73491457
submission
StartsWithABang writes:
Wherever large, dense collections of cool gas gather together under the force of their own gravity, new stars are bound to form. Every galaxy goes through peaks and lulls in star formation, yet at any given time, one star cluster will always be the largest and most massive. Discovered only in the 1960s due to its location in the galactic plane, Westerlund 2 holds that distinction, as far as we know. Recently imaged in great detail by the Hubble Space Telescope for its 25th anniversary, a huge slew of interesting features abound, including some of the hottest, youngest stars known and ridges, pillars and valleys formed by the UV radiation. Most interestingly, it may yet turn out to be the location of the next supernova visible from Earth within our galaxy.
73439139
submission
StartsWithABang writes:
It’s a difficult fact to accept: our two most fundamental theories that describe reality, General Relativity for gravitation and the Standard Model / Quantum Field Theory for the other three forces, are fundamentally incompatible with one another. When an electron moves through a double slit, for example, its gravitational field can’t move through both slits, at least not without a quantum theory of gravity. String Theory is often touted as the only game in town as far as formulating a quantum theory of gravity is concerned, but in fact there are five viable options, each with different pros, cons, and approaches to the problem. Many of them, in fact, have undergone significant developments in the past 5-10 years, something String Theory cannot claim.
73410009
submission
StartsWithABang writes:
When you travel towards an object like a moon, planet or star, the closer you get, the larger it appears. Halve the distance and its angular size doubles; reduce the distance to a quarter and it appears four times as large. But for black holes, their gravitation is so strong that relation no longer holds as you approach the event horizon. Instead, the region of “blackness” increases much faster than you’d expect, eventually taking over a full half of the sky as you crossed the event horizon and causing all the light-paths to contract down to a point behind you the instant before you hit the singularity.
73381395
submission
StartsWithABang writes:
Few things in this world are as regular as sunrise and sunset. With the application of a little physics, you can predict exactly where and when the sun will rise or set from any location on Earth. Thus far, every world in our Solar System — planet, moon and asteroid — has had the exact same experience as us. But out in the Kuiper belt, Pluto is different. The only known world in the Solar System where a significant fraction of the system’s mass is not in a single component, the outer moons of the Pluto-Charon system provide a unique environment to study how planets might behave in orbit around binary stars. The amazing takeaway? The rotational part of the orbit is chaotic; the worlds tumble, and hence sunrises and sunsets are no longer predictable.
73320785
submission
StartsWithABang writes:
The beauty of a sunset (or sunrise) is rare and unique, happening but once a day for those of us on Earth. But aboard a spacecraft like the ISS, these are sights that happen sixteen times a day. While we’re used to dramatic, slow sunsets where it takes between two and three minutes simply for the Sun’s disk to drop below the horizon, it takes mere seconds for the Sun to go from a barely-visible red glow to a brilliant, blinding white. In the space of a few breaths, the entire thing is over, a sight that only around 500 people have ever experienced firsthand. Here's the science of how and why sunsets (and sunrises) in space appear so dramatically different than from Earth's surface.
73270245
submission
StartsWithABang writes:
If you strike the upper atmosphere with a cosmic ray, you produce a whole host of particles, including muons. Despite having a mean lifetime of just 2.2 microseconds, and the speed of light being 300,000 km/s, those muons can reach the ground! That’s a distance of 100 kilometers traveled, despite a non-relativistic estimate of just 660 meters. If we apply that same principle to particle accelerators, we discover an amazing possibility: the ability to create a collider with the cleanliness and precision of electron-positron colliders but the high energies of proton colliders. All we need to do is build a muon collider. A pipe dream and the stuff of science fiction just 20 years ago, recent advances have this on the brink of becoming reality, with a legitimate possibility that a muon-antimuon collider will be the LHC’s successor.
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.
