73666685
submission
StartsWithABang writes:
This past weekend, the Philae lander reawakened after seven dormant months, the best outcome that mission scientists could've hoped for with the way the mission unfolded. But the first probe to softly land on a comet ever would never have needed to hibernate at all if we had simply built it with the nuclear power capabilities it should've had. The seven months of lost data were completely unnecessary, and resulted solely from the world's nuclear fears.
73613947
submission
StartsWithABang writes:
If you take all the kinetic motion out of a system, and have all the particles that make it up perfectly at rest, somehow even overcoming intrinsic quantum effects, you’d reach absolute zero, the theoretically lowest temperature of all. But what about the other direction? Is there a limit to how hot something can theoretically get? You might think not, that while things like molecules, atoms, protons and even matter will break down at high enough temperatures, you can always push your system hotter and hotter. But it turns out that the Universe limits what’s actually possible, as any physical system will self-destruct beyond a certain point.
73581697
submission
StartsWithABang writes:
There are four known fundamental forces: gravitation, electromagnetism, the strong nuclear force and the weak nuclear force. But while we often speak of gravitation as an attractive force between masses (or anything with energy), of the electric force as charged particles attracting or repelling, of quarks and gluons attracting one another and keeping nuclei bound together, we describe the weak force as “responsible for radioactive decay.” Is this right? Shouldn’t the weak force, you know, be a force? Shouldn’t there be a weak charge and attraction or repulsion based on that charge? As it turns out, there ought to be one, but due to the fact that it’s less than one-millionth the strength of the electromagnetic interaction, we were unable to measure it. Until 2013, that is, when we did for the first time!
73555733
submission
StartsWithABang writes:
Shortly after the Big Bang, the first nuclear fusion reactions occurred in the Universe, filling it with hydrogen, helium, and little else. Billions of years later, huge numbers of stars have lived and died, creating copious amounts of heavy elements, running the full gamut of the periodic table. After all this time, hydrogen is still the most abundant element, followed by helium, although the gap is closer now than it was to start. But who’s third? You might think it’s carbon, because three heliums fuse into one carbon, but there’s one element that has it beat! Spoiler: it's oxygen, and here's why.
73531147
submission
StartsWithABang writes:
If we want to understand the Universe at a fundamental level — all the forces on all scales — the biggest obstacle facing us is to come up with a correct, consistent, testable and verifiable theory of quantum gravity. To no one’s great surprise, we’re not quite there yet. In 2001, Lee Smolin — one of the leading thinkers in quantum gravity — made the bold prediction that,
“We shall have the basic framework of the quantum theory of gravity by 2010, 2015 at the outside.”
While we’re not at all there yet, it’s still fascinating in its own right to take a look at where we actually are. In an exclusive interview, Sabine Hossenfelder gets Lee talking about the state of the field, where we’ve come, and what we have left to do.
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.
