Nobel Prize In Physics 2017: Gravitational Waves

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics 2017 with one half to Rainer Weiss, LIGO/VIRGO Collaboration, and the other half jointly to Barry C. Barish, LIGO/VIRGO Collaboration and Kip S. Thorne, LIGO/VIRGO Collaboration “for decisive contributions to the LIGO detector and the observation of gravitational waves.”

Gravitational waves finally captured

On 14 September 2015, the universe’s gravitational waves were observed for the very first time. The waves, which were predicted by Albert Einstein a hundred years ago, came from a collision between two black holes. It took 1.3 billion years for the waves to arrive at the LIGO detector in the USA.

The signal was extremely weak when it reached Earth, but is already promising a revolution in astrophysics. Gravitational waves are an entirely new way of observing the most violent events in space and testing the limits of our knowledge.

LIGO, the Laser Interferometer Gravitational-Wave Observatory, is a collaborative project with over one thousand researchers from more than twenty countries. Together, they have realised a vision that is almost fifty years old. The 2017 Nobel Laureates have, with their enthusiasm and determination, each been invaluable to the success of LIGO. Pioneers Rainer Weiss and Kip S. Thorne, together with Barry C. Barish, the scientist and leader who brought the project to completion, ensured that four decades of effort led to gravitational waves finally being observed.

In the mid-1970s, Rainer Weiss had already analysed possible sources of background noise that would disturb measurements, and had also designed a detector, a laser-based interferometer, which would overcome this noise. Early on, both Kip Thorne and Rainer Weiss were firmly convinced that gravitational waves could be detected and bring about a revolution in our knowledge of the universe.

Gravitational waves spread at the speed of light, filling the universe, as Albert Einstein described in his general theory of relativity. They are always created when a mass accelerates, like when an ice-skater pirouettes or a pair of black holes rotate around each other. Einstein was convinced it would never be possible to measure them. The LIGO project’s achievement was using a pair of gigantic laser interferometers to measure a change thousands of times smaller than an atomic nucleus, as the gravitational wave passed the Earth.

So far all sorts of electromagnetic radiation and particles, such as cosmic rays or neutrinos, have been used to explore the universe. However, gravitational waves are direct testimony to disruptions in spacetime itself. This is something completely new and different, opening up unseen worlds. A wealth of discoveries awaits those who succeed in capturing the waves and interpreting their message.

Astronomers Reveal Evidence Of Dynamical Dark Energy

An international research team, including astronomers from the University of Portsmouth, has revealed evidence of dynamical dark energy.

The discovery, recently published in the journal Nature Astronomy, found that the nature of dark energy may not be the cosmological constant introduced by Albert Einstein 100 years ago, which is crucial for the study of dark energy.

Lead author of the study Professor Gong-Bo Zhao, from the Institute of Cosmology and Gravitation (ICG) at the University of Portsmouth and the National Astronomical Observatories of China (NAOC), said: “We are excited to see that current observations are able to probe the dynamics of dark energy at this level, and we hope that future observations will confirm what we see today.”

Co-author Professor Bob Nichol, Director of the ICG, said: “Since its discovery at the end of last century, dark energy has been a riddle wrapped in an enigma. We are all desperate to gain some greater insight into its characteristics and origin. Such work helps us make progress in solving this 21st Century mystery.”

Revealing the nature of dark energy is one of key goals of modern sciences. The physical property of dark energy is represented by its Equation of State (EoS), which is the ratio of pressure and energy density of dark energy.

In the traditional Lambda-Cold Dark Matter (LCDM) model, dark energy is essentially the cosmological constant, i.e., the vacuum energy, with a constant EoS of -1. In this model, dark energy has no dynamical features.

In 2016, a team within the SDSS-III (BOSS) collaboration led by Professor Zhao performed a successful measurement of the Baryonic Acoustic Oscillations (BAO) at multiple cosmic epochs with a high precision.

Based on this measurement and a method developed by Professor Zhao for dark energy studies, the team found an evidence of dynamical dark energy at a significance level of 3.5 sigma. This suggests that the nature of dark energy may not be the vacuum energy, but some kind of dynamical field, especially for the quintom model of dark energy whose EoS varies with time and crosses the -1 boundary during evolution, according to NAOC.

The dynamics of dark energy needs to be confirmed by next-generation astronomical surveys. The team points to the upcoming Dark Energy Spectroscopic Instrument (DESI) survey, which aims to begin creating a 3D cosmic map in 2018.

In the next five to ten years, the world largest galaxy surveys will provide observables which may be key to unveil the mystery of dark energy.

The new study was supported by the National Natural Science Foundation of China (NSFC), Chinese Academy of Sciences and a Royal Society Newton Advanced Fellowship.

Professor Nichol added: “This work is the culmination of many years of work in collaboration between scientists in China and the UK. Gong-Bo is one of our brightest stars holding a joint position between NAOC and here at the ICG.”

Did Life On Earth Start Due To Meteorites Splashing Into Warm Little Ponds?

Life on Earth began somewhere between 3.7 and 4.5 billion years ago, after meteorites splashed down and leached essential elements into warm little ponds, say scientists at McMaster University and the Max Planck Institute in Germany. Their calculations suggest that wet and dry cycles bonded basic molecular building blocks in the ponds’ nutrient-rich broth into self-replicating RNA molecules that constituted the first genetic code for life on the planet.

The researchers base their conclusion on exhaustive research and calculations drawing in aspects of astrophysics, geology, chemistry, biology and other disciplines. Though the “warm little ponds” concept has been around since Darwin, the researchers have now proven its plausibility through numerous evidence-based calculations.

Lead authors Ben K.D. Pearce and Ralph Pudritz, both of the McMaster’s Origins Institute and its Department of Physics and Astronomy, say available evidence suggests that life began when the Earth was still taking shape, with continents emerging from the oceans, meteorites pelting the planet — including those bearing the building blocks of life — and no protective ozone to filter the Sun’s ultraviolet rays.

“No one’s actually run the calculation before,” says Pearce. “This is a pretty big beginning. It’s pretty exciting.”

“Because there are so many inputs from so many different fields, it’s kind of amazing that it all hangs together,” Pudritz says. “Each step led very naturally to the next. To have them all lead to a clear picture in the end is saying there’s something right about this.”

Their work, with collaborators Dmitry Semenov and Thomas Henning of the Max Planck Institute for Astronomy, has been published today in the Proceedings of the National Academy of Science.

“In order to understand the origin of life, we need to understand Earth as it was billions of years ago. As our study shows, astronomy provide a vital part of the answer. The details of how our solar system formed have direct consequences for the origin of life on Earth,” says Thomas Henning, from the Max Planck Institute for Astronomy and another co-author.

The spark of life, the authors say, was the creation of RNA polymers: the essential components of nucleotides, delivered by meteorites, reaching sufficient concentrations in pond water and bonding together as water levels fell and rose through cycles of precipitation, evaporation and drainage. The combination of wet and dry conditions was necessary for bonding, the paper says.

In some cases, the researchers believe, favorable conditions saw some of those chains fold over and spontaneously replicate themselves by drawing other nucleotides from their environment, fulfilling one condition for the definition of life. Those polymers were imperfect, capable of improving through Darwinian evolution, fulfilling the other condition.

“That’s the Holy Grail of experimental origins-of-life chemistry,” says Pearce.

That rudimentary form of life would give rise to the eventual development of DNA, the genetic blueprint of higher forms of life, which would evolve much later. The world would have been inhabited only by RNA-based life until DNA evolved.

“DNA is too complex to have been the first aspect of life to emerge,” Pudritz says. “It had to start with something else, and that is RNA.”

The researchers’ calculations show that the necessary conditions were present in thousands of ponds, and that the key combinations for the formation of life were far more likely to have come together in such ponds than in hydrothermal vents, where the leading rival theory holds that life began in roiling fissures in ocean floors, where the elements of life came together in blasts of heated water. The authors of the new paper say such conditions were unlikely to generate life, since the bonding required to form RNA needs both wet and dry cycles.

The calculations also appear to eliminate space dust as the source of life-generating nucleotides. Though such dust did indeed carry the right materials, it did not deposit them in sufficient concentration to generate life, the researchers have determined. At the time, early in the life of the solar system, meteorites were far more common, and could have landed in thousands of ponds, carrying the building blocks of life. Pearce and Pudritz plan to put the theory to the test next year, when McMaster opens its Origins of Life laboratory that will re-create the pre-life conditions in a sealed environment.

“We’re thrilled that we can put together a theoretical paper that combines all these threads, makes clear predictions and offers clear ideas that we can take to the laboratory,” Pudritz says.