Please create an account to participate in the Slashdot moderation system


Forgot your password?
For the out-of-band Slashdot experience (mostly headlines), follow us on Twitter, or Facebook. ×

+ - The science of 4th of July fireworks

StartsWithABang writes: There are few things as closely associated with American independence as our willingness and eagerness to celebrate with fiery explosions. I refer, of course, to the unique spectacle of fireworks, first developed nearly a millennium ago halfway across the world. But these displays don’t happen by themselves; there’s an intricate art and science required to deliver the shows we all expect. So what’s the science behind fireworks? Here's the physics (and a little chemistry) behind their height, size, shape, color and sound, just in time for July 4th!

+ - How everything we know about science could come crashing down, almost

StartsWithABang writes: If there’s one thing you can be certain of when it comes to the fundamental, scientific truths of our Universe, it’s this: someday, in the not too distant future, those truths will be superseded by more fundamental ones. And even those, quite likely, won’t be the final truths, but just one step further along the line towards our understanding of reality. Does this mean that we’ve necessarily got it all wrong, and that we might just as well ignore the successes of our best theories so far? Does it mean that all we know about the Universe could easily be upended and replaced, leading to vastly different conclusions to questions like where everything came from? These are exceedingly unlikely, for a myriad of reasons. Instead, this is what the next major scientific revolution will probably look like.

+ - First human colonies should be among Venus' clouds

StartsWithABang writes: When we talk about humans existing on worlds other than Earth, the first choice of a planet to do so on is usually Mars, a world that may have been extremely Earth-like for the first billion years of our Solar System or so. Perhaps, with enough ingenuity and resources, we could terraform it to be more like Earth is today. But the most Earth-like conditions in the Solar System don't occur on the surface of Mars, but rather in the high altitudes of Venus' atmosphere, some 50-65 km up. Despite its harsh conditions, this may be the best location for the first human colonies, for a myriad of good, scientific reasons.

+ - Lithium, Beryllium and Boron are the only three elements not made in stars

StartsWithABang writes: From helium up through uranium continuously, every element in the periodic table can be found, created by natural processes, somewhere in the Universe. (With many trans-uranic nuclides found as well.) Yet out of all of those, only three of them aren't created in stars: lithium, beryllium and boron. Boron in particular is necessary for life as we know it, as without it, there would be no such things as plants. Here's the cosmic story of the only three heavy elements to exist that aren't made in stars.

+ - How does gravity escape from a black hole?

StartsWithABang writes: There’s something puzzling about black holes, if you stop to consider it. On the one hand, they’re objects so massive and dense — compacted into such a small region of space — that nothing can escape from it, not even light. That’s the definition of a black hole, and why “black” is in the name. But gravity also moves at the speed of light, and yet the gravitational influence of a black hole has absolutely no problem extending not only beyond the event horizon, but infinite distances out into the abyss of space. The resolution involves some intricate physics about the event horizon itself, but the net result is that gravity works just the same outside the event horizon as if there were no horizon at all.

+ - A view beneath the clouds of Venus

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

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

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

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

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

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?

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

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

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

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.

Top Ten Things Overheard At The ANSI C Draft Committee Meetings: (5) All right, who's the wiseguy who stuck this trigraph stuff in here?