Slashdot is powered by your submissions, so send in your scoop

 


Forgot your password?
Close
typodupeerror
×

Submission + - The Sun only shines because of quantum mechanics

Submitted by StartsWithABang
StartsWithABang writes: The Sun consists of some 10^57 particles, nearly 10% of which are in the core, which ranges from 4-15 million K, hot enough for nuclear fusion to occur. A whopping 4 × 10^38 protons fuse into helium-4 every second, and due to the temperatures and densities inside, the raw protons undergo billions of collisions during that time. Yet none of those collisions have a sufficient energy to overcome the Coulomb barrier; it's only through the power of quantum mechanics that any fusion occurs. Without this inherent indeterminism, the Sun and practically every star in the night sky would be eternally dark.

Submission + - The Milky Way has a skeleton, and its first "bone" may be huge

Submitted by StartsWithABang
StartsWithABang writes: Spiral galaxies contain high density dust at the centers of their spiral arms, forming the skeleton of galactic structure. While these arm-tracing infrared dark clouds had been seen in many galaxies external to our own, none had ever been discovered in the Milky Way. Until, that is, one of these “skeletal” features was discovered using the Spitzer Space Telescope in 2010. Recently, that “bone” was discovered to be even longer than suspected, and may be the central feature of the Scutum-Centaurus arm, the closest major spiral arm to the Sun.

Submission + - What if all your atoms randomly moved the same direction at once?

Submitted by StartsWithABang
StartsWithABang writes: Take a common, macroscopic object and imagine what’s going on inside at the level of individual particles. At a small, fundamental scale, they’re just bouncing off of one another, rapidly in motion due to the nature of kinetic theory. Each particle has a certain amount of energy, collides with other particles, and on average moves at a specific speed. If you aligned all these motions — somehow — how fast could you get that object to go? Pretty fast, it turns out: some 147 m/s, but there are two big physical reasons why that will never happen, one being momentum conservation and the other being that objects are solids.

Submission + - Cosmic inflation has five great predictions; four have been confirmed

Submitted by StartsWithABang
StartsWithABang writes: Cosmic inflation is alternately talked about by serious scientists as either the definitive beginning to our Universe, the thing that happened before and set up the Big Bang with absolute certainty, or a speculative fiction that can never be falsified, leading to nothing but untestable predictions and things that only mattered after-the-fact of their discovery. But inflation has five unique predictions that it made intrinsic to all (reasonable) models back in the 1980s, before any of them were known:
  1. A Flat Universe,
  2. A Universe with fluctuations on scales larger than light could’ve traveled across.
  3. A Universe whose fluctuations were adiabatic, or of equal entropy everywhere.
  4. A Universe where the spectrum of fluctuations were just slightly less than having a scale invariant (n_s
  5. And finally, a Universe with a particular spectrum of gravitational wave fluctuations.

Four of the five have been confirmed, and that's why we're way more confident in it than most people realize!

Submission + - Philae's lost seven months were completely unnecessary

Submitted by StartsWithABang
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.

Submission + - Past a certain critical temperature, the Universe will be destroyed

Submitted by StartsWithABang
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.

Submission + - The Weak Force does more than just cause radioactive decays

Submitted by StartsWithABang
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!

Submission + - What's the third most common element in the Universe?

Submitted by StartsWithABang
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.

Submission + - Lee Smolin talks about predicting that quantum gravity would be solved by 2015

Submitted by StartsWithABang
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.

Submission + - Largest Star Cluster In Milky Way May House Undiscovered Supernovae

Submitted by StartsWithABang
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.

Submission + - Quantum gravity will be just fine without string theory

Submitted by StartsWithABang
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.

Submission + - What would you see as you fell into a black hole?

Submitted by StartsWithABang
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.

Submission + - Pluto's outer moons orbit chaotically, with unpredictable sunrises and sunsets

Submitted by StartsWithABang
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.

Submission + - How sunsets and sunrises differ in space from on Earth

Submitted by StartsWithABang
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.

Submission + - The case for a muon collider succeeding the LHC just got stronger

Submitted by StartsWithABang
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.

Slashdot Top Deals

Be careful when a loop exits to the same place from side and bottom.

Close