PREVIOUS “HABITABLE PLANETS” – NEXT “ASTROBIOLOGY” There is on average one planet orbiting every star in the Universe . If this sounds exciting, you might wanna read the previous post in this series. Our Galaxy (the Milky Way) is an immense disk of gas and stars with a diameter of about 100 000 light years, hosting about 100 billion stars and, therefore, also about 100 billion planets. Take a deep breath. Now, it turns out the Milky Way is just one of 100 billion galaxies that populate our Universe, a colossal expanding stretch of spacetime with an age of 13.7 billion years. The math is trivial: There are about 10 000 000 000 000 000 000 000 = 10²² planets out there. This number is extremely large. Apparently larger than the number of grains of sand found in every beach and every desert on Earth. But how many of these planets host life? And in particular, HOW MANY PLANETS HOST INTELLIGENT LIFE WE MIGHT BE ABLE TO COMMUNICATE WITH? In order to estimate the number of technological civilizations that might exist among the stars, in 1961 Frank Drake proposed the following simple equation:

Retraction Watch is a blog that tracks retractions in science -- and it's probably a site you never want your research to be on. To many, retracting your work means that you've committed fraud, and in most cases can be the end of a researcher's career. However, that's not always the case: in fact, retracting your work for the right reasons can even be good for your career and good for science (Lu 2013). Retraction Watch highlights cases where scientists did not retract their work due to fraud, but rather because it was "the right thing."  Here we take the opportunity to further highlight these pieces and the courageous scientists that did the right thing despite an enormous stigma.We believe the future of scholarly communication will be more dynamic than it is today. By definition, this will require more corrections and retractions.  Authorea was built to show the full history of a document, from creation to final publication. We allow annotations of the literature and believe that a more dynamic and robust form of communication is the future -- it's what we're building. Join us!

A revolution has occurred in the last two decades in the world of astrophysics. It all started in the mid ’90s with the first discovery of new worlds around other stars. The term “Extrasolar planet” (or Exoplanet) became widely used to identify planets orbiting a star other than the Sun. A planet is a celestial body massive enough to be bounded by its self gravity (unlike a rock or an asteroid, that are kept together by electromagnetic forces), but not massive enough to produce energy through nuclear fusion (as stars do). Planetary scientists have confirmed the existence of more than 1500 exoplanets and have identified a few thousand exoplanet candidates that require more investigation before they can join the planet club (see exoplanets.org for the most recent figures). The most remarkable discoveries came only in the last couple of years thanks to the Kepler space telescope. This amazing instrument has been patiently looking for the extremely tiny dimming induced by the passage of a planet in front of its host star. The wealth of data provided by Kepler has revealed an astonishing fact: “When you wish upon a star, you are wishing upon a star with planets” (W. Borucki). There is on average ONE PLANET ORBITING EVERY STAR IN THE UNIVERSE . Just in our Galaxy this means we have 100 billion planets. Since we have about 100 billion galaxies in the Universe, there are about 10,000,000,000,000,000,000,000 = 10²² planets out there.

In this short post series I try to tackle one of the biggest questions out there: ARE WE ALONE? The reasoning leads to some radical implications for the VERY NEAR FUTURE OF HUMANKIND. Read till the end and feel free to comment as you go. Hopefully this will spark interesting discussions. 1. Habitable Planets How many habitable planets exist in the Universe? 2. The Drake Equation How to estimate the number of technological civilizations in our Galaxy? 3. Astrobiology Is biological life common in the Universe? 4. The Fermi Paradox Is intelligent life common in the Universe? And if yes, does it last? 5. Interactive Drake Equation Use your own intuition to calculate the chance of being alone or not

Einstein published in 1916 a paper containing the prediction of the existence of gravitational waves. It has just one author (A.E. himself) and consists of a few pages of text and equations . Fast forward exactly 100 years, the LIGO collaboration announced in a paper that they observed what Einstein had predicted. The paper has more than 1000 co-authors and it condenses, in just a few pages of text, equations and figures, an enormous amount of technical information .

PREVIOUS “DRAKE EQUATION” – NEXT “FERMI PARADOX” We are thinking creatures living on a planet orbiting a pretty common star in a pretty common galaxy. Our home planet has been around for about 4.5 billion years, while the Universe is about 13.7 billion years old. We just learned that there are about 1 000 000 000 000 000 000 000 = 10²¹ planets potentially similar to the Earth in the cosmos, a number larger than the amount of grains of sand found on every beach and every desert on Earth. ARE WE ALONE? To answer this question in 1961 scientist Frank Drake formulated his famous equation, which I discussed in the previous post of this series. The Drake equation calculates the number N of communicative civilizations in our Galaxy. In its 2015 form it reads: N ≈ 2 fl fi fc L

Authorea is on a mission to build the best research document editor and publishing platform ever made. We believe that the best way to accelerate scientific discovery is to give full control of document creation and distribution to the researcher, and that the best way to do that is to build a web-based editor that enables researchers to collaborate and disseminate their work seamlessly.Authorea,  like many research projects, started with a question: Why is the research writing process so slow? We started with the rough notion that the internet age was failing to deliver optimal tools for things like collaborative writing and submitting works to publishers.  We refined this core idea and launched Authorea two years ago.Since then, we've devoted tens of thousands of hours to understand how to build software that makes it easier for researchers to do groundbreaking work. At the beginning of this year, we started building our new editor -- Authorea Beta -- the editor that will bring Authorea to the mainstream to benefit researchers in every discipline.Today, we're happy to share with you Authorea Beta. Writing research online has tremendous potential for collaboration, dissemination, and discovery. We're here to bring writing online to researchers and we'll be with you every step. 

A BIG DISCOVERY On 14 September 2015 at 4:50:45 AM Eastern standard time, the LIGO experiment detected for the first time the passage of gravitational waves. Scientists saw a very specific pattern of stretching and compression of space-time called a “chirp”. The detection was done independently at the two locations of the experiment, one in Hanford (Washington) and the other one in Livingstone (Louisiana). This amazing discovery has occurred almost exactly 100 years after Albert Einstein published his General Theory of Relativy , and represents the last verification of this beautiful theory of gravity. How did the waves look like? Glassy and double-overhead!

FABIO, WHEN DID YOU DECIDE TO GO WATCH AN ECLIPSE IN THE ARCTIC? I’ve been feeling this urge to visit the northernmost parts of Earth for a while now. My PhD in Stockholm gave me the opportunity to explore the Norwegian coastline and Lapland, but the Arctic was a different story. A sort of forbidden dream. Then last year I started a postdoc at Yale, in the research group led by John Wettlaufer, who’s an expert on sea ice and the Arctic. When I heard there was gonna be a total solar eclipse at Svalbard I knew I had to go. WHERE IS SVALBARD, EXACTLY? Svalbard is an archipelago situated about half way between continental Norway and the North Pole, and it is an outpost for research and arctic exploration. In Longyearbyen, a little city of about 2000 people, and Svalbard’s capital, there is the world’s northernmost institution for higher education and research: the University Center in Svalbard.

The power of the atomAt the beginning of the 20th century, major advancements in our understanding of fundamental physics led scientists to the discovery of nuclear energy. An unprecedented amount of power could in principle be released by combining (nuclear fusion) or breaking (nuclear fission) certain atomic species under special conditions. Nuclear fusion in particular was understood to be the process powering the immense luminosity of stars, including our Sun. Nuclear fusion is the energy source illuminating our Universe.Why so much energy?Burning fossil fuels releases chemical energy. This chemical energy is stored in the mild electromagnetic interactions between atoms in a compound. Nuclear energy, on the other hand, comes from the very central regions of the atom.  As the name suggests, it is stored in the nuclei, which are kept together by the strong force. The strong force is much stronger than all the other forces, including the electromagnetic one. As a result, nuclear fuel has an energy density about ten million times larger than chemical fuel. If your car was running on nuclear fuel, its gas mileage would be something like hundreds of millions of MPG. From light to darknessThe physics revolution that characterized the first three decades of the 20th century and led to the development of quantum mechanics and nuclear physics, was followed by the second World War. In 1942, the United States started a very ambitious project to build a nuclear weapon. The Manhattan Project, led by Robert Oppenheimer and gathering some of the best physicists on the planet, culminated with the successful Trinity experiment in 1945 (Fig.\ref{982837}). The first detonation of a nuclear weapon was the most shocking demonstration of the great power of science and the scientific method. Only less than a month later, two nuclear bombs were dropped over the Japanese cities of Hiroshima and Nagasaki, resulting in the end of WWII and the death of hundreds of thousands of people. The sheer destruction inflicted by the atomic bomb left an indelible mark on humankind's consciousness, formally starting a new era in the history of man. An era of greater responsibility. While no nuclear weapons have been purposely used in war ever since, more than 2000 nuclear tests have been performed after the Trinity, Hiroshima and Nagasaki explosions.  

RISE AND FALL OF THE BIGGEST DISCOVERY OF THE CENTURY HIGHLIGHTS THE IMPORTANCE OF OPEN, COLLABORATIVE SCIENCE. On 17 March 2014 BICEP2, a South Pole based experiment aimed at studying the very first moments of the universe, made a sensational announcement. They claimed to have detected for the first time the signature of an extremely rapid expansion of space that occurred right after the universe’s birth. This expansion, also called inflation, is believed to be responsible for the existence of large-scale structures like clusters of galaxies, as well as to explain why the properties of the universe appear to be the same for all observers. If confirmed, the existence of inflation would represent the first evidence of a fundamental connection between gravity (general relativity) and quantum physics.

How researchers communicate with one another and the world has changed very little over the last 350 years. Attempts to improve the process have been implemented throughout the years, not all of which have been to the benefit of research. Here we highlight some policies implemented by various publishers that we believe are antithetical to research communication and what we're doing to try to fix them.

A recent article titled The spin rate of pre-collapse stellar cores: wave driven angular momentum transport in massive stars was written on Authorea and submitted to the Astrophysical Journal (ApJ) and to the arXiv as a pre-print. While waiting on peer review from the ApJ, the authors want to test Authorea as a platform for OPEN PEER-REVIEW. By going to the document’s page, you can comment on a section, figure, observation, sentence, or the whole piece. The authors and other commenters can respond and further the discussion. And it’s all out in the open, just how science was meant to be. But it doesn’t stop there. You can also view full-size, high-resolution versions of the paper’s figures, as well as easily follow links in the References at the bottom of the page. In the paper, show for the first time how internal gravity waves, excited in the turbulent layers of stars at least ten times larger than the Sun, can radically change their internal rotation rate. In particular, these waves – somewhat analogous to ocean waves – can determine how rapidly the stellar core spins around its axis when the star is about to die and become a supernova. The spin of a pre-supernova core is important because it deeply affects the stellar explosion and determines the rotation rate of the stellar remnant (neutron star or black hole).

OPEN SCIENCE “Open science commonly refers to efforts to make the output of PUBLICLY FUNDED RESEARCH MORE WIDELY ACCESSIBLE in digital format to the scientific community, the business sector, or society more generally” writes the Organisation for Economic Cooperation and Development (OECD) in its newly released study “Making Open Science a Reality”. In the digital age the role of tools like Authorea is to increase the efficiency of research as well of its diffusion. The benefits of open science identified by the OECD are multiple: 1. Reducing duplication costs in collecting, creating, transferring and reusing data and scientific material; allowing more research from the same data; and multiplying opportunities for domestic and global participation in the research process. 2. The greater scrutiny offered by open science allows a more accurate verification of research results. 3. Increased access to research results (in the forms of both publications and data) can foster spillovers not only to scientific systems but also innovation systems more broadly. (Firms and individuals may use and reuse scientific outputs to produce new products and services.) 4. Open science also allows the closer involvement and participation of citizens.

A document by Matteo Cantiello. Click on the document to view its contents.

What better way to argue for the benefits of open access than to publish a research paper with restricted access rights? While open access has been shown to be beneficial for researchers and the public by numerous studies (some of which are listed below), these same papers make it pretty self-evident that the move to full open access is going to take some time. It is true that more and more open access articles appear each year -- some predict that the volume of open access publications will overtake subscription publications by 2018 -- yet despite the increase in publishers and researchers adopting open access as a modus operandi, paywalls still remain on the vast majority of articles, including many which tout the benefits of open research. The following is a list of articles that while advocating for open research remain, ironically, behind paywalls:

Scholarly communication is advancing culturally and technologically towards a better future.  There are an increasing number of disciplines and people publishing their content under open-access licenses, publishing their work as preprints, and publishing different types of content from data to posters to single figures. We're happy to be part of this push towards a more dynamic and transparent system of communication. In fact, it's one of the reasons we exist--to improve how leading researchers and student's alike communicate their ideas amongst each other and to the world. These are the world's most important ideas, how we communicate them is important.

MLT These notes are mostly inspired from reading Cox & Giuli (“Principles of stellar structure”); some insights are from A.Maeder (“Physics, formation and evolution of rotating stars”) and Kippenhahn & Weigert (“Stellar Structure and Evolution”) Pressure Scale Height In hydrostatic equilibrium we can define the total pressure scale height, $\hp$, as -{\D r} \equiv {\hp} = {\p} where $\p$ is the total pressure ($ + $). The pressure scale height is a measure of the distance over which the pressure changes by an appreciable fraction of itself.