful of dim pinpoints of light remaining. These stars will be white dwarfs, brown dwarfs, and neutron stars.
These "degenerate stars" will also be much cooler and less light-emitting than the current stars.
In this era, the small brown dwarfs will end up holding most of the available hydrogen, leading to the growth of black holes fed on stellar remains.
The Universe will grow duller and colder as the hydrogen around for the formation of new stars decreases. The protons, which have been around since the beginning of the Universe will start dying off, dissolving matter, leaving behind a Universe consisting of subatomic particles, unclaimed radiation as well as black holes.
The fourth era of the Universe, The Black Hole era, will see black holes dominate the Universe for a length of time – pulling in what mass and energy still remain.
Black holes do eventually evaporate, where they will be leaking small bits of their contents as they do. When a black hole finally drips its last drop, a small pop of light occurs, letting out some of the only remaining energy in the Universe.
At that point, scientists believe that the Universe will be pretty much history, and contain only low-energy and very weak subatomic particles and photons.
The last era of the Universe is called The Dark Era.
Even though stars aren't going anywhere for a long, long time, the dark era will be the phase where there will be complete darkness in the Universe.