There are 5 eras in the universe's lifecycle. Right now, we're in the second era.

Astronomers find these five chapters to be a handy way of conceiving the universe's incredibly long lifespan.

There are 5 eras in the universe's lifecycle. Right now, we're in the second era.

Image based on logarithmic maps of the Universe put together by Princeton University researchers, and images produced by NASA based on observations made by their telescopes and roving spacecraft

Image source: Pablo Carlos Budassi
  • We're in the middle, or thereabouts, of the universe's Stelliferous era.
  • If you think there's a lot going on out there now, the first era's drama makes things these days look pretty calm.
  • Scientists attempt to understand the past and present by bringing together the last couple of centuries' major schools of thought.

    If you're fortunate enough to get yourself beneath a clear sky in a dark place on a moonless night, a gorgeous space-scape of stars waits. If you have binoculars and point them upward, you're treated to a mind-bogglingly dense backdrop of countless specks of light absolutely everywhere, stacked atop each other, burrowing outward and backward through space and time. Such is the universe of the cosmological era in which we live. It's called the Stelliferous era, and there are four others.

    The 5 eras of the universe

    There are many ways to consider and discuss the past, present, and future of the universe, but one in particular has caught the fancy of many astronomers. First published in 1999 in their book The Five Ages of the Universe: Inside the Physics of Eternity, Fred Adams and Gregory Laughlin divided the universe's life story into five eras:

    • Primordial era
    • Stellferous era
    • Degenerate era
    • Black Hole Era
    • Dark era

    The book was last updated according to current scientific understandings in 2013.

    It's worth noting that not everyone is a subscriber to the book's structure. Popular astrophysics writer Ethan C. Siegel, for example, published an article on Medium last June called "We Have Already Entered The Sixth And Final Era Of Our Universe." Nonetheless, many astronomers find the quintet a useful way of discuss such an extraordinarily vast amount of time.

    The Primordial era

    Image source: Sagittarius Production/Shutterstock

    This is where the universe begins, though what came before it and where it came from are certainly still up for discussion. It begins at the Big Bang about 13.8 billion years ago.

    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.

    That having been said, within a second after the Big Bang finished Big Banging, inflation began, a sudden ballooning of the universe into 100 trillion trillion times its original size.

    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.

    About 380,000 years after the Big Bang, the universe had cooled enough that the first stable atoms capable of surviving began forming. With electrons thus occupied in atoms, photons were released as the background glow that astronomers detect today as cosmic background radiation.

    Inflation is believed to have happened due to the remarkable overall consistency astronomers measure in cosmic background radiation. Astronomer Phil Plait suggests that inflation was like pulling on a bedsheet, suddenly pulling the universe's energy smooth. The smaller irregularities that survived eventually enlarged, pooling in denser areas of energy that served as seeds for star formation—their gravity pulled in dark matter and matter that eventually coalesced into the first stars.

    The Stelliferous era

    Image source: Casey Horner/unsplash

    The era we know, the age of stars, in which most matter existing in the universe takes the form of stars and galaxies during this active period.

    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.

    Scientists predict that our Milky Way galaxy, for example, will crash into and combine with the neighboring Andromeda galaxy in about 4 billion years to form a new one astronomers are calling the Milkomeda galaxy.

    Our solar system may actually survive that merger, amazingly, but don't get too complacent. About a billion years later, the Sun will start running out of hydrogen and begin enlarging into its red giant phase, eventually subsuming Earth and its companions, before shrining down to a white dwarf star.

    The Degenerate era

    Image source: Diego Barucco/Shutterstock/Big Think

    Next up is the Degenerate era, which will begin about 1 quintillion years after the Big Bang, and last until 1 duodecillion after it. This is the period during which the remains of stars we see today will dominate the universe. Were we to look up — we'll assuredly be outta here long before then — we'd see a much darker sky with just a handful of dim pinpoints of light remaining: white dwarfs, brown dwarfs, and neutron stars. These"degenerate stars" are much cooler and less light-emitting than what we see up there now. Occasionally, star corpses will pair off into orbital death spirals that result in a brief flash of energy as they collide, and their combined mass may become low-wattage stars that will last for a little while in cosmic-timescale terms. But mostly the skies will be be bereft of light in the visible spectrum.

    During this era, small brown dwarfs will wind up holding most of the available hydrogen, and black holes will grow and grow and grow, fed on stellar remains. With so little hydrogen around for the formation of new stars, the universe will grow duller and duller, colder and colder.

    And then the protons, having been around since the beginning of the universe will start dying off, dissolving matter, leaving behind a universe of subatomic particles, unclaimed radiation…and black holes.

    The Black Hole era

    Image source: Vadim Sadovski/Shutterstock/Big Think

    For a considerable length of time, black holes will dominate the universe, pulling in what mass and energy still remain.

    Eventually, though, black holes evaporate, albeit super-slowly, leaking small bits of their contents as they do. Plait estimates that a small black hole 50 times the mass of the sun would take about 1068 years to dissipate. A massive one? A 1 followed by 92 zeros.

    When a black hole finally drips to its last drop, a small pop of light occurs letting out some of the only remaining energy in the universe. At that point, at 1092, the universe will be pretty much history, containing only low-energy, very weak subatomic particles and photons.

    The Dark Era

    Image source: Big Think

    We can sum this up pretty easily. Lights out. Forever.

    Tonight, if it's clear, maybe you want to step outside, take a nice deep breath, and look up, grateful that we are where we are, and when we are, in spite of all the day's hardships. We've got a serious amount of temporal elbow room here, far more than we need, so not to worry, and those stars aren't going anywhere for a long, long time.

    A landslide is imminent and so is its tsunami

    An open letter predicts that a massive wall of rock is about to plunge into Barry Arm Fjord in Alaska.

    Image source: Christian Zimmerman/USGS/Big Think
    Surprising Science
    • A remote area visited by tourists and cruises, and home to fishing villages, is about to be visited by a devastating tsunami.
    • A wall of rock exposed by a receding glacier is about crash into the waters below.
    • Glaciers hold such areas together — and when they're gone, bad stuff can be left behind.

    The Barry Glacier gives its name to Alaska's Barry Arm Fjord, and a new open letter forecasts trouble ahead.

    Thanks to global warming, the glacier has been retreating, so far removing two-thirds of its support for a steep mile-long slope, or scarp, containing perhaps 500 million cubic meters of material. (Think the Hoover Dam times several hundred.) The slope has been moving slowly since 1957, but scientists say it's become an avalanche waiting to happen, maybe within the next year, and likely within 20. When it does come crashing down into the fjord, it could set in motion a frightening tsunami overwhelming the fjord's normally peaceful waters .

    "It could happen anytime, but the risk just goes way up as this glacier recedes," says hydrologist Anna Liljedahl of Woods Hole, one of the signatories to the letter.

    The Barry Arm Fjord

    Camping on the fjord's Black Sand Beach

    Image source: Matt Zimmerman

    The Barry Arm Fjord is a stretch of water between the Harriman Fjord and the Port Wills Fjord, located at the northwest corner of the well-known Prince William Sound. It's a beautiful area, home to a few hundred people supporting the local fishing industry, and it's also a popular destination for tourists — its Black Sand Beach is one of Alaska's most scenic — and cruise ships.

    Not Alaska’s first watery rodeo, but likely the biggest

    Image source: whrc.org

    There have been at least two similar events in the state's recent history, though not on such a massive scale. On July 9, 1958, an earthquake nearby caused 40 million cubic yards of rock to suddenly slide 2,000 feet down into Lituya Bay, producing a tsunami whose peak waves reportedly reached 1,720 feet in height. By the time the wall of water reached the mouth of the bay, it was still 75 feet high. At Taan Fjord in 2015, a landslide caused a tsunami that crested at 600 feet. Both of these events thankfully occurred in sparsely populated areas, so few fatalities occurred.

    The Barry Arm event will be larger than either of these by far.

    "This is an enormous slope — the mass that could fail weighs over a billion tonnes," said geologist Dave Petley, speaking to Earther. "The internal structure of that rock mass, which will determine whether it collapses, is very complex. At the moment we don't know enough about it to be able to forecast its future behavior."

    Outside of Alaska, on the west coast of Greenland, a landslide-produced tsunami towered 300 feet high, obliterating a fishing village in its path.

    What the letter predicts for Barry Arm Fjord

    Moving slowly at first...

    Image source: whrc.org

    "The effects would be especially severe near where the landslide enters the water at the head of Barry Arm. Additionally, areas of shallow water, or low-lying land near the shore, would be in danger even further from the source. A minor failure may not produce significant impacts beyond the inner parts of the fiord, while a complete failure could be destructive throughout Barry Arm, Harriman Fiord, and parts of Port Wells. Our initial results show complex impacts further from the landslide than Barry Arm, with over 30 foot waves in some distant bays, including Whittier."

    The discovery of the impeding landslide began with an observation by the sister of geologist Hig Higman of Ground Truth, an organization in Seldovia, Alaska. Artist Valisa Higman was vacationing in the area and sent her brother some photos of worrying fractures she noticed in the slope, taken while she was on a boat cruising the fjord.

    Higman confirmed his sister's hunch via available satellite imagery and, digging deeper, found that between 2009 and 2015 the slope had moved 600 feet downhill, leaving a prominent scar.

    Ohio State's Chunli Dai unearthed a connection between the movement and the receding of the Barry Glacier. Comparison of the Barry Arm slope with other similar areas, combined with computer modeling of the possible resulting tsunamis, led to the publication of the group's letter.

    While the full group of signatories from 14 organizations and institutions has only been working on the situation for a month, the implications were immediately clear. The signers include experts from Ohio State University, the University of Southern California, and the Anchorage and Fairbanks campuses of the University of Alaska.

    Once informed of the open letter's contents, the Alaska's Department of Natural Resources immediately released a warning that "an increasingly likely landslide could generate a wave with devastating effects on fishermen and recreationalists."

    How do you prepare for something like this?

    Image source: whrc.org

    The obvious question is what can be done to prepare for the landslide and tsunami? For one thing, there's more to understand about the upcoming event, and the researchers lay out their plan in the letter:

    "To inform and refine hazard mitigation efforts, we would like to pursue several lines of investigation: Detect changes in the slope that might forewarn of a landslide, better understand what could trigger a landslide, and refine tsunami model projections. By mapping the landslide and nearby terrain, both above and below sea level, we can more accurately determine the basic physical dimensions of the landslide. This can be paired with GPS and seismic measurements made over time to see how the slope responds to changes in the glacier and to events like rainstorms and earthquakes. Field and satellite data can support near-real time hazard monitoring, while computer models of landslide and tsunami scenarios can help identify specific places that are most at risk."

    In the letter, the authors reached out to those living in and visiting the area, asking, "What specific questions are most important to you?" and "What could be done to reduce the danger to people who want to visit or work in Barry Arm?" They also invited locals to let them know about any changes, including even small rock-falls and landslides.

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