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10 Methods Scientists Use to Date Things

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Left and right, archaeologists are radiocarbon dating objects: fossils, documents, shrouds of Turin. They do it by comparing the ratio of an unstable isotope, carbon-14, to the normal, stable carbon-12. All living things have about the same level of carbon-14, but when they die it begins to decay at uniform rate—the half-life is about 5,700 years, and you can use this knowledge to date objects back about 60,000 years.

However, radiocarbon dating is hardly the only method that creative archaeologists and paleontologists have at their disposal for estimating ages and sorting out the past. Some are plainly obvious, like the clockwork rings of many old trees. But there are plenty of strange and expected ways to learn about the past form the clues it left behind.

1. Camel on Your Knife

It's wasn't so long ago that megafauna ruled the American continent. Sloths and wooly mammoths pushed their weight around; horses and camels had their day. But after the end of the last Ice Age those animals disappeared, so when scientists turn up traces of those animals on archaeological remains, those remains go way back.

Last year, the University of Colorado's Doug Bamforth analyzed a cache of 80-plus tools that a Boulder, Colorado, man accidentally unearthed in his yard. Those tools showed protein residue from camels and horses, so Bamforth dated them to the Clovis people who lived around about 13,000 years ago. (Not all scientists accept the accuracy of these tests, but that's nothing new in archaeology).

2. Locked Away DNA

Medieval manuscripts have a lot more to say than simply the words on their pages; often they're written on parchment made from animal skins, and organic material keeps its secrets for a long time. Literary historian Timothy Stinson developed a way to extract the DNA from parchment itself, and if you can tell what animal a parchment was derived from, you might be able to tell more about what time and place the document originated.

3. The Secret Life of Dung

Moa, the giant flightless birds of New Zealand, may have been extinct for at least 500 years, but their dung is surprisingly resilient. On cave floors and buried in shelters, researchers found dung from the moa, with some of the samples being 15 cm (nearly six inches) in length. The contents of the droppings give more than a window into the giant bird's eating habits—they preserve a record of what the long-gone moa's ecosystem was like.

The arid conditions of New Zealand caves provide the perfect place for poo preservation. Australia should, too, the researchers say, but the droppings of ancient marsupials just haven't turned up. As professor Alan Cooper says, "A key question for us is 'where has all the Australian poo gone?'"

4. Nuclear Forensics


If you think your metal detector has uncovered some treasures, try finding vintage plutonium in the backyard. Jon Schwantes of the Pacific Northwest National Laboratory was called in to analyze a sample of plutonium-239 accidentally discovered in a safe during the cleanup of the Hanford nuclear site in Washington. One clue was the "signature" left by the reactor—every reactor's is different. The fingerprint of this discarded material led him to a reactor not in Hanford, but in Oak Ridge, TN. It also led him to the conclusion that it was created in 1944, meaning it was created during the Manhattan Project, making it one of the world's oldest-known samples of enriched plutonium. [Image courtesy of Popular Mechanics.]

5. Chemical Warfare

A pile of skeletons probably wouldn't tell us much more than the obvious. But University of Leicester archaeologist Simon James sees evidence that, to him, dates the first known chemical warfare attack back to 256 A.D.

In that year, Persians attacked a Roman garrison at Dura-Europos in Syria; when they tried to mine under the walls, Romans tried to counter by mining under the Persian tunnels. Archaeologists found the pile of Roman bodies in one of the tunnels, but no cause of death. James thinks it was asphyxiation. In the tunnels, he says, there was bitumen and sulfur—materials that, when burned, give off toxic gas. So, he says, the Persians probably used chemical warfare to do in their rivals.

6. The Magnetic Fields

One classical way to date objects is to take note of what strata of rock they occupy—rocks come in layers, with the oldest at the bottom. But those rocks also carry less obvious information—their magnetic signatures. The Earth's magnetic field varies all the time, by both strength and orientation. At the time rocks form, however, their magnetic materials acquire the particular orientation of the planet's magnetism at the time, giving geologists a window into the Earth's magnetic past.

7. Ice Cores


You've probably heard about ice cores, but what are they exactly? Ice sheets are laid down in layers, and the layer corresponding to each year is a little different. The important thing for climate researchers is that the oxygen isotopes present in a layer can help show what the temperature was that year. So by extracting a cylindrical core sample containing layers that go way back, they can build a model of the climate of the past. [Image courtesy of]

8. Pollen

Finally, pollen is good for something besides making you sneeze. Deposits of pollen deep in the ground can reveal what the vegetation was like at that time, and ergo, what the area's climate might have been like. Radiocarbon dating has become the standard method to date organic material, making pollen deposits sort of useless in that regard. But pollen can still help scientists interpret the environment of the past.

9. Volcanic Ash

Everything, it seems, has a fingerprint, and volcanoes are no exception—each eruption contains a chemical mix that is all its own. So if you knew the specific signature of say, the 79 A.D. eruption of Mt Vesuvius that buried Pompeii, you could look for that signature elsewhere in Italy and know that it came from the same eruption. Thus, any objects in that "tephra," the name for solids ejected during a single eruption, date to that era of Roman history, and anything below it would be older. This dating system is called tephrochronology.

10. Thermoluminescence

You probably know that radiation you can't see is flying all around you, but you might not know that not only do objects absorb that radiation, they also let their trapped radiation go when heated up. Knowing this, an archaeologist could heat up an object, watch how much radiation is released and determine how old the thing might be.

It's particularly useful for ceramics. When a potter in Ancient Greece fired his kiln and baked a pot, that released the clay's stored electrons and reset the clock to zero. During all those centuries it sat in the ground, it began storing radiation again at a steady rate. So when a curious 21st century scientist unearths the pot and heats it again, she can measure the radiation released, crunch some numbers and figure out how long ago the pot was first fired.

Andrew Moseman writes about science for publications like Popular Mechanics, Discover, Scientific American and Big Think from his Brooklyn apartment beneath the elevated tracks. He's from Nebraska, and he claims that ex-Huskers are starting a hive in New York City. Just so you know.



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iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Opening Ceremony
These $425 Jeans Can Turn Into Jorts
May 19, 2017
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Opening Ceremony

Modular clothing used to consist of something simple, like a reversible jacket. Today, it’s a $425 pair of detachable jeans.

Apparel retailer Opening Ceremony recently debuted a pair of “2 in 1 Y/Project” trousers that look fairly peculiar. The legs are held to the crotch by a pair of loops, creating a disjointed C-3PO effect. Undo the loops and you can now remove the legs entirely, leaving a pair of jean shorts in their wake. The result goes from this:


Opening Ceremony

To this:


Opening Ceremony

The company also offers a slightly different cut with button tabs in black for $460. If these aren’t audacious enough for you, the Y/Project line includes jumpsuits with removable legs and garter-equipped jeans.

[h/t Mashable]