New Worlds: How to trace the history of the Universe

astronomers from Tel Aviv, Beijing, Paris suggest that history of expanding Universe can be traced by observing massive black holes.

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November 24, 2013 03:16
3 minute read.
Space (illustrative).

space 311. (photo credit: REUTERS)

A group of astronomers from Tel Aviv, Beijing and Paris suggest that the history of the expanding Universe can be traced by observing a special king of massive black holes. The scientists come from the Chinese Academy of Sciences’ Institute of High Energy Physics (IHEP), the Observatoire de Paris and Tel Aviv University. The group was led by Dr. Jian-Min Wang of the IHEP, Prof. Hagai Netzer from TAU and Dr. David Valls-Gabaud from Paris.

They investigated the properties of a special type of active black holes that reside in the centers of many galaxies. The mass of such black holes ranges from about a million to several billions times the mass of the Sun. They are observed during times when they absorb large amounts of gas from their surroundings which cause them to shine to levels up to 1,000 times the energy produced by a large galaxy containing 100 billion stars.

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The fact that we live in an accelerating expanding Universe earned scientists a Nobel Prize in 2011 for work they did in the late Nineties. However, measuring the rate of acceleration at very large distances is highly challenging and very problematic. The new paper suggests a method, based on the properties of black holes, which will improve the accuracy of such measurements, the team said. The article illustrates how to implement the method over a wide range of distances that can be translated into measuring the rate of expansion of the Universe at very early times.

The new method makes use of the properties of those black holes that absorb gas at the highest possible rate and, therefore, are the most luminous black holes in their mass group. The paper shows that the amount of energy emitted in the process of accretion is proportional to the black hole mass. Thus, measuring the mass using well-established methods enables to derive the amount of energy released in the vicinity of the black hole. Measuring the fraction of this radiation that reaches the Earth, using ground-based telescopes, can be used to derive the distance to the black hole and also the time in the history of the Universe when the radiation was emitted. Such measurements, over a range of distances, can be used to derive the rate of acceleration of the Universe.

MUSICAL MISTAKES Teens listening to their preferred music while driving commit a greater number of errors and miscalculations, according to a new study from Ben-Gurion University of the Negev researchers that was recently published in Journal of Accident Analysis and Prevention.

Male novice drivers in particular make more frequent and serious mistakes listening to their preferred music than their less aggressive, female counterparts, the researchers noted.

The BGU study evaluated 85 young novice drivers accompanied by a researcher/ driving instructor. Each driver took six challenging, 40-minute trips – two with music from their own playlists; two with background music designed to increase driver safety (easy listening, soft rock, light jazz) and two additional trips without any music.

The study was conducted by BGU director of music science research Warren Brodsky and researcher Zack Slor to assess distraction by measuring driver deficiencies (miscalculation, inaccuracy, aggressiveness, and violations) and decreased vehicle performance.

When the teen drivers listened to their preferred music, virtually all (98 percent) demonstrated an average of three deficient driving behaviors in at least one of the trips. Nearly a third of those (32%) needed a sudden, verbal warning or command for action, and 20% an assisted steering or braking maneuver to prevent an imminent accident. These errors included speeding, tailgating, careless lane switching, passing vehicles and one-handed driving.

Without any music, 92 percent made errors. However, when driving with an alternative music background designed by Brodsky and Israeli music composer Micha Kisner, deficient driving behaviors and mechanical events decreased by onefifth.

“Most drivers worldwide prefer to listen to music in a car and those between ages 16 to 30 choose driving to pop, rock, dance, hip-hop and rap,” Brodsky explained. “Young drivers also tend to play this highly energetic, fast-paced music very loudly – approximately 120 to 130 decibels. Drivers in general are not aware that as they get drawn-in by a song, they move from an extra-personal space involving driving tasks, to a more personal space of active music listening.”


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