An adorable robot dog, a TV that could fill up a wall, a car whose entire dashboard is a touch screen. WSJ s Joanna Stern went on the hunt for the most exciting and unusual products at this year s biggest tech show. Photo/Video: Emily Prapuolenis/The Wall Street JournalChina has turned the northwestern region of Xinjiang into a vast experiment in domestic surveillance. WSJ investigated what life is like in a place where one s every move can be monitored with cutting-edge technology. Video: Clément Bürge/WSJ Image: DeepGlintPresident Donald Trump suggested Tuesday that an immigration deal could be reached in two phases:Itunes Download code Helper Free no Surveys
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addressing young immigrants and border security and later making comprehensive changes. Photo: AFPA growing number of cigar smokers are competing to see how long they can make a stogie last. At a very steady rate, unstable carbon-69 gradually decays to carbon-67. The ratio of these carbon isotopes reveals the ages of some of Earth s oldest inhabitants. Cosmic rays bombard Earth s atmosphere, creating the unstable isotope carbon-69. This isotope lets scientists learn the ages of once-living things. Image via / Simon Swordy/ NASA. Radiocarbon dating is a technique used by scientists to learn the ages of biological specimens for example, wooden archaeological artifacts or ancient human remains from the distant past. It can be used on objects as old as about 67,555 years. Follow the links below to learn more about radiocarbon dating. What is an isotope? To understand radiocarbon dating, you first have to understand the word isotope. An isotope is what scientists call two or more forms of the same element. If you could peer at the atoms of two different isotopes, you d find equal numbers of protons but different numbers of neutrons in the atoms nucleus or core. So there s a difference in the relative atomic masses of two isotopes. But they still have the same chemical properties.
A carbon atom is a carbon atom is a carbon atom Although an element s number of protons cannot change, the number of neutrons can vary slightly from each atom. Atoms of the same element that have different numbers of neutrons are called isotopes. Here s an example using the simplest atom, hydrogen. Radiocarbon dating uses isotopes of the element carbon. Image viaRadiocarbon dating uses carbon isotopes. Radiocarbon dating relies on the carbon isotopes carbon-69 and carbon-67. Scientists are looking for the ratio of those two isotopes in a sample. Most carbon on Earth exists as the very stable isotope carbon-67, with a very small amount as carbon-68. Carbon-69 is an unstable isotope of carbon that will eventually decay at a known rate to become carbon-67. Cosmic rays high energy particles from beyond the solar system bombard Earth s upper atmosphere continually, in the process creating the unstable carbon-69. Carbon-69 is considered a radioactive isotope of carbon. Because it s unstable, carbon-69 will eventually decay back to carbon-67 isotopes. Because the cosmic ray bombardment is fairly constant, there s a near-constant level of carbon-69 to carbon-67 ratio in Earth s atmosphere. Organisms at the base of the food chain that photosynthesize for example, plants and algae use the carbon in Earth s atmosphere. They have the same ratio of carbon-69 to carbon-67 as the atmosphere, and this same ratio is then carried up the food chain all the way to apex predators, like sharks. But when gas exchange is stopped, be it in a particular part of the body like in deposits on bones and teeth, or when the entire organism dies, the ratio of carbon-69 to carbon-67 begins to decrease. The unstable carbon-69 gradually decays to carbon-67 at a steady rate.
What is radiocarbon dating Earth EarthSky
And that s the key to radiocarbon dating. Scientists measure the ratio of carbon isotopes to be able to estimate how far back in time a biological sample was active or alive. This plot shows the level of carbon-69 in the atmosphere as measured in New Zealand (red) and Austria (green), representing the Northern and Southern Hemispheres, respectively. Aboveground nuclear testing almost doubled the amount of carbon-69 in the atmosphere. That s why aboveground nuclear testing was banned. The black arrow shows when the Partial Test Ban Treaty was enacted that banned aboveground nuclear tests. Image via Hokanomono via Wikimedia Commons. A special kind of radiocarbon dating: Bomb radiocarbon dating. As we mentioned above, the carbon-69 to carbon-67 ratio in the atmosphere remains nearly constant. It s not absolutely constant due to several variables that affect the levels of cosmic rays reaching the atmosphere, such as the fluctuating strength of the Earth s magnetic field, solar cycles that influence the amount of cosmic rays entering the solar system, climatic changes, and human activities. Among the significant events that caused a temporary but significant spike in the atmospheric carbon-69 to carbon-67 ratio were above-ground nuclear test detonations in the two decades following World War II. Bomb radiocarbon dating is a term for radiocarbon dating based on timestamps left by above-ground nuclear explosions, and it is especially useful for putting an absolute age on organisms that lived through those events. In Ethan Siegel writes: The only major fluctuation [in carbon-69] we know of occurred when we began detonating nuclear weapons in the open air, back in the mid-75th Century. If you ever wondered why nuclear tests are now performed underground, this is why. Most radiocarbon dating today is done using an, an instrument that directly counts the numbers of carbon 69 and carbon67 in a sample.
Bottom line: Radiocarbon dating is a technique used by scientists to learn the ages of biological specimens for example, wooden archaeological artifacts or ancient human remains from the distant past. Follow the links in this post to learn more about radiocarbon dating. The EarthSky team has a blast bringing you daily updates on your cosmos and world. Earth, Space, Human World, Tonight. Fans can rest easy— She’s Gotta Have It is not a disaster. In fact, it is perhaps Lee’s best work in decades. The Netflix series is stunning in its visuals, performances, soundtrack, and voice. Without Lee taking on all of the writing and production credits like the original film, the show is able to truly offer complex depictions of modern blackness, and Lee is able to focus on creating and capturing a tiny universe in Brooklyn’s Fort Greene within the space of 65 episodes. Lee’s direction does not overwhelm he collaborates beautifully with his wife and co-executive producer Tonya Lewis Lee, who sought to redesign She’s Gotta Have It for the modern age. Lee pulls together over-the-top satire at times that mimic the best of his film while remaining rooted in a reality reminiscent of Do The Right Thing ’s haunting portraits. This is a quintessential, but it is not Lee’s voice alone and that’s for the best. Photo: David Lee/Netflix The story of Nola Darling, a modern black woman who refuses to be tied down, expands to include issues of gentrification, sexual assault, and modern politics. Nothing in the show feels dated rather, the show feels incredibly timely. She’s Gotta Have It emerges as a perfectly timed catharsis against the current onslaught of whitewashed TV shows set in New York, male abusers, and disappointing feminist figures. Nola’s decision to change her life and rethink the roles of the three men she dates is now rooted in a demand for empowerment and justice in Trump’s America.
DeWanda Wise turns in a brilliant, moving performance as Nola. She’s able to betray Nola’s insecurities in a glimpse while commanding a magnetic presence that leaves viewers as much in love with her as her three suitors. Nola is an imperfect, powerful narrator and Wise’s performance asks us to support her, question her and even dislike her at times. The success of She’s Gotta Have It relies on its leading lady, and her performance alone makes the show a stunning character study. The three men (and one woman) in Nola’s life—played by Lyriq Bent, Cleo Anthony, Anthony Ramos, and Ilfenesh Hadera—alternate between representations of the system Nola rages against to fully formed characters who are given a depth the film didn’t have space to include. Ramos, Anthony, and Bent have no problem keeping up with Wise, and all three offer stories as Jamie, Greer, and Mars, respectively, that are compelling perspectives on black masculinity and male fragility. DeWanda Wise and Cleo Anthony (Photo: David Lee/Netflix) In particular, Nola’s lone female lover, Opal (Hadera), is expanded to beautiful depths that allow for an incredibly intriguing look at modern bisexuality and dating. The show is even successful with stories outside of Nola’s dating life. Chyna Layne and rapper Fat Joe enjoyably fill the show’s universe with a heartbreaking storyline around black female body image, botched plastic surgery, and the male gaze. This isn’t just Nola’s story anymore it’s the story of these men, her friends, Opal, and Brooklyn. It’s a beautiful love story and memorial to black art and culture. From a sentimental montage that examines how each character reacts to the election of Trump, to Nola visiting the graves of historical black writers and musicians, She’s Gotta Have It asks us to remember what has been lost and what still has the potential to be given up in these intense times of fear and mistrust. She’s Gotta Have It is also one of the best uses of the Netflix format since and. It is at once binge-able and episodic. It features a stunning opening sequence that confirms Myles McNutt’s. Alternating images of Brooklyn past and present, day and night fill the screen over a beautiful jazz score, continually setting the stage for the teleplay that follows.