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+ - A view beneath the clouds of Venus

Submitted by StartsWithABang
StartsWithABang writes: Of all the worlds in our Solar System, Venus is perhaps the most like Earth. It’s the closest to us in size, in mass, in orbit, and in elemental content. The biggest difference, of course, is Venus’ atmosphere. Over 90 times as thick as Earth’s and composed of carbon dioxide and thick sulfuric acid clouds, the surface of Venus is at a constant 465C (870 F), making it the hottest planet in the Solar System. Yet we’ve both landed on the surface and imaged the entire world through its clouds, finding out exactly what the Venusian surface looks like. Come learn what you're looking at in advance of Tuesday evening's big conjunction!

+ - What it will take to refute the existence of dark matter

Submitted by StartsWithABang
StartsWithABang writes: When we look out at the galaxies in the Universe, watching how they rotate, we find that the starlight we see is woefully insufficient to explain why the galaxies move as they do. In fact, even if we add in the gas, dust, and all the known matter, it doesn’t add up. Normally, we talk about dark matter as the only viable solution, but it turns out that MOND, or MOdified Newtonian Dynamics, is actually superior at explaining galactic rotation to dark matter. Could it be the solution to the “missing mass” (or “missing light”) problem? A look at the full suite of cosmological evidence reveals the answer, and sets out definitive challenges for MOND to overcome.

+ - We thought we understood static electricity; we were wrong

Submitted by StartsWithABang
StartsWithABang writes: Static electricity is often the first exposure to physics beyond gravity that we encounter in our lives. Simply rub a balloon against a piece of fabric, and you can stick it to almost anything (or anyone) you like, possibly to their chagrin. But the way you probably learned that it happens — rub two materials together, one picks up a positive charge and the other gets a negative charge — is not only a little naive, it turns out not to account for the static electricity effects we observe at all. And oddly enough, we only determined this back in 2011 for the first time, shocking for one of the oldest known physical phenomena!

+ - How we know we just found the first stars in the Universe

Submitted by StartsWithABang
StartsWithABang writes: When we look out into the Universe, farther back to greater distances, we’re also looking back in time, farther and farther into the past. If we could look back far enough, close enough to the Big Bang, we’d be able to see the very first stars ever formed in the Universe: stars formed from the Big Bang’s leftover material itself. We’d never been able to find these before, but by looking at a starburst galaxy at extremely high redshifts, and measuring its signature spectroscopically, we were able to find strong evidence of hydrogen and helium, but none of carbon, oxygen, or any of the other “first-processed” elements we’d expect had we formed stars before. Here's why we think we've finally found the first true sample of Population III stars, with an actual exclusive interview with the lead scientist who made the discovery.

+ - 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.

+ - 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.

+ - 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.

+ - 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!

+ - 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.

+ - 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.

+ - 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!

+ - 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.

+ - 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.

+ - 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.

+ - 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.

The universe is like a safe to which there is a combination -- but the combination is locked up in the safe. -- Peter DeVries

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