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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:

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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.

What is radiocarbon dating Earth EarthSky

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.

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