Carbon 14 dating is a key tool archaeologists use to determine the age of plants and objects made with organic material. But new research shows that commonly accepted radiocarbon dating standards can miss the mark—calling into question historical timelines.
Archaeologist Sturt Manning and colleagues have revealed variations in the radiocarbon cycle at certain periods of time, affecting frequently cited standards used in archaeological and historical research relevant to the southern Levant region, which includes Israel, southern Jordan and Egypt. These variations, or offsets, of up to 20 years in the calibration of precise radiocarbon dating could be related to climatic conditions.
Manning, professor of archaeology at Cornell University and director of the Cornell Tree-Ring Laboratory, is the lead author of “Fluctuating Radiocarbon Offsets Observed in the Southern Levant and Implications for Archaeological Chronology Debates,” published in the Proceedings of the National Academy of Sciences.
Premodern radiocarbon chronologies rely on standardized Northern and Southern Hemisphere calibration curves to obtain calendar dates from organic material. These standard calibration curves assume that at any given time radiocarbon levels are similar and stable everywhere across each hemisphere. The Cornell-led team questioned those assumptions:
“We went looking to test the assumption behind the whole field of radiocarbon dating,” Manning said. “We know from atmospheric measurements over the last 50 years that radiocarbon levels vary through the year, and we also know that plants typically grow at different times in different parts of the Northern Hemisphere. So we wondered whether the radiocarbon levels relevant to dating organic material might also vary for different areas and whether this might affect archaeological dating.”
The authors measured a series of carbon-14 ages in southern Jordan tree rings, with established calendar dates between AD 1610 and 1940. They found that contemporary plant material growing in the southern Levant shows an average offset in radiocarbon age of about 19 years compared to the current Northern Hemisphere standard calibration curve.
Manning noted that “scholars working on the early Iron Age and Biblical chronology in Jordan and Israel are doing sophisticated projects with radiocarbon age analysis, which argue for very precise findings. This then becomes the timeline of history. But our work indicates that it’s arguable their fundamental basis is faulty—they are using a calibration curve that is not accurate for this region.”
Applying their results to previously published chronologies, the researchers show how even the relatively small offsets they observe can shift calendar dates by enough to alter ongoing archaeological, historical, and paleoclimate debates.
“There has been much debate for several decades among scholars arguing for different chronologies sometimes only decades to a century apart—each with major historical implications. And yet these studies … may all be inaccurate since they are using the wrong radiocarbon information,” Manning said.
“Our work,” he added, “should prompt a round of revisions and rethinking for the timeline of the archaeology and early history of the southern Levant through the early Biblical period.”
June, 2018: Daniel Aloi, Cornell University
CAPTION: Juniperus phoenicea sample from Taybet Zaman, Jordan.
The Clarke Exobelt—A Way to Search for ET Civilizations?
A new study published in the Astrophysical Journal by Hector Socas-Navarro, a researcher at the Institute of Astrophysics of the Canaries (IAC), examines the possibility of detecting hypothetical artificial satellites orbiting around other worlds.
Finding life in other parts of the universe has been one of humanity’s constant dreams. For the first time in history the scientific community has hopes based on some degree of possibility that this dream will become a reality in the not-too- distant future. This is, in part, due to the new generation of giant telescopes, presently in the planning phase, with which we hope to be able to make a detailed analysis of the atmospheres of planets beyond the Solar System. For this reason researchers are making efforts to investigate “biomarkers,” which is the term for observable evidence, which we could use to give us firm evidence of life on these planets.
However, it is one thing to find some form of life, but another, very different, to find intelligent civilizations, or technological capacity, which seems even less likely. To begin, we don’t know who we are looking for. We lack “technomarkers” (the analogues of biomarkers, but which reveal the presence of technology). Since the 1980s there have been many searches—so far unsuccessful—for radio signals from other civilizations. This is not surprising, if we remember that radio emissions from a society such as ours would not be detectable at interstellar distances, unless they were deliberately focused in the direction of the receiver. In the scientific literature there have been proposals to look for technomarkers, for instance the well-known “Dyson Spheres,” hypothetical artificial megastructures constructed around a star to collect its light to supply energy to a civilization far more advanced than ours.
An article published in May by the IAC researcher Hector Socas proposed a new technomarker, characterized by the fact that it could be produced by present day technology on Earth. There is a very interesting region in space around planets called the “Clarke Belt” in honor of Arthur C. Clarke, who in 1945 published an article about the use of geostationary orbits for telecommunications. In this belt, orbit the geostationary satellites, which we use for a large number of practical applications.
Socas’ article presents a variety of simulations of “Clarke exobelts” to investigate what would be the imprint they would leave on the light of the parent star as the planet transits across its disk. The optimum conditions for observing them are found for planets in orbit round red dwarf stars, which are also the best places to look for exoplanets in general. In the article published in The Astrophysical Journal, details are given on how such artificial belts can be distinguished from natural rings. Using this technique, current projects and space missions designed to detect exoplanets and their moons and rings could also be used to detect this marker. “It is a search which we will have for nothing” says Hector Socas, and he adds “We have to keep our eyes open, just in case we detect these traces in the data.”
Humanity’s Clarke Belt (our geostationary and geosynchronous satellites) is not densely populated enough to be detected at interstellar distances, at least with our present observing capabilities. Around two-thirds of existing satellites are in the region termed “low orbit,” which means the first few hundred kilometers above the Earth, where space debris is already a significant problem. The Clarke Belt orbit is it 36,000 km above Earth, and it is so far less populated, but the article shows that during recent decades the density of satellites in these orbits has been growing exponentially. If this rate continues our Clarke Belt would be detectable from other stars by the year 2200.
The rate could even be speeded up if access to these orbits was reduced in cost, for example by the new reusable rockets, or by the construction of a future space elevator. Or it could be slowed down if technological advance looked for other priorities. In any case there is an active debate about whether humanity should actively send messages into space or whether, on the contrary, we ought to listen discreetly without revealing our presence. “In this context, the exponential increase in our population of satellites could end up by becoming a signal which could gives us away, whether we like it or not. This is a point which should be taken into account in this debate,” says Socas.
Faced with the question of whether one day we will discover a “Clarke exobelt,” and thereby find an extraterrestrial civilization, the researcher comments that: “It seems unlikely, but it costs nothing to take a look. It is as if someone gave you a lottery ticket. You know that it is very unlikely that you will win, but as you have it, you check up on the result, just in case.”
May, 2018: Héctor Socas Navarro, Institute (firstname.lastname@example.org) Instituto de Astrofísica de Canarias (IAC)
Does Dim Light Make Us Dim-Witted?
Spending too much time in dimly lit rooms and offices may actually change the brain’s structure and hurt one’s ability to remember and learn, indicates groundbreaking research by Michigan State University neuroscientists.
The researchers studied the brains of Nile grass rats (which, like humans, are diurnal and sleep at night) after exposing them to dim and bright light for four weeks. The rodents exposed to dim light lost about 30 percent of capacity in the hippocampus, a critical brain region for learning and memory, and performed poorly on a spatial task they had trained on previously.
The rats exposed to bright light, on the other hand, showed significant improvement on the spatial task. Further, when the rodents that had been exposed to dim light were then exposed to bright light for four weeks (after a month-long break), their brain capacity—and performance on the task—recovered fully.
The study, funded by the National Institutes of Health, is the first to show that changes in environmental light, in a range normally experienced by humans, leads to structural changes in the brain. Americans, on average, spend about 90 percent of their time indoors, according to the Environmental Protection Agency.
“When we exposed the rats to dim light, mimicking the cloudy days of Midwestern winters or typical indoor lighting, the animals showed impairments in spatial learning,” said Antonio ‘Tony’ Nunez, psychology professor and co-investigator on the study. “This is similar to when people can’t find their way back to their cars in a busy parking lot after spending a few hours in a shopping mall or movie theater.’
Nunez collaborated with Lily Yan, associate professor of psychology and principal investigator on the project, and Joel Soler, a doctoral graduate student in psychology. Soler is also lead author of a paper on the findings published in the journal Hippocampus.
Soler said sustained exposure to dim light led to significant reductions in a substance called brain derived neurotrophic factor—a peptide that helps maintain healthy connections and neurons in the hippocampus—and in dendritic spines, or the connections that allow neurons to “talk” to one another.
“Since there are fewer connections being made, this results in diminished learning and memory performance that is dependent upon the hippocampus,” Soler said. “In other words, dim lights are producing dimwits.”
Interestingly, light does not directly affect the hippocampus, meaning it acts first on other sites within the brain after passing through the eyes. Yan said the research team is investigating one potential site in the rodents’ brains—a group of neurons in the hypothalamus that produce a peptide called orexin that’s known to influence a variety of brain functions. One of their major research questions: If orexin is given to the rats that are exposed to dim light, will their brains recover without being re-exposed to bright light?
The project could have implications for the elderly and people with glaucoma, retinal degeneration or cognitive impairments.
“For people with eye disease who don’t receive much light, can we directly manipulate this group of neurons in the brain, bypassing the eye, and provide them with the same benefits of bright light exposure?” Yan said. “Another possibility is improving the cognitive function in the aging population and those with neurological disorders. Can we help them recover from the impairment or prevent further decline?”
February, 2018: Andy Henion, Michigan State University