First observational tests of eternal inflation theory

According to eternal inflation theory, new universes bubble into existence all the time, within a space called the “multiverse”.

Hiranya Peiris, a cosmologist at University College London, and her colleagues have now worked out that when bubble universes are created adjacent to our own, they may leave a characteristic pattern in the Cosmic Microwave Background radiation revealed by the Planck telescope.

They explain:

In the picture of eternal inflation, our observable universe resides inside a single bubble nucleated from an inflating false vacuum. Many of the theories giving rise to eternal inflation predict that we have causal access to collisions with other bubble universes, providing an opportunity to confront these theories with observation. We present the results from the first observational search for the effects of bubble collisions, using cosmic microwave background data from the WMAP satellite. Our search targets a generic set of properties associated with a bubble collision spacetime, which we describe in detail. We use a modular algorithm that is designed to avoid a posteriori selection effects, automatically picking out the most promising signals, performing a search for causal boundaries, and conducting a full Bayesian parameter estimation and model selection analysis. We outline each component of this algorithm, describing its response to simulated CMB skies with and without bubble collisions. Comparing the results for simulated bubble collisions to the results from an analysis of the WMAP 7-year data, we rule out bubble collisions over a range of parameter space. Our model selection results based on WMAP 7-year data do not warrant augmenting LCDM with bubble collisions. Data from the Planck satellite can be used to more definitively test the bubble collision hypothesis.

Full text at

Does natural selection still function in human populations?

Whether and how human populations exposed to the agricultural revolution are still affected by Darwinian selection remains controversial among social scientists, biologists, and the general public. Although methods of studying selection in natural populations are well established, our understanding of selection in humans has been limited by the availability of suitable datasets. Here, we present a study comparing the maximum strengths of natural and sexual selection in humans that includes the effects of sex and wealth on different episodes of selection. Our dataset was compiled from church records of preindustrial Finnish populations characterized by socially imposed monogamy, and it contains a complete distribution of survival, mating, and reproductive success for 5,923 individuals born 1760–1849. Individual differences in early survival and fertility (natural selection) were responsible for most variation in fitness, even among wealthier individuals. Variance in mating success explained most of the higher variance in reproductive success in males compared with females, but mating success also influenced reproductive success in females, allowing for sexual selection to operate in both sexes. The detected opportunity for selection is in line with measurements for other species but higher than most previous reports for human samples. This disparity results from biological, demographic, economic, and social differences across populations as well as from failures by most previous studies to account for variation in fitness introduced by nonreproductive individuals. Our results emphasize that the demographic, cultural, and technological changes of the last 10,000 y did not preclude the potential for natural and sexual selection in our species.

via Natural and sexual selection in a monogamous historical human population.

Organic Synthesis via Irradiation and Warming of Ice Grains in the Solar Nebula

New experimental results imply that organic compounds are natural by-products of protoplanetary disk evolution and should be important ingredients in the formation of all planetary systems, including our own.

Complex organic compounds, including many important to life on Earth, are commonly found in meteoritic and cometary samples, though their origins remain a mystery. Scientists examined whether such molecules could be produced within the solar nebula by tracking the dynamical evolution of ice grains in the nebula and recording the environments to which they were exposed. They found that icy grains originating in the outer disk, where temperatures were less than 30 kelvin, experienced ultraviolet irradiation exposures and thermal warming similar to that which has been shown to produce complex organics in laboratory experiments.

from Science Journal: Organic Synthesis via Irradiation and Warming of Ice Grains in the Solar Nebula.

The Story of Earth is retold in a new book due out tomorrow

Another History of the Earth book is due out tomorrow.

Dr. Robert M. Hazen, a research scientist at the Carnegie Institution of Washington’s Geophysical Laboratory and Clarence Robinson Professor of Earth Science at George Mason University, is the author of more than 300 articles and books on science, history, and music.

In his new book, The Story of Earth: The First 4.5 Billion Years, from Stardust to Living Planet, he tells the story of how Earth evolved from first atom to molecule, mineral to magma, granite crust to single cell to verdant living landscape.

The publishers call it a “radical new approach to Earth’s biography”. It explains how what Hazen calls “co-evolution” of the geosphere and biosphere—of rocks and living matter—has shaped our planet.

An interesting feature of the book is the description of pioneering men and women behind the sciences. Readers will meet black-market meteorite hawkers of the Sahara Desert, the gun-toting Feds who guarded the Apollo missions’ lunar dust, and the World War II Navy officer whose super-pressurized “bomb”—recycled from military hardware—first simulated the molten rock of Earth’s mantle. As a mentor to a new generation of scientists, Hazen introduces the intrepid young explorers whose dispatches from Earth’s harshest landscapes will revolutionize geology.

Earth Day 2012 – Mobilize the Earth with the Earth Day Network

On April 22, more than one billion people around the globe will participate in Earth Day 2012 and help Mobilize the Earth™. People of all nationalities and backgrounds will voice their appreciation for the planet and demand its protection. Together we will stand united for a sustainable future and call upon individuals, organizations, and governments to do their part.

Attend a local Earth Day event and join one of our Earth Day campaigns as we collect A Billion Acts of Green® and elevate the importance of environmental issues around the world. Together we will Mobilize the Earth™ on April 22 and demand change.

via Earth Day 2012 – Mobilize the Earth | Earth Day Network.