Dark energy: The apocalyptic wild card of the universe
Dr. Katie Mack explains what dark energy is and two ways it could one day destroy the universe.
KATIE MACK: Understanding what dark energy is, understanding what it is that's making the universe expand faster is an incredibly important thing for understanding the future of the universe. Right now, the evolution of the cosmos is dominated by this mysterious dark energy that we can't see, we don't understand. If we figure out what it's doing, if we figure out what it's made of, how it's going to change in the future, then we will have a much better idea for how the universe will end.
Dark matter is very different from dark energy. People often get these two ideas confused because they're both called dark. And also because there are connections between matter and energy. People might have heard of E = mc2, this idea that there's a way to relate the mass of something to its energy, that's from Einstein. In this case, dark matter and dark energy don't seem to be related to each other in any way, that we know. They're both called dark because we cannot see them and they're mysterious. That's where the similarity ends. Neither one is dark in the sense of being black. They're dark in the sense of being invisible. They don't emit light, they don't absorb light, they don't reflect light. They don't seem to interact with light at all, as far as we can tell.
Dark matter seems to be something that interacts via gravity so it has mass, it's matter. But it doesn't seem to interact via the other forces of nature in any way that we've been able to tell. Dark energy only does this thing where it makes space expand, it interacts only with space. And there's a possibility that dark energy is just a property of space that every little bit of space has a little bit of expansion built in, and as the universe gets bigger and bigger, there's more and more space, and so that expansion starts to win out over the gravity that's trying to slow it down. And so, the universe starts expanding faster and faster. That's one possibility for dark energy, that it's just a cosmological constant, it's just part of how the universe works, that it has this expansiveness built into it.
But it's possible it's something else. It's possible that whatever is making the universe expand faster and faster is something weird and different, something that acts in a totally different way. That also accelerates the expansion of the universe, but maybe it changes over time in some way that we don't understand. One of the possibilities for that is something called phantom dark energy. Phantom dark energy would be something where dark energy is getting more powerful over time. That means that in a particular volume of space, the amount of dark energy in that volume starts growing. And that would actually lead to a total apocalypse in a relatively short time. What it would do is it would start tearing apart things in the universe. If dark energy is not a cosmological constant, if it's this phantom dark energy, then the amount of dark energy is going to get higher over time. And so, the stars that have been orbiting very stably in the past will start to feel pushed out by more and more of this expansion happening inside the galaxy.
So, in the scenario that dark energy is this weird stuff, this phantom dark energy, then it does start to actually pull matter apart. So it would first start to pull galaxies away from other galaxies in these giant galaxy clusters. Then it would start to pull stars away from galaxies, so we'd see the stars in the Milky Way would start to drift away. And then it would start to pull planets away from their suns. And then, it would start to actually pull apart planets and stars, and even eventually atoms and particles—it would start to just rip everything apart. And in some, at some point in the future, it would kinda tear apart the whole universe in a process we know as The Big Rip.
So, based on our current data, there's some uncertainty in our current measurements of the expansion of the universe. And that uncertainly leaves some space for the possibility that our universe is headed toward a Big Rip. And based on the uncertainties in the measurements, what we can say is that we're almost certain not to have a Big Rip in the next 200 billion years or so. But we can't say for sure that it will never happen. And even as we get more and more precise measurements, all that's really going to do is push this scenario farther into the future, and say, well, maybe we'll get much better measurements in a few years, and then that'll tell us we definitely won't have a Big Rip for the next hundred thousand billion years. You might, at some point, get to that, but you'll never be able to say that it'll never happen because no measurement is ever 100% complete. So unless we really understand what dark energy is, which at the moment, we don't, we can't say for certain that it won't at some point, rip the universe apart. We can just say that if it's going to do that, it'll be a really long time from now.
Alternatively, dark energy could be something that changes fundamentally over time, that doesn't get more powerful, but gets less powerful and actually changes direction. So, dark energy could be something that's currently making the universe expand faster, but it could be something that changes and at at some point, starts to pull the universe back together again. Right now, we know that the universe is expanding, galaxies are getting farther apart from each other. And for a long time, we were trying to measure how quickly that expansion was slowing down. And we figured it should be slowing down because the Big Bang happened in the beginning, that kicked off the expansion, and since then, all the gravity of all the stuff in the universe should be kinda putting on the brakes, kinda pulling things back.
For a long time, we didn't know if the gravity would eventually win, or if the expansion was so powerful that everything will be moving away from everything else forever. And if the gravity were to win, then what would happen is the expansion, at some point, would stop. And distant galaxies, instead of moving away from us, would start barreling toward us in the future. And the way that it would look to us is that we would see distant galaxies kinda coming toward us. We would see collisions of galaxies much more often. Other galaxies would collide with our galaxy. There would be a lot more stuff in the smaller region of space, just everywhere in the universe. The universe would get much more dense.
And the thing that would actually get dangerous about that, the first thing that would get dangerous about that is that as the universe is compressing, it's not just compressing like the galaxies, the stars, and stuff like that, it's compressing all of the radiation in the universe as well. And we know that there's background radiation in our universe today that's leftover from the time when the early universe was very hot and dense. It dissipated. It sort of spread out, but that radiation is still out there. And so, if you're compressing the universe, you're bringing all that radiation back into a smaller space. And so, you're moving toward being back in that plasma state, you're evolving toward being, the whole universe being hot and dense, and in sort of this roiling plasma. As the universe is compressing, not only is it bringing back all that radiation from the primordial fire, it's also compressing all the radiation from all of the stars that ever burned in the universe.
More and more, any random point in the universe would feel a lot more like being right next to a star. And all of these high energy processes in the universe that create gamma rays and x-rays, that radiation also would be compressed. And so, at some point, as you're evolving toward a Big Crunch scenario, as the universe is compressing, you get to a point when there's so much radiation in the universe, just an empty space, just so much radiation that it's enough to ignite the surfaces of stars. And what I mean by that is that there's so much of this high energy radiation just flowing through the universe, that the outsides of stars start carrying out thermonuclear explosions. So stars will start to just burn from the outside in. And at that point, you know, it's all over. Nothing can survive conditions like that. And you end up with just total destruction. That's The Big Crunch. The only way we can see that happening is if dark energy is so weird that it doesn't just cause expansion, it actually stops, turns around, and causes compression. And because we don't know what dark energy is, we don't know if it's something that can change over time. We don't know if it's on some trajectory. We can't rule out the idea that it could, at some point, reverse directions. We think that's probably not going to happen.
- The universe is expanding faster and faster. Whether this acceleration will end in a Big Rip or will reverse and contract into a Big Crunch is not yet understood, and neither is the invisible force causing that expansion: dark energy.
- Physicist Dr. Katie Mack explains the difference between dark matter, dark energy, and phantom dark energy, and shares what scientists think the mysterious force is, its effect on space, and how, billions of years from now, it could cause peak cosmic destruction.
- The Big Rip seems more probable than a Big Crunch at this point in time, but scientists still have much to learn before they can determine the ultimate fate of the universe. "If we figure out what [dark energy is] doing, if we figure out what it's made of, how it's going to change in the future, then we will have a much better idea for how the universe will end," says Mack.
- Heat death: How will the universe end? - Big Think ›
- Dark Matter and Dark Energy Don't Exist. New Theory Says the ... ›
- Mystery effect speeds up the Universe – not dark energy, says study ... ›
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Eating veggies is good for you. Now we can stop debating how much we should eat.
- A massive new study confirms that five servings of fruit and veggies a day can lower the risk of death.
- The maximum benefit is found at two servings of fruit and three of veggies—anything more offers no extra benefit according to the researchers.
- Not all fruits and veggies are equal. Leafy greens are better for you than starchy corn and potatoes.
An open letter predicts that a massive wall of rock is about to plunge into Barry Arm Fjord in Alaska.
- 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 .
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.
The famous cognition test was reworked for cuttlefish. They did better than expected.
- Scientists recently ran the Stanford marshmallow experiment on cuttlefish and found they were pretty good at it.
- The test subjects could wait up to two minutes for a better tasting treat.
- The study suggests cuttlefish are smarter than you think but isn't the final word on how bright they are.
Proof that some people are less patient than invertebrates<iframe width="730" height="430" src="https://www.youtube.com/embed/H1yhGClUJ0U" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe><p> The common cuttlefish is a small cephalopod notable for producing sepia ink and relative intelligence for an invertebrate. Studies have shown them to be capable of remembering important details from previous foraging experiences, and to adjust their foraging strategies in response to changing circumstances. </p><p>In a new study, published in <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2020.3161" target="_blank" rel="noopener noreferrer">The Proceedings of the Royal Society B</a>, researchers demonstrated that the critters have mental capacities previously thought limited to vertebrates.</p><p>After determining that cuttlefish are willing to eat raw king prawns but prefer a live grass shrimp, the researchers trained them to associate certain symbols on see-through containers with a different level of accessibility. One symbol meant the cuttlefish could get into the box and eat the food inside right away, another meant there would be a delay before it opened, and the last indicated the container could not be opened.</p><p>The cephalopods were then trained to understand that upon entering one container, the food in the other would be removed. This training also introduced them to the idea of varying delay times for the boxes with the second <a href="https://www.sciencealert.com/cuttlefish-can-pass-a-cognitive-test-designed-for-children" target="_blank" rel="noopener noreferrer">symbol</a>. </p><p>Two of the cuttlefish recruited for the study "dropped out," at this point, but the remaining six—named Mica, Pinto, Demi, Franklin, Jebidiah, and Rogelio—all caught on to how things worked pretty quickly.</p><p>It was then that the actual experiment could begin. The cuttlefish were presented with two containers: one that could be opened immediately with a raw king prawn, and one that held a live grass shrimp that would only open after a delay. The subjects could always see both containers and had the ability to go to the immediate access option if they grew tired of waiting for the other. The poor control group was faced with a box that never opened and one they could get into right away.</p><p>In the end, the cuttlefish demonstrated that they would wait anywhere between 50 and 130 seconds for the better treat. This is the same length of time that some primates and birds have shown themselves to be able to wait for.</p><p>Further tests of the subject's cognitive abilities—they were tested to see how long it took them to associate a symbol with a prize and then on how long it took them to catch on when the symbols were switched—showed a relationship between how long a cuttlefish was willing to wait and how quickly it learned the associations. </p>
All of this is interesting, but what use could it possibly have?<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTcxNzY2MS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY2MTM0MzYyMH0.lKFLPfutlflkzr_NM6WmnosKM1rU6UEIHWlyzWhYQNM/img.jpg?width=1245&coordinates=0%2C10%2C0%2C88&height=700" id="77c04" class="rm-shortcode" data-rm-shortcode-id="7eb9d5b2d890496756a69fb45ceac87c" data-rm-shortcode-name="rebelmouse-image" data-width="1245" data-height="700" />
A diagram showing the experimental set up. On the left is the control condition, on the right is the experimental condition.
Credit: Alexandra K. Schnell et al., 2021<p> As you can probably guess, the ability to delay gratification as part of a plan is not the most common thing in the animal kingdom. While humans, apes, some birds, and dogs can do it, less intelligent animals can't. </p><p>While it is reasonably simple to devise a hypothesis for why social humans, tool-making chimps, or hunting birds are able to delay gratification, the cuttlefish is neither social, a toolmaker, or is it hunting anything particularly <a href="https://gizmodo.com/cuttlefish-are-able-to-wait-for-a-reward-1846392756" target="_blank" rel="noopener noreferrer">intelligent</a>. Why they evolved this capacity is up for debate. </p><p>Lead author Alexandra Schnell of the University of Cambridge discussed their speculations on the evolutionary advantage cuttlefish might get out of this skill with <a href="https://www.eurekalert.org/pub_releases/2021-03/mbl-qc022621.php" target="_blank" rel="noopener noreferrer">Eurekalert:</a> </p><p style="margin-left: 20px;"> "Cuttlefish spend most of their time camouflaging, sitting and waiting, punctuated by brief periods of foraging. They break camouflage when they forage, so they are exposed to every predator in the ocean that wants to eat them. We speculate that delayed gratification may have evolved as a byproduct of this, so the cuttlefish can optimize foraging by waiting to choose better quality food."</p><p>Given the unique evolutionary tree of the cuttlefish, its cognitive abilities are an example of convergent evolution, in which two unrelated animals, in this case primates and cuttlefish, evolve the same trait to solve similar problems. These findings could help shed light on the evolution of the cuttlefish and its relatives. </p><p> It should be noted that this study isn't definitive; at the moment, we can't make a useful comparison between the overall intelligence of the cuttlefish and the other animals that can or cannot pass some variation of the marshmallow test.</p><p>Despite this, the results are quite exciting and will likely influence future research into animal intelligence. If the common cuttlefish can pass the marshmallow test, what else can?</p>