73267207
submission
StartsWithABang writes:
When you think about a black hole, you very likely think about a large amount of mass, pulled towards a central location by the tremendous force of gravity. While black holes themselves may be perfectly spherical (or for rotating black holes, almost perfectly spherical), there are important physical cases that can cause them to look tremendously asymmetrical, including the possession of an accretion disk and, in the most extreme case, a merger with another black hole.
73263271
submission
StartsWithABang writes:
The heat death of the Universe is the idea that increasing entropy will eventually cause the Universe to arrive at a uniformly, maximally disordered state. Every piece of evidence we have points towards our unfortunate, inevitable trending towards that end, with every burning star, every gravitational merger, and even every breath we, ourselves, take. Yet even while we head towards this fate, it may be possible for intelligence in an artificial form to continue in the Universe for an extraordinarily long time: possibly for as long as a googol years, but not quite indefinitely. Eventually, it all must end.
73244869
submission
StartsWithABang writes:
Newtonian gravity is just an approximation to a more correct theory of gravity, but for over 200 years, it was unchallenged as the science that explained the entire Universe. When a simple puzzle — the orbital mechanics of just one of the planets — failed to line up with its predictions, it was assumed there was a problem with the Solar System, not with the law of gravity. But when Einstein put forth General Relativity, he not only explained Newton’s laws as a special case, as well as this orbital curiosity, he also made a new prediction that differed from Newton’s: that light, when it passed near the Sun, would see its path bend! Confirmed on May 29, 1919, our understanding of the Universe changed forever because of it.
73212107
submission
StartsWithABang writes:
Every rocky world in the solar system is covered with craters. But while the ones on Mercury and the Moon might be many billions of years old, the craters on Earth are much younger, due to volcanism, plate tectonics and general geological activity. But one place in our Solar System — Jupiter's moon Io — has us totally beat. The reason why? Jupiter acts like a cosmic zamboni, completely resurfacing Io in lava every few thousand years.
73208719
submission
StartsWithABang writes:
The Large Hadron Collider has just been upgraded, and is now making the highest energy collisions of any human-made machine ever. But even at 13 TeV, what are the prospects for testing String Theory, considering that the string energy scale should be up at around 10^19 GeV or so? Surprisingly, there are a number of phenomenological consequences that should emerge, and looking at what we've seen so far, they may disfavor String Theory after all.
73176259
submission
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.
73147495
submission
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!
73132833
submission
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.
73093717
submission
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.
73052695
submission
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.
73039377
submission
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.
72987361
submission
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.
72974871
submission
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.
72938219
submission
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!
72936049
submission
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.
