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What Is Dark Matter? Roughly 80% of the mass of the universe is made up of material that scientists cannot directly observe. Known as dark matter, this bizarre ingredient does not emit light or energy. So why do scientists think it dominates? Since at least the 1920s, astronomers have hypothesized that the universe contains more matter than seen by the naked eye. Support for dark matter has grown since then, and although no solid direct evidence of dark matter has been detected, there have been strong possibilities in recent years. "Motions of the stars tell you how much matter there is," Pieter van Dokkum, a researcher at Yale University, said in a statement. "They don't care what form the matter is, they just tell you that it's there." Van Dokkum led a team that identified the galaxy Dragonfly 44, which is composed almost entirely of dark matter. The familiar material of the universe, known as baryonic matter, is composed of protons, neutrons and electrons

Introduction to Quantum Field Theory in Curved Spacetime Prerequisites, Timetable, Outline, Literature, and more ... Summary and Overview The main aim of this course is to explain what are (some of) the obstacles that one faces when trying to generalise the standard formalism and procedures of Minkowski space Poincare-covariant QFT to curved spacetimes, and to illustrate the new phenomena that one encounters by some typical and important examples: particle creation by time-dependent gravitational fields, the Unruh effect, and (some elementary aspects of) Hawking black hole radiation and black hole thermodynamics. Many of the key-issues can already be understood in a purely quantum-mechanical context by studying the Heisenberg picture quantisation of a time-dependent harmonic oscillator, so I will spend some time to discuss the issue of quantisation ambiguities, Bogoliubov transformations, mode creation etc., in this setting. When moving on to field theory, we will consider the simplest

Using a machine-learning algorithm, MIT researchers have identified a powerful new antibiotic compound. In laboratory tests, the drug killed many of the world’s most problematic disease-causing bacteria, including some strains that are resistant to all known antibiotics. It also cleared infections in two different mouse models. The computer model, which can screen more than a hundred million chemical compounds in a matter of days, is designed to pick out potential antibiotics that kill bacteria using different mechanisms than those of existing drugs. “We wanted to develop a platform that would allow us to harness the power of artificial intelligence to usher in a new age of antibiotic drug discovery,” says James Collins, the Termeer Professor of Medical Engineering and Science in MIT’s Institute for Medical Engineering and Science (IMES) and Department of Biological Engineering. “Our approach revealed this amazing molecule which is arguably one of the more powerful antibiotics that has

The mediocre teacher tells. The good teacher explains. The superior teacher demonstrates. The great teacher inspires. ’ A teacher has the power to transform souls and touch someone’s life in a positive way. It is one of the noblest of professions that deal with life-changing and destiny-altering powers. The teacher has the present as raw material on which she will finally carve and design the future … the children. It’s an ever evolving yet challenging and lifelong learning environment of which we are an integral part. Teaching is a chance to touch someone’s life in a positive way. Teachers are the pillars of society for they educate and mould the future citizens of a country. Teaching, like any other activity, emerges from ones inwardness. Motivating and exciting students is the key. Passion for teaching is innate. At the core of caring relationships are positive and high expectations that not only structure and guide behaviours, but also challenge students to perform what they believ

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The mathematical physicist Freeman Dyson was famed for his visionary ideas that stretched far beyond pure science. Hamish Johnston looks at the life of a scientist who was never afraid to speak his mind The British-born mathematical physicist and public intellectual Freeman Dyson, who died on 28 February 2020 at the age of 96, was one of the most celebrated figures in 20th-century physics. He had spent most of his professional life at the Institute for Advanced Study (IAS) in Princeton, New Jersey, where he was a professor emeritus and remained active until his final few days. Dyson died at a hospital near Princeton, due to complications from a fall, according to his son, the science historian George Dyson. Dyson began his career in the 1940s, making important contributions to the development of quantum electrodynamics (QED) . Early on, however, he broadened his interests to include nuclear reactors, space travel, climate and biology – both on Earth and elsewhere in the cosmos. Dyson a

Just as physics is not a list of facts about the world, history is not a list of names and dates. It is a way of thinking that can be powerful and illuminating   Some things about physics aren’t well covered in a physics education. Those are the messy, rough edges that make everything difficult: dealing with people, singly or in groups; misunderstandings; rivals and even allies who won’t fall in line. Physicists often do not see such issues as contributing to science itself. But social interactions really do influence what scientists produce. Often physicists learn that lesson the hard way. Instead, they could equip themselves for the actual collaborative world, not the idealized solitary one that has never existed. History can help. An entire academic discipline—history of science—studies the rough edges. We historians of science see ourselves as illustrating the power of stories. How a community tells its history changes the way it thinks about itself. A historical perspective on sci

A couple of weeks back I posted an answer to a question from a Twitter follower’s child, who asked “How Strong Is Space?” That was fun, so here’s another kid-question answered, this one from my own eight-year-old who goes by “The Pip” for Internet purposes. The other night, he asked “Why can’t atoms touch each other?” I’m not sure the exact reason why he asked this, but the phrasing suggests it’s related to the observation that there’s almost always some microscopic empty space between things that appear to be touching on a macroscopic scale. Possibly it’s even connected to the “Atoms are mostly empty space” idea that Ethan talked about recently. The short and simple version of the answer is that it’s not really correct to think of atoms as solid objects like little balls that can be forced into physical contact with one another. Most of the “size” of an atom is just the electron cloud that surrounds the nucleus, and that’s not a solid thing— it will shift around in response to electri

I greatly enjoyed David Kaiser’s How the Hippies Saved Physics (here’s my review from 2011), so when I ran across a mention of this new book with “Quantum” in the title, I immediately sought out a copy. This sort of thing is highly relevant to my interests. Kaiser is a professor at MIT with a joint appointment in both physics and history of science, and as you would expect this collection of essays splits time between those two fields. The book contains a handful of pieces relating to Kaiser’s work in physics, chiefly about a “cosmological” test of quantum physics, using light from distant quasars as a random number generator for a Bell’s Inequality test (I talked briefly about this idea in the context of football in 2015). There are also a larger number of pieces primarily about the historical and social context of physics, mostly in the mid-to-late 20th century. Almost all of these were previously published (I think there’s only one that doesn’t have a “A version of this previously..

As someone who derives significant income from writing for money, I end up spending a fair bit of time reading writing advice. Not because I'm in need of tips, myself-- after many years of this, I've got a routine that mostly works for me. Rather, I'm looking for good advice to pass on to other people, because I get asked for advice on a regular basis, and I don't really have much of my own to offer. That's how I came to read this advice post from Alyx Dellamonica, making an analogy between figuring out how fiction works and trying to learn about cars from a junkyard. I like the junkyard analogy quite a bit, but along the way she makes a couple of passing mentions to physics that I absolutely hate. Here's the first: With the arts, you not a physics professor laying out a formula, some cut-and-dried procedure for which there is one satisfactory answer. You’re not showing someone how to paint the perfect yellow line down the middle of a strip of road, or fly an ai