Learn why Easter Island never had a population collapse; and how scientists are measuring the expansion of our universe. Easter Island never had a population collapse, as commonly believed by Grant Currin Resilience, not collapse: What the Easter Island myth gets wrong. (2021, July 13). EurekAlert! https://www.eurekalert.org/news-releases/793195 Johnson, S. (2021, July 16). Busting the Easter Island myth: there was no civilization collapse. Big Think; Big Think. https://bigthink.com/culture-religion/easter-island DiNapoli, R. J., Crema, E. R., Lipo, C. P., Rieth, T. M., & Hunt, T. L. (2021). Approximate Bayesian Computation of radiocarbon and paleoenvironmental record shows population resilience on Rapa Nui (Easter Island). Nature Communications, 12(1). https://doi.org/10.1038/s41467-021-24252-z Scientists can't decide how fast the universe is expanding, but this scientist says there's no conflict at all by Briana Brownell “There may not be a conflict after all” in expanding universe debate. (2021). EurekAlert! https://www.eurekalert.org/pub_releases/2021-06/uoc-mn062921.php Freedman, W. L. (2021). Measurements of the Hubble Constant: Tensions in Perspective. arXiv preprint https://arxiv.org/abs/2106.15656 Follow Curiosity Daily on your favorite podcast app to learn something new every day withCody Gough andAshley Hamer. Still curious? Get exclusive science shows, nature documentaries, and more real-life entertainment on discovery+! Go to https://discoveryplus.com/curiosity to start your 7-day free trial. discovery+ is currently only available for US subscribers.
Learn why Easter Island never had a population collapse; and how scientists are measuring the expansion of our universe.
Easter Island never had a population collapse, as commonly believed by Grant Currin
Scientists can't decide how fast the universe is expanding, but this scientist says there's no conflict at all by Briana Brownell
Follow Curiosity Daily on your favorite podcast app to learn something new every day with Cody Gough and Ashley Hamer. Still curious? Get exclusive science shows, nature documentaries, and more real-life entertainment on discovery+! Go to https://discoveryplus.com/curiosity to start your 7-day free trial. discovery+ is currently only available for US subscribers.
Find episode transcript here: https://curiosity-daily-4e53644e.simplecast.com/episodes/easter-island-mythbusting-and-the-universes-expansion-rate
CODY: Hi! You’re about to get smarter in just a few minutes with Curiosity Daily from curiosity-dot-com. I’m Cody Gough.
ASHLEY: And I’m Ashley Hamer. Today, you’ll learn about why the rumors of a population collapse on Easter Island are greatly exaggerated; and the debate over how fast the universe is expanding might be no problem at all.
CODY: Let’s satisfy some curiosity.
Rapa Nui is an isolated island in the South Pacific, between Chile and Australia. It’s more popularly known as Easter Island, and it’s famous for two things: giant stone heads and civilizational collapse. The statues are definitely real, but a new study suggests that rumors of collapse may be just that — rumors.
Rapa Nui is not the easiest place to live. The island is about the size of Washington, D.C., and so remote that humans didn’t settle there until around 1200 CE. The climate got a lot drier about 300 years later because of natural changes to global weather patterns. And all kinds of problems emerged after 1722, when Europeans quote-unquote “discovered” the island — on Easter Sunday — and killed about a dozen inhabitants. Later visitors enslaved about half the island’s population.
But in the western imagination, Easter Island is a cautionary tale about what can happen when a society over-exploits the resources it depends on. That story goes something like this: indigenous people got to the island and started cutting down most of the palm trees. The population boomed, but an ecological collapse led to starvation and soon decimated that population. Europeans arrived to find the remnants of a once-great society.
Researchers have poked a few holes in the theory over the years, but a new study suggests that it’s entirely wrong. Archaeologists created new models to estimate changes in the island’s population over time, which incorporated data from about 200 radiocarbon-dated artifacts from the island along with data about changes to the environment and climate. To crunch the numbers, the team used new statistical techniques originally designed for genetics research. They concluded that the human population on Rapa Nui didn’t collapse at all. In fact, it seems to have grown, slowly and steadily, during the 500 years between settlement and contact with Europeans.
The indigenous people did cut down a lot of trees, but they replaced them with gardens and used a nutrient-rich stone mulch to grow a lot of food. As droughts became more frequent, they probably relied on groundwater stored in the island’s volcanic rock. The population was only a few thousand when Europeans made landfall, but those people weren’t the survivors of a great catastrophe. They were the descendents of a population that had been growing for a long, long time.
The people of Rapa Nui seem to have thrived, despite being largely isolated from the rest of humanity for half a millennium and facing challenging ecological conditions and climate change. At least, they thrived as long as they were isolated. While many of the famous statues still watch over the island, the civilization and culture have been all but destroyed in the centuries since 1722. But not because the indigenous people cut down trees.
Although we know the universe is expanding, we’re still puzzling out how fast. And to make it even more confusing, two main ways astronomers measure this speed have sometimes come up with two different answers. If that difference is a result of how we measure the expansion of the universe, it’s fine — we won’t need to rework our current understanding of physics. But if not… we might have the first evidence of something new that can’t be explained by our theories.
A new paper from an American scientist is the latest in the long back-and-forth on this point. Using new methods and better technology to make more accurate measurements, her work suggests that the two ways do come up with the same result.
It all comes down to one important value: the Hubble constant. The Hubble constant describes how quickly galaxies are moving away from each other.
There are two major ways to measure this value.
The first way to measure it is with cosmic background radiation. That’s the energy left over from the Big Bang. Scientists use various telescopes to measure this radiation energy and compare it with what it should be, given the age of the universe.
The second is a lot more direct. Scientists measure how quickly various stars and galaxies are moving away from us and how far away they are. For the last few decades, scientists have done this using a special kind of star called a Cepheid [SEFF-ee-id]. These stars pulse, getting bigger and smaller and hotter and cooler in a steady rhythm. Scientists can use their brightness to figure out how far away they are — and how fast they’re moving away from us.
But a Cepheid isn’t the only celestial object that can give us a guess at its movement, and the new research adds another method: Red giants.
Red giants have a similar tell-tale sign of their distance from us. It has to do with their aging process. Red Giants are late-in-life stars that are converting the very last of their hydrogen fuel into helium. These stars peak in brightness before fading out thanks to what’s called the helium flash. When the red giant reaches a specific temperature — about 100 million degrees Kelvin — the helium core undergoes a chain reaction that fuses helium into carbon in a very short amount of time.
Scientists can watch for that flash, and use it to estimate the distance. When scientists measured several of these red giants, the numbers showed that the expansion of the universe is close to that measured by cosmic background radiation.
This gives more evidence that the two methods are in fact measuring the same thing. And, in the words of lead scientist, Dr. Wendy Freedman: “No new physics are required.”
For now anyway. Her team plans to make further observations of more Cepheids and Red giants in the next few years to add even more data to these results.
Let’s do a quick recap of what we learned today
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ASHLEY: Today’s writers were Grant Currin and Briana Brownell.
CODY: Our managing editor is Ashley Hamer
ASHLEY: Our producer and audio editor is Cody Gough.
CODY: [AD LIB SOMETHING FUNNY] Join us again tomorrow to learn something new in just a few minutes.
ASHLEY: And until then, stay curious!