A time zone is a region of the globe that observes a uniform standard time for legal, commercial, and social purposes. Time zones tend to follow the__16__ of countries and their subdivisions because it is convenient for areas in close communication and interaction to keep the same time. From east to west, four time zones, __17__ , Eastern, Central, Mountain, and Pacific, spread across the continental United States. Noticeably, a recent study found that living on the “wrong” side of a time zone can be __18__ to one’s health. 

       The researchers tracked about one million people’s sleep times. They found that bedtimes shift from east to west, with a sharp __19__ happening once one crosses into a new time zone. The key to understanding the finding is knowing the link between time zones and local sunset times. Traveling east to west, one can find sunrise and sunset times get later. In general, people on the late sunset side of a time zone are more likely to be sleep __20__ , more likely to sleep less than 6 hours, and less likely to sleep at least 8 hours. Given what is known about the importance of sleep for good physical and mental health, it is no surprise that a greater incidence of health problems, including overweight, diabetes, heart attack, and breast cancer, was found in areas where the sun sets later.

       When Howard Carter unsealed the tomb of Tutankhamun in 1922, he set off a series of discoveries that would capture the imagination of the world. Almost a century later, a team of scientists has now completed a decade-long project of a painstaking study and conservation of the tomb that has not only solved some mysteries but also raised new questions. 

       One of the hallmarks of the tomb is the ubiquitous brown freckles across all of the wall paintings, present when Carter opened the burial chamber. A study of the spots revealed that they are microbial in origin. DNA analysis of swabs taken from the tomb walls turned up modern organisms, but electron microscope imaging showed no remnants of the original organisms that created the spots. The conservators theorize that because Tutankhamun died unexpectedly, the tomb might be prepared in a rush, and the moisture retained in the freshly plastered walls allowed microbes to thrive in the tomb after it was sealed. However, the spots have been dead for a long time—a fact confirmed by comparisons of photographs taken immediately after the tomb opening with those from present day.

       The constant presence of dust is another serious problem. Fine-grained and thirsty, the desert dust brought in by visitors clings to every tomb surface, and is made even more tenacious after absorbing humidity from human breath. What’s even worse is that there was no damage-free remedy for the fine, streaky veils of dust that accumulated on the tomb’s fragile paintings. To tackle the dust problem, the conservators installed a sophisticated air filtration and ventilation system which not only filters the dusty scourge out of the tomb environment, but also prevents excess particulates from wafting in. The regular exchange of air has also stabilized temperature and humidity within the tomb. And, upon removing the old viewing platform over the burial chamber to mount the system’s air vents, project workers were surprised to find scraps of paper with entreaties to Tutankhamun for blessings and calls for pharaonic curses on other people.

       Even though the most thorough inspection of Tutankhamun’s tomb has now completed, several questions about its future still remain. The long-term impact of dust is still unknown. Found to be comprised primarily of calcium, magnesium, aluminum, and phosphorous, it’s unclear how the dust may chemically interact with the natural minerals in the paints and pigments on the tomb walls over a longer period of time. The physical dangers of increased flooding linked to climate change is another concern and has not yet been considered. Although the tomb is safe from direct flooding, if adjacent tombs flood, vapor could seep through the walls and rip apart the tomb’s plastered walls and their paintings.

       Tourism remains the greatest immediate threat to the tomb. Despite the existence of a high-quality, ultradetailed replica just a mile away, it’s unclear whether the Egyptian government will ultimately restrict public access to the original tomb (and therefore reduce a guaranteed revenue stream). The conservators hope that, at the very least, the recent conservation work on Tutankhamun’s tomb can result in a higher awareness of its significance for visitors in the future.