StartsWithABang writes: It’s one of the cardinal laws of physics and the underlying principle of Einstein’s relativity itself: the fact that there’s a universal speed limit to the motion of anything through space and time, the speed of light, or c. Light itself will always move at this speed (as well as certain other phenomena, like the force of gravity), while anything with mass — like all known particles of matter and antimatter — will always move slower than that. But if you want something to travel faster-than-light, you aren’t, as you might think, relegated to the realm of science fiction. There are real, physical phenomena that do exactly this, and yet are perfectly consistent with relativity.
StartsWithABang writes: At the center of almost every galaxy is a supermassive black hole (SMBH); at the center of almost every cluster is a supermassive galaxy with some of the largest SMBHs in the Universe. And every once in a while, a galactocentric black hole will become active, emitting tremendous amounts of radiation out into the Universe as it devours matter. This radiation can cut across the spectrum, from the X-ray down to the radio. At the heart of MS 0735.6+7421, there’s a >10^10 solar mass black hole that appears to have been active for hundreds of millions of years, something unheard of!
StartsWithABang writes: “There are 12 men on an island. 11 weigh exactly the same amount, but one of them is slightly lighter or heavier. You must figure out which. The island has no escapes, but there is a see-saw. The exciting catch? You can only use it three times.” Here is the set of all possible solutions, worked out in illustrated form.
StartsWithABang writes: The Universe had two periods where light was abundant, separated by the cosmic dark ages. The first came at the moment of the hot Big Bang, as the Universe was flooded with (among the matter, antimatter and everything else imaginable) a sea of high-energy photons, including a large amount of visible light. As the Universe expanded and cooled, eventually the cosmic microwave background was emitted, leaving behind the barely visible, cooling photons. It took between 50 and 100 million years for the first stars to turn on, so in between these two epochs of the Universe being flooded with light, we had the dark ages. Yet the dark ages may not be totally invisible, as the forbidden spin-flip-transition of hydrogen may illuminate this time period after all.
StartsWithABang writes: When it comes to risk assessment, there’s one type that humans are notoriously bad at: the very low-frequency but high-consequence risks and rewards. It’s why so many of us are so eager to play the lottery, and simultaneously why we’re catastrophically afraid of ebola and plane crashes, when we’re far more likely to die from something mundane, like getting hit by a truck. One of the examples where science and this type of fear-based fallacy intersect is the science of asteroid strikes. With all we know about asteroids today, here's the actual risk to humanity, and it's much lower than anyone cares to admit.
StartsWithABang writes: Imagine you wanted to know what your acceleration was anywhere on Earth; imagine that simply saying “9.81 m/s^2" wasn’t good enough. What would you need to account for? Sure, there are the obvious things: the Earth’s rotation and its various altitudes and different points. Surely, the farther away you are from Earth’s center, the less your acceleration’s going to be. But what might come as a surprise is that if you went up to the peak of the highest mountains, not only would the acceleration due to gravity be its lowest, but there’d also be less mass beneath your feet than at any other location.
StartsWithABang writes: Bet you thought you knew it all about the asteroid belt. These frozen, ice-and-rock worlds orbit farther out from Mars, closer in than Jupiter, and occasionally get hurled towards the inner Solar System by gravitational interactions. But the largest world, Ceres, at just about half the diameter of the Moon (or the size of Texas), exhibits an unusual surprise: a brilliant set of white spots at the bottom of one of its largest craters. While the speculation abounds from simple (water-ice) to the astounding (aliens!), there are only three realistic possibilities given what Dawn has seen so far. What’s even more exciting? It’s already got the equipment on board to decide which possibility is the right one.
StartsWithABang writes: If you’re not a theoretical physicist yourself, you might think that physics is physics — we ask questions about the Universe, do experiments/make observations, and get the answers — and math is just a tool that we use to help us get there. But that really sells the power of mathematics short. For a physical theory to be valid, there are a whole host of mathematical properties that theory needs to possess, including being free of logical inconsistencies, making predictions about observables, and that those predictions agree with observations. Yet when we look at our theory of gravitation at the smallest scales and with the strongest gravitational fields, our theory itself fails, which is precisely why we need a quantum theory of gravity.
StartsWithABang writes: Get a supermassive black hole feeding on matter, particularly on large amounts of cool, dense gas, and you're likely to get a quasar: a luminous, active galaxy emitting radiation from the radio all the way up through the X-ray. Our best understanding and observations indicate that these objects should be rare, transient, and isolated; no more than two have ever been found close together before. Until this discovery, that is, where we just found four within a million light years of one another, posing a problem for our current theories of structure formation in the Universe.
StartsWithABang writes: Originating from well out beyond the planets we’re accustomed to, the cold, icy worlds of the outer Solar System normally roam in isolation, hardly noticed by anything at all in the Universe. But once in a while, a gravitational interaction will cause one of those bodies to fly towards the Sun. And when it does, all sorts of interesting phenomena will develop, including tails, a coma, and a variety of spectacular colors, all taking place at breakneck speeds. What causes all of this? A combination of gravitational, electromagnetic and atomic transitions make it all possible, including tails as long as 500 million km!
StartsWithABang writes: When it comes to the farthest thing we can see in the Universe, that’s the Cosmic Microwave Background, or the leftover glow from the Big Bang, emitted when the Universe was a mere 380,000 years old. But what, exactly, does this mean? Does it mean that we’re seeing the “edge” of the Universe? Does it mean that there’s nothing to see, farther back beyond it? Does it mean that, as time goes on, we’re going to be able to see farther back in time and space? The answers are no, no, and yes, respectively. If we want to see farther than ever before, we've got two options: either wait for more time to pass, or get moving and build that cosmic neutrino background detector.
StartsWithABang writes: If there’s nothing else that science has to offer, it’s this elegant notion: that anyone, anywhere, at anytime, can investigate and uncover the mysteries and workings of the Universe simply by asking it the right questions in the right ways, listening to its answers, and putting the pieces together for themselves. Anyone can do it. Only, for various and sundry reasons, not everyone gets to do it. Some people don’t have the economic ability, some don’t have the sustained drive or interest, and some simply can’t cut the mustard. But some people — some really, really good people — are driven from their passions for a sad, simple and completely unnecessary fact: that they were treated in unacceptable ways that they refused to just accept. And in a great many cases, that unacceptable treatment came simply because of their gender. Sexism sometimes looks like what you expect, and sometimes not. Here’s one opinion on what we can all do about it to create the world we really want: where science really is for everyone.
StartsWithABang writes: When you think about dark matter, you probably think of a few things: how mass and gravity don’t appear to line up, how there isn’t enough normal matter to account for the motions we see on scales of galaxies and up, and how it’s necessary to form the structure we see on the largest scales, from the early times of the cosmic microwave background to the cosmic web spanning billions of light years we see today. But what you might not realize is that without dark matter — a substance that doesn’t interact in any (yet) measurable, non-gravitational way with anything else (or even itself) in the Universe — life as we know it would be unable to exist. But what you might not realize is that without dark matter — a substance that doesn’t interact in any (yet) measurable, non-gravitational way with anything else (or even itself) in the Universe — life as we know it would be unable to exist. The gravitation from dark matter is the only thing keeping supernova ejecta from escaping from our galaxy, and enabling heavy elements to participate in later generations of stars, planets, and biochemical reactions.
StartsWithABang writes: Since its discovery as the first asteroid more than 200 years ago, Ceres has been one of the most poorly understood objects in the Solar System as even imagery from the Hubble Space Telescope is unable to resolve very much. But NASA's Dawn mission, since moving on from Vesta, has begun to map Ceres, constructing the highest resolution global map ever, with better data to come. The greatest mystery so far are two bright white spots at the bottom of a deep crater, brighter and more reflective than anything else on the planet's surface. Right now, three leading possibilities for the origin of these features exist, with Dawn possessing the capabilities to teach us which one (if any) is correct, hopefully by the end of the year!
StartsWithABang writes: When you think of our own cosmic backyard — our planets, Sun, the nearby stars, and even the closest galaxies to us — you probably don’t think of them in the context of the entire Universe. But if you want to understand where we come from and how we got to be this way, perhaps you ought to. We could have been a single, isolated galaxy hanging out all by our lonesome in the void: but we aren’t. We could have been part of a large, rich cluster of galaxies, where the Milky Way was just one of many thousands like us: but we aren’t. Instead, it’s us, Andromeda, and about 50 other, much smaller neighbors, and no one else. Here's how all that fits into the cosmic picture of everything we know.